Fish Wet Weight Research Articles

Dietary potassium requirement of juvenile chinook salmon

Juvenile chinook salmon ( Oncorhynchus tshawytscha) were fed casein-gelatin-based diets containing graded levels of potassium (0.01–1.20%) for 10 weeks to determine their dietary potassium requirement. The fish were able to sequester potassium directly from the water but they were unable to meet their requirement without additional dietary potassium. Signs of potassium deficiency included anorexia, convulsions, tetany, and death. Although the potassium levels were not replicated in this study, growth-response data suggest that a dietary potassium concentration of 0.8% should produce maximum growth. Whole body potassium saturation (3200 ppm wet fish weight) occurred at a dietary potassium concentration between 0.6 and 1.2% of the diet. Whole body sodium and magnesium were significantly elevated in fish fed potassium-deficient diets.

Uncoupling of Somatic and Otolith Growth Rates in Arctic Char (Salvelinus alpinus) as an Effect of Differences in Temperature Response

Experiments were conducted to study the effect of temperature, fish size, and somatic growth rate on mean daily otolith growth rate in Arctic char (Salvelinus alpinus) fry fed maximum rations. Long-term experiments at two different temperatures (8 and 13 °C) showed exponential relationships between otolith weight and fish wet weight, with the exponent of wet weight for the higher temperature being significantly higher than for the lower temperature. Increasing exponents at each sampling date indicated a difference in growth rates of the char and its otoliths. Short-term experiments showed that specific growth rate of the fry at six different temperatures was that of an optimum curve whereas the otolith growth rate continued to increase with increasing temperatures. A clear uncoupling between otolith growth rate and fish growth rate was demonstrated whereas temperature and fish wet weight modeled otolith growth rate reasonably well. It was found that otolith growth rate expressed as daily increase in weight gave a model with better fit and higher generality than growth rate along various radii. Several examples of uncoupling between fish growth rate and otolith growth rate in the literature were reexamined, and an explanation of otolith growth rate in terms of a metabolic expression was suggested.

Growth of Juvenile Barramundi (Lates calcarifer) on Dry Feeds

Abstract A suitable feeding program for juvenile barramundi (Lates calcarifer) includes rotifers (Brachionus plicatilis) and Artemia sp. nauplii for larvae, followed by dry starter and production feeds for juveniles. When 9–62-g barramundi were fed similar diets containing 9.3 and 12.9% fat, daily ration (2.4%) and growth (2.5%) were similar, but feed conversion ([dry weight of feed eaten]! [wet fish weight gained]: 0.93 and 1.01 for the low- and high-fat diets, respectively) was significantly lower (P < 0.05) with 12.9% fat. When 15–71-g barramundi were fed a series of six dry diets, the feed containing the most fish meal (60%) and fat (16.9%) produced the best feed conversion (0.89); however, a diet containing 20% fish meal and 13.4% fat gave practically the same results. When 74–150-g fish were fed one or two meals a day, daily growth was similar (1.7%), but daily ration (1.9% for one meal and 2.0% for two meals) and feed conversion (1.09 and 1.21, respectively) were significantly lower (P < 0.05) with...

Bioaccumulation of Kepone by spot (Leiostomus xanthurus): Importance of dietary accumulation and ingestion rate

The relative extent of dietary accumulation and bioconcentration of Kepone by spot (Leiostomus xanthurus) was quantitatively evaluated at food rations of 4, 8 or 20% of the average wet weight of fish. [ 14C]Kepone was utilized to determine bioconcentration and dietary accumulation separately, while [ 14C]Kepone-contaminated food (grass shrimp, Palaemonetes pugio) and unlabeled Kepone in water were used to determine simultaneously accumulation from both sources. Grass shrimp and spot were exposed to the same aqueous Kepone concentration (0.04 μg/l). A first-order pharmacokinetic equation was used to model Kepone accumulation kinetics during the 19-day uptake and 28-day clearance phases. A doubling of contaminated food ration caused a doubling of the whole-body Kepone concentration in spot. Spot fed an 8% ration of uncontaminated food and exposed to aqueous Kepone did not bioconcentrate significantly greater amounts of the pesticide than fish fed a 4% ration and exposed to the same aqueous concentration. When spot were exposed to contaminated water and food, Kepone contributions from each source were additive. Feeding rate, however, was very important in determining final Kepone body burdens in spot. The dietary source of Kepone represented approximately 9, 18 and 37% of the total body burden bioaccumulated by fish fed 4, 8 and 20% food rations, respectively, but assimilation efficiencies of Kepone from the food source were low. The laboratory results further suggest that dietary accumulation of Kepone by spot may play an important role in determining final Kepone concentrations in spot in the James River, Virginia.

Diet and Digestion Rates of Slimy Sculpin, Cottus cognatus, in an Alaskan Arctic Lake

In arctic Toolik Lake, slimy sculpin (Cottus cognatus) rely on a diet of larval chironomids (Diptera: Chironomidae). Dry weight of sculpin gut contents was not correlated with fish wet weight. This finding, combined with age and growth data, suggested that sculpin may be food limited in Toolik Lake, particularly as they approach reproductive size. Since three taxonomically distinct chironomids were digested at similar rates, one chironomid species was used as a marker to measure gut passage. Gut passage rate as a function of temperature fits an inverse quadratic model slightly better than a negative exponential model. Sculpins took approximately 1 d to digest food at typical summer temperatures (8–16 °C), but approximately 2 d at a typical winter temperature (4 °C). Since winter is three times longer than summer, winter feeding by sculpins may have greater impact on chironomid density than summer feeding. If sculpin are important in the diet of other Toolik Lake fishes, they may serve as an important trophic link between benthic and pelagic production.

POND CULTURE OF STRIPED BASS X WHITE BASS HYBRIDS

ABSTRACTFour 0.1‐hectare earthen ponds were stocked with two densities (10,000 and 15,000 fish/hectare) of female striped bass (Morone saxatilis) X male white bass (M. chrysops) hybrids on 30 October 1980. Mean weight at stocking was 20 g. Fish were fed ad libitum 2 or 3 times daily with a dry commercial salmon diet, and ponds were aerated mechanically during periods of low dissolved oxygen in warm months. Survival to harvest about 13 months later (22 November 1981) averaged 50% in the low density ponds and 93% in one high density pond. Total mortality of fish in the other high density replicate occurred in late August after an aerator failed. Survival until then was 92%. At harvest, mean weight of fish was 465 g in the low density ponds and 351 g in the high density pond. The average food conversion ratio of dry food to wet fish weight was 1.58:1. Standing crop at harvest averaged 2,312 kg/hectare in the low density ponds and was 4,886 kg/hectare in the high density pond. Growth was positively correlated with temperature, with the most rapid growth rates occurring during periods of high mean water temperatures. The study demonstrated that the hybrids can be grown to marketable sizes in ponds within 15–18 months of age at densities similar to those used in culture of channel catfish (Ictalurus punctatus). In view of their high market value, we believe that this hybrid has considerable potential for culture as a commercial food fish or perhaps for use in fee‐fishing ponds.

ESTUARINE CAGE CULTURE OF HYBRID STRIPED BASS

ABSTRACTNine 0.5‐m3 cages were stocked with three densities (100, 150 and 200/m3) of female striped bass X male white bass hybrids that averaged 44.6 g on 10 April 1981. Fish received a dry, floating commercial trout diet ad libitum 2 or 3 times daily. Survival to harvest (22 November 1981) for all densities averaged 95% with a mean weight per fish of 333 g. Growth of the hybrids was positively correlated with temperature, and greatest growth occurred during the period of highest water temperatures. Growth was negatively correlated with salinity. The mean coefficient of condition (K) was approximately 1.5 for the hybrids. No significant differences (P ≤ 0.05) were found in terms of growth in length, weight or condition of the hybrids, between densities. Biomass at harvest averaged 46.6 kg/m3 with a maximum of 62.2 kg/m3 for a high density replicate. A combined feed conversion ratio of dry feed to wet fish weight was 1.58:1. Results demonstrate the potential of the hybrid striped bass for use in aquaculture and indicate that the hybrids can be grown to commercial size within 18 months in small cages at densities as high as 200 fish/m3. Additional information was obtained for striped bass held in cages at a density of 50 fish/m3.

The accumulation and disposition of benz(a)acridine in the fathead minnow, Pimephales promelas.

The bioconcentration and metabolism of benz(a)acridine in fathead minnows (Pimephales promelas) was investigated using 14C-labelled benz(a)acridine. The rates of uptake, elimination, and metabolic transformation of benz(a)acridine were estimated in the fish. The equilibrium concentration factor [ratio of benz(a)acridine concentration in fish (wet weight) to benz(a)acridine concentration in water] was estimated at 106 +/- 17. The observed bioconcentration factor was about one tenth of that predicted by octanol-water partitioning models. Metabolic alteration was estimated to reduce the degree of bioconcentration 50 to 90% from the hypothetical case in which metabolic transformation did not occur. Benz(a)acridine metabolites attained concentrations in the fish considerably in excess of benz(a)acridine itself.

Diets of Pygoscelid Penguins at King George Island, Antarctica

The species composition and characteristics of prey consumed by sympatrically breeding Adélie, Chinstrap, and Gentoo penguins were determined by analysis of whole stomachs collected at Point Thomas, King George Island, South Shetland Islands, Antarctica (62°10′S, 58°30′W) during the 1977-1978 breeding season. All three penguins consumed primarily one species of euphausiid, Euphausia superba, although Gentoo Penguins ate significantly more fish, Pleurogramma antarcticum, than either Adélie or Chinstrap penguins. E. crystallorophias, and pelagic and benthic species of amphipods were minor components of the pygoscelid diet. The penguins differed in euphausiid size and in the ratios of male, female, and adolescent euphausiids eaten. These differences were consistent over the entire reproductive cycle. In addition, the species differed in the wet weight of fish consumed by Gentoo Penguins, and in the length of euphausiids consumed by Adélie Penguins. We suggest that these differences in diets are due, in part, to geographical and temporal differences in feeding areas and habitats.

An experimental study on the effects of grazing by parrotfishes and role of refuges in benthic community structure

In an experimental study on the effect of parrotfish (probably Scarus taeniurus) grazing on the structure of benthic reef communities, fishes in densities of 0.6 to 1.5 parrotfish per m2 or 9 to 17 g wet weight of fish per m2 of feeding surface were found to have an optimum effect, resulting in the greatest benthic species richness and biomass on 2-dimensional surfaces. The presence of refuges (3-dimensional habitats), however, has a greater impact on bemthic community structure (number of species and biomass) than does just the density of parrotfish in such an experimental system. Coral recruitment is enhanced by the presence of refuges and, like coralline algae, is more successful under increased grazing pressure. These optimum densities of parrotfishes relate well to observed field densities where, in a collection from a Hawaiian patch reef, there were 1.1 fish or 10.8 g wet weight of parrotfish per square meter of collection area. The success of coralline algae and corals under high grazing pressure may have important consequences for the stability and structure of modern coral reefs.

Uptake and loss of dissolved zinc by the stickleback Gasterosteus aculeatus L.

Uptake and loss by sticklebacks of both stable zinc and 65Zn in hard and soft water have been studied for periods of upto400 h. In calcium‐free water, the 65Zn uptake curve is approximately asymptotic over a period of 24 h, while in hard water internal 65Zn levels are dropping at 24 h. Over 5 h, however, fish in hard tapwater absorb about 3.5 times more 65Zn than those in calcium‐free water. There is a positive linear relationship between log 65Zn uptake and log wet weight of fish. Whole‐body concentration factors (c.f.) at 16 h reach a maximum of 12.2 (mean=2.9), highest concentrations of 65Zn being found in the gills (mean c.f.=5.l) and lowest concentrations in the gonads (mean c.f.=0.8). Over longer periods (400 h), internal stable zinc levels offish exposed to 1 and 4 p.p.m. Zn2+ remain little higher (max 28 %) than controls. 65Zn efflux into zinc‐free water falls to zero after 5 h, more zinc (78 %) being lost after uptake in tapwater than in calcium‐free water (56 %).

Influence of bovine growth hormone on growth rate, appetite, and food conversion of yearling coho salmon (Oncorhynchus kisutch) fed two diets of different composition.

Paired groups of yearling coho salmon at 10 °C and on a natural photoperiod were fed twice daily either Oregon moist pellets (OMP) or a diet with poultry offal (PO) as the main protein source. The fish were fed either 0.8% body weight per day (dry weight of food (g)/wet weight of fish (g)) or to satiation. Coho in one of the groups for each diet–ration combination received, by intramuscular injection, 10 μg (0.0092 IU) of bovine growth hormone (bGH) per gram body weight one time per week for 56 days. Those in the other group were not treated.Administration of bGH significantly enhanced growth and improved food and protein conversion. Ration level altered the effect of bGH on food and protein conversion as did diet formulation at satiation. The voluntary food intake of bGH-treated fish fed OMP was higher but not significantly different from that of the controls. Diet formulation differences did not significantly affect the growth rate of either bGH-treated or untreated coho at each ration level. Irrespective of the diet–ration combination, bGH administration lead to a significant decline in condition factor.At 56 days, bGH-treated fish had a significantly lower percentage of muscle protein and a significantly higher percentage of muscle water than untreated fish. At present, the use of bGH as a growth promoter for coho salmon is not economical.

Effects of Dietary Carbohydrate-to-Lipid Ratios on Growth and Body Composition of Fingerling Channel Catfish

Abstract Eight isonitrogenous, isocaloric semipurified diets were formulated with varying levels of digestible carbohydrate (white dextrin) and lipid (salmon-oil — corn-oil mixture) to determine the effect of each as energy sources for fingerling channel catfish (Ictalurus punctatus). After an initial 2-wk conditioning period, the experimental diets were fed in triplicate to groups of channel catfish fingerlings weighing 201 ±2 g per 110-liter flow-through aquarium. The diets were fed at a rate of 3% of the total wet weight of fish per day, divided into three equal feedings and adjusted weekly for 9 weeks. At the end of the feeding period no significant differences were observed in the growth rates, feed conversion, protein deposition, or energy retention of fish fed diets containing carbohydrate-to-lipid ratios (CHO:L) of 0.45 to 4.5. The observed effects of dietary CHO:L ratio on liver histology and on liver and carcass composition had no adverse effects on growth rates or feed conversion. These data in...

An Energy Budget for a Rainbow Trout Farm

An industrial energy-budget for a Rainbow Trout farm shows that 93% of the energy costs of production are incurred in feeding the fish, seven-tenths of which is due to fishnieal incorporated in the food pellets. Only one-tenth of the input energy is converted into fish, but the energy subsidy of the farming operation compares favourably with conventional fishing and is 423 input megajoules per kg of output fish protein (55 MJ per kg wet-weight of fish landed). However, if the Trout could be fed on a diet composed of suitable vegetable protein, this performance would be improved to an overall conversion efficiency of one-third, and a subsidy of about 160 MJ per kg. A smaller but similar improvement could result if the Peruvian anchovy fishery regained its former production level.As these improved energy-costs are comparable with those of crops of potatoes, and with those of bread and milk production, a 2-men Rainbow Trout farm yielding 25 tonnes per year on one hectare would become an attractive protein-producing enterprise in localities where the necessary water-supply is available.

Dehydroabietic Acid Accumulation by Rainbow Trout ( Salmo Gairdneri) Exposed to Kraft Mill Effluent

Rainbow trout ( Salmo gairdneri) were examined for the presence of dehydroabietie acid after exposure to kraft mill effluent. Levels of 2 to 10 μg/g dehydroabietie acid on a whole fish wet weight basis were found in fish exposed to 3 to 18% effluent for 48 to 144 hours. Less than 1 μg/g dehydroabietie acid was found in control fish which had been acclimated in Nipigon Bay water for two weeks and no residue was detected in an unexposed fish. It is concluded that fish exposed to kraft mill effluent accumulate dehydroabietie acid to a level which is likely to result in sublethal toxic effects.

Influence of body size and food ration on the energy budget of rainbow trout Salmo gairdneri Richardson

Three size classes (3 g, 200 g, 1–3 kg) of rainbow trout, Salmo gairdneri Richardson, were each fed five rations ranging from zero to a ‘maximum’ ration and the relationships among body size, food ration, metabolism and growth examined. Water temperature was constant at 11–4°C. The gross growth efficiency in wet weight, K, increased asymptotically with increasing ration but decreased with increasing body size. Changes in fat and moisture content of the body, however, were such that Kin terms of energy utilization was independent of body size when the fish were feeding at the same level. This result was not apparent when wet weight values only were considered and use of a constant to convert wet weight offish to calorific values can lead to errors in interpretation of results. Assimilation efficiency averaged 71 ‐7 % over all feeding groups and was independent of body size and food ration. Total metabolic expenditure, however, increased with increasing body size and feeding level, but at any given feeding level a similar proportion of the energy of the assimilated ration was used for metabolism. At a single feeding level, therefore, the percentage utilization of energy in each category of the energy budget remained similar over all body sizes. Such a result can only be expected under laboratory conditions but it provides a base‐line for comparison with the performance of other more complicated systems.

B-group vitamin deficiency in cultured herring

A mortality of cultured herring caused by vitamin B deficiency was successfully treated with yeast extract (‘Marmite’) with added vitamin B 6. The supplementation to the diet comprised approximately Riboflavin 0.21 mg, Niacin 2.33 mg and Pyridoxine (B 6) 0.6 mg, all per kg wet-weight of fish per day.