Mass Production of Atlantic Cod Juveniles Gadus morhua in a Norwegian Saltwater Pond

Øiestad, Victor; Kvenseth, Per Gunnar; Folkvord, Arild

doi:10.1577/1548-8659(1985)114<590:mpoacj>2.0.co;2

Cited by 62 publications

(12 citation statements)

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“…From the present results, it is concluded that under controlled conditions, food availability appeared to be the most important experimental variable determining the rate of cannibalism. This observation supports several field and laboratory studies on other species (Hunt & Carbine, 1951;Kipling & Frost, 1970;Goldspink & Goodwin, 1979;Mann, 1982;Davis, 1985;Oiestad, Kvenseth & Folkvord, 1985;Loadman et al, 1986). However, it was demonstrated that the rate of cannibalism is also affected by shelter and sibling density.…”

Section: Conclusion and Applied Implicationssupporting

confidence: 85%

Observations on intraspecific aggression and coeval sibling cannibalism by larval and juvenile Claias gariepinus (Clariidae: Pisces) under controlled conditions

1988

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Factors influencing the rate of sibling cannibalism in larval and juvenile sharptooth catfish, Clarias gariepinus, were investigated under controlled conditions. The circum‐oral barbels were found to be more important for the capture of prey than the eyes. Cannibalism starts at a mean total length of 8 mm, three and a half days after the start of feeding and ceases to be of significance at approximately 80 mm, 47 days after the start of feeding. Two distinct types of cannibalism were evident, both of which are primary functions of the relationships between predator mouth width and prey head width. Type I cannibalism, which occurs in the length range from 8 to 45 mm, is characterized by the prey being caught tail‐first and swallowed up to the head, which is subsequently bitten off and discarded. Type II cannibalism on the other hand is characterized by the prey being swallowed head first and whole. During this phase, the larger fish in the population have a mouth width exceeding the head width of the smaller fishes. Type I induced mortality was higher than that induced by Type II. It was concluded that the rate of cannibalism is a consequence of intraspecific aggressive behaviour, the level of which is determined by experimental conditions. Sibling cannibalism was found to be positively density dependent, significantly suppressed by shelter and negatively correkated to food availability. Food availability was shown to have the greatest effect on the behaviour of the fish and hence on the rate of cannibalism. Cannibals grow at a faster rate than non–cannibals. It was concluded that the high rate of Type 1 cannibalism enhances the natural differential growth rate of the fish which leads to Type I1 cannibalism. There is a strong positive correlation between predator and prey size. Electivity analysis showed that the larvae and the juveniles appear to select for larger prey items. The applied implications of these observations are discussed. It was concluded that sibling cannibalism is a highly specialized predation strategy which, under a given set of environmentally induced limiting factors, acts as a density dependent population regulatory mechanism.

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Section: Conclusion and Applied Implicationssupporting

confidence: 85%

Observations on intraspecific aggression and coeval sibling cannibalism by larval and juvenile Claias gariepinus (Clariidae: Pisces) under controlled conditions

1988

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“…About 90 years later, these experiments were continued, first in the same basins at Flødevigen and later in a 60 000‐m 3 seawater enclosure at Austevoll, western Norway. Here, the scientists finally managed to produce large numbers (75 000) of viable cod in 1983 ( Øiestad et al . 1985 ), making the start of a new ‘cod period’ involving both stock enhancement and net pen rearing ( Dahl et al .…”

Section: Production Of Juveniles For Releasementioning

confidence: 99%

The enhancement of cod stocks

et al. 2000

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Atlantic cod have been a primary target for marine stock enhancement since the 1880s. In the early part of this period, hatched larvae were released in Norway, the USA and Canada. The last larval releases were conducted in Norway in 1971, and a century of cod larvae releases were halted without any clear evidence of benefit. Since the early 1980s, the focus has been on production of larger, more viable juvenile cod. Emphasis has been given to the design of tag–release programmes involving large‐scale releases and ecosystem analysis in selected ecosystems. Most of this research has been carried out in Norway, where more than one million tagged juvenile cod have been released. Smaller stocking experiments have also been performed in Denmark, Sweden, the Faroe Islands and the USA. This paper reviews the major findings from these programmes. We include summaries and evaluations of rearing techniques for juvenile cod, methods of tagging and recapture, experimental fishing, migration, mortality and growth rates in the different habitats, genetic analysis, and ecosystem studies that have tried to describe the variation in the cod carrying capacity of selected release areas. Despite relatively large variation in environmental conditions, in cod production and in fishing mortality along the Norwegian coast, results indicate that, under the conditions experienced during the 1980s and 1990s, releases of juvenile cod did not significantly increase cod production and catches. The biological limitations and future prospects of Atlantic cod stock enhancement are addressed.

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“…Cod is becoming increasingly important in Norwegian aquaculture. The breakthrough in hatching and raising of cod larvae was in 1983 (Oiestad et al, 1985). The larval length is positively correlated to the egg size (Solemdal, 1970;Knutsen & Tilseth, 1985).…”

Section: Introductionmentioning

confidence: 99%

The spawning activity of cod, Gadus morhua L.

Kjesbu

1989

Journal of Fish Biology

276

223

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Aspects of the reproduction of reared cod, Gadusmorhua L., with special emphasis on the females, were studied under laboratory conditions. The fecundity and condition factor were 2.5 and 1.5 times. respectively, that of wild cod. A total of 18 spawning females were kept in separate tanks/ chambers, each with one or two males. Seven of the 18 females were classified as stressed, based upon behaviour, irregular spawning intervals and low fertilization rates of the eggs. The reared cod were found to spawn 17-19 batches. The number of eggs liberated in each batch normally followed a smooth, dome-shaped curve with time. The fertilization rate was normally 100%. Egg size decreased from first to last batch and the egg dry weight decreased by about 2&30%. The reared cod showed the same egg diameter to dry weight relation as wild cod. Egg diameter of first batch and maternal fish length were significantly positively correlated. The mean spawning interval for the female and the mean water temperature during its spawning were negativelycorrelated. Therearedcodspawnedin both the night and theday forabout 5C60days.

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Mass Production of Atlantic Cod Juveniles Gadus morhua in a Norwegian Saltwater Pond

Cited by 62 publications

References 0 publications

Observations on intraspecific aggression and coeval sibling cannibalism by larval and juvenile Claias gariepinus (Clariidae: Pisces) under controlled conditions

Observations on intraspecific aggression and coeval sibling cannibalism by larval and juvenile Claias gariepinus (Clariidae: Pisces) under controlled conditions

The enhancement of cod stocks

The spawning activity of cod, Gadus morhua L.

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