Seafood Watch Seafood Report

Transcription

1 Seafood Watch Seafood Report Courtesy: NOAA Wahoo/Ono Acanthocybium solandri Final Report March 23, 2004 Melissa Mahoney Stevens Fisheries Research Analyst Monterey Bay Aquarium

2 About Seafood Watch and the Seafood Reports Monterey Bay Aquarium s Seafood Watch program evaluates the ecological sustainability of wild-caught and farmed seafood commonly found in the United States marketplace. Seafood Watch defines sustainable seafood as species, whether fished or farmed, that can exist into the long-term by maintaining or increasing stock abundance and conserving the structure, function, biodiversity and productivity of the surrounding ecosystem. Seafood Watch makes its sciencebased recommendations available to the public in the form of regional pocket guides that can be downloaded from the web ( or obtained from the program by ing seafoodwatch@mbayaq.org. The program s goals are to raise awareness of important ocean conservation issues and to shift the buying habits of consumers, restaurateurs and other seafood purveyors to support sustainable fishing and aquaculture practices. Each sustainability recommendation on the regional pocket guides is supported by a Seafood Report. Each report synthesizes and analyzes the most current ecological, fisheries and ecosystem science on a species then evaluates this information against the program s conservation ethic to arrive at a recommendation of Best Choices, Good Alternative or Avoid. In producing the Seafood Reports, Seafood Watch seeks out research published in academic, peer-reviewed journals whenever possible. Other sources of information include government technical publications, fishery management plans and supporting documents, and other scientific reviews of ecological sustainability. Seafood Watch Fishery Analysts also communicate regularly with ecologists, fisheries and aquaculture scientists, and members of industry and conservation organizations when evaluating fisheries and aquaculture practices. Capture fisheries and aquaculture practices are highly dynamic; as the scientific information on each species changes, Seafood Watch s sustainability recommendations and the underlying Seafood Reports will be updated to reflect these changes. Parties interested in capture fisheries, aquaculture practices and the sustainability of ocean ecosystems are welcome to use Seafood Reports in any way they find useful. For more information about Seafood Watch and Seafood Reports, please contact the Seafood Watch program at Monterey Bay Aquarium by calling or sending an to seafoodwatch@mbayaq.org. Disclaimer Seafood Watch strives to have all Seafood Reports reviewed for accuracy and completeness by external scientists with expertise in ecology, fishery science and aquaculture. Scientific review, however, does not constitute an endorsement of the Seafood Watch program or its recommendations on the part of the reviewing scientists. Seafood Watch is solely responsible for the conclusions reached in this report. Seafood Watch and Seafood Reports are made possible through a grant from the David and Lucile Packard Foundation. 2

3 Executive Summary Wahoo (Acanthocybium solandri), a member of the Scombrid family, is a pelagic (open ocean) species found worldwide in tropical and warm-temperate seas. It is fished throughout its range by artisanal, recreational, and commercial fishers. The degree of stock delineation throughout the worlds oceans is unknown. Off the Main Hawaiian Islands (MHI), the highest volume of wahoo is landed by commercial trollers (an unknown amount is taken by sport fishers). It is also caught incidentally as a minor component of the tuna/swordfish longline fishery, the biggest fishery off Hawai i (in terms of landings and revenue). Wahoo, or ono as it is called in Hawai i, is marketed to upscale restaurants, and is sometimes a substitute for the more popular mahi-mahi, or dolphinfish (Coryphaena hippurus). Wahoo is thought to be extremely prolific due to a fast growth rate, early maturity, and extreme fecundity. This conclusion is based on only a few studies, mainly on individuals inhabiting the southern Atlantic and Caribbean oceans, but likely holds true for the species throughout its range. Very little is known about wahoo population structure in the Pacific, and no stock assessment has been performed to date. Catch rates have remained constant over time, so management has assumed stock status is stable. Because it is caught mainly in mixed-species commercial or recreational trolling fisheries, the level of bycatch associated with wahoo landings is significantly less than that of other pelagic species caught primarily by longline. Pelagic longline fisheries have been observed to interact with and cause mortalities of protected and endangered marine species, such as sea turtles and seabirds, as well as other vulnerable fishes such as sharks and rays. Managers and fishers in the U.S. fleet have made great strides in reducing interactions in recent years. However, population estimates for many species of sea turtles and seabirds are extremely low, so even a minor amount of bycatch mortality may affect their long-term survival. Table of Ranks Sustainability Criteria Inherent Vulnerability Status of Wild Stocks Nature of Bycatch Habitat Effects Management Effectiveness Conservation Concern Low Moderate High Critical Troll - Caught Longline Overall Seafood Recommendation: Troll-Caught and Longline Best Choices Good Alternative Avoid 3

4 Introduction Wahoo/ono is a wide-ranging pelagic species inhabiting in the worlds warm tropical and temperate seas. A relative of the king mackerel, this species is known to travel solitarily or in small schools of two to twenty fish (Iverson and Yoshida 1957), and is attracted to banks, pinnacles and islands, as well as flotsam drifting in the open ocean (NMFS 2001a). It seems that wahoo is surface oriented (<160 meters depth), based on observance of catch rates at different depths in the longline fishery (Nakano et al. 1997). It is thought to associate with warm, productive oceanic fronts, especially when these fronts are near coastal shelves and banks (NMFS 2001a). Wahoo may also migrate seasonally away from the equator, following oceanic temperature patterns (Iverson and Yoshida 1957). Wahoo/ono is targeted directly by subsistence, recreational (sport/charter boat), and commercial troll fishers. It is also an indirect target of the tuna, swordfish, and mixed species pelagic longline fishery in the U.S. s Exclusive Economic Zone (EEZ) in the Western central Pacific (Polovina et al. 2003). It is landed in Hawai i, Guam, American Samoa, and the Commonwealth of the Northern Marianna Islands (CNMI), with the volume of landings descending in that order (Ito and Machado 2001). In 2000, approximately 318 metric tons (mt, ~ 700,000 pounds) were landed in the state of Hawai i, 33 mt were landed in Guam, 22 mt were landed in American Samoa, and less than 2 mt were landed in CNMI (WPRFMC 2002). Total wahoo landings were approximately 374 mt, just 2.5% of the total pelagic landings in the western Pacific region for 2000 (~15,100 mt;wprfmc 2002). Scope of the analysis and the ensuing recommendation: Because its distribution is circumtropical, wahoo is caught in many other areas around the globe (Gulf of Mexico, Caribbean, south Atlantic). This report, however, deals only with the stocks inhabiting the western central Pacific, and their fisheries. Figure 1. Exclusive Economic Zones (EEZs) of the Pacific Islands. Western Pacific Regional Fishery Management Council managed areas are shaded. Note: In some cases the boundaries shown here are provisional since not all them have been legally delimited (WPRFMC IN: NMFS 2001a). 4

5 Availability of Science Very little is known about the biology of wahoo and even less is known about its population structure. A few researchers have studied the life history characteristics (age, growth, maturity and fecundity) of this species, but only in certain areas, and those age and maturity estimates have not been validated (Brown-Peterson et al. 1998; Franks et al. 1998). Indeed, too little is known about this species to allow an assessment of stock abundance or structure. Consequently, there are no estimates of biomass, optimum yield (OY), or maximum sustainable yield (MSY). The only indication of abundance trends may be inferred from catch and effort data, so the uncertainty of abundance weighs heavily in the overall recommendation. The main method of catch, trolling, is not as well documented or monitored as the longline fishery. Issues relating to bycatch, therefore, are not well known for the troll fishery. Because few studies on wahoo have been carried out, few primary literature sources (peerreviewed journals) were available for this analysis. Most of the abundance and fishery data comes from unpublished government reports produced by management agencies. Market Availability Common/Market names Country/Area American Samoa Hawai i Guam Caroline and CNMI Mainland U.S. Local/Market name Paala Ono Toson Ngaal Wahoo/ Pacific Kingfish/ Ocean Barracuda Seasonal Availability The supply of wahoo and other indirect targets of the pelagic fishery is erratic, but monthly landings trends indicate wahoo is most available in Hawai i from spring through fall (DBEDT 1995). Product forms According to the Hawai i Seafood Buyers Guide, Local fishermen market their ono as fresh, whole fish.upscale restaurants on the islands and mainland prefer to receive the fish filleted, or headed and gutted (H&G) to retain better quality (DBEDT 1995). Because of its high quality meat, it is not usually smoked, but eaten fresh. In 2000, ono had the greatest average wholesale price of all miscellaneous pelagic species at US$2.20/pound (Ito and Machado 2001). For comparison, this price is slightly higher than mahi-mahi (US$1.70/lb), but cheaper than most tunas (US$2.80/lb for yellowfin tuna to US$10.40/lb for bluefin tuna). Import/export Statistics The NMFS tracks import and exports of seafood through U.S. customs districts. There is no data relating to either the import or export of wahoo (NMFS 2001b). 5

6 Analysis of Criteria Criterion 1: Inherent Vulnerability to Fishing Pressure Primary Factors: Intrinsic rate of increase is unknown. Age at 50% sexual maturity is estimated to be approximately 2 years (1,020mm Fork length, FL) for females, and 1-2 years (<935mm FL) for males (Brown-Peterson et al. 1998). Maximum age is approximately 4 to 6 years (Hogarth 1976; Franks et al. 1998). Additional Factors: Fecundity is thought to be high, from 600,000 eggs (Hogarth 1976) to over 6 million eggs per spawn (Iverson and Yoshida 1957). Once mature, estimated spawning frequency is once every 2-6 days during June (peak spawning month) (Brown-Peterson et al. 1998) for wahoo in the Caribbean. In subtropical waters they may spawn repeatedly but only on a seasonal basis (NMFS 2001a). Natural population size and how it is affected by physical environmental change is unknown. The species range is worldwide in tropical and warm-temperate seas; this species seems to be more abundant near islands, seamounts, and oceanic fronts (NMFS 2001a). Wahoo have not been observed to school in large aggregations or display site fidelity (Iverson and Yoshida 1957; DBEDT 1995). These behaviors make wahoo less vulnerable to heavy fishing pressure. Criterion 1: Inherent Vulnerability Rank Due to its life history characteristics and lack of special behaviors (such as aggregations), wahoo are inherently resilient to fishing pressure. ( Vulnerable Neutral Resilient X ) Criterion 2: Status of Wild Stocks Primary and Additional Factors: Current population abundance for wahoo is unknown, making it very difficult to discern the health of the stock, its age, size, and sex distribution, or the appropriate level of fishing effort. There is no estimate for fishing mortality, but natural mortality has been reported as high as 38% (Hogarth 1976), which seems logical given the high fecundity, fast growth and maturity and short life span of this species. An indication of stock status can be inferred from landings and effort data (Figs. 2-4), such as are recorded by the State of Hawai i, Division of Aquatic Resources (HDAR) and NMFS logbook and observer data. Based on landings data, the abundance of wahoo in Hawaiian waters exhibits some seasonality, with higher landings recorded during the second and third quarters. Elevated landings of wahoo are presumed to be linked to a higher local abundance during these periods of the year, although this was not specifically examined. Annual commercial landings indicate some inter-annual variability but exhibit an increasing trend over time 1. Wahoo caught by trollers has been increasing since the mid 1970s, with pounds per trip increasing slightly after 1994 (Fig.3). Longline catch has generally increased over the last 1 David Itano Personal commun. Joint Institute for Marine & Atmospheric Research, University of Hawai i, 1000 Pope Road, Honolulu, Hawai i

7 decade, probably in response to the rapid growth in the Hawai i-based longline fishery after the implementation of the Pelagics Fishery Management Plan (FMP; Ito and Machado 2001). The plan called for a moratorium on permits, so the number of fishers attempting to enter the fishery before this time caused a four-fold increase of vessels into the fleet. Handline catch remains consistently lower than other gear types due to the fact that it is inherently a smaller fishery that concentrates on tuna, and that fishes in a manner ineffective for wahoo capture (i.e. smaller boats, fewer hooks, stationary baits, etc.). According to the Western Pacific Regional Fishery Management Council (WPRFMC), Wahoo landings in the state of Hawai i decreased from 1 million lb (454 mt) to 0.7 million lb (318 mt) between 1999 and The 2000 trolling catch rate was down by 12.2% but still above the long term average (+16.7%) (WPRFMC 2002). In 2001, there were 1,632 active fishermen in the Hawai i-based troll fishery, landing approximately 2.7 million pounds (1,225 mt), 20% of which was wahoo (NMFS 2002). Reported landings (1000s pounds) Troll Handline Longline Figure 2. Reported commercial landings of wahoo/ono in the State of Hawai i, by gear type, Courtesy: HDAR 7

8 Figure 3. Hawai i-based commercial trolling catch per year for blue and striped marlin, mahimahi, and ono (wahoo). Source: (WPRFMC 2002) Another indication of abundance may be inferred from catch per unit effort (CPUE) data, which was recorded for tuna longline trips on a quarterly basis from 1991 to 2000 (Fig. 4). Catch per unit effort decreased in 2002, compared to 2001, but the quarterly means were not significantly less than the mean CPUE. This is an indication that abundance (with respect to fishing, not migration patterns) is relatively stable, although area effects on the data have not been examined. Figure 4. Mean quarterly CPUE for ono on tuna longline trips, compared to mean CPUE from (NMFS 2003a) 8

9 Criterion 2: Status of the Stocks Rank There is no formal stock assessment for wahoo, so its abundance in the western Pacific may only be inferred from landings and effort data. This data is affected by market demand (which in turn affects the amount of fishing activity and target species), so the trends in abundance are not clear. Because of this, the status of the stock is unknown. ( Poor Unknown X Healthy ) Criterion 3: Nature of Bycatch The issue of bycatch (unwanted and discarded catch) for central Pacific pelagic fisheries mainly relates to the longline fishery. Wahoo is mainly taken as an incidental, retained byproduct of the tuna longline fishery, comprising a very small portion of the total catch (~ 3% in 2000). The baited hooks of the longline can attract endangered and protected sea turtles, seabirds, and marine mammals. These animals may become hooked or entangled on longline gear, causing injury or death. Interactions with these species occur more often with the shallow-setting technique used for targeting swordfish (5-60 m), because the bait (squid) does not sink as fast, and stays closer to the surface where birds and sea turtles may be present. The deeper-set technique used to catch tunas ( m) has been shown to have much fewer interactions than with swordfish sets, due to the baited line sinking faster and deeper (Cousins 1999; Ito and Machado 2001). Consequently, the deeper-set technique, which achieves a line depth of at least 100 m, is currently the only style of longline fishing allowed in Hawai i (Ito and Machado 2001), and is also the method that accounts for higher catch rates of wahoo. Other methods have been employed to reduce interactions with protected species, including an observer program and area closures. These are discussed further in the management section (Criterion 5). The majority of wahoo caught off the MHI is by the troll fishing method. Commercial troll fisheries have not been monitored as well with respect to bycatch, although NMFS has begun logbook reporting requirements similar to the longline fishery, effective October 2002 (NOAA 2002). The active-fishing nature of trolling (when a fish is hooked, it is reeled in immediately) implies that bycatch would be minimal, but there is no information to document this. Criterion 3: Nature of Bycatch Rank Bycatch in the troll fishery, where the majority of wahoo is caught, is unknown, but is assumed to be negligible 2. Hawai i Troll-caught wahoo ( High Medium Low X ) Bycatch of endangered and protected species in the Hawai i-based tuna longline fishery occurs, but management has reduced interactions significantly. It is clear that interactions before the year 2000 were great for both sea turtles and seabirds and were likely a contributing factor in the decline of these species (see other pelagic fishery reports for further information). Current bycatch rates for both turtles and seabirds are now two orders of magnitude lower than those from the mid 1990s. These drops were due to strong management measures, the most effective 2 David Itano Personal Commun. Joint Institute for Marine & Atmospheric Research, University of Hawai i, 1000 Pope Road, Honolulu, HI

10 of which was to completely prohibit swordfish-style (shallow-set) longlining. The management plan is in a state of flux, however, as the WPFMC may modify current regulations for the 2004 Hawai i longline fishing season 3. An additional two years of continued low bycatch rates combined with population studies indicating these rates no longer threaten certain species, would warrant a rank of Moderate (Yellow) for Nature and Extent of Bycatch for the Hawai i longline fishery. International take of wahoo is unknown, either by troll or handline. Hawai i Longline-caught wahoo ( High X Medium/Unknown Low ) Criterion 4: Effect of Fishing Practices on Habitats and Ecosystems Fishing methods that come into physical contact with the seafloor or other critical habitat structures (seamounts, FADs, etc.) may inflict damage upon those areas and ultimately reduce the health of the habitat and ecosystems in which the targeted species lives. Due to the pelagic nature of the longline and troll fisheries in which wahoo is retained, tangible habitat structure is unaffected. The ecosystem effects relating to the removal of wahoo and other pelagic species is still relatively unknown. Many researchers, however, have postulated that trophic webs are altered by significant fishery removals, and that over time, overfishing can alter the composition and distribution in pelagic communities, inducing drastic changes of state (Jennings and Kaiser 1998; Cury et al. 2000). Since wahoo is a prolific species and is not landed in high numbers (relative to other commercially-important pelagic fishes), the effect of its removal on the central Pacific pelagic ecosystem is probably minor. ( Severe Average Benign X ) Criterion 5: Effectiveness of the Management Regime Wahoo is managed through the Western Pacific Region Pelagic Fisheries Fishery Management Plan (FMP), which was first implemented in 1987 (WPRFMC 2002). This FMP applies to all pelagic fisheries that occur in the EEZ of the Western Pacific Region (see page 4). The plan regulates the size of the U.S. fleet and the potential for interaction between fishers and protected or endangered species. This is done through limited entry permits for all commercial fisheries, gear modifications (to reduce bycatch), and time/area closures, such as the closure of a 50-mile radius around the Northwest Hawaiian Islands (NWHI) to protect monk seal and nesting albatross populations. 3 A lawsuit was filed recently (August 2003) by the Hawai i Longline Association, challenging the seasonal closures in certain areas south of Hawai i in April/May each year. The WPFMC is currently considering alternatives to the current measure that would enable more longlining opportunities for Hawaiian vessels. A decision is expected at the council meeting in September

11 Although one of the objectives of the FMP is to gather biological information for all commercially important species, stock assessment information is currently lacking for many species, including wahoo. Fishing for all species, assessed or not, is allowed with no estimate of maximum sustainable yield (MSY) or a set quota. Without this estimate, management cannot determine the sustainability of the current catch rate. Pelagic fishes, including wahoo, are highly migratory and are caught in international waters by several countries, some with limited or no regulations. Although there are several international regulatory bodies working towards sustainable high seas fishing (Cousins et al. 2002), there is currently no international cooperation to conduct fisheries research and manage these stocks collectively (other than those attempting to manage tunas). In essence, the efforts of U.S. fishers (~164 longline vessels) to reduce bycatch and conserve fish stocks may be overshadowed by international fishing effort (3,000+ vessels) on the high seas (Cousins et al. 2002). Over time, however, a shift in market preference for U.S.-caught pelagic fishes may motivate the international fleet to modify their fishing practices. Criterion 5: Effectiveness of U.S. Management Rank Management has significantly reduced bycatch through regulatory action. The wahoo stock, however, has not been assessed, so the sustainability of the current catch rate cannot be accurately determined. ( Ineffective Moderately effective X Highly effective ) Recommendation Table of Ranks Sustainability Criteria Inherent Vulnerability Status of Wild Stocks Nature of Bycatch Habitat Effects Management Effectiveness Conservation Concern Low Moderate High Critical Troll - Caught Longline Overall Seafood Recommendation: Troll-Caught and Longline Best Choices Good Alternative Avoid 11

12 Acknowledgements Seafood Watch staff would like to thank David Itano of the University of Hawai i, and Paul Dalzell of the Western Pacific Regional Fishery Management Council for their review of this document. Scientific review does not constitute an endorsement of Seafood Watch on the part of the reviewing scientists; the Seafood Watch staff is solely responsible for the conclusions reached in this report. 12

13 References Brown-Peterson, N. J., J. S. Franks and A. M. Burke Preliminary observations on the reproductive biology of wahoo, Acanthocybium solandri, from the Northern Gulf of Mexico and Bimini, Bahamas R. L. Creswell. 51st Gulf and Caribbean Fisheries Institute Meeting, St. Croix, U.S. Virgin Islands. Gulf and Caribbean Fisheries Institute, Inc. 51. Cousins, K. L The black-footed albatross population biology workshop: A step to understanding the impacts of longline fishing on seabird populations E. F. Melvin and J. K. Parrish. Seabird Bycatch: Trends, Roadblocks, Solutions, Honolulu, HI. Alaska Sea Grant. AK-SG Cousins, K. L., P. Dalzell and E. Gilman Managing pelagic longline-albatross interactions in the North Pacific Ocean. Western Pacific Regional fishery Management Council, 1164 Bishop Street, Suite 1400, Honolulu HI 96813: 27pp. Available online: Cury, P., A. Bakun, R. J. M. Crawford, A. Jarre, R. A. Quinones, L. J. Shannon and H. M. Verheye Small pelagics in upwelling systems: patterns of interaction and structural changes in "wasp-waist" ecosystems. ICES Journal of Marine Science 57: DBEDT Hawai i Seafood Buyers' Guide. State of Hawai i, Department of Business, Economic Development & Tourism Accessed: Available online: i/pdfs/hiseafod.pdf. Franks, J. S., N. J. Brown-Peterson, M. S. Griggs, N. M. Garber, J. R. Warren and K. M. Larson Potential of the first dorsal fisn spine for estimating the age of wahoo, Acanthocybium solandri, from the Northern Gulf of Mexico, with comments on specimens from Bimini, Bahamas R. L. Creswell. 51st Gulf and Caribbean Fisheries Institute Meeting, St. Croix, U.S. Virgin Islands. Gulf and Caribbean Fisheries Institute, Inc. 51. Hogarth, W. T Life history aspects of the wahoo, Acanthocybium solandri (Cuvier and Valenciennes), from the south Pacific. Ph.D. Dissertation. North Carolina State University. Raleigh, N.C. Ito, R. Y. and W. A. Machado Annual report of the Hawai i-based longline fishery for Administrative Report H Southwest Fisheries Science Center, NMFS/NOAA: 39pp. Available online: i/edu/fmpi/fmep/hilong/hi2000t.pdf Iverson, E. and H. Yoshida Notes on the biology of the wahoo in the Linde Islands. Pacific Science 11: Jennings, S. and M. J. Kaiser The Effects of Fishing on Marine Ecosystems. Advances in Marine Biology 34: Nakano, H., M. Okazaki and O. H Analysis of catch depth by species for tuna 13

14 longline fishery based on catch by branch lines. Bull Nat Res Inst Far Seas Fish 34: NMFS. 2001a. Final Environmental Impact Statement: Pelagic Fisheries of the Western Pacific Region. Prepared by: URS Corporation, 615 Pi'ikoi St, Ste 900, Honolulu HI Southwest Fisheries Science Center, NMFS/NOAA. Available online: NMFS. 2001b. Import/Export Statistics, U.S. Customs Districts. Fisheries Statistics and Trade Division NMFS Endangered Speices Act Section 7 Consultation Biological Opinion. NMFS - Southwest Region Sustainable Fisheries Division: 394 pp. Available online: NMFS. 2003a. Hawai i Longline 4th Quarter 2002 Report - Charts. NMFS - Honolulu Laboratory, Fishery Monitoring Economics Program Available online: i.edu/fmpi/fmep/hilong/hilong.htm. NMFS. 2003b. Record of Decision: Fishery Management Plan, Pelagic Fisheries of the Western Pacific Region. Southwest Fisheries Science Center, NMFS/NOAA: 12pp. Available online: NOAA Fisheries off West Coast states and in the Western Pacific; Western Pacific pelagics fisheries; Pacific remote island areas; permit and reporting requirements for the pelagic troll and handline fishery. Federal Register 50 CFR Part 660. Polovina, J. J., E. Howell, D. M. Parker and G. H. Balazs Dive-depth distribution of loggerhead (Carretta carretta) and olive ridley (Lepidochelys olivacea) sea turtles in the central North Pacific: Might deep longline sets catch fewer turtles? Fishery Bulletin 101(1): WPRFMC Pelagic fisheries of the Western Pacific Region: 2000 Annual Report. Western Pacific Regional fishery Management Council, 1164 Bishop Street, Suite 1400, Honolulu HI Available online: 14