Multiple daily feedings with automatic feeders improve growth and feed conversion rates of channel catfish
No abstract available.
Progressive Fish-Culturist↗
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Atlantic salmon embryos and fry: Effects of various incubation and rearing methods on hatchery survival and growth
Significantly heavier fry of Atlantic salmon (Salmo salar) and greatly reduced mortality apparently resulted from the use of matrix substrates during egg incubation and alevin development. Salmon fry produced by this method fed readily and did not have the constricted yolk sacs that commonly occur when conventional rearing methods are used.
Progressive Fish-Culturist↗
PCBs and DDE in commercial fish feeds
Three commercial fish feeds were analyzed for PCBs and p,p' DDE and were reported in dry weight concentrations. In various sizes of Oregon Moist Pellets, concentrations of PCBs ranged from less than 0.10 to 0.30 I?g/g and those of p,p' DDE from less than 0.01 to 0.47 I?g/g. In Silver Cup, concentrations of PCBs were 0.06 to 0.07 I?g/g, and p,p' DDE, 0.01 to 0.06 I?g/g. Nauplii of brine shrimp (Artemia salina) contained 0.14 I?g/g PCB and 0.03 I?g/g p,p' DDE.
Progressive Fish-Culturist↗
Survival of one- and two-year-old monosex grass carp in small ponds
Limited information has become available on the survival of monosex (female) grass carp (Ctenopharyngodon idella) reared in earthen ponds. Monosex fish produced in 1975 (Stanley 1976) were reared 27 months in earthen ponds at the Fish Farming Experimental Station, Stuttgart, Arkansas. Periodic transfers of these fish to different ponds afforded the opportunity to obtain survival information. Thomas and Carter (1977) reported first-year survival percentages of 22.9 to 60.2% (average 34%) for fry stocked in six 0.1-ha ponds in June and July 1975 in a test of different stocking densities and pond conditions. Overall, of 31,887 3-mm fry stocked. 10,035 survived to reach the large fingerling stage (80-250 mm) when they were removed from the ponds in April 1976.
Progressive Fish-Culturist↗
Residues of formaldehyde undetected in fish exposed to formalin
No abstract available.
Progressive Fish-Culturist↗
Effects of diet on survival and growth of the Atlantic silverside
Effects of two live and seven prepared diets on the survival and growth of postlarval and juvenile Atlantic silversides ( Menidia menidia ) were determined. Two experiments were conducted, one with 23-day-old postlarvae and one with 57-day-old juveniles. In both experiments, growth rate and survival were greatest on the live diet of brine shrimp ( Artemia salina ) nauplii. Survival was lowest on a prepared diet originally designed for freshwater fish species. Growth was similarly low for all lots fed prepared diets . A commercial flake food was the best of the prepared diets tested. Response to the diet was more sensitively reflected in growth than in survival . Younger fish showed a greater and more immediate growth response to diets than did juveniles. Postlarval fish that were fed brine shrimp gained 36.6 mg (from an initial body wet weight of 9.3 mg), whereas those fed the flake diet gained 4.5 mg. The reduced growth and survival of fish fed the artificial diets cannot be attributed to a single nutritional deficiency.
Progressive Fish-Culturist↗
Inhibition of nitrite-induced toxicity in channel catfish by calcium chloride and sodium chloride
Environmental chloride has been shown to inhibit methemoglobin formation in fish, thereby offering a protective effect against nitrite toxicity. Channel catfish (Ictalurus punctatus) were simultaneously exposed to various environmental nitrite and chloride levels (as either CaCl 2 or NaCl) in dechlorinated tap water (40 mg/L total hardness, 47 mg/L alkalinity, 4 mg/L chloride, pH = 6.9-7.1, and temperature 21-24°C). Methemoglobin levels in fish simultaneously exposed to 2.5 mg/L nitrite and up to 30 mg/L chloride as either CaCl 2 or NaCl were similar but significantly lower than in unprotected fish. Exposure to 10 mg/L nitrite and 60 mg/L chloride resulted in methemoglobin levels similar to those of the controls; most unprotected fish died. Fish exposed to 10 mg/L nitrite had significantly lower methemoglobin levels when protected with 15.0 mg/L chloride as CaCl 2 than with NaCl. Fish exposed to nitrite in the presence of 60 mg/L chloride (as either CaCl 2 or NaCl) had similar 24-h LC50 values that were significantly elevated above those obtained in the absence of chloride. Calcium had little effect on tolerance to nitrite toxicity in channel catfish in contrast to its large effect reported in steelhead trout (Salmo gairdneri).
Progressive Fish-Culturist↗
Handling as a factor in mortality of trout with or without furunculosis
Mortalities of brook trout ( Salvelinus fontinalis ), brown trout ( Salmo trutta ), and rainbow trout ( Salmo gairdneri ) in 1978 and 1979 were significantly higher in clinically diseased than in subclinically diseased or healthy fish in both years. Mortalities in diseased fish within 24 h after sampling were not statistically different from those in specific-pathogen-free controls; however, the crowding offish lots for stocking resulted in significantly higher mortalities in furunculosis -infected brown trout in 1979. Crowding and handling for stocking thus caused higher mortality in diseased fish than just sampling. Healthy trout were able to tolerate more handling stress.
Progressive Fish-Culturist↗
Modified fyke net for the capture and retention of salmon smolts in large rivers
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Progressive Fish-Culturist↗
Development and survival of embryos of lake herring at different constant oxygen concentrations and temperatures
Eggs of lake herring (Coregonus artedii) were incubated in a continuous-flow system at four constant water temperatures (2-8°C) and five dissolved oxygen (DO) concentrations (1-12 mg/L). In comparison with incubation time at 12 mg/L DO, time to median hatch was significantly longer (P<0.05) at 2 mg/L at 6°C (no hatch at 1 mg/L), at 3 mg/L or less at 4°C, and at 4 mg/L or less at 2°C. The time between hatching of the first and last eggs varied inversely with temperature. Mean total lengths of newly hatched fry were significantly shortened (P < 0.05) at 1 and 2 mg/L DO. At 6 and 8°C, percent survival through hatching was greater than at 2 and 4°C at DO of 4 mg/L or more, but fell to zero at 1 mg/L. The percentage of normal fry produced decreased noticeably below 4 mg/L DO. The optimum temperature for highest percentage survival of normal fry decreased directly with the level of dissolved oxygen. The temperatures at which the highest percentages of normal fry hatched from eggs incubated at DO concentrations of 4 or 8, 2, and 1 mg/L, were 6, 4, and 2°C, respectively-indicating a decreasing DO demand by embryos incubated at the lower temperatures. Our findings supported a previously published hypothesis that DO concentrations below 4 mg/L can be adverse to survival and development of coregonid embryos in nature.
Progressive Fish-Culturist↗
Electroshocking in tropical insular streams
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Progressive Fish-Culturist↗
Depletion sampling in stream ecosystems: assumptions and techniques
Reliable fish and invertebrate population estimates depend on meeting the assumptions of the methods used for organism capture and data analysis. A review of several population estimation studies has indicated that assumptions of the removal method for population estimation are often violated. This paper outlines (1) procedures to assist in meeting the removal method assumptions (2) an economical procedure to obtain reliable invertebrate population estimates by the removal method and (3) a computer program (CAPTURE) designed to test the adequacy of study design and to analyze capture data where variable probability of removal exists.
Progressive Fish-Culturist↗
Riboflavin requirement of fingerling rainbow trout
Fingerling rainbow trout (Salmo gairdneri) were fed purified diets containing graded levels (0, 3, 6, 12, 18, 24, and 54 mg/kg) of supplemental riboflavin for 20 weeks. The cellular riboflavin supply of the fingerlings was estimated on the basis of the activity of the FAD‐dependent enzyme, erythrocyte glutathione reductase (EGR). The dietary riboflavin level that produced the fastest growth, an efficient feed: gain ratio, and normal values for the EGR activity coefficient was about 3 mg of supplemental riboflavin per kilogram of diet.
Progressive Fish-Culturist↗
Growth and survival of Atlantic salmon fed various starter diets
Growth and survival were compared for groups of first‐feeding fry of Atlantic salmon (Salmo salar) fed various commercially available and experimental starter diets. In two separate 8‐ to 9‐week studies, survival was highest (more than 90%) in fish fed a semimoist closed‐formula commercial diet (BioDiet). In one study, fish grew fastest on BioDiet, whereas in the second study they grew fastest on a liver‐supplemented diet. Some diets were not eaten by the fish, resulting in little growth and less than 40% survival.
Progressive Fish-Culturist↗
Culture, feeding, and growth of alewives hatched in the laboratory
Alewives (Alosa pseudoharengus) were reared from the egg to the early juvenile life stage. The major obstacle to rearing alewives from the egg — providing an acceptable food that facilitates first feeding — was overcome by presenting a mixture of wild Zooplankton to the larvae twice daily, beginning on the day of hatching. Initial feeding by larvae held at 20°C was observed 2 days after hatching, when the yolk was nearly absorbed. Comparison of stomach contents and the wild Zooplankton composition suggested that the diet of larvae during the first 15 days of life shifted with changes in the availability of food but remained within a fairly narrow range of food sizes. Larvae hatched at a mean total length of 3.8 mm and grew at an average rate of 0.62 mm per day, to a mean of 35.5 mm after 50 days. At 50 days most fish had transformed into juveniles. The daily instantaneous mortality coefficient was 0.018. About half of the mortality occurred during the first 13 days after hatching.
Progressive Fish-Culturist↗
Dairy-processing wastes as a replacement protein source in diets of rainbow trout
Dairy‐processing wastes, not previously used in domestic animal and fish feeds, were evaluated as a replacement protein source in the diet of rainbow trout (Salmo gairdneri). Dairy residue replaced 10% dried whey without reducing growth or feed efficiency, and feed costs were reduced. Growth and feeding efficiency were somewhat reduced when dairy‐processing wastes in the diet were 15 or 20%.
Progressive Fish-Culturist↗