Progress 10/01/00 to 09/30/04
Outputs
Two production strategies were compared across years during the 2003 and 2004 production seasons. Specifically, in 2003, bait minnows and crayfish were stocked into production ponds in both monoculture and polyculture to compare these production strategies. In all cases, minnow eggs were transferred to growout ponds from remote spawning ponds and crayfish were stocked as nursed juveniles in the spring of 2003. Ponds were harvested in the fall of 2003. Details of the 2003 experimental design are included above (Progress 2000/10 TO 2003/09). In contrast, for 2004, adult minnows and crayfish were stocked directly into 15 0.05-ha production ponds during the fall of 2003. Three sets of 3 monoculture ponds were stocked with golden shiners, mummichogs and crayfish. Two sets of 3 polyculture ponds were stocked with golden shiners and crayfish or mummichogs and crayfish. The following spring, water levels were partially drawn down and rye grass was planted along the pond edges
to provide spawning structure, and when the rye grass was approximately 15 cm water levels were returned to normal. In the fall of 2004, ponds were harvested and the data was compared to the data from 2003. In the fall of 2003, mummichog survival was approximately 35% in both the mono- and polyculture ponds. Golden shiner survival was approximately 20% under each production method, and survival of crayfish appeared to vary with the production method used. Monoculture crayfish survival averaged 9%, while crayfish survival in polyculture ponds was 30%. In the fall of 2004, mummichog survival averaged only 87%, for both the monoculture and polyculture production methods, and survival of crayfish grown via polyculture was 21%. Despite these net losses of mummichogs and crayfish, numbers of golden shiners and the number crayfish grown in monoculture increased by a minimum of 90%. Crayfish grown in monoculture exhibited the largest net increase. Eight times more crayfish were harvested in
the fall of 2004 then were stocked in the fall of 2003. Overall, it appears as though single pond production of crayfish and golden shiners appears to be a viable alternative to more traditional egg transfer production methods. In addition to the ponds based research, survey instruments were developed and administered to 26 anglers and 22 bait retailers in Delaware. Results from these surveys indicate, among other things,that there are seasonal shortages of bait in some parts of the state, anglers have no preference for either wild caught or cultured baitfish, many local retailers are catching their own bait, and mummichogs are one of the most popular bait species.
Impacts
When combined with current market prices and the survey data, this research suggests that baitfish aquaculture could, in fact, be a viable aquaculture business opportunity in the mid-Atlantic region. Culture parameters for golden shiners appear to be very similar to those reported from other regions of the United States. To date, however, no detailed economic assessments of golden shiner production have been made for the mid-Atlantic. Therefore, economic models based on production in the southeast region may not be accurate. Also, due to competition from the southeastern region, the culture of a saltwater bait species such as the mummichog is likely a better option for mid-Atlantic producers. Besides the preliminary research trials described here, little research has been done culturing mummichogs.
Publications
- Daniels, W. H. 2004. Small-Scale Production of Crawfish for Either Bait or Food Markets. Pages 24-26 in P. Perschbacher, editor. Small-Scale Aquaculture: Proceedings of a Special Session of Aquaculture America 2002. Association of 1890 Research Directors, Inc.
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Progress 10/01/00 to 09/30/03
Outputs
Evaluations of culture techniques for two bait minnow species and food size crayfish took place in 15, 0.05ha ponds from May through September 2003. Three sets of 3 monoculture ponds were stocked with golden shiners, mummichogs and crayfish. Two sets of 3 polyculture ponds were stocked with golden shiners and crayfish and mummichogs and crayfish. Prior to filling pond bottoms were seeded with rye grass to provided crayfish forage and encourage zooplankton production. Ponds were filled and fertilized with liquid nitrogen and phosphorous. Crayfish were stocked as nursed hatchlings at 1750/pond. Minnows were stocked as eggs produced from remote broodstock ponds. Golden shiner eggs were stocked at 26,000/pond, mummichogs at 22,000/pond. Minnows and crayfish in monoculture ponds were fed 3% of mean (within treatments) biomass, daily. Polycultured species were each fed 2.25% of mean biomass daily. Aeration was used when dissolved oxygen dropped below 3.0mg/L. Air breathing
predacious insects were controlled with soybean oil (2L/pond) as needed. In September, ponds were drawn down, minnows and crayfish were harvested, counted, weighed, and stocked to other ponds. Treatment mean survival was highest for all species in polyculture ponds. Mean weights were higher for the minnows in monoculture ponds. At $1.00 per dozen, the highest pond production value for golden shiners was $807.25, $758.48 for mummichogs. At $3.58/kg the best food size crayfish pond production value was $42.22. In 2004, spawning in growout ponds will be compared to egg-transfer method used this year.
Impacts
It appears from the preliminary production data and the current retail price for these minnows, that bait minnows represent a viable alternative agriculture crop in the mid-Atlantic region. In addition these species are often available during peak demand periods. As most of the minnows sold in the area are wild fish obtained from local waters, commercial production will help to reduce commercial exploitation on these important forage species from local waters where they also provide some degree of biological mosquito control. A survey of retail bait dealers is currently in progress to obtain detailed demand and value parameters.
Publications
- No publications reported this period
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Progress 01/01/02 to 12/31/02
Outputs
Experiments will be conducted this year at the DSU Aquaculture Facility to evaluate polyculture techniques for 2 baitfish species grown in combination with white river crayfish, which will be grown to food size. Macrophyte and algae control will be accomplished with grass carp and barley straw respectively, supplemented with chemical control as needed. Results from earlier tests indicated this to be the best management option for total vegetative control. One grass carp and 11.5kg of barley straw will be added to each of 18 (0.05ha) ponds. Pond bottoms will be planted with rye several weeks before filling, to provide cover and forage for crayfish hatchlings. There will be 5 treatments, 3 ponds each, consist of golden shiner / crayfish, mummichog /crayfish, golden shiner only, mummichog only, and crayfish only. Additionally, 3 ponds will be stocked with nursed crayfish hatchlings (still attached to mother) to compare this method to the direct hatchling stocking method
used in previous tests. Survival of hatchling stocked crayfish was poor previously. Minnow brood stock will come from last year's production and will be stocked at 200kg/ha directly into grow out ponds along with spawning structure. Last year, eggs on spawning mats were transferred to grow out ponds and survival rates were only 45% for golden shiners, and 36% for mummichogs. Although this egg - transfer method is labor intensive, and survival rates were relatively low, this method provides the benefit of a size graded product. This year utilizing the wild spawn method, grading at harvest will be necessary.
Impacts
(N/A)
Publications
- No publications reported this period
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Progress 01/01/01 to 12/31/01
Outputs
Crayfish research focused on broodstock management and pond production. Mature crayfish were held indoors during the winter at densities of 100 or 200 per tray and induced to spawn in mid-March under a photo phase of 15L and 20 degrees centigrade. The total hatchlings per female and the number of days to spawning, hatching and hatchling were compared. Hatchling crayfish crayfish from the winter study were stocked into ponds in mid-May at densities of 4, 6, and 8 per m2 to determine optimal density for production of food-size crayfish by October. To increase available surface area, safety netting was vertically hung within the water. The effects on mean final yield, weight, and survival were compared. Growth and production of crayfish stocked at 4 per m2 were compared between Delaware and South Carolina (Clemson University). To evaluate the effect of treatments on both control of nuisance aquatic weeds, particularly Najas sp., and crayfish production, additional ponds
were stocked at 4 per m2. The four treatments were control (no treatment), herbicide (Aquathol), and triploid grass carp stocked at 13 per ha or 26 per ha. Dissolved oxygen, temperature, pH, alkalinity and hardness were monitored regularly. Ponds were harvested from September 28-October 19 and data collected on total number and yield. Within a few weeks of photo phase and temperature adjustments, crayfish broodstock began to spawn, the eggs hatched within three weeks and the first crayfish were ready to stock into the ponds by mid-May. On average, the crayfish produce between 250 to 300 hatchlings per female (20-25 g). Increasing stocking density had no apparent effect on the mean number of hatchlings produced per female. While data are still being analyzed, preliminary pond results indicate that food market-size crawfish (20-29g) can be reached by October regardless of treatment. However, yields were poor because survival was low. Poor survival in both Delaware and South Carolina may
relate to poor water quality associated with low water alkalinity and high pH common in coastal states or the use of hatchlings for stocking, which may be susceptible to predation due to small size. Triploid grass carp appeared effective for weed control, but other herbicides were needed to control filamentous algae. The immediate impact of this study will be to modify management to exclude aquatic weeds using a combination of triploid grass carp and herbicides. Chemical treatments using either pulverized gypsum or calcium chloride will be utilized in future research to attempt to minimize high pH associated with the carbonate system. Research is needed to evaluate crayfish survival when using nursed juveniles versus hatchlings.
Impacts
(N/A)
Publications
- No publications reported this period
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