A Management Oriented Model of an Abalone Fishery Whose Substocks are Subject to Pulse Fishing

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Abstract
I present a model of the exploitation of a fishery whose substocks are subject to periodic fishing during which most fish over the legal minimum length IR are removed. Managers should find the model useful because the period P between successive fishing visits to each substock is an index to exploitation rate, which is usually more easily measured and controlled than the fishing mortality F. Each management choice of IR and closure period P affects both long-term biomass yield and egg production. Using a portion of the South Australian abalone (Haliotis sp.) fishery as a case study, I conclude that increases in either control variable can be used to increase significantly egg production while causing only a marginal decrease in yield. Longer closures also offer potential economic benefits. Depending on alternative hypotheses regarding the recruitment process, controls presently in use may threaten survival of the stock by reducing fertile egg production to critical levels.