Hatchery Propagation and Reintroduction of Wounded Darters, Etheostoma vulneratum, into the Cheoah River, North Carolina

Transcription

1 Hatchery Propagation and Reintroduction of Wounded Darters, Etheostoma vulneratum, into the Cheoah River, North Carolina by M.A. Petty, C.L. Ruble, P.L. Rakes and J.R. Shute Conservation Fisheries, Inc. March 18, 2010 FINAL REPORT TO: NC DIVISION OF WATER RESOURCES, CHEOAH FUND RALEIGH, NORTH CAROLINA SUMMARY OF SERVICES PERFORMED January 1, 2009 December 31, 2009 Contract No. DENR 2463 Adult male wounded darter at CFI 4/21/08; adult tagged propagated darter in Cheoah River 10/1/09

2 Introduction On January 25, 2005, the Federal Energy Regulatory Commission (FERC) issued an Order Approving Settlement and Issuing a New License for the Tapoco Hydroelectric Project (FERC No. 2169). The Tapoco Project Relicensing Settlement Agreement (RSA), filed with FERC in May 2004, established two funds, the Tallassee Fund and the North Carolina Resource Management and Enhancement Fund (now Cheoah Fund) to support restoration, recovery, and conservation efforts in Tennessee and North Carolina, respectively. In accordance with the RSA, for the next 40 years seasonal and base flow regimens are being regulated in the Cheoah River, along with gravel augmentations and efforts to restore indigenous fish and other fauna that were extirpated when the river was bypassed by a hydroelectric diversion flume. Conservation Fisheries, Inc. (CFI) was contracted to develop captive propagation techniques for several species which are too difficult to translocate in significant numbers. These include the stonecat (Noturus flavus), the sicklefin redhorse (Moxostoma sp.), and the wounded darter (Etheostoma vulneratum). Propagation and restoration efforts for 2008 and 2009 of the wounded darter are described herein. Methods Twelve wounded darters (Etheostoma vulneratum) were collected from Little Tennessee River, North Carolina, on 1 May 2007 from the bend below Wiggins Branch (Little Tennessee River Mile [LTRM] 92.3). Additionally, on 13 August 2007 two males were collected from near the mouth of Tellico Creek (LTRM 99.2), and another male and female was collected from above Dean Island (LTRM 101.2). These fish were used for propagation efforts in 2008 and The fish were placed in plastic bags with water from the river and topped off with oxygen. The bags were then placed in coolers to help maintain a consistent temperature for the travel back to CFI. At CFI the fish were floated for minutes in water in a dedicated multi-aquarium system in order to acclimate to the appropriate temperature. After acclimation the bags were opened and the fish were set up in three different 76 liter tanks. All fish collected on 1 May 2007 were set up in two tanks with six fish each. On the 3 May one small male was found dead, likely due to handling and transport stress. The fish collected on 13 August were placed in a separate tank isolated for quarantine. The 76 liter (76 cm long) glass aquaria were part of a larger recirculating system of approximately 760 liters (similar to other systems at CFI, see Rakes et al. 1999). Each tank was set up with appropriate cover items consisting of ceramic slates, PVC pipes, and natural stone slabs. Filtration included individual tank sponge filters as well as system filters (for multiple redundancy back-up). A 15kW generator insured back-up power for essential life support functions for the entire facility in the event of an electrical outage. Because the fish were collected during or after their natural spawn time in 2007, no spawning occurred that year. During winter months, like all fish at CFI, wounded darters were maintained and conditioned through water temperature and photoperiod manipulation in preparation for spawning. Photoperiod was controlled with an astronomic timer to mimic natural winter conditions with slowly decreasing then increasing day length on a schedule comparable to the actual season. Temperatures were

3 similarly manipulated. By using ventilation of outdoor air we maintained water temperatures as low as 40 F to "winter condition" the fish. Temperatures were logged into a Microsoft Excel database. An example of seasonal water temperature fluctuations during 2009 is presented in Appendix 1. Food quantities were provided dependent upon water temperature and the accompanying activity levels and willingness of the fish to feed. Fish were provided live blackworms, and live Daphnia as a first food. The recirculating system was treated with salt (~2%) to reduce stress and fight parasitic infections. The darters were distributed into 76 liter breeder tanks after it was determined that there were 11 males and 6 females (N=17) for the 2008 spawning season and later 15 breeders remaining for Each tank was ultimately set up with 2-3 males and 2-3 females each. Spawning sites for each tank were set up, each consisting of two slates positioned to form a wedge. The slates used were ~10 long and 6 wide and made of either cut up tiles or terra cotta slates. With one piece forming the flat floor, the second piece was placed on top to form an acute-angled V (~40-60 ), held open with ½ PVC tubes. The males were periodically shuffled to new tanks to increase genetic diversity of the propagates. From April through July, nests were collected from the breeding tanks at least weekly. Tiles with eggs were removed and placed in an empty egg incubation tank for passive capture of the larvae as they hatched and swam up. The incubation tank consisted of an empty 76 liter tank draining into an oval catch tub measuring 63 x 53 and 18 Wounded darter eggs attached to a slate. Seven day old wounded darter eggs cm deep with a PVC standpipe drain in the center. The ¾ standpipe was widened at the top to 1.5 with a micron screen around the top to prevent overflow of the larvae. A flexible air wand was set around the PVC stand pipe to prevent larval drift into the screen. A collection of eggs from an early spawn were used to trace development. Several eggs were removed from this nest with a razor and placed in a flow through tray to monitor and photograph development. Egg size at spawn was mm, roughly spherical in shape. At hatch eggs were oblong, with the short diameter of ~2.2 mm and the long diameter of ~2.5 mm. Larval size at hatch was ~7.75 mm total length (TL). Hatch times for nests laid in late April were 7-9 days. As temperatures increased hatch times decreased.

4 Hatching larvae were monitored by checking the overflow collection tub daily from early April through the end of July. The attraction of early larvae to an illuminated overflow from the incubation tank facilitated their collection and seemed to increase subsequent survivorship. At hatch, larvae swam up for brief periods of time, during which they might be captured in the collection tub, but Day old wounded darter larva (~9.75 mm TL) rested on the bottom for much of the time in either the incubation tank or the tub. Once they were fully pelagic in the collection tub (12-24 hours post-hatch?), they were collected with a baster and transferred to a larger rearing tub measuring 69 cm diameter by 33 cm deep. This tub also had a central PVC standpipe widened at the top with a micron screen, and a flexible air wand to prevent larval drift into the overflow screen, but was provided with a fine stream of fresh system water to create gentle circular current at a much slower flow rate than the capture tub. The rearing of such tiny pelagic larvae required a balance between providing adequate zooplanktonic food densities while simultaneously maintaining adequate water quality and avoiding excessive larval densities. The rearing tub was supplied with food via a reservoir, timer and solenoid for constant dispersal during the day. The feeding reservoir consisted of an 11 liter plastic tub with a spout at the bottom connected to tubing to the rearing tub. A solenoid valve, controlled by a repeat timer released food for 8-10 seconds every 2 Spout Solenoid Feeding reservoir and solenoid. minutes during daylight hours. The reservoir was filled with water from the system, to which a portion of Brachionus rotifers, Nanno 3600 Nannochloropsis sp. (Instant Algae produced by Reed Mariculture, Inc.), and Ceriodaphnia dubia neonates were added twice daily. Newly hatched brine shrimp (Artemia) nauplii were added to the mix when larvae were large enough to eat them. To supplement the reservoir feeding, powder foods were lightly dusted directly on top of the rearing tub several times daily. These consisted of equal parts of: A.P.R. (Artificial Plankton Rotifer) [Ocean Systems International], Larval AP 100 (<100 µ and µ), [Zeigler Bros., Inc.], and spirulina [Salt Creek, Inc.]. Regular (twice weekly) cleaning of the feeding reservoir was necessary to prevent excessive algal and bacterial growth. Likewise, maintaining a clean bottom of the rearing tub was necessary to

5 prevent opportunistic bacterial infections of the larvae (which rest on the bottom at night). This was somewhat facilitated by using snails to eat excess food and waste, but manual removal with a large baster, or a small flexible siphon tube was performed as needed. As larvae grew and transformed to benthic juveniles they were separated from younger larvae and transferred to empty 20 gallon tanks for further grow out. Feeding of these juveniles was supplemented with larger food items such as chopped blackworms, and later frozen chopped bloodworms. Brine shrimp nauplii and Ceriodaphnia dubia adults were also offered for smaller individuals. Results In 2008, the total number of eggs spawned was estimated to be ~2,000. Some of these eggs were possibly infertile, but many succumbed during a period of poor water quality due to a period of heavy organics building up in the system from the automatic feeder. The 3 breeding groups (pairs of females) varied in production from 187 to eggs per female (average of 345). Number of clutches per breeding group ranged from 13 to 17, with 29 eggs per clutch in the former and 47 to 53 in the latter. A total of 705 larvae were transferred from the catch tub to the feeding tub. Approximately 539 juveniles were transferred out into tanks, yielding a 76.5% survival rate from pelagic larvae to benthic juveniles. A total of 494 juveniles survived for release to the Cheoah River in fall 2008 and spring In 2009, the total number of eggs spawned was approximately 1600 and some of these eggs were infertile. The 3 breeding groups (pairs of females) varied in production from 218 to 352 eggs per female (average of 278). Number of clutches per breeding group again ranged from 13 to 17, with eggs per clutch. A total of 680 larvae were transferred from the catch tub to the feeding tub. Approximately 405 juveniles were transferred out into tanks for grow-out, yielding a survival rate of ~60% from pelagic larvae to benthic juveniles. Ultimately, 388 juveniles survived for a fall 2009 release to the Cheoah River. On 19 August 2008, the first propagated wounded darters were reintroduced to the Cheoah River (Map, Appendix). A total of 342 juveniles were released at three sites: just below the dam above the flume crossing (~123), adjacent to Santeetlah Church (~120), and at the pull-off ~0.1 mi above Cochran Creek (~99). These were the oldest and largest individuals, but were mostly too small (~20-40 mm TL) to safely tag with visible elastomer implants (VIE). The remaining individuals were held over winter to grow larger and were released at two new sites on 28 April 2009 after receiving red VIE tags: ~73 at the lowest bridge above the TAPOCO lodge, and ~79 at the mouth of Yellow Creek (Table 1). A pre-release snorkel survey at the latter site detected only one darter species, Etheostoma chlorobranchium, the greenfin darter, which was observed spawning. River chubs and warpaint shiners were also breeding, on pebble nests constructed by the chubs with the introduced gravel. The first monitoring to search for released darters was conducted on 23 July 2009 at the lowest bridge site in a brief survey while returning from a trip to Cherokee. A lone male wounded darter was observed with tag still visible (released in April). Additional monitoring and releases were conducted 1 October when 138 darters were stocked at the

6 Santeetlah Church site and 250 at the mouth of Yellow Creek. These were all VIE tagged green. A snorkel survey detected no wounded darters at the upper flume crossing site and habitat conditions were deemed unsuitable for any further releases there. A prerelease survey at Yellow Creek located a large, robust female wounded darter released in April (title page photo). Both fish were located in what we consider fast glide mesohabitat, peripheral to the thalweg, with an abundance of cobble, boulders, and slab rocks over finer gravel and sand (depositional rather than erosive areas). This habitat is not common at this time in the areas we have snorkeled in the Cheoah River. Young greenfin darters were syntopic with the wounded darters adult greenfins were more typically found in deeper, swifter water. Additional brood stock (N=8) was collected from the Little Tennessee River in August, but more will be needed prior to 2010 efforts to increase production and diversify genetic representation. Documentation of survival of stocked fish over winter will be a critical benchmark next year, with wild reproduction and recruitment observations not expected before 2012 or 2013 (based on our experience with the closely related boulder darter). Locating 2 tagged fish out of only 150 released earlier in the year in a river this size is more remarkable than most realize. Date Field # Locality R Mi # released Lat Long 8/19/08 CFI /19/08 CFI /19/08 CFI /28/09 CFI Adjacent to Santeetlah Baptist Church Just below dam, 50 m above flume crossing Pull-off ~1/10 mi above Little Cochran Creek Lowest bridge above TAPOCO lodge N W N W N W N W /28/09 CFI Mouth of Yellow Crk N W /1/09 CFI Adjacent to Santeetlah Baptist Church N W /1/09 CFI Mouth of Yellow Crk N W TOTAL RELEASED: 882 Table 1. Wounded darters released to Cheoah River 2008 and Discussion Wounded darter propagation protocols, as expected, were found to be essentially identical to those we have developed and refined since 1995 for a close relative, the boulder darter, Etheostoma wapiti (Rakes et al. 1999). Only minor differences in sizes of eggs and larvae and developmental times were noted. One significant difference, however, was duration of the spawning season. While boulder darters have reliably spawned for only 6 weeks (typically early April to mid-june) at CFI for approximately 10 years now, the wounded darters spawned for more than 12 weeks. Termination of spawning appeared to be linked to water temperatures exceeding 80ºF.

7 Survivorship of eggs and larvae were also roughly similar to those observed for boulder darters, with most losses occurring during the sensitive pelagic larval stage. Losses of both eggs and larvae occurred during early June, likely due to water quality declines during peak automatic feeding time. After a water change and system medication of formalin semi-daily, losses stopped. It is also possible that some cannibalism took place. Growth of larvae greatly increased as water temperatures increased, making it hard to transfer older larvae and juveniles out of the larval rearing tub fast enough to maintain similar-sized larvae. Some older larvae and juveniles were seen chasing new larvae, and we have observed cannibalism in other species. Juvenile survivorship, as with boulder darters, approached 100%. Future efforts will include refining all protocols to increase egg and early larval survivorship, experimenting with breeding ratios and breeding population sizes, and determining maximum reproductive age and age/size-related egg production. We will acquire additional broodstock to further diversify genetic variation of propagated darters and in the reintroduced population. We will continue with snorkel monitoring to determine survivorship and status of the reintroduced population, with an emphasis later in the year to detect evidence of wild reproduction. Acknowledgements Funding provided by North Carolina Division of Water Resources, Cheoah Fund. Field assistance thanks to Mark Cantrell (USFWS), as well as Steve Fraley and T. R Russ (NCWRC). Literature Cited Rakes, P.L., J.R. Shute and P.W. Shute Reproductive behavior, captive breeding, and restoration ecology of endangered fishes. Environmental Biology of Fishes. 55:31-42.

8 Appendix Water temperatures at CFI during 2009.

9 Wounded darter release sites on the Cheoah River