Portable zooplankton sampling apparatus for hatchery ponds
No abstract available.
Progressive Fish-Culturist↗
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Survey of striped bass hatchery management in the southeastern United States
No abstract available.
Progressive Fish-Culturist↗
Feeding habits of larval and fingerling striped bass and zooplankton dynamics in fertilized rearing ponds
Fertilization of freshwater striped bass rearing ponds with cottonseed meal or chicken manure and chicken litter in combination with liquid inorganic fertilizers and zooplankton inoculation were evaluated in 10 0.04‐ha (0.10 acre) ponds over a 4‐week period. Chlorophyll α levels and pH were significantly higher, and alkalinity and Secchi disk visibility significantly lower, in ponds fertilized with cottonseed meal. Ponds fertilized with cottonseed meal produced more crustacean zooplankton than did ponds fertilized with chicken manure and chicken litter. Fish survival and production averaged 63% and 49 kg/ha (43.7 lbs/acre) in ponds fertilized with cottonseed meal and 46% and 26 kg/ha (23.3 lbs/acre) in ponds fertilized with chicken manure and chicken litter. Adult copepods and small cladocerans were the dominant food items found in the diets of the fish.
Progressive Fish-Culturist↗
Movement of underyearling walleyes in response to odor and visual cues
Underyearling walleyes, allowed to move freely in a Y‐shaped chamber into which various substances were added to one arm or another, were attracted to sodium chloride, sucrose, glutathione, vitamin B 12 , betaine, arginine, Daphnia slurries, some fish slurries, washings from live Daphnia and Artemia, and some commercial fish foods. They avoided cysteine, glycine, glycine‐betaine, Artemia slurries, some fish slurries, and fish mucus; and showed little reaction to valeric and caproic acid, and some commercial fish foods. Tests of visual response, in which beakers containing live food organisms were placed in the arms of the chamber, indicated that walleyes respond strongly to the movement of food organisms. Walleyes usually surrounded the beakers containing live food organisms and repeatedly struck the glass. They were attracted more strongly to Artemia than to Daphnia. Results indicate that odor plays an important role in movement of walleyes to food and that there is a potential for attracting intensively cultured walleyes to man‐made diets with odorants.
Progressive Fish-Culturist↗
Growth of tiger muskellunge fed different amounts of protein at three water temperatures
Growth rates of tiger muskellunge (muskellunge Esox masquinongy ♀ x northern pike E. lucius ♂) fed diets containing 35, 45, or 55% crude protein for 5 weeks at 17, 20, or 23°C were compared. Fish fed diets containing 45 or 55% protein grew faster at all temperatures than those fed 35% protein. Growth of tiger muskellunge fed a diet containing either 45 or 55% protein did not increase significantly at optimum growth temperatures (20 or 23°C). At 17°C, below the optimum temperature range, growth did increase when the percentage of protein in the diet was increased.
Progressive Fish-Culturist↗
Computer program calculation of gas supersaturation in water
A short computer program, written in BASIC for the Apple IIe or IBM PC computer, efficiently performs all the calculations required to determine gas pressure and percent saturation values for water. Input for the program is limited to empirical determinations of barometric pressure, water temperature, differential dissolved gas pressures, dissolved oxygen, and salinity. An optional routine is included for obtaining a printed report of input data and results. The program can be easily modified to run on most other microcomputers that use BASIC programming language.
Progressive Fish-Culturist↗
Effects of supplemental feeding on growth, production, and feeding habits of striped bass in ponds
Production of fingerling striped bass (Morone saxatilis) was increased by feeding fish every hour. In a 42‐d study, survival and production averaged 52.8% and 167.9 kg/hectare (150 lb/acre) in ponds to which feed was delivered hourly and 34.9% and 110.6 kg/hectare (99 lb/acre) in ponds to which feed was delivered only twice a day. Types of food items selected by larvae and fingerlings in treatment and control groups were similar. Cladocerans, adult copepods, and chironomid larvae were the predominant food organisms eaten. Particles of supplemental prepared feed were found in 92% of the fish sampled from treatment ponds and in 89% of those from control ponds. The addition of supplemental feed appeared to enhance rather than to replace the natural diet.
Progressive Fish-Culturist↗
Design and application of vacuum degassers
Designs of vacuum degassers, which alleviate gas supersaturation in hatchery waters, have progressed greatly in recent years. Basic rules of thumb now exist by which the feasibility of vacuum degassers can be determined for particular facilities, and by which complete systems can be designed and built to meet local needs. These rules are presented in the form of step‐by‐step procedures and guidelines directed to practicing hatchery operators. The flexibility of vacuum degasser designs is illustrated for large‐, medium‐, and small‐volume systems.
Progressive Fish-Culturist↗
An integrated system for treating nitrogen supersaturated water
Groundwater is commonly supersaturated with nitrogen and must be treated before it is used for culturing fish–especially sensitive species such as lake trout (Salvelinus namaycush) and Atlantic salmon (Salmo salar). We treated water with an integrated system that passed water through a packed column aerator, then through a vacuum degasser, and finally through another packed column aerator (installed as a backup system). Packed‐column aeration prior to vacuum degassing provided increased efficiency because only a small amount of vacuum was required to remove the remaining excess nitrogen, and oxygen levels were not affected by the vacuum degasser. In well water passed through packed columns, nitrogen gas was reduced from 131 to 105% of saturation and oxygen was increased from 23 to 86% of saturation. With a vacuum pressure of 3 in Hg, the degasser further reduced the nitrogen gas from 105 to 99% of saturation, and oxygen saturation remained near 86%. The integrated system provided water in which all gases were near saturation. No effects of gas supersaturation have been observed among the 18 species of cold‐water, coolwater, or warmwater fish that have been cultured in this water.
Progressive Fish-Culturist↗
Potential for nitrosamine formation in seven fishery chemicals
In recent years, nitrosamines have been reported as possible causes of cancer, mutations, or birth defects. Inasmuch as these compounds may be formed by the interaction of certain amines with nitrite in the aquatic environment, we evaluated seven fishery chemicals for their potential to form nitrosamines: the experimental fish toxicant digeranylethanolamine (GD‐174); the four therapeutants Terramycin, erythromycin, Hyamine 1622, and Hyamine 3500; and the two tracer dyes rhodamine B and rhodamine WT. The results indicate that the controlled use of the seven fishery chemicals in natural environments will not lead to the formation of nitrosamines.
Progressive Fish-Culturist↗
Diet related anemia in channel catfish: Case history and laboratory induction
Severe anemia among fingerling to adult channel catfish (Ictalurus punctatus) and blue catfish (Ictalurus furcatus) was reported by 39 of 166 catfish farmers in west‐central Alabama in 1983. The hematocrits of moribund fish in ponds ranged from 0 to 5%. Weekly mortalities as high as 5% in individual ponds were recorded. The gills of affected fish were pale or white, the kidneys and spleen were pink, and the liver was gray to tan. In 27 of 29 ponds where the type or brand of feed was changed, deaths ceased within 1 week. However, the disease was noted among fish regardless of the major brand or type of feed used. Under laboratory conditions, the feeding of diets from affected farms induced anemia in fry, but not in subadults. The cause of the anemia was associated with an unidentified factor or factors in diets.
Progressive Fish-Culturist↗
Review of the intensive culture of walleye fry
Efficient intensive culture of larval walleyes (Stizostedion vitreum) may soon be realized due to results of research on larval development, culture environment, preferred food organisms, and feeding techniques. Larval behavior and morphology (developmental state) can be used as indicators for appropriate handling and feeding techniques. Certain environmental conditions such as a rearing unit color that contrasts with food organisms, water temperatures of 18‐22°C, uniform lighting, and a stocking density of no more than 35,000 fish/m 3 reportedly contribute to increased growth and survival. Successful culture requires that suitable food such as cladocerans, copepods, and brine shrimp be continuously available at a high density (0.1 organism/mL). Cannibalism among walleye larvae has not been prevented but has been reduced through the use of suitable fish and food densities.
Progressive Fish-Culturist↗
Increased walleye egg hatch and larval survival after protease treatment of eggs
Various techniques for eliminating the clumping of newly spawned walleye eggs (Stizostedion vitreum) were evaluated by measuring hatch, growth, and survival. Percent hatch was highest (83%) in egg groups water hardened in 0.01% protease solution. Other water‐hardening techniques tested were: (1) continuous stirring; (2) 250 mg/L tannic acid solution; and (3) bentonite clay suspension. Low hatching percentages for eggs continuously stirred or treated with bentonite were attributed to fungus. Fungus was minimal on eggs treated with protease or tannic acid. Fish hatched from each egg treatment group were intensively cultured for 21 d in one of four rearing environments: (1) well water; (2) well water receiving 1% sea salt for the initial 3 d; (3) well water receiving a 6‐mL daily addition of antifoam emulsion for the initial 9 d; or (4) well water receiving both the 1% sea salt and antifoam treatments. There was slightly higher survival in larval fish hatched from eggs treated with protease or tannic acid and reared in well water containing 1% sea salt. We observed no differences in average fish length among the test groups.
Progressive Fish-Culturist↗
Feed conversion indices: Controversy or convention?
Various methods of calculating and reporting the efficiency of food use in fish husbandry are examined. The effects of moisture content of feed and fish flesh, supplemental feeds augmented with natural feed items, differences in energy content due to feed formulations, and the usefulness of the various feed efficiency indices to aquaculturists and fish husbandry researchers are discussed.
Progressive Fish-Culturist↗
Acceptability of fairy shrimp (Streptocephalus seali) as a diet for larval fish
Fairy shrimp (Streptocephalus seali), brine shrimp (Artemia salina), and a pelleted food were fed to tiger muskellunge (the hybrid of muskellunge, Esox masquinongy, and northern pike, E. lucius) to compare acceptability and nutritional value of the diets. Fairy shrimp, although less nutritious than the pelleted diet, provided a suitable freshwater alternative to brine shrimp.
Progressive Fish-Culturist↗
Methods of controlling growth of steelhead
Steelhead (Salmo gairdneri) held at 15°C and fully fed from demand feeders grow larger than desired by the time of their normal release into streams. The effect of limited feed intake on growth, body composition, and potential for migration to the sea was investigated. Dilution of feed by 10‐40% with sodium bentonite was not effective in reducing growth; the fish used the nutrients more efficiently and their growth was nearly equal to that of controls. Hand feeding of a decreased ration reduced growth rate, but about a 50% reduction in feed was required to effect the desired reduction in growth rate. Fish were able to compensate for fasting periods of short duration and significant growth reduction did not occur until the fasting periods were 4 d or longer. Alternate feeding and fasting periods of equal lengths produced the desired growth rate reduction. Estimated potential for emigration by these anadromous fish was not reduced by fasting periods as long as 28 d.
Progressive Fish-Culturist↗
Effects of rearing density on growth, survival, and fin condition of Atlantic salmon
Parr of Atlantic salmon (Salmo salar) were reared to final densities of 0.53‐4.29 lb/ft 2 of rearing container bottom area under conditions of constant temperature, water quality, and diet. Growth and survival were not affected by density. After 171 d, the condition of pectoral and dorsal fins had not changed from that initially recorded and did not differ among treatments. We conclude that rearing density alone does not affect growth, survival, or fin condition of Atlantic salmon reared at densities likely to occur at production hatcheries.
Progressive Fish-Culturist↗