Publication Abstract

The growth and death of fish larvae

D.H. Cushing and J.W. Horwood

The Stock and Recruitment Relationship remains the most difficult problem in fisheries research. As data have accumulated, the pattern of the relationship has been more fully described, but its nature remains obscure. The reason for this is that part of the life history remains to some degree unexplored, namely larval life; this may be because estimates of larval mortality are expensive in ship's time. In contrast, there are many estimates of mortality on the nursery ground (see, for example, Pearcy, 1962; Beverton and lies, 1992a,b). Sissenwine et al. (1984) showed that, for many stocks, there was no relationship between numbers of larvae and subsequent recruitment. This might imply that we should examine the older larvae which are not always well sampled.

Another way of approaching the problem is explored here: to utilize the large quantity of experimental material on larval growth and physiology. An essential part of this approach is to make use of the maximal growth rate (at temperature) when the larvae are fed ad libitum. We have made considerable use of the work of Laurence (1982) on the larvae of the Georges' Bank haddock (Melanogrammus aeglefinus L.).

As developed, the model provides a quantitative basis for two complementary components of the match/mismatch hypothesis in that the model can be seen as simulating a matched condition as the larval fish grow alongside their food and variations of food are environmentally driven, or that the initial level of food reflects the initial match/mismatch with the larvae, but then subsequently sampling the two. An unexpected result of the model is the relatively high density-dependent mortality; if it really exists outside the imaginary world of the model, then it must play an important part in the regulation of fish populations.

Reference:

D.H. Cushing and J.W. Horwood, 1994. The growth and death of fish larvae. Journal of Plankton Research, 16(3): 291-300.