Progress 05/01/06 to 06/30/07
Outputs
Freshwater pond culture of commercially valuable species is an underutilized resource in the Northeast. High real estate and labor costs discourage construction of new ponds and existing farm ponds are often unsuitable for traditional aquaculture species because depths and obstructions limit the ability to seine-harvest fish. The use of existing ponds for the production of baitfish in the Northeast offers new opportunities for interested parties to "test the waters" of aquaculture without the enormous initial expenditures. Most baitfish are sold for recreational ice fishing in Northern New England and estimates from the 1990s place the value of baitfish in Maine in excess of $5 million (Maine Aquaculture Innovation Center). One species with considerable potential for pond culture is the rainbow smelt, (Osmerus mordax). Rainbow smelt is the preferred prey of predacious game species and for this reason rainbow smelt is often the preferred bait of anglers. Previously, we
developed methods for smelt spawning and intensive larviculture. For commercial-scale production, however, methodologies for feed entrainment and harvest needed to be developed. We were successful in developing these methodologies during this Phase I research. Wild rainbow smelt were captured during their spawning migration and manually spawned to produce over a million viable embryos. The resulting larvae were successfully feed-entrained in both intensive (tank) and extensive (pond) culture. In hatchery/laboratory studies examining feed entrainment, three commercially available diets were compared during weaning experiments. Larvae were initially fed live prey (rotifers and artemia) and systematically weaned to formulated diets. Survival through weaning ranged from 9.9-15.3% and did not differ among diet treatments. Mean growth rate during this study was high but not significantly different among treatments. In extensive studies, 10,000 larvae were stocked in 6- 0.25 acre ponds at
both 5 and 75 days post hatch (DPH) and feed-entrained with the use of phototaxia. Larval survival was extremely high and significantly greater with larvae stocked at 5 DPH (38-55%), likely due to lower water temperature at the time of stocking. Fish from both stocking groups were harvested by automated mechanical harvesting devices and marketed as baitfish. Two iterations of automated mechanical harvesting devices were designed and tested. The initial design consisted of a lighted feed station that utilized timers that triggered the lift of the nets. The concept was to operate the feed station for several hours and then trigger the automated lift net to rise from the bottom of the pond and capture the feeding smelt concentrated at the lighted station. Capture results from 4 ponds ranged from 16-50% using this design. The harvester was modified by the addition of a plastic "leader" that directed the fish into a continuously-acting lighted collection chamber. Harvest results from a
single pond using the modified collector were 87%. All project goals were achieved and unexpected additional findings during this research project indicate that full-scale intensive/extensive smelt culture is eminent.
Impacts
Feed entrainment and capture methods are vital to future rainbow smelt culture. Without development of these methods, smelt culture would be virtually impossible. Our research has developed and utilized both feed entrainment and capture methods that have proven successful. Mounting concerns about movement of live wild fish and associated diseases like VHS have many consumers searching for alternative sources for rainbow smelt. Utilizing state-of-the-art fish health procedures and testing, cultured rainbow smelt can be certified disease free. Continued research effort will expand on this successful project and continue the development of rainbow smelt culture. Present smelt market demands exceed commercial wild harvest production and seasonal harvest limits year-round availability, future rainbow smelt producers could expect a significant expansion of existing markets once culture operations come on line. Redirecting rainbow smelt production from commercial fishing
(wild harvest) to aquaculture will have a significant positive environmental benefit also.
Publications
- No publications reported this period
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Progress 05/01/06 to 05/01/07
Outputs
The objectives of this project were to 1) develop methodologies for feed entrainment of larval rainbow smelt and 2) investigate the use of phototaxia as a tool to harvest market size rainbow smelt. The 10-day harvest experiment, using lift nets, has been completed on all project ponds, but the final draining and population assessment has not been completed. Inclement weather (rain/snow/sleet) slowed the harvest activities and conditions encountered during drawdown of the ponds, silt and ice formation, caused elevated mortalities during capture. Therefore, the harvest was suspended we are requesting a project extension with plans to complete the final drawdown and evaluations in the spring. Thousands of smelt have been harvested to date and are being held at Maine Smelt Hatchery for evaluation and trial sales to specific markets. Overall, the project has proceeded well and any problems encountered have been handled without significant interruption to the whole project.
Extending the project for an additional 6 months will be very beneficial for completing the remaining objective .
Impacts
Results of this research will assist in the development and implementation of a new aquaculture fish. Present supply is harvested from wild populations and cannot meet market demands. In many areas, rainbow smelt are approaching threatened status; therefore, developing methods of aquaculture production are desirable. Our research has shown that cultivating rainbow smelt is possible.
Publications
- No publications reported this period
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