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At least 73 records · Page 4Linked to original sources
USGS1987

Growth and survival of fingerling lake trout reared at four densities

Fingerling lake trout (Salvelinus namaycush) were reared at density indexes (fish density, in pounds per cubic foot, divided by fish length in inches) of 0.25, 0.50, 1.0, and 2.0. Final lengths, weights, condition factors, and mortality rates did not differ among the treatments. We conclude that fingerling lake trout may be successfully reared at a density index of at least 2.0 if water requirements for respiration and waste dilution are met. Our results indicate that fish length may be less important in determining allowable fish densities than was previously suspected.

Progressive Fish-Culturist↗
USGS1987

Studies on vertical transmission of Aeromonas salmonicida

In four attempts to effect vertical transmission of Aeromonas salmonicida, the cause of furunculosis, transmission did not occur. Progeny of both naturally infected and artificially infected brood stock of rainbow trout (Salmo gairdneri) and brook trout (Salvelinus fontinalis) did not develop furunculosis during a 10‐12‐month posthatching observation period.

Progressive Fish-Culturist↗
USGS1987

Safe pre-release disease treatment with formalin for fall chinook salmon smolts

Standard formalin treatment (167 μL/L for 1 h) applied to presmolts and smolts of fall chinook salmon ( Oncorhynchus tshawytscha) 80, 62, 52, 38, 24, and 10 d prior to seawater exposure did not affect freshwater growth or survival during a 20-d period in seawater. There was no consistent effect of treatment on gill Na + , K + -ATPase activity.

Progressive Fish-Culturist↗
USGS1988

Lack of dietary effects on the timing of smoltification in Atlantic salmon

Six commercially available diets varying in lipid, protein, water, ash, and carbohydrate contents were fed to Atlantic salmon ( Salmo salar ) for 2 years to determine if diet affected smoltification. Each month, from March to September of the second year, sampled fish were exposed to 33‰ seawater for 24 h to determine smolt readiness, defined as the ability to maintain water and salt balance in a seawater challenge. Regardless of diet, Atlantic salmon were able to regulate plasma sodium and chloride ions (smoltify) only during early May. It is unlikely that hatchery managers could effectively use high‐energy diets to control the time of smoltification in Atlantic salmon.

Progressive Fish-Culturist↗
USGS1988

Effect of dietary propylene glycol on growth, survival, histology, and carcass composition of Atlantic salmon

Atlantic salmon ( Salmo salar ) were fed diets containing 0, 5, 10, 15, or 25% propylene glycol (a compound used to maintain high dietary moisture levels) to determine beneficial or detrimental effects. Weight gain and feed conversion efficiency were better for fish fed the diets containing 5–15% propylene glycol than in those fed diets containing either 0 (control) or 25% propylene glycol. No histological aberrations were noted in fish from any treatment. These results indicate that propylene glycol can effectively be used to elevate moisture level in diets for Atlantic salmon and may enhance diet palatability by improving texture, flavor, or moisture content.

Progressive Fish-Culturist↗
USGS1988

Effects of cage encrustation by the bryozoan Plumatella casmiana on production of channel catfish

Fouling by the bryozoan Plumatella casmiana was observed on cages in which channel catfish ( Ictalurus punctatus ) were being reared for a strain evaluation study at the Fish Farming Experimental Station, Stuttgart, Arkansas. Channel catfish growth was inversely correlated with encrustation. The extent of the encrustation was inversely related to pond water depth and to the distance of the cage from the pond water supply inlet. Fish growth was reduced in the cages most heavily fouled, which were in the shallowest water and nearest the water inflow.

Progressive Fish-Culturist↗
USGS1988

Residues of benzocaine in rainbow trout, largemouth bass, and fish meal

Residues of the anesthetic benzocaine in muscle tissue of rainbow trout ( Salmo gairdneri ) and largemouth bass ( Micropterus salmoides ) were determined after exposure of the fish to 50 mg benzocaine/L for 15 min and withdrawal times of 0–24 h. The mean concentration of benzocaine residues in fish sampled immediately after exposure was 14.0 μg/g in rainbow trout and 10.6 μg/g in largemouth bass. Residues were below the control value after 8 h of withdrawal in largemouth bass and near the control value after 4 h of withdrawal in rainbow trout. Although residues of benzocaine were high in fish immediately after exposure, the concentration declined rapidly when the fish were held in flowing fresh water. Fish meal prepared from Pacific salmon ( Oncorhynchus sp.) that had been anesthetized with benzocaine or trieaine (MS‐222) contained residues of 45.1 μg benzocaine/g or 47.7 μg trieaine/g.

Progressive Fish-Culturist↗
USGS1988

Interrelations of oxygen concentrations, fish density, and performance of Atlantic salmon in an ozonated water reuse system

In a 16‐week study, we stocked duplicate groups of 3.3‐g Atlantic salmon ( Salmo salar ) in 25‐fish increments (25 to 100 fish/6.5‐L jar) and in 250‐fish increments (250 to 1,000 fish/144‐L trough), in an ozonated, 100% closed water reuse system, to examine changes in fish performance in response to rearing at different densities and loadings within the system. Maximum rearing density (kg!m 3 ) reached 219 in jars and 125 in troughs. Maximum loading (ratio of fish weight to water flow) reached 0.45 kg/(L/min) in jars, and 0.79 kg/(L/min) in troughs. A rise in water temperature from 18.9 to 21°C during weeks 11 and 12 was accompanied by a drop in effluent dissolved oxygen (DO), followed by an increase in mortality and a decline in biweekly weight gain. Later declines in water temperature to 18.4°C, and reductions in biomass, were followed by reduced mortality and increased weight gain. In both jars and troughs, mortality increased when dissolved oxygen dropped to 6.5 mg/L or lower, water temperature reached 19.6°C, and biomass reached 50–75 kg/m 3 , or 0.1–0.2 kg/(L/min) flow. Changes in DO, weight gain, and mortality per unit change in density (kg biomass/m 3 ), were lower in jars than in troughs, but changes in these responses in terms of flow (kg/[L/min]) were lower in troughs. Results of this study suggest that, for optimum growth, survival, and feed conversion of Atlantic salmon in an ozonated water reuse system, dissolved oxygen should be at least 6.5 mg/L. Maintenance of an acceptable level of oxygen should minimize detrimental effects offish density or elevated water temperature.

Progressive Fish-Culturist↗
USGS1988

Control of nuisance populations of crayfish with traps and toxicants

Crayfish have long been a nuisance in fishrearing ponds at fish hatcheries. The rusty crayfish ( Orconectes rusticus ) has displaced endemic species and caused serious declines of aquatic plants in some ponds and lakes in the midwestern USA. We attempted to evaluate the effect of intensive trapping on a crayfish population and to identify a selective chemical control agent and evaluate its effectiveness under field conditions. A crayfish population in a small pond was suppressed but not eliminated by trapping; adults were effectively harvested but efficiency diminished sharply as the population declined. Of 19 chemicals tested as possible control agents for crayfish, a synthetic pyrethroid (Baythroid) was by far the most toxic; 25 μg/L produced a complete kill of crayfish in the pond and was also the most selective for crayfish in laboratory tests.

Progressive Fish-Culturist↗
USGS1988

Daily variation in feed consumption by channel catfish

Daily feed consumption by 0.09‐lb channel catfish ( Ictalurus punctatus ) stocked at 50 and 75 lb offish per 0.25‐acre pond, and by 0.57‐lb channel catfish stocked at 100 and 200 lb offish per 0.25‐acre pond, was measured for 157 d. Demand feeders were used to determine feed consumption. Feed consumption routinely varied, on successive days, an average of 61 and 31%, for the 0.57‐lb fish stocked at the higher and lower rates, respectively, and 58% for both stocking densities of the 0.09‐lb fish.

Progressive Fish-Culturist↗
USGS1988

Motor-operated valve for fish culturists

Many fish culture systems require motoroperated valves to regulate water flow. The expense of commercial units can be prohibitive but, by using inexpensive components and a little assembly time, a manual valve can be motorized for a fraction of the cost.

Progressive Fish-Culturist↗
USGS1988

Optimum protease exposure time for removing adhesiveness of walleye eggs

Increasing concentrations of protease solution reduce the treatment time required for removal of the adhesive layer surrounding eggs of the walleye ( Stizostedion vitreum ). When concentrations were increased from 0.01 to 0.1%, treatment time decreased from 30 to 5 min; however, treatment with a 1.0% solution for more than 1 min resulted in 100% egg mortality.

Progressive Fish-Culturist↗
USGS1988

High calcium concentration in water increases mortality of salmon and trout eggs

Several experiments were conducted to investigate the effect of water chemistry during water hardening on survival of eggs of Atlantic salmon ( Salmo salar ), rainbow trout ( Salmo gairdneri ), and. brook trout (Salvelinus fontinalis). Results of these experiments showed that survival was very low when eggs were exposed to very hard water containing high concentrations of calcium (approximately 520 mg/L or greater) during the first few hours of water hardening. Such high concentrations of calcium were associated with gypsum (calcium sulfate) in the water supply. In contrast, survival of eggs significantly increased when they were initially water‐hardened (1–3 h) in softer water (Ca concentrations, 34–64 mg/L). Incubation of eggs in high‐calcium water after the initial water‐hardening period did not significantly affect survival. Results of another experiment on water hardening of rainbow trout eggs showed a significant increase in survival when eggs were initially water‐hardened in either low‐gypsum water or in high‐gypsum water softened by ion exchange to markedly reduce the calcium; but not the sulfate, content.

Progressive Fish-Culturist↗
USGS1988

Water reuse systems: A review of the principal components

Principal components of water reuse systems include ammonia removal, disease control, temperature control, aeration, and particulate filtration. Effective ammonia removal techniques include air stripping, ion exchange, and biofiltration. Selection of a particular technique largely depends on site-specific requirements (e.g., space, existing water quality, and fish densities). Disease control, although often overlooked, is a major problem in reuse systems. Pathogens can be controlled most effectively with ultraviolet radiation, ozone, or chlorine. Simple and inexpensive methods are available to increase oxygen concentration and eliminate gas supersaturation, these include commercial aerators, air injectors, and packed columns. Temperature control is a major advantage of reuse systems, but the equipment required can be expensive, particularly if water temperature must be rigidly controlled and ambient air temperature fluctuates. Filtration can be readily accomplished with a hydrocyclone or sand filter that increases overall system efficiency. Based on criteria of adaptability, efficiency, and reasonable cost, we recommend components for a small water reuse system.

Progressive Fish-Culturist↗
USGS1988

Prototype water reuse system

A small-scale water reuse system (150 L/min) was developed to create an environment for observing fish under a variety of temperature regimes. Key concerns of disease control, water quality, temperature control, and efficiency and case of operation were addressed. Northern squawfish ( Ptychocheilus oregonensis ) were held at loading densities ranging from 0.11 to 0.97 kg/L per minute and at temperatures from 10 to 20°C for 6 months with no disease problems or degradation ofwater quality in the system. The system required little maintenance during 2 years of operation.

Progressive Fish-Culturist↗