James W. Meade

Allowable Ammonia for Fish Culture

Abstract A review of the published literature on effects of ammonia on fish indicates that un-ionized ammonia alone is probably not the cause of gill hyperplasia, indicative of, or previously attributed to, chronic ammonia poisoning. The maximum safe concentration of un-ionized ammonia is unknown, but in many cases it is not close to the 0.0125 mg/L value commonly accepted by fish culturists.

Effects of Rearing Density on Growth, Survival, and Fin Condition of Atlantic Salmon

Abstract Parr of Atlantic salmon (Salmo salar) were reared to final densities of 0.53-4.29 lb/ft2 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.

Changes in phototaxis during early development of walleye

Abstract Phototaxis of walleyes Stizostedion vitreum vitreum was examined during the first 11 weeks of larva and juvenile development. Fish were subjected to six light intensities ranging from 2 to 34 lux, plus 7,800 lux as an extreme. The number of fish positioned in each light intensity was used to determine the phototactic response. Larvae and juveniles 1 to 8 weeks old (9 to 32 mm total length) were attracted to the highest light intensity (7,800 lux), and juveniles older than 8 weeks (32 to 40 mm long) aggregated at the lowest intensities (2 and 4 lux). The change from positive to negative phototaxis was more closely related to fish size than to age. Received July 16, 1982 Accepted February 8, 1983

Review of the intensive culture of walleye fry

Abstract 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/m3 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.

Growth, Survival, and Food Conversion of Atlantic Salmon Reared at Four Different Densities with Common Water Quality

Abstract Our objective was to determine the maximum effective rearing density for Atlantic salmon (Salmo salar) at 17.5°C, a temperature typically used in hatcheries to accelerate growth. We reared 5.8-g (mean weight) parr for 80 d to final rearing densities of 14–55 kg/m2 (rearing unit bottom area) or 80–310 kg/m3 (rearing unit volume). Weight gain was slightly depressed in fish at a final rearing density of 26 kg/m2 (146 kg/m3), but mortality, food conversion, and gain in length were not affected. At densities greater than 26 kg/m2, fish growth was slower and food conversion was higher, but mortality was unaffected. Atlantic salmon may be reared at 17.5°C to densities of at least 14 kg/m2 (80 kg/m3) without adverse effects on growth and health, but final rearing densities should not exceed 26 kg/m2.

The Effects of Ionic Strength on Un-ionized Ammonia Concentration

Abstract Ionic strength affects the ionization of ammonia and the resulting un-ionized ammonia (NH3) concentration. The error introduced by failure to account for this effect can be substantial in marine or brackish water. We present a simple method for correcting the calculation of the NH3 fraction in an ammonia solution for ionic strength.

Acceptability of Fairy Shrimp (Streptocephalus seali) as a Diet for Larval Fish

Abstract 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.

Effect of Feeding Rate and Gas Supersaturation on Survival and Growth of Lake Trout

Abstract Fingerling lake trout (Salvelinus namaycush) were reared for 35 d in water with total dissolved gas pressures of 46, 78, 108, or 159 mm Hg above ambient conditions (▵P). Within each gas pressure treatment, daily feeding rations were (1) 1.7% of the total weight offish in the heaviest of three replicates, (2) 1.7% of the weight of fish in each individual tank, or (3) 0.9% of the weight in each tank (underfeeding). Signs of gas bubble trauma were first observed as hemorrhagic spots on the eyes of some fish reared at ▵P = 46, and external evidence of trauma increased as ▵P increased. All fish sampled at ▵P = 159 showed signs of gas bubble disease; the most common were eye hemorrhage and bubble formation inside the mouth. Mortality was 11% or less among fish reared at gas levels up to ▵P = 108. Mortality was as high as 55% at ▵P = 159, but did not differ among feeding treatments. Net weight gain by fish was low at ▵P = 159 because of both high mortality and slow growth. Growth was slowest for underfe...

Effect of temperature on production of tiger muskellunge in intensive culture

Abstract Tiger muskellunge ( Esox masquinony × E. lucius ) juveniles were reared at constant temperatures in the temperature range 14–28°C. For fish 3–4 cm long, growth, production and feed conversion efficiency were greatest at 20–22°C. Survival was reduced and unaccountable mortality (cannibalism index) was greatest at 24°C. Growth per unit of temperature was about equal over the range 16–22°C. For fish 12–13 cm long, feed conversion efficiency and mean individual growth were greatest at 23°C; growth per unit of temperature was nearly equal over the range 20–24°C.

A bioassay for production capacity assessment

Abstract Given sufficient oxygen, fish production can be limited by a multiplicity of factors. Accurate determination of production capacity requires something other than an estimate of the biomass at which ambient un-ionized ammonia will reach a recommended, non-site-specific, maximum safe concentration. A chronic (1- to 2-month) bioassay can be used to determine the point at which metabolite buildup reduces growth by some predetermined proportion, or causes unacceptable tissue damage. The bioassay is conducted as a series reuse, single-pass system, in which incoming water to each rearing unit is aerated to 90% dissolved oxygen saturation. The assessment of production capacity is based on the relation between cumulative oxygen consumption and growth reduction.