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Experiments were conducted to investigate the growth and survival of Atlantic cod (Gadus morhua) larvae at high stocking densities. The larvae were reared in replicated 22 l tanks that were part of a 7500-l recirculating system. Survival through day 44 was 41.6%±1.9 (Mean±SE) at 300 larvae/l, which verifies that they can be reared at high densities. However, lower growth rates were experienced at 300 larvae/l than at 150 larvae/l as food appeared to be a limiting factor at the higher density. As a result, a second experiment was performed where cod larvae were reared at 50, 100, 200, and 300 larvae/l and food was not limiting. No differences were observed in survival, length or dry weight among the four treatments through 36 days post-hatch (dph). High stocking density also had no effect on specific growth rate, supporting the proposition that food was a limiting factor in the earlier trial. However, there is greater risk of mortality at high stocking densities as a result of deteriorating water quality. In the light of these findings, optimal stocking densities need to be reexamined under commercial culture conditions. |
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