Individual haddock, Melanogrammus aeglefinus (L.) were maintained at different feeding levels in an aquarium from November until the completion of spawning. The mean duration of spawning was 33.2 days (range 19-59) during which an average of 16.6 (range 10-25) batches of eggs were produced. The size and dry weight of the eggs declined during the spawning period. Egg production and feeding level were correlated positively. There was some suggestion that when female haddock received low rations (< 5 kcal day-') a lower proportion spawned, and the dry weights of the eggs were lower compared with females on high rations (> 13 kcal day-'). The relation between daily growth in wet weight, g, and daily surplus energy intake, kcal, was: G=(0.295E)-0.328. When food energy is restricted, haddock appear to achieve a balance between somatic growth and reproduction. I. INTRODUCTIONIt is often found that the fecundities of individual female fish of the same size and age, drawn from the same population, differ considerably. The cause of this variability is not yet understood but it seems that fecundity might be influenced by factors such as the availability of space or food, and may be part of a density dependent population control mechanism.There are few published results of experiments to determine if there is a relationship between food intake and fecundity. Scott (1962), showed that when groups of rainbow trout, Salmo gairdneri Richardson, were kept on different ration levels, shortage of food reduced both the percentage of females spawning, and their fecundity. Scott did not detect significant differences between the wet weights of the intra-ovarian eggs of fish on different rations. Bagenal(1969), working with batches of brown trout, Salmo frutta L. also found that a reduction in diet lowered the percentage of spawning females and their fecundity. However, Bagenal found the dry weights of the intraovarian eggs of the low ration fish to be significantly higher than those of the high ration fish. Wootten (1973) kept pairs of female three-spined sticklebacks, Gasterosfeus aculeatus L. at three different ration levels. He found the percentage of females spawning, and the number of eggs produced, increased with ration size but he did not detect a relationship between food intake and the dry weight of spawned eggs. The experiments described in this paper differ from those referred to in that data were obtained on the influence of feeding level on individual females, rather than on groups of fish.

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