Plankton-generated chaos in the modelled dynamics of haddock

This study illustrates the feasibility of regimes of chaotic dynamics in gadoid populations. A previously developed plankton model related fish larval survival to larval density and their copepod food supply. This model is extended to a full-population model, incorporating age structure, fishing and a stockrecruitment relation implicit in the plankton model. Parameterization is based upon the Georges’ Bank haddock. It is shown that regions of stability, aperiodic and chaotic-like dynamics exist as both the copepod food-supply and fishing rates are varied. The deterministic aperiodic dynamics are significantly complicated by additional stochastic elements. The implications are that chaotic dynamics are plausible and that analyses of output data on stock and recruitment can reveal relatively little; field and laboratory studies are needed to elucidate the underlying mechanisms. Traditional fitting of stock and recruitment relations may give an overly optimistic interpretation for fisheries managers.