A SERIES SPONSORED BY THE AFS FISH HEALTH SECTION REVIEWS IN FISH HEALTH

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1 A SERIES SPONSORED BY THE AFS FISH HEALTH SECTION REVIEWS IN FISH HEALTH Spread of an exotic fish-gill trematode: A far-reaching and complex problem Centrocestus formosanus, the gill trematode, has caused serious losses among fish raised by tropical fish producers since the early 1980s and is believed to be harmful to wild fish populations, including the federally listed endangered fountain darter (Etheostoma fonticola), in the Comal River near San Marcos, Texas. The parasite appears to infect in many fishes from Hawaii, Florida, Texas, and Utah. The gill trematode has a complex life cycle involving definitive hosts (aquatic birds and occasionally some mammals) and intermediate hosts (aquatic snails and several fish species). In the United States, the green heron (Butorides virescens) and the great egret (Ardea alba) serve as definitive hosts. The first intermediate host, the red-rim melania (Melanoides tuberculatus), an exotic snail, has been found in 15 southern and western states. This snail exhibits resistance to desiccation, molluscicides, and disinfectants and has been documented to out-compete established mollusks. Both the gill trematode and its exotic snail host continue to spread in the United States. ABSTRACT feature fish health Introduction An exotic trematode, often referred to as the gill trematode, affects the health of both wild and cultured fish species. The trematode is identified tentatively as Centrocestus formosanus and for more than 20 years has been a subject of interest and concern among fisheries scientists and fish producers. This trematode evokes broad interest because it is carried by federally-protected aquatic birds and the invasive exotic snail Melanoides tuberculatus and infects many fish hosts, including several endangered species. This article contains information on the history, identification, biology, pathology, spread, and unusual aspects of an exotic trematode now infecting fish in the United States. The information recorded here comes from biological observations and research efforts. History of the gill trematode in the United States In 1956, Walter Martin and some colleagues found larval stages of a trematode identified as C. formosanus emerging from the aquatic snail Stenomelania newcombi that was collected from ditches in Kaneohe, Oahu, Hawaii (Martin 1958). After finding the trematode in the snail, Martin (1958) reported the western mosquitofish (Gambusia affinis), green swordtail (Xiphophorus hellerii), black-crowned night-heron (Nycticorax nycticorax), and an unidentified rat as natural hosts for other stages of the same parasite. Several other species, including the goldfish (Carassius auratus) and cat (Felix domesticus), were experimentally infected. For the next 27 years, there was no additional report of this or a similar parasite from any region of the presently recognized United States. Heavy losses among cichlids, tetras, and tropical cyprinids were first reported by Florida tropical fish producers in the early 1980s (Blazer and Gratzek 1985; Vogelbein and Overstreet 1988). These losses were attributed to an unidentified trematode infecting the gills of the fish. Wolfgang Vogelbein, Richard Heard, and one of the authors (RMO) completed initial life cycle studies on the trematode in 1985 at the Gulf Coast Research Laboratory (GCRL) using the cercaria (the larval stage of a trematode that invades intermediate hosts) from an aquatic snail, the red-rim melania (M. tuberculatus), found on ornamental fish farms in Central Florida (Vogelbein and Overstreet 1988). These studies were replicated in 1992 (and at later dates) using similar or identical cercaria in M. tuberculatus from wild populations in Texas. Independently, James Sullivan (Centers for Disease Control, Atlanta, Georgia) found identically infected M. tuberculatus from a lake in Pasco County, Florida, in December 1985 and later. In 1990, K. E. Knott found an unidentified cercaria from the red-rim melania in the San Antonio River near the San Antonio Zoo, Bexar County, Texas, and at Landa Park, New Braunfels, Comal County, Texas (Alberto Santos and Harold D. Murray, Trinity University, unpublished studies). Knot and Murray (1991) reported the responsible agent as the mystery fluke. This trematode, sent to one of the authors (RMO) in January 1992, was determined to be the same trematode previously studied and observed. The metacercaria, a juvenile form of the trematode, was Andrew J. Mitchell Robin M. Overstreet Andrew E. Goodwin Thomas M. Brandt Mitchell is a fisheries biologist and researcher at the Harry K. Dupree Stuttgart National Aquaculture Research Center, U. S. Department of Agriculture, Agricultural Research Service, Stuttgart, Arkansas. He can be contacted at dmitchell@spa.ars.usda.gov. Overstreet is a professor at The University of Southern Mississippi, Gulf Coast Research Laboratory, Ocean Springs, Mississippi. Goodwin is a professor at the Aquaculture/Fisheries Center, University of Arkansas at Pine Bluff. Brandt is director of the U. S. Fish and Wildlife Service, National Fish Hatchery and Technology Center, San Marcos, Texas. August Fisheries 11

2 also found in five fish species (Mexican blind/cave tetra Astyanax fasciatus, common carp Cyprinus carpio, blue tilapia Oreochromis aureus, redbelly tilapia Tilapia zillii, and green swordtail) from the San Antonio River. Although the destructive gill trematode was not identified, it was noted that the parasites found in Florida and Texas represented an introduction of a single species that was similar to C. formosanus found in other parts of the world. The destructive nature of the trematode was recognized by Blazer and Gratzek (1985) and Vogelbein and Overstreet (1988) who described the damage to the gills that resulted from the trematode infection. Juvenile tropical fish losses associated with this trematode were estimated at $3.5 million (USD) annually (Francis-Floyd et al. 1997). The problem was serious enough that in the mid-1990s research efforts were directed to find means to control the snails that serve as vectors for the trematode. In 1997, a study was published to support an application by the Florida s Department of Agriculture and Consumer Services, Division of Pesticides for an EPA Special Local Needs (SLN) registration for the chemical Bayluscide to control snails (Francis-Floyd et al. 1997). The trematode is still a serious problem within the tropical fish industry, but snail control efforts have made the problem manageable. On 19 July 1996, 11 specimens of fountain darter (Etheostoma fonticola), federally listed as an endangered species, were collected from the Comal River, Comal County, Texas, inspected, and then released (Figure 1). One of the specimens had inflamed gills, but it was not examined microscopically. On 2 October 1996, 85% of 70 specimens of the darter collected from the Comal River were observed with inflamed and protruding gills (Figure 2). The next day, three of these fish were examined by David Huffman of Texas State University at San Marcos, and the abnormal gills were found to be associated with encysted metacercariae. Most encysted individuals had Figure 1. The fountain darter (Etheostoma fonticola), a federally-listed endangered species. Figure 2. Fountain darters infected (top) and not infected with Centrocestus formosanus. Proliferation of branchial tissue in infected fish may cause the opercular flaps to remain flared. Figure 3. Complex life-cycle of the gill trematode Centrocestus formosanus involving a definitive bird (or mammal) host (A), the first intermediate snail host (B), and an intermediate fish host (C). (a) Metacercaria from fish eaten by bird, (b) metacercaria released from cyst in intestinal tract of definitive host, where it attaches to gut epithelium and matures into an adult worm within in a few days producing eggs that are shed into the host s lumen and then defecated into the water; (c) released trematode egg is eaten by snail and then hatches, releasing the miracidium; (d) germinal cells from miracidium develop, ultimately producing a redia; (e) redia asexually produces large numbers of the cercaria that are shed into water; (f) cercaria passively engulfed by fish or actively penetrate it; the tailless cercaria locates near a cartilage support in the gill filament; (g) cercaria develops into an encysted metacercaria and becomes encapsulated by a moderate to extensive cartilaginous response; large numbers can harm gills and fish host; (h) metacercaria exhibiting cartilaginous encapsulation. GLENN LONGLEY, TEXAS STATE UNIVERSITY, SAN MARCOS CERCARIAE WITH HEART-SHAPED BODY BY CHRIS WILSON, UTAH DIVISION OF WILDLIFE RESOURCES, LOGAN FOUNTAIN DARTERS BY GLENN LONGLEY, TEXAS STATE UNIVERSITY, SAN MARCOS GREEN HERON BY TOM VEZO WILDLIFE PHOTOGRAPHY, 12 Fisheries vol 30 no 8

3 undergone necrosis, but still exhibited recognizable eye-spots. Over the next 2 months, fishes of 10 different species, including the fountain darter, were collected from the Comal and San Marcos (Hays County, Texas) rivers and sent to three fish disease diagnostic laboratories (Fish Health Center, Pinetop, Arizona; Fish Technology Center, Bozeman, Montana; and Harry K. Dupree Stuttgart National Aquaculture Research Center [HKD-SNARC], Stuttgart, AR). The majority of the fish from the Comal River were found to be infected with cysts of the same trematode. The fountain darter and greenthroat darter (Etheostoma lepidum) contained the most severe infections. The Texas shiner (Notropis amabilis), Mexican tetra (Astyanax mexicanus), and yellow bullhead (Ameiurus natalis) also exhibited heavy infections. In the two darters, most of the encysted trematodes appeared necrotic. The host reaction of the darters apparently affected the trematode but also detrimentally affected the gills (host response will be discussed later). In 1996, no cyst was found in the gills of fish from the San Marcos River. From April 1997 until May 1998, more than 350 specimens of the fountain darter from the Comal and San Marcos rivers were sent to HKD-SNARC to determine the significance of the trematode infection on health and survival of this darter. Only 4 of 145 of these fish collected from the San Marcos River had the cysts in their gills, and the mean intensity for the 4 fish was 0.25 cysts per gill arch. All 209 fish examined from the Comal River exhibited infections, with 48 fish averaging more than 50 cysts per gill arch and 17 having more than 100 per arch (one with 191 per arch). In light of the evident gill damage, we consider it surprising that any of these 21 to 35 mm TL individuals with more than 100 per arch could survive. We noticed flared opercular flaps associated with heavy infections (average of 50 or more per arch) on the Comal River fountain darters (Figure 2). Both river systems harbored large populations of the exotic red-rim melania. Information on the trematode found in the fountain darters was presented by one of the authors (AJM) at the Third International Symposium on Aquatic Animal Health in 1998 in Baltimore, Maryland. A parasitologist (Rokkam Madhavi) from India attending the symposium observed the presentation on the Comal River trematode and suggested that the parasite was C. formosanus, a trematode native to Asia but now found in a number of countries. After further consultation with one of the authors (RMO), it was clear that this appeared to be an appropriate tentative identification for the trematode (Mitchell et al. 2000). However, the identification of U.S. material still remains questionable because of slight morphological differences and recent molecular data. The study by Dzikowski et al. (2004) using species-specific polymerase chain reaction assays against material identifiable as Centrocestus sp. from Israel and the United States, indicated two distinct species of Centrocestus. Additional DNA sequences are needed to better understand the taxonomy of this genus. After metacercariae of the gill trematode were evaluated from the Comal and San Marcos rivers, they were documented at three west Texas springs (San Felipe Creek, Val Verde County; San Solomon Springs, Reeves County; and Phantom Lake Springs, Jeff Davis County) where they infected five state or federally listed fishes (endangered): Devils River minnow (Dionda diaboli), proserpine shiner (Cyprinella proserpina), Rio Grande darter (Etheostoma grahami), Comanche Springs pupfish (Cyprinodon elegans), and Pecos gambusia (Gambusia nobilis; McDermott 2000). Mitchell et al. (2002) reported that four major aquaculture species (channel catfish Ictalurus punctatus, golden shiner Notemigonus crysoleucas, fathead minnow Pimephales promelas, and sunshine bass female Morone chrysops male M. saxatilis) could be experimentally infected with cercariae (similar to cercariae of C. formosanus) from red-rim melania taken from the Comal River. In 2004, 50.0% (5 of 10) of the fountain darters examined from the San Marcos River were positive (1 to 3 cysts per fish) for trematode cysts; this value compared with a 2.8% (4 of 145) prevalence for infection in darters collected from the San Marcos River in 1997 and There are a few reports and observations of fish infected with this or a similar trematode that are not from Florida, Texas, or Hawaii. Olsen and Pierce (1997) reported a similar trematode infecting steelhead trout in cages in the Willamette River, Oregon, but there is at least one meristic difference between described material of C. formosanus and their specimens. The red-rim melania has been found in geothermal waters in Oregon but not in the Willamette River or its tributaries (T. Anderson, University of Colorado, unpublished data). During 2002, tropical fish from Georgia exhibiting the gill trematode were submitted to HKD-SNARC; but, considering that the red-rim melania has not been reported from Georgia, we think the parasite might have been imported within the fish from another state. In the spring of 2003, the parasite was observed in western Utah in speckled dace (Rhinichthys osculus) and Gambusia sp. at Gandy Warm Springs, Millard County, and Goshen Warm Springs, Utah County, respectively (Chris Wilson, Utah Division of Wildlife Resources, personal communication). Both springs contain red-rim melania populations. This observation is sufficient to add Utah to the list of states with the gill trematode. Hosts of the gill trematode Centrocestus formosanus has a complex life cycle that involves three life stages (Figure 3). The metac- feature fish health August Fisheries 13

4 fish health feature Figure 4. Melanoides tuberculatus, showing spire-shaped shells with shell heights of 5 to 40 mm. This snail, the red-rim melania, is the only known first intermediate host of Centrocestus formosanus in the Americas. ercarial stage infects the gills of many fish species and occasionally the intestinal wall and muscles of frogs Rana spp. (Salgado-Maldonado et al. 1995). In the United States, known fish hosts include members of the centrarchid, characid, cichlid, cyprinid, cyprinodontid, gobid, ictalurid, kuhliida, mugilids, percid, percichthyid, and poecilid families. The adult stage occurs in the GI tract of specific piscivorous birds and mammals. Many piscivorous birds may host the parasite, but to date, we have confirmed only the green heron (Butorides virescens) and the great egret (Ardea alba) as hosts in the continental United States. Fisheating mammals, including members of the Carnivora and Rodentia orders, might also serve as final hosts (Martin 1958; Premvati and Pande 1974; Vogelbein, Heard and Overstreet, USM, unpublished studies). The early larval stages asexually develop in the redrim melania, the first intermediate host. That snail, also called the Malaysian burrowing snail, Malaysian trumpet snail, and cornucopia snail, belongs in the family Thiaridae (Dudgeon 1989). It, along with two other members of the same family not found in the continental United States, host the trematode worldwide. The snail host usually serves as the target for controlling trematode infections; therefore, a more indepth discussion of this host is warranted. The red-rim melania has an elongate conical shell with rounded whorls and fleshy protuberances on the mantle s edge, and its shell can reach a height of more than 70 mm (Figure 4; Murray 1975; Burch 1982). Experimentally, the snail can survive temperatures above 17.0 C and below 32.5 C (Mitchell and Brandt 2005). It occurs primarily in freshwater but can survive salinities up to 30 ppt (Roessler et al. 1977; Smith 1989). Even though native to Asia, it presently inhabits tropical and subtropical locations throughout the world (Abbott 1973; Dudgeon 1986; Amaya-Huerta and Almeyda-Artigas 1994). Based on information where the red-rim melania has been found in the United States (T. Anderson, University of Colorado unpublished data), it appears that the snail is restricted to year-round warm waters. Melanoides tuberculatus was first documented in the continental United States in Texas in 1964 (Murray 1964). At least 15 states, including the most southern states and several western ones with geothermal waters, had or now have confirmed wild stocks of the red-rim melania (T. Anderson, University of Colorado unpublished data). Because the red-rim melania has an operculum, it exhibits resistance to desiccation, molluscicides, and disinfectants (Dudgeon 1982; Francis-Floyd 1991). The snail can live up to 8 days in a dry pan and 3 of 10 individuals survived full strength household bleach for 60 min (Dudgeon 1982; Mitchell and Brandt unpublished data). The snail out-competes some established mollusks, partly because of its ability to reproduce parthenogenically and to brood young internally (Jacobson 1975; Perera et al. 1990). Lastly, the red-rim melania harbors other trematodes including two human pathogens, the human liver fluke (Opisthorchis sinensis) and the oriental lung fluke (Paragonimus westermani), as well as an eye fluke (Philopthalmus gralli) of birds (Abbott 1952; Dundee and Paine 1977; Nollen and Murray 1978). The two human trematodes have not yet been found in red-rim melania in the United States. Pathology of the gill trematode Few trematodes cause harm to their fish hosts, and few fish mount host responses that affect the trematodes. Migration of cercariae through host tissues may produce minimal mechanical damage and hemorrhaging (Hoffman 1999) and may also modify host behavior in a manner that improves the chance for the fish being eaten by a definitive vertebrate host (e.g., Overstreet and Curran 2004). Occasionally, heavy trematode infections in fish result in serious tissue displacement, secondary bacterial infection, and death (Mitchell et al. 1982; Overstreet and Curran 2004). Centrocestus formosanus, unlike most trematodes, produces serious alterations in the gills of many freshwater fishes (Mitchell et al. 2000, 2002). Within 1 h after infection, the cercaria lodges next to the gill filament cartilage (Blazer and Gratzek 1985). The parasite induces an unusual inflammatory response characterized by a proliferation of host fibroblasts that apparently differentiate into chondroblasts and then chondrocytes that form a cartilaginous encapsulation around the parasite (Blazer and Gratzek 1985; Vogelbein and Overstreet 1988) (Figure 5). The encapsulations may continue to thicken, ultimately destroying the normal gill architecture, reducing the surface area of the respiratory epithelium. Gill function may be further compromised by an influx of other inflammatory cells, including macrophages, eosinophils, heterophils, and lymphocytes (Blazer and Gratzek 1985). The encapsulation may incorporate more than one cyst (Figure 6). In the two species of Etheostoma in the Comal River, the trematode dies within the cyst, but the host response still destroys much functional gill tissue, probably resulting in the death of heavily-infected individuals. Response to this parasite is in contrast to well-adapted host-parasite relationships, where damage to the host is not life 14 Fisheries vol 30 no 8

5 threatening. Perhaps one reason some groups of fishes, both native and introduced, are so susceptible to mortality results from their being naive to the introduced parasite. Control of the gill trematode The control of C. formosanus in the United States is complex because of the involvement of three life stages, some of which include exotic and endangered species. Managing the parasite will be difficult because the avian hosts are highly mobile, human intervention has and is spreading infected fish and snails, and many different fish species are susceptible. The most practical approach will be to develop methods to treat and prevent the further spread of this very prolific and hardy exotic snail. Research has shown that red-rim melania with shell heights of 2 to 40 mm can be killed by a 3 min exposure to 50 C (temperature of most residential and commercial hot water systems; Mitchell and Brandt 2005). Therefore, items such as dipnets, boots, and seines that contact waters containing red-rim melania should be dipped in this hot water bath for at least 5 min before being used in any waters without the snail. No other effective method of disinfection is presently reported; however, a low concentration of Roccal- D Plus (10 ppm), a quaternary ammonium product, for 24 h appears promising in killing all red-rim melania tested (Mitchell and Brandt Figure 5. Proliferated cartilage surrounding metacercarial cyst of Centrocestus formosanus. unpublished studies). In ornamental fish ponds, a treatment of Bayluscide at 1.1 kg/ha of pond bottom is effective for controlling nuisance snail populations including M. tuberculatus (Francis- Floyd et al. 1997). Fish should not be stocked for at least 10 days after application. Bayluscide has U.S. Environmental Protection Agency Special Local Needs labels for use in Florida and Arkansas only, and has been legal under single season Section 18 Emergency Exemptions in other southeastern states. The red-rim melania can be purchased in many pet shops throughout the country and over the Internet. Care must be taken not to allow it to become established in melania-free warm waters. The snail can also be transferred on vegetation from one site to another (snail hatchlings, 2 to 3 mm shell height, readily attach to aquatic vegetation); therefore, we do not advise anyone to transport vegetation from water inhabited by red-rim melania to those not inhabited by the snail. Limiting the spread of the carrier snail will limit the spread of the gill trematode. feature Figure 6. Gill filaments of an experimentally infected hybrid striped bass containing multiple metacercariae of Centrocestus formosanus encapsulated by proliferated cartilage tissue. fish health References Abbott, R. T A study of an intermediate snail host (Thiara granifera) of the oriental lung fluke (Paragonimus). Proceedings of the United States National Museum 102: Spread of Melanoides tuberculata. The Nautilus 87:29. Amaya-Huerta, D., and R. J. Almeyda- Artigas Confirmation of Centrocestus formosanus (Nishigori, 1924) Price, 1932 (Trematoda: Heterophyidae) in Mexico. Research and Reviews in Parasitology 54: Blazer, V. S., and J. B. Gratzek Cartilage proliferation in response to metacercarial infections of fish gills. Journal of Comparative Pathology 95: Burch, J. B North American freshwater snails. V. Keys to the freshwater gastropods of North America. Society for Experimental and Descriptive Malacology, Niwot, Colorado. Dudgeon, D Aspects of the desiccation tolerance of four species of benthic mollusca from Plover Cove Reservoir, Hong Kong. The Veliger 24: The life cycle, population dynamics and productivity of Melanoides tuberculata (Muller, 1774) (Gastropoda: Prosobranchia: Thiaridae) in Hong Kong. Journal of Zoology 208: Ecological strategies of Hong Kong Thiaridae (Gastropoda: Prosobranchia). Malacological Review 22: Dundee, D. S., and A. Paine Ecology of the snail, Melanoides tuberculata (Muller) intermediate host of the human liver fluke (Opisthorchis sinensis) in New Orleans, Louisiana. The Nautilus 91: Dzikowski, R., M. G. Levy, M. F. Poore, J. R. Flowers, and I. Paperna Use of rdna polymorphism for identification of heterophyidae infecting freshwater fishes. Diseases of Aquatic Organisms 59: Francis-Floyd, R Use of Bayer 73 to control snails in ornamental fish ponds. Pages in Aquaculture Report Series. Florida Department of Agriculture and Consumer Services, Tallahassee. Francis-Floyd, R., J. Gildea, P. Reed, and R. Klinger Use of Bayuluscide (Bayer 73) for snail control in fish ponds. Journal of Aquatic Animal Health 9: Hoffman, G. L Parasites of North American freshwater fishes, 2nd ed., Comstock Publishing Associates, Cornell University Press, Ithaca, New York. Knot, K. E., and H. D. Murray Mystery fluke in Melanoides tuberculata (Gastropoda: Thiaridae) in the San Antonio Zoo, San Antonio, Texas. Combined Annual Meetings, Western Society of Malacologists and American Malacological Union, August Fisheries 15

6 Proceedings and Abstracts from the Joint Annual Meeting. Berkeley, California Jacobson, M. K The freshwater prosobranch, Tarebia ganifera, in Oriente, Cuba. The Nautilus 89:106. Martin, W. E The life histories of some Hawaiian heterophyid trematodes. Journal of Parasitology 44: McDermott, K. S Distribution and infection relationships of an undescribed digenetic trematode, its exotic intermediate host, and endangered fishes in springs of West Texas. Thesis, Southwest Texas State University, San Marcos. Mitchell, A. J., and T. M. Brandt Temperature tolerance of red-rimmed melania, an exotic aquatic snail established in the United States. Transactions of the American Fisheries Society 134: Mitchell, A. J., C. E. Smith and G. L. Hoffman Pathogenicity and histopathology of an unusually intense infection of white grubs (Posthodiplostomum m. minimum) in the fathead minnow (Pimephales promelas). Journal of Wildlife Diseases 18: Mitchell, A. J., M. J. Salmon, D. G. Huffman, A. E. Goodwin, and T.M. Brandt Prevalence and pathogenicity of a heterophyid trematode infecting the gills of an endangered fish, the fountain darter, in two central Texas spring-fed rivers. Journal of Aquatic Animal Health 12: Mitchell, A. J., A. E. Goodwin, M. J. Salmon and T. M. Brandt Experimental infection of an exotic heterophyid trematode, Centrocestus formosanus, in four aquaculture fishes. North American Journal of Aquaculture 64: Murray, H. D Tarebia granifera and Melanoides tuberculata in Texas. Abstract. Annual Reports American Malacological Union 1964: Melanoides tuberculata (Muller), Las Moras Creek, Bracketville, Texas. Bulletin of the American Malacological Union 1975:43. Nollen, P. M., and H. D. Murray Philophthalmus gralli: identification, growth characteristics, and treatment of an oriental eyefluke of birds introduced into the continental United States. Journal of Parasitology 64: Olsen, R. E., and J. R. Pierce A trematode metacercaria causing gill cartilage proliferation in steelhead trout from Oregon. Journal of Wildlife Diseases 33: Overstreet, R. M., and S. S. Curran Defeating diplostomoid dangers in USA catfish aquaculture. Folia Parasitologica 51: Perera, G., M., Yong, J. R. Ferrer, C. Arrinda, and O. Amador Effectiveness of three biological control agents against intermediate hosts of snail-mediated parasites in Cuba. Malacological Review 23: Premvati, G., and V. Pande On Centrocestus formosanus (Nishigori, 1924) Price, 1932 and its experimental infection in white leghorn chicks. Japanese Journal of Parasitology 23(3): Roessler, M. A., C. L. Beardsley, and D. C. Tabb New records of the introduced snail, Melanoides tuberculata (Mollusca: Thiaridae) in South Florida. Florida Scientist 40: Salgado-Maldonado, G., M. I. Rodriguez- Vargas and J. J. Campos-Perez Metacercariae of Centrocestus formosanus (Nishigori, 1924) (Trematoda) in freshwater fishes in Mexico and their transmission by the thiarid snail Melanoides tuberculata. Studies on Neotropical Fauna and Environment 30(4): Smith, B. J Traveling snails. Journal of Medical and Applied Malacology 1: Vogelbein, W. K., and R. M. Overstreet Life-history and pathology of a heterophyid trematode infecting Florida-reared ornamental fishes. International Association for Aquatic Animal Medicine Proceedings 19: Fisheries vol 30 no 8

7 fisheries management feature ABSTRACT A re-evaluation of U.S. state fish-stocking recommendations for small, private, warmwater impoundments Stocking fish into small impoundments for recreational angling has been practiced over the last half-century. As a result, many state agencies have developed recommendations for stocking fish into small impoundments that are often based on early regional research. We obtained current state fish-stocking recommendations, compared them to a 1980 summary, and reviewed literature since 1980 to determine if states were incorporating recent research into their current recommendations. Most states expanded their recommendations from the bass-bluegill strategy to include other species. Such changes are probably related to research that suggested quality fisheries for most desired species can exist, but depends on managing specifically for that fishery. The little research on bass-bluegill stockings suggests that states are content with historical stocking strategies, and employ an adaptive management approach to ponds that reach an undesirable state. Research has shown that anglers can have substantial impacts on both prey and predator populations, which suggests that anglers can be used in an adaptive management framework. However, such a framework developed specifically for small impoundments does not exist. Identifying current research needs for small impoundment management is important because many states still allocate resources to small waterbodies that can provide anglers with quality fishing opportunities. Daniel C. Dauwalter John R. Jackson Dauwalter was a research associate and Jackson was an assistant professor with the Aquaculture/ Fisheries Center at the University of Arkansas at Pine Bluff. Dauwalter is currently a graduate research associate in the Oklahoma Cooperative Fish and Wildlife Research Unit and Department of Zoology, Oklahoma State University. He can be reached at daniel.dauwalter@okstate.edu. Jackson is an assistant professor of fisheries at Arkansas Tech University and can be reached at john.jackson@atu.edu. Small impoundments and farm ponds are generally considered to be waterbodies less than 40 ha in surface area, but are often much smaller. Historically, small impoundments have provided many services. Early on, many impoundments were constructed for fish-rearing purposes, fish-management investigations, as part of a Midwestern pond-building program, and to meet World War II protein demands (Regier 1962). Small impoundments have also been constructed for irrigation, livestock watering, or other water-supply needs (Flickinger et al. 1999). Many small impoundments have also been used for recreational purposes such as wildlife watching, waterfowl hunting, swimming, or other aesthetic reasons. One of the most recognized opportunities afforded by small impoundments is recreational fishing. Because small impoundments have been recognized as important recreational fisheries, much effort has been allocated to small-impoundment fisheries management. Auburn University researchers E. V. Smith and H. S. Swingle were pioneers in small impoundment management (Swingle and Smith 1938; Smith and Swingle 1939; Swingle 1946). Soon thereafter, many researchers became interested in small-impoundments (Carlander 1952; Clark 1952) and their often undesirable fish communities (Sharp 1950; Meehean 1952). Accordingly, further investigations were conducted regarding the best fish-stocking strategies. Fish species, stocking densities, and stocking ratios of species were all studied (Surber 1949; Swingle 1951; Regier 1963a,b; Dillard and Novinger 1975). Realizing the importance of small impoundment fisheries, many U.S. state fisheries management agencies developed small-impoundment management strategies, especially fish stocking recommendations. A review of state fish-stocking strategies concluded that there was little agreement among states regarding species combinations, stocking densities, stocking chronology, and other aspects of fish stocking in small impoundments (Dillard and Novinger 1975). It was suggested that fishery managers need to better consider pond owner/angler preferences for species, desired results from stocking, geographic location of the waterbody, and specific conditions of the waterbody to be stocked (e.g., physical and chemical). In another review, Modde (1980) reported that a largemouth bass (Micropterus salmoides), and bluegill (Lepomis macrochirus; and sometimes redear sunfish L. microlophus), combination was often recommended, but that geographical differences existed. He suggested that slower growth rates of fishes in northern latitudes, coupled with more variation in survival and spawning success than in southern states, led to more difficulty in recommending an optimal stocking rate needed to achieve a desired fishery. Modde (1980) also suggested that winterkill in northern latitudes requires that ponds be larger and deeper, which makes them less manageable. Finally, although he reported that the bass-bluegill stocking strategy was commonplace in the South, Modde (1980) questioned whether it was the optimal strategy in northern latitudes because some 18 Fisheries vol 30 no 8

8 states recommended it, while other states recommended bass only or a bass-golden shiner (Notemigonus crysoleucus) combination. We reviewed current U.S. state agency fish-stocking recommendations (excluding cold-water impoundments) and compared them to small impoundment research conducted since 1980 to determine if stocking strategies have changed or incorporated research since they were reported by Modde (1980). To do so, we obtained agency fishstocking recommendations from fisheries management agencies from the contiguous 48 U.S. states. Fishery personnel in each agency were contacted by or telephone to obtain updated booklets, fact sheets, or other printed recommendations for stocking fish into small impoundments. Verbal recommendations were not considered. State Recommendations and Recent Research State Recommendations Thirty-four of 48 (75%) states had specific recommendations for stocking fingerling fishes into small impoundments, and they varied by region (Table 1, Figure 1). Sunfish stocking rates appeared to have no geographic pattern, and were often recommended for stocking at 1,236/ha. In contrast, largemouth bass stocking rates did show latitudinal variation. Seven states did not have specific recommendations and reported that they make recommendations on a caseby-case basis, whereas seven additional agencies stated that they do not make recommendations. Most agencies (65%) had modified their recommendations to some extent since Changes typically included expanded options on fish stocking from those reported by Modde (1980). However, one state changed from having specific stocking recommendations to not having any (Rhode Island), and two states changed from having specific recommendations to working on a case-by-case basis (Maryland and Oregon). Some states expanded their recommendations to include bluegill (Texas and Wisconsin), redear sunfish (Arkansas, Indiana, Kentucky, Missouri, Tennessee, Texas, and Virginia), largemouth bass only (Arizona), and/or supplemental channel catfish (Ictalurus punctatus) or catfish only (Delaware, Florida, and Ohio). Ten states reported stocking hybrid sunfish as an alternative stocking option (Arkansas, Illinois, Indiana, Louisiana, Michigan, Missouri, Mississippi, North Carolina, Oklahoma, and Wisconsin). Six states provided recommendations for small impoundment crappie fisheries (Arkansas, Colorado, Missouri, Oklahoma, South Dakota, and Wisconsin). Three states (Michigan, South Dakota, and Wisconsin) included stocking options for smallmouth bass (Micropterus dolomieu) only or in combination with minnows. Juvenile and adult stocking options were provided by 11 states (Arkansas, California, Kansas, Michigan, New Jersey, Ohio, Pennsylvania, South Carolina, South Dakota, Virginia, and Wisconsin). Thirty-four states mentioned grass carp (Ctenopharyngodon idella) in their printed fish stocking recommendations. Most states were less explicit about stocking other introduced strains of native species. For example, there has been concern over stocking Florida-strain largemouth bass (M. s. floridanus) outside of its native range (Maceina and Murphy 1992; Philipp 1992). Some researchers have declared it a separate species, the Florida bass (M. floridanus), and called for a termination of stocking outside of Florida state boundaries (Kassler et al. 2002). Eleven states previously reported stocking rates for fertilized ponds (Modde 1980), and we found that 15 had fertilized rates. Some agency booklets had guidelines for fertilization, and for determining if fertilization was necessary or desired for a given waterbody. Observed changes may have resulted from recommendations by researchers to stock at unfertilized rates because many pond owners did not properly fertilize their ponds (Geihsler and Holder 1983). Figure 1. State stocking rates and ratios for bluegill and largemouth bass. feature fisheries management August Fisheries 19

9 Table 1. Stocking density (fingerling number/ha) recommendations made by state agencies for small, warmwater impoundments. Multiple densities per fish species indicate rates for unfertilized fertilized (or unfed-fed; hybrid sunfish) impoundments. Stocking chronology is indicated by season; S, late spring-early summer; F, fall; or W, winter; and year if needed; 1, year 1; 2, year 2. Some species were optional (o). Minnow species, when specified, were fathead minnows (FHM) or golden shiners (GS), and a weight was sometimes recommended (kg/ha). Grass carp stocking densities were dependent on vegetation abundance, and pertain to all stocking options. Grass carp are either diploid (D) or triploid (T). States with a required grass carp permit are noted (P). Largemouth Redear Hybrid Channel State Option Bass Bluegill Sunfish Sunfish Catfish Minnows Grass Carp AL S a W D AR S F F F1-S2 o D o AZ FHM b T P CA S F1 124 F1o b T P S2 865 F1 371 F1 124 F1o F1 CO o 2471 FHM T P CT GS b T P DE S F1 247 S2o c FL S F F S2 o b T P GA S2 988 F1 247 F1 124 F1 o b T P F IA S F1 247 F D ID 1 c c IL d o 2.2kg FHM or 7-37 T P 2471 GSo o 2.2kg FHM or 2471 GSo o 2.2kg FHM or 2471 GSo IN o T P o KS S F1 247 F1o 3.4kg FHMo D S2 828 F1 408 F1 247 F1o 3.4kg FHMo KY S2 988 F1 124 F1o T S2 593 F1 395 F1 124 F1o LA S F o T P S F F o MA 1 e c MD 1 e c ME 1 c c MI S f 1236 So Illegal S S S1o S1-F S f 1236 S MN 1 c c MO S F1 247 F1o 5-50 D S2 927 F1 309 F1 247 F1o S F F1 247 F1o MS S F1 W1 124 F1o 1236 FHMo D S2 865 F1 W1 371 F1 W1 124 F1o 1236 FHMo S MT c 20 Fisheries vol 30 no 8

10 Largemouth Redear Hybrid Channel State Option Bass Bluegill Sunfish Sunfish Catfish Minnows Grass Carp NC S F F F1o T P S 247 S ND 1 e c NE S F1 247 F1o : 247 F2o D NH c NJ S S1 247 S FHM or b T P 988 GSo NM 1 e c NV 1 e b T P NY S S T P S 494 S GS S S FHM OH o T P o OK S F1 247 F D FHM b o S S1 247 F1o OR 1 e c PA Yr Yr T P RI 1 c c SC S F F T SD S 3.4kg FHM or b T P GSo S1 247 g S3 or F2 247 S1o h TN S a F o T TX S F F1o 17 T P S F F F1o kg FHM UT c VA S1 : 124 S F1 124 S T P S1 : 124 S2 865 F1 371 F1 124 S VT 1 c c WA 1 e b T P WI S f 1236 So Illegal S S S1o S1-F S f 1236 S WV 1 c T P WY 1 c T P a Combined bluegill and redear sunfish with ratio not indicated b Rate not specified c No recommendation d Stocking rates for IL are based on water alkalinity and soil type e No specific recommendations case-by-case basis f Stock after minnows spawn g Bluegill 8-13cm h Stocking rate for muddy ponds August Fisheries 21

11 fisheries management feature Twenty-eight states made recommendations regarding fish harvest (Table 2). Twenty-one states had recommended length restrictions for largemouth bass. Number or biomass/ha for largemouth bass and bluegill/redear sunfish was reported by 28 and 17 states, respectively. We made additional contact with seven selected state agencies in an attempt to determine why they changed their stocking rates or ratios, or recommended alternative species. Of those contacted, three states claimed that stocking-rate changes were not based on research (California, Tennessee, and Wisconsin). California reported that changes were based on stocking cost and professional experience of what works in the state. Tennessee s changes were based on professional experience. Wisconsin stated that their changes to stocking rates and options were based on recommendations made by Michigan. Michigan reported that changes were based on a literature review, surrounding state recommendations, and professional experience. Two states reported that their changes to stocking rates were supported by statefunded research (Oklahoma and South Dakota). Oklahoma changed their largemouth bass and bluegill stocking rates based on research conducted solely for that purpose. An Oklahoma Department of Wildlife Conservation study evaluated different stocking rates of largemouth bass and bluegill, and recommended that stocking rates of 1,250 bluegill and 250 bass/ha be used for most Oklahoma ponds (Boxrucker 1982). In South Dakota, changes were based on research findings of slow growth and high winter mortality (Stone and Modde 1982; Shelley and Modde 1982). The current recommendation is to establish the bass population through spring stocking and supplemental minnow forage prior to stocking bluegill. Although some states appear to have changed their recommendations based on recommendations of adjacent states, or on what state biologists have found, informally, to work in their regions, we speculate that some additional states have made changes based on research that may not have been published in the primary literature, but that exists in the grey literature. For example, Because small impoundments have been recognized as important recreational fisheries, much effort has been allocated to small-impoundment fisheries management. Illinois recommends a range of stocking rates based on unpublished research of water alkalinity and soil type within the state. These unpublished data along with professional experience contributed to Illinois current stocking recommendations of reduced stocking density with lower alkalinity water and soil type. Recent Research Prey species Several species combinations were researched early on to determine a preferable species combination for stocking in small impoundments (Swingle 1952), and it was often concluded that a bass-bluegill combination was the best combination. The bass-bluegill combination was subsequently recommended by many states, and research continued to be conducted on the best stocking ratios and rates of bass and bluegill (with redear sunfish sometimes replacing a fraction of the bluegill stocked) (Dillard and Novinger 1975; Modde 1980). However, as Dillard and Novinger (1975) pointed out, pond owners and anglers may not always want bass or bluegill stocked into their waterbodies. Since 1980 research has focused not only on bluegill, but on the feasibility of using other prey species in small impoundments. Researchers have shown that many different prey species can be successfully stocked into small impoundments. Black crappie (Pomoxis nigromaculatus) and black bullhead (Ameiurus melas) were questioned by early researchers regarding their use as a prey species in small impoundments because of their tendency to overpopulate (Mitzner 1984), or for unspecified reasons (Swingle and Smith 1942). However, research has shown that both species, and also yellow perch (Perca flavescens), can have desirable population structures, but is often contingent on having high densities of predators such as largemouth bass (Shelley and Modde 1982; Cichra et al. 1984; Gabelhouse 1984; Boxrucker 1987; Saffel et al. 1990; Guy and Willis 1991). Coppernose bluegill (L. m. purpurescens) are also available from private fish hatcheries as a fish stocking option. Coppernose bluegill are thought to grow faster and attain larger sizes than other bluegill strains, but we did not find any published studies on growth rates. Continued research regarding bluegill and largemouth bass has shown that bluegill size structure is also related to largemouth bass density (Guy and Willis 1990). Other bluegill research has shown that the presence of large, mature males delays sexual maturity in juveniles via chemical interactions (Aday et al. 2002, 2003). Delayed maturity allows juveniles to put more energy towards growth, and could possibly alleviate stunting problems in ponds. It remains to be seen whether management options, such as chemical treatments or stocking adults, evolve from such research to control or inhibit stunted bluegill populations. Hybrid bluegill and crappie have also been evaluated for use in small impoundments. Several researchers have concluded that bluegill male green sunfish (L. cyanellus) female F 1 hybrids grew faster than 22 Fisheries vol 30 no 8

12 Table 2. State agency annual harvest recommendations for unfertilized small impoundments stocked with largemouth bass (LMB) and bluegill/redear sunfish managed for an existing balanced/all purpose fishery. Largemouth Bass Bluegill/Redear Sunfish State No./ha kg/ha Restrictions No./ha kg/ha Restrictions AL AR <33 cm cm protected slot AZ a CA cm minimum 5 kg/kg LMB CO <30 cm cm protected slot CT DE cm minimum FL 62 <30 cm cm protected slot 4-6 kg/kg LMB GA cm minimum 84 IA cm minimum ID a IL b cm minimum cm minimum IN cm minimum KS 74 <30 cm cm protected slot KY cm minimum LA kg/kg LMB MA a MD a ME a MI cm protected slot 4 kg/kg LMB MN a MO cm minimum MS kg/kg LMB MT a NC or 36 cm minimum 4-5 kg/kg LMB ND a NE a NH or 36 cm maximum NJ a NM a NV a NY a OH 25 <30 cm; cm protective slot cm 2-12 >38 cm OK <30 cm cm protective slot OR a PA 30% of biomass 38 cm minimum RI a SC SD <30cm cm protective slot TN TX 62 <30 cm cm protective slot UT a VA VT a WA a WI cm protective slot 4 kg/kg LMB WV a WY a a No harvest recommendations b Harvest rates for IL are based on water alkalinity and soil type August Fisheries 23

13 fisheries management feature bluegill, and that stocking them into small impoundments with largemouth bass was a good stocking combination (Kurzawski and Heidinger 1982; Brunson and Robinette 1986; Hayward and Wang 2002). Others have experimented with female white crappie (P. annularis) male black crappie, and have suggested that they may result in put-and-take fisheries (Hooe and Buck 1991; Hooe et al. 1994). Both hybrids were researched to produce fast-growing panfish with limited reproduction. Shad (Dorosoma spp.) have continued to be evaluated for their potential as a prey species into small impoundments. Their intended positive effects on other fish populations varies among waterbodies, and is difficult to predict (DeVries et al. 1991; Pope and DeVries 1994; Hale 1996; Irwin et al. 2003). Noble (1981) and DeVries and Stein (1990) each recite literature on positive and negative results from stocking either gizzard (D. cepedianum) or threadfin (D. petenense) shad. State agencies apparently have used research on the aforementioned prey species, whether by direct access to the research or borrowing recommendations from other states that used information directly from research studies. Hybrid sunfish are a popular species option, and nine states had recommended stocking densities. Some states even recommended black crappie as a species option. Clearly research has shown that desirable black crappie, yellow perch, and black bullhead populations can exist under certain management scenarios, and that information was communicated to state agencies that now mention black crappie (Arkansas, Colorado, Missouri, Oklahoma, South Dakota, and Wisconsin), yellow perch (Colorado, Connecticut, Michigan, Pennsylvania, and South Dakota), and bullheads (e.g., Pennsylvania, South Dakota) as alternative species for small impoundments. However, we found no state recommendations for stocking hybrid crappie even though reproduction is limited and overcrowding and stunting problems could be avoided by stocking them. Interestingly, the unpredictable effects of shad on other sportfish has led some states to encourage (Texas) or discourage (Arkansas, Florida, Oklahoma, Ohio, and Tennessee) stocking them into small impoundments. Furthermore, despite the fact that there is no readily available research on coppernose bluegill, an Internet search found that they are readily available from private south and southeastern U.S. hatcheries for stocking. Predator species Although largemouth bass are generally regarded as the most desirable predator species, other predatory fish species have been proposed for use in small impoundments. The reported ability of northern pike (Esox lucius) to control stunted prey populations is variable. In a Colorado small impoundment northern pike were reported to be important in controlling crappie population structure (Willis et al. 1984). In contrast, northern pike did not control bluegill abundance when bluegills were the only prey species available in two small Michigan lakes (Beyerle 1971). Other researchers have reported a low abundance of small yellow perch in a South Dakota impoundment, and suggested that predation by northern pike may have adversely affected the population (Gurtin et al. 1996). In a 25 ha Nebraska lake, it was reported that bluegill and yellow perch abundances and size structures were lower four years after northern pike were first documented in the fish community (DeBates et al. 2003). The researchers cautioned that northern pike should be excluded from the fish community if high quality bluegill and yellow perch fisheries are desired. Another predator evaluated for use in small impoundments is the hybrid striped bass (Morone saxitilis M. chrysops). They have been successfully stocked as an additional predatory sportfish in conjunction with an abundant largemouth bass population (Ebert et al. 1990). Researchers have also reported hybrid striped bass as able (Neal et al. 1999) and unable (Layzer and Clady 1984) to control prey populations. Additionally, introductions of hybrid striped bass into small impoundments adversely affected largemouth bass relative weights, but did not affect largemouth bass catch-per-effort (Neal et al. 1999). States also have used research on predatory species, and have begun to recommend them as candidates for stocking. Five states stated that hybrid striped bass could be used to diversify sportfisheries or control prey populations (Arkansas, Florida, Illinois, Oklahoma, and Texas). Northern pike (Iowa, Illinois, and South Dakota) and walleye (Sander vitreus; Iowa, Illinois, Indiana, and South Dakota) were also mentioned by states for stocking, but usually as a way to diversify fishing opportunities after largemouth bass and bluegill have been stocked. Interestingly, although we found no research specifically related to stocking walleye in small impoundments, some states still reported them as candidates for stocking. Supplemental species Some species have been evaluated as a supplement to existing predator-prey combinations, as a single species alternative, or to control pond conditions. Channel catfish have been well evaluated for use in small impoundments. Stocking densities of channel catfish have been researched, with somewhat conflicting results regarding the best stocking density (Powell 1975; Shaner et al. 1996). Size at stocking effects on survival, predation, harvest, and cost:return ratios have also been studied, and larger fish are generally more cost effective to stock (Spinelli et al. 1985; Storck and Newman 1988; Santucci et al. 1994; Shaner et al. 1996); however, hatchery requirements may limit the size of fish available (Shaner et al. 1996). Catfish stocked into small impoundments by state agencies are usually of larger size than those stocked in other waterbodies (Michaletz and Dillard 1999). 24 Fisheries vol 30 no 8

14 Grass carp were introduced into the United States in 1963 for use in controlling nuisance aquatic vegetation (Shelton et al. 1981). Their successful control of vegetation, although not guaranteed, had been reported when stocked up to 8/ha (Shireman and Maceina 1981; Kirk 1992; Cassani et al. 1995; Blackwell and Murphy 1996). Diploid and triploid grass carp have been reported to feed similarly (Wattendorf and Anderson 1986), and there is much interest in using triploid fish only to prevent naturalized populations. Consequently, many states have restrictions on diploid grass carp or prohibit their use (Allen and Wattendorf 1987). Many states now offer stocking rates and procedures for channel catfish and grass carp (Table 1). Twenty-eight states gave stocking rates for channel catfish, and most states gave specific rates for stocking into existing largemouth bass-bluegill fisheries, stocking for catfish-only fisheries, and some states even gave recommendations for intensive culture. States were less specific about grass carp stocking rates, however. As mentioned previously, 34 states made some type of recommendation for stocking grass carp, and 23 states had specific stocking rates. Twenty-four states required that only triploid fish be used, 21 states mentioned that a permit is needed to stock them, and 2 states stated that it was illegal to stock grass carp (Michigan, Wisconsin). Angler Harvest and Regulations In addition to studying alternative species for stocking, the effects of supplemental stocking, angling, and fishing regulations on small impoundment fish populations have subsequently been studied. Boxrucker (1985) reported that stocking 448 fingerling largemouth bass/ha in a 81.8 ha impoundment contributed 76% of that year class. However, Boxrucker (1986) found that supplemental stocking of largemouth bass to enhance year-class strength did not lead to increased angler catch and harvest of largemouth bass. This single water body was twice as large as a small impoundment defined herein and further investigations into supplemental stocking need to be conducted. Coble (1988) stated that anglers can remove more than 25% of harvestable bluegills, and reported that bluegill exploitation rates ranged from 4 to 64%. Willis et al. (1994) concluded that anglers can also have a substantial impact on black crappie populations. Additionally, Lindgren and Willis (1990) estimated that 11% of largemouth bass were caught by 12 anglers fishing for a total of 218 hours in a 18.2 ha impoundment. In a 1.3 ha impoundment, 4 anglers fishing for 20 hours combined caught 33% of the estimated largemouth bass population. It was concluded that anglers can have a large impact on the predator populations of small impoundments. Consequently, fishing regulations that require angler harvest can be used to alter prey and predator population structures in small impoundments. Neumann et al. (1994) showed that imposing cm protective slot length limits on largemouth bass in small impoundments less than 20 ha improved the size structure of largemouth bass populations, and also changed the size structure of coexisting prey populations. Eder (1984) reported that a cm protective slot limit improved a stunted largemouth bass population with 130 angler hours/ha, which can be attributed to anglers harvesting fish below the slot limit. Novinger (1990) also reported that a cm protective slot limit improved largemouth bass size structures. Gabelhouse (1987) simulated a cm protective slot limit for largemouth bass, and concluded that removal of an insufficient number individuals below the limit resulted in an undesirable largemouth bass size structure, condition, and growth. He suggested that the number of largemouth bass below the slot limit that needed to be harvested to achieve a desirable largemouth bass population in that pond probably was more than anglers would be willing to harvest, or exceeded that of annual fishing pressure. Consequently, each of the aforementioned studies suggested that success of slot length limits was dependent on angler participation. Anglers cannot always be depended on to harvest below, or even above, a protective slot limit (Novinger 1990). They also do not always release fish caught within the protective slot limit; 30% of fish caught by anglers within the protective slot limit were illegally harvested in one Missouri lake (Eder 1984). Some states have developed several different strategies for managing small impoundment fisheries that require some type of regulation and annual harvest (Table 2). Many states recommended some type of harvest for pond management, but the number was less than the bass harvest model presented by Anderson (1975). Some management options are solely based on harvest quotas (Flickinger et al. 1999). Channel catfish have been well evaluated for use in small impoundments. feature fisheries managaement August Fisheries 25

15 Conclusion As suggested by Modde (1980), many states seem to have adopted, and continue to support, fish stocking strategies that were originally developed in their region of the United States; Swingle s recommendations in the Southeast (Swingle 1946, 1950,1951), Reiger s in the Northeast (Regier 1960,1962, 1963a,b), and several researcher s recommendations around the Midwest and Great Plains regions (Bennett 1943,1951; Brown 1951; Carlander 1952; Barnickol and Campbell 1952; Carlander and Moorman 1957). Despite the apparent adoption of regional stocking strategies or those of adjacent states, agencies have not collaborated to develop multistate or regional guidelines or booklets, as discussed by Weigmann and Helfrich (1992). This may result from managers currently employing an adaptive management approach to existing small impoundment fisheries, but using historical stocking recommendations as a starting point for new impoundments. This would not require a synthesis of new strategies, and several states stated that they make recommendations on a case-by-case basis. However, the adaptive management process for small impoundments has not been completely outlined in a single document intended solely for that purpose. A synthesis discussing management options for existing fish communities in small impoundments is warranted, especially regarding supplemental and corrective stocking (Heidinger 1999), fishing regulations (Noble and Jones 1999), and removal of undesirable fishes as they relate directly to small impoundments. Nevertheless, some states still appear to be supporting and using research to refine their recommendations for stocking fish into small impoundments. Most states appeared to have expanded their fish stocking recommendations, in terms of species, based on recent research, especially when considering channel catfish and hybrid sunfish. Some states have even made recommendations for offering trophy largemouth bass and trophy bluegill fisheries (e.g., Arkansas, Kansas, Oklahoma, South Dakota), strategies that are also summarized by Flickinger et al. (1999). Although many aspects of small impoundments have been studied over the last half-century, research is still being used by some states to expand their recommendations. As such, current needs for small impoundment research must be identified and synthesized if they exist, whether considering initial fish stockings in, adaptive management of, or better understanding of multispecies strategies in small impoundments. Identification of existing needs is important because many states are still putting forth an effort to provide quality fishing opportunities for anglers in a resource that is widely used. Acknowledgments We thank S. Clark for helping summarize agency recommendations. We also thank J. W. Neal, N. Stone, and two anonymous reviewers for comments on earlier manuscript drafts. Although many aspects of small impoundments have been studied over the last half-century, research is still being used by some states to expand their recommendations. 26 Fisheries vol 30 no 8

16 References Aday, D. D., C. M. Kush, D. H. Wahl, and D. P. Philipp The influence of stunted body size on the reproductive ecology of bluegill Lepomis macrochirus. Ecology of Freshwater Fish 11: Aday, D. D., D. H. Wahl, and D. P. Philipp A mechanism for social inhibition of sexual maturation in bluegill. Journal of Fish Biology 62: Allen, S. K., and R. J. Wattendorf Triploid grass carp: status and management implications. Fisheries 12(4): Anderson, R. O Factors influencing the quality of largemouth bass fishing. Pages in H. Clepper, ed. Black bass biology and management. Sport Fishing Institute, Washington, D.C. Barnickol, P. G., and R. S. Campbell Summary of selected pond studies in Missouri. Journal of Wildlife Management 16: Bennett, G. W Management of small artificial lakes. Illinois Natural History Survey Bulletin 22: Experimental largemouth bass management in Illinois. Transactions of the American Fisheries Society 80: Beyerle, G. B A study of two northern pike-bluegill populations. Transactions of the American Fisheries Society 100: Blackwell, B. G. and B. R. Murphy Low-density triploid grass carp stockings for submersed vegetation control in small impoundments. Journal of Freshwater Ecology 11: Boxrucker, J Improving Oklahoma pond management. Oklahoma Department of Wildlife Conservation, Federal Aid Project F-40-R, Oklahoma City, Oklahoma First year growth and survival of stocked largemouth bass in a small Oklahoma impoundment. Proceedings of the Annual Conference of the Southeastern Association of Fish and Wildlife Agencies 36: Evaluation of supplemental stocking of largemouth bass as a management tool in small impoundments. North American Journal of Fisheries Management 6: Largemouth bass influence on size structure of crappie populations in small Oklahoma impoundments. North American Journal of Fisheries Management 7: Brown, W. H Results of stocking largemouth black bass and channel catfish in experimental Texas ponds. Transactions of the American Fisheries Society 80: Brunson, M. W., and H. R. Robinette Evaluation of male bluegill x female green sunfish for stocking Mississippi farm ponds. North American Journal of Fisheries Management 6: Carlander, K. D Farm fish pond research in Iowa. Journal of Wildlife Management 16: Carlander, K. D. and R. B. Moorman Some experiments in changing population balance in farm ponds. Progressive Fish- Culturist 19: Cassani, J. R., E. Lasso de la Vega, and H. Allaire An assessment of triploid grass carp stocking rates in small warmwater impoundments. North American Journal of Fisheries Management 15: Cichra, C. E., R. L. Noble, and B. W. Farquhar Relationships of white crappie populations to largemouth bass and bluegill. Proceedings of the Annual Conference of the Southeastern Association of Fish and Wildlife Agencies 35: Clark, M Kentucky s farm fish pond program. Journal of Wildlife Management 16: Coble, D. W Effects of angling on bluegill populations: management implications. North American Journal of Fisheries Management 8: DeBates, T. J., C. P. Paukert, and D. W. Willis Fish community responses to the establishment of a piscivore, northern pike (Esox lucius), in a Nebraska Sandhill lake. Journal of Freshwater Ecology 18: DeVries, D. R., and R. A. Stein Manipulating shad to enhance sport fisheries in North America: an assessment. North American Journal of Fisheries Management 10: DeVries, D. R., R. A. Stein, J. G. Miner, and G. G. Mittelbach Stocking threadfin shad: consequences for young-of-year fishes. Transactions of the American Fisheries Society 120: Dillard, J. G., and G. D. Novinger Stocking largemouth bass in small impoundments. Pages in H. Clepper, ed. Black bass biology and management. Sport Fishing Institute, Washington, D.C. Ebert, D. J., K. E. Shirley, and J. J. 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Brown, and C. G. Scalet Dynamics of sympatric northern pike and largemouth bass populations in small prairie impoundments. Pages in R. Soderberg, ed. Warmwater workshop proceedings: ecosid management and culture. Northeast Division, American Fisheries Society, Bethesda, Maryland. Guy, C. S., and D. W. Willis Structural relationships of largemouth bass and bluegill populations in South Dakota ponds. North American Journal of Fisheries Management 10: Evaluation of largemouth bass-yellow perch communities in small South Dakota impoundments. North American Journal of Fisheries Management 11: Hale, R. S Threadfin shad use as supplemental prey in reservoir white crappie fisheries in Kentucky. North American Journal of Fisheries Management 16: Hayward, R. S., and H. P. Wang Inherent growth capacity and social costs of bluegill and hybrids of bluegill and green sunfish: which fish really grows faster? North American Journal of Aquaculture 64: Heidinger, R. C Stocking for sport fisheries enhancement. Pages in C. C. Kohler and W. A. Hubert, eds. Inland fisheries management in North America. American Fisheries Society, Bethesda, Maryland. Hooe, M. L., and D. H. Buck Evaluation of F 1 hybrid crappies as sport fish in small impoundments. North American Journal of Fisheries Management 11: Hooe, M. L., D. H. Buck, and D. H. Wahl Growth, survival, and recruitment of hybrid crappies stocked in small impoundments. North American Journal of Fisheries Management 14: Irwin, B. J., D. R. DeVries, and R. A. Wright Evaluating the potential for predatory control of gizzard shad by largemouth bass in small impoundments: a bioenergetics approach. Transactions of the American Fisheries Society 132: Kassler, T. W., J. B. Koppelman, T. J. Near, C. B. Dillman, J. M. Levengood, D. L. Swofford, J. L. VanOrman, J. E. Claussen, and D. P. Philipp Molecular and morphological analyses of the black basses: implications for taxonomy and conservation. August Fisheries 27

17 Pages in D. P. Philipp and M. S. Ridgway, eds. Black bass: ecology, conservation, and management. American Fisheries Society, Symposium 31, Bethesda, Maryland. Kirk, J. P Efficacy of triploid grass carp in controlling nuisance aquatic vegetation in South Carolina farm ponds. North American Journal of Fisheries Management 12: Kurzawski, K. F., and R. C. Heidinger The cyclic stocking of parentals in a farm pond to produce a population of male bluegill x female green sunfish F 1 hybrids and male redear sunfish x female green sunfish F 1 hybrids. North American Journal of Fisheries Management 2: Layzer, J. B., and M. D. Clady Evaluation of the striped bass x white bass hybrid for controlling stunted bluegills. Proceedings of the Annual Conference of the Southeastern Association of Fish and Wildlife Agencies 35: Lindgren, J. P., and D. W. Willis Vulnerability of largemouth bass to angling in two small South Dakota impoundments. Prairie Naturalist 22: Maceina, M. J., and B. R. Murphy Stocking Florida largemouth bass outside its native range (comment). Transactions of the American Fisheries Society 121: Meehean, O. L Problems of farm fish pond management. Journal of Wildlife Management 16: Michaletz, P. H., and J. G. Dillard A survey of catfish management in the United States and Canada. Fisheries 24(8):6-11. Mitzner, L Crappie management: problems and solutions. North American Journal of Fisheries Management 4: Modde, T State stocking policies for small warmwater impoundments. Fisheries 5(5): Neal, J. W., R. L. Noble, and J. A. Rice Fish community response to hybrid striped bass introduction in small warmwater impoundments. North American Journal of Fisheries Management 19: Neumann, R. M., D. W. Willis, and D. D. Mann Evaluation of largemouth bass slot length limits in two small South Dakota impoundments. Prairie Naturalist 26: Noble, R. L Management of forage fishes in impoundments of the southern United States. Transactions of the American Fisheries Society 110: Noble, R. L., and T. W. Jones Managing fisheries with regulations. Pages in C. C. Kohler and W. A. Hubert, eds. Inland fisheries management in North America. American Fisheries Society, Bethesda, Maryland. Novinger, G. D Slot length limits for largemouth bass in small private impoundments. North American Journal of Fisheries Management 10: Philipp, D. P Stocking Florida largemouth bass outside its native range (response to comment). Transactions of the American Fisheries Society 121: Pope, K. L., and D. R. DeVries Interactions between larval white crappie and gizzard shad: quantifying mechanisms in small ponds. Transactions of the American Fisheries Society 123: Powell, D. H Management of largemouth bass in Alabama s state-owned public fishing lakes. Pages in H. Clepper, ed. Black bass biology and management. Sport Fishing Institute, Washington, D.C. Regier, H. A Bass, bluegills, shiners and farm ponds. New York State Conservationist 14: On the evolution of bass-bluegill stocking policies and management recommendations. Progressive Fish-Culturist 24: a. Ecology and management of largemouth bass and bluegills in farm ponds in New York. New York Fish and Game Journal 10: b. Ecology and management of largemouth bass and golden shiners in farm ponds in New York. New York Fish and Game Journal 10: Saffel, P. D., C. S. Guy, and D. W. Willis Population structure of largemouth bass and black bullheads in South Dakota ponds. Prairie Naturalist 22: Santucci, V. J. Jr., D. H. Wahl, and T. W. Storck Growth, mortality, harvest, and cost-effectiveness of stocked channel catfish in a small impoundment. North American Journal of Fisheries Management 14: Shaner, B. L., M. J. Maceina, J. J. McHugh, and S. F. Cook Assessment of catfish stocking in public fishing lakes in Alabama. North American Journal of Fisheries Management 16: Sharp, R. W Summary of farm-pond inspections, Progressive Fish-Culturist 12: Shelley, J. J., and T. Modde First-year growth and survival of bluegill and black bullhead stocked with largemouth bass in South Dakota ponds. Progressive Fish-Culturist 44: Shelton, W. L., R. O. Smitherman, and G. L. Jensen Density related growth of grass carp, Ctenopharyngodon idella (Val.) in managed small impoundments in Alabama. Journal of Fish Biology 18: Shireman, J. V., and M. J. Maceina The utilization of grass carp, Ctenopharyngodon idella Val., for hydrilla control in Lake Baldwin, Florida. Journal of Fish Biology 19: Smith, E. V., and H. S. Swingle The relationships between plankton production and fish production in ponds. Transactions of the American Fisheries Society 68: Spinelli, A. J., B. G. Whiteside, and D. G. Huffman Aquarium studies on the evaluation of stocking various sizes of channel catfish with established largemouth bass. North American Journal of Fisheries Management 5: Stone, C. C., and T. Modde Growth and survival of largemouth bass in newly stocked South Dakota ponds. North American Journal of Fisheries Management 2: Storck, T., and D. Newman Effects of size at stocking on survival and harvest of channel catfish. North American Journal of Fisheries Management 8: Surber, E. W Results of varying the ratio of largemouth black bass and bluegills in the stocking of experimental farm ponds. Transactions of the American Fisheries Society 77: Swingle, H. S Experiments with combinations of largemouth black bass, bluegills, and minnows in ponds. Transactions of the American Fisheries Society 76: Relationships and dynamics of balanced and unbalanced fish populations. Alabama Polytechnic Institute, Agricultural Experiment Station, Auburn Experiments with various rates of stocking bluegills, Lepomis macrochirus Rafinesque, and largemouth bass, Micropterus salmoides (Lacepedee), in ponds. Transactions of the American Fisheries Society 80: Farm pond investigations in Alabama. Journal of Wildlife Management 16: Swingle, H. S., and E. V. Smith Fertilizers for increasing the natural food for fish in ponds. Transactions of the American Fisheries Society 68: Management of farm fish ponds. Alabama Polytechnic Institute, Alabama Agriculture Experiment Station, Auburn. Wattendorf, R. J., and R. S. Anderson Hydrilla consumption by triploid grass carp. Proceedings of the Annual Conference of the Southeastern Association of Fish and Wildlife Agencies 38: Weigmann, D. L., and L. A. Helfrich Content analysis of the pond management literature. Fisheries 17(5): Willis, D. W., R. M. Neumann, and C. S. Guy Influence of angler exploitation on black crappie population-structure in a rural South Dakota impoundment. Journal of Freshwater Ecology 9: Willis, D. W., J. F. Smeltzer, and S. A. Flickinger Characteristics of a crappie population in an unfished small impoundment containing northern pike. North American Journal of Fisheries Management 4: Fisheries vol 30 no 8

18 economic growth forum C. Alwyn Rose Rose is a fish habitat resource management practitioner in Peterborough, Ontario, Canada. He can be contacted at v_alrose@nexicom.net. Economic Growth as a Threat to Fish Conservation in Canada Introduction The Economic Growth Forum has clearly demonstrated the links between economic growth and fish conservation from an American perspective. Czech and Pister (2005) introduced the macroeconomics of the fundamental conflict between economic growth and fish conservation; Krall (2005) provided a critique of conventional microeconomics as it applies to fisheries management and related natural resources; Whitehead et al. (2005) clarified aspects of the neoclassical economics perspective; Lackey (2005) outlined the conflict between economic growth and salmon recovery in the western United States; Ericson (2005) linked the threat of invasive species to economic growth via international trade; and Thompson and Alam (2005) illustrated the threat to fish conservation from the growing live bait industry in the United States. Miller Reed and Czech (2005) established the links between fish endangerment and the structure of the American economy. Such observations are not limited to the United States and evidence will be presented showing that the inland freshwater fisheries resources of Canada are suffering the consequences of the conflict between economic growth and conservation. Furthermore, it will also be demonstrated that threats faced by Canadian inland freshwater fish species are linked to Canadian economic sectors, and as the economy grows the threats will increase. Threatened Freshwater Fishes in Canada The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) was established by the government of Canada in 1977 as an independent body of experts responsible for identifying and assessing Canadian species considered to be at risk of extinction. COSEWIC uses a process based on science, aboriginal traditional knowledge, and community knowledge to classify species at risk of extinction. The function of COSEWIC was brought into law in 2003 with the passing of the Species at Risk Act (SARA). The purpose of SARA is to protect wildlife species (including vertebrates, invertebrates, plants, mosses, and lichens) at risk in Canada. Species that have been designated by COSEWIC may then qualify for legal protection and recovery under SARA. COSEWIC has listed 467 species as extinct, extirpated, endangered, threatened, or of special concern (Canadian Wildlife Service 2004). Vertebrates account for 56% (262 records) of the listed species, and fish account for 32% (83 records) of that list. Canada is home to 230 resident species of freshwater fishes (Canadian Endangered Species Conservation Council 2001) and they make up the largest group of listed fishes with 83% (69 records). Of the freshwater fishes listed there are 4 extinct species and 3 extirpated species; 11 freshwater fishes and 3 anadromous fishes are listed as endangered; 18 are listed as threatened; and, 27 are listed as of special concern. Sources of Fish Endangerment COSEWIC catalogues the general reasons for fish endangerment. The threats faced by freshwater fishes include: habitat loss or degradation, pollution, exotic species, dams and barriers, water management, urban development, over-exploitation, climate change, and aquaculture. The most common threats are habitat loss or degradation, pollution, and exotic species. On average, the 69 different freshwater fishes are endangered by 2.4 causes each (i.e., they are being threatened by more than one factor). Table 1 summarizes the causes endangering the listed freshwater fish species in Canada. All of the threats faced by the listed fishes can be linked directly or indirectly to specific economic sectors. The three leading sources of fish endangerment are examples of the effects of economic activity: habitat loss and degradation are linked most closely to the resource extraction sectors (e.g., mining and forestry) and the construction sector (e.g., transportation corridors, pipelines, utilities, and housing and business infrastructure); pollution is primarily a by-product of the mining, forestry, agricultural, chemical, petrochemical, and manufacturing sectors (e.g., heavy metals, herbicide, pesticide, PCBs, chlorine, dioxins, furans, endocrine disruptors, etc,); and alien invasive species are a byproduct of the transportation sector (e.g., zebra mussels Dreissena polymorpha introduction from ship ballast water), the aquatic live food trade, the live bait industry, and the aquarium trade. The effects of dam construction and related water management are a result of the energy sector (e.g., hydroelectricity generation) and also the necessity of flood control to protect municipal and private infrastructure, thereby interfering in natural flow regimes, wetland and flood plain functions, and altering or eliminating important fish habitats. The other listed sources are related to economic sectors as follows: urban development, including road construction, is linked to the construction sector and represents the proliferation of the labor force, light manufacturing, and service sectors (Miller Reed and Czech. 2005); over-exploitation is a result of the aboriginal, recreational, and commercial fishing industries (e.g., the primary cause of the 36 Fisheries vol 30 no 8

19 extinction of the blue walleye Sander vitreum glaucus); climate change is an indirect consequence of the energy, transportation and the manufacturing sectors (i.e., mainly an effect of our dependence on fossil fuels). Impacts associated with the aquaculture industry are habitat destruction, accidental release of alien invasive species, etc. These finding are consistent with those of Freese and Trauger (2000) who reported that economic interests lead to loss of wildlife populations and biodiversity in four basic ways: over-harvesting of wild populations; conversions of habitat to alternative land uses; economic specialization in production of wild species, leading to habitat change and biodiversity loss; and negative environmental externalities, particularly contaminants. Natural habitat changes were only linked to the endangerment of three fish species (e.g., Banff longnose dace Rhinichthys cataractae smithi) and in all cases habitat fragmentation or water fluctuations resulting from beaver activity were responsible for the threat. endangerment were sectors of the American economy. Therefore as the economy grows, species become endangered at an increasing rate. Consider a system without humans; all natural capital is available as habitat for non-human species. As the scale of the human economy expands, natural capital is re-allocated from non-human uses to the human economy (Czech 2000). This demonstrates the ecological principle of competitive exclusion, with the human economy growing at the expense of other species. The above mentioned relationship was also reported to be generally true for Canada (Trauger et al. 2003). The Canadian economy has been reasonably prosperous since Between 1997 and 2003, gross domestic product (GDP) growth was positive for the economy and the mean compound annual growth rate was 3.6% (Industry Canada 2005). The Canadian GDP in 2001 was roughly the GDP of the U.S. in the early 1970s and the number of listed species was also in the same range as the number of listed species in the United States during forum economic growth Economic Objectives and the Continued Threat Table 1. Sources of freshwater fish species endangerment in Canada. Trauger et al found that economic growth and wildlife conservation are conflicting societal goals and that economic growth is the overriding goal in the United States. This situation is mirrored in Canada. For example the mandate of the Department of Finance Canada (2003) states the Department is committed to making a difference for Canadians by helping the government develop and implement economic, social, security and financial policies and programs that foster strong and sustainable economic growth, emphasizing fiscal, economic, social, and security objectives. The Canadian government also has the responsibility of fisheries conservation, which is one of several mandates of Fisheries and Oceans Canada. However economic growth appears to be the much higher priority of the Canadian government, which included in its overview of the 2005 budget a priority of achieving a productive and growing economy (Department of Finance Canada 2005). Perhaps this was tempered by another listed priority, moving towards a green economy and sustainable communities, but the listing of both priorities suggests the Canadian government may not recognize the conflict between economic growth and economic sustainability. The most compelling empirical evidence for the fundamental conflict between economic growth and fish and wildlife conservation was described by Trauger et al They noted that a strong correlation exists between species endangerment and economic growth in the United States (R 2 =98.4%) and that this correlation was no coincidence, but was based upon the fact that the causes of species Ranking Source of Endangerment Number % of Listed of Species Species 1 Habitat Loss/Degradation % 2 Pollution % 3 Alien Invasive Species % 4 Barriers/Dams % 5 Water Management % 6 Urban Development % 7 Over Exploitations % 8 Natural Habitat Change 3 4.3% 9 Climate Change 3 4.3% 10 Aquaculture 1 1.4% Source: Canadian Wildlife Service 2004 ( the early 1970s (Trauger et al. 2003). Therefore considering the relationship between economic growth and species endangerment, the fact that both the Canadian economy and number of listed species are similar to the United States in the 1970s, and the growth of U.S. and Canadian economies, it is reasonable to assume that the rate of species endangerment in Canada is also increasing. Conclusion The arguments put forth in the Economic Growth Forum are not limited to the United States. The inland freshwater fisheries resources of Canada are suffering similar consequences from the conflict between economic growth and biodiversity conservation. Thirty percent of Canada s freshwater fish species are listed by COSEWIC (Canadian Endangered Species Conservation Council 2001) August Fisheries 37

20 and they are threatened by the activities of economic sectors within the Canadian economy. Economic growth is a national Canadian goal. The economic growth rate is related to the rate of species endangerment, and as the economy grows so do the threats endangering our fisheries resources. Therefore fisheries resources will continue to be threatened, at an increasing rate, as long as the Canadian economy continues to grow, ensuring the competitive exclusion of fishes and other aquatic species. Acknowledgements The author would like to give a special thanks to Valerie Rose for her editorial input and support during the creation of this article. A thank you is also due to David Evans, Ontario Ministry of Natural Resources, for his input, suggestions, and editorial comments. Finally, thanks to Bruno Tomberli, University of Guelph, and Gareth Goodchild, Brent Valere, and Calvin Wenghofer, all of Fisheries and Oceans Canada, for their editorial comments. References Canadian Endangered Species Conservation Council (CESCC) Wild species 2000: the general status of species in Canada. Minister of Public Works and Government Services Canada, Ottawa. Available online at Canadian Wildlife Service Species at risk. Canadian Wildlife Service, Environment Canada, Ottawa. Available online at Czech, B Economic growth as the limiting factor for wildlife conservation. Wildlife Society Bulletin 28(1):4-14. Czech, B., and P. Pister Economic growth, fish conservation, and the American Fisheries Society: introduction to a special series. Fisheries 30(1): Department of Finance Canada Performance report for the period ending March 31. Department of Finance Canada, Ottawa. Available online at FIN-FIN/FIN-FIN03D_e.asp. Department of Finance Canada Budget 2005: overview. Department of Finance Canada, Ottawa. Available online at Ericson, J The economic roots of aquatic species invasions. Fisheries 30(5): Freese, C., and D. Truager Wildlife markets and biodiversity conservation in North America. Wildlife Society Bulletin 28: Industry Canada Canadian industry statistics, the Canadian economy. Available online at sio/cisgdpe.html. Krall, L An ecologically economic perspective on microeconomics and fisheries conservation. Fisheries 30(2): Lackey, R. T Economic growth and salmon recovery: an irreconcilable conflict? Fisheries 30(3): Reed, K. M., and B. Czech Causes of fish endangerment in the United States, or the structure of the American economy. Fisheries 30(7): Thompson, J., and S. Alum Analysis of customs trade data tocharacterize importation of live bait. Fisheries 30(6): Trauger, D. L., B. Czech, J. D. Erickson, P. R. Garrettson, B. J. Kernohan, and C. A. Miller The relationship of economic growth to wildlife conservation. Wildlife Society Technical Review 03-1, Bethesda, Maryland. Whitehead, J., D. Lipton, F. Lupi, and R. Southwick Economic growth and environmental protection: a clarification about neoclassical economics. Fisheries 30(4): Fisheries vol 30 no 8