A Length-Structured Model of the Western Rock Lobster Fishery of Western Australia
By monitoring the settlement of the 9 to 11 month old first post-larval (puerulus) stage of the rock lobsters on coastal reefs, estimates are made of the level of recruitment expected to enter the fishery four years later. These predictions are further improved by introducing into the predictive models the abundance of 4 year old juvenile rock lobsters caught in rock lobster pots.
A model of the fishery, which uses these predictions, has been developed to examine alternative management strategies. The model is a discrete, deterministic simulation model. The state of the system at each time step is represented by the number of rock lobsters within each of a number of batches. Each batch represents rock lobsters of similar carapace length, within the same depth category and fishing region, and with the same characteristics of moult stage, migratory status, and reproductive state. Growth of rock lobsters, through moulting, has a major impact on catchability and hence the fishery, especially since moulting is relatively synchronous. The resulting changes in catchability and its effect on recruitment to the exploited (legal-sized) population are essential elements of the model. An additional feature of the fishery is the more vulnerable, migratory phase of the life history of the rock lobsters. Subsequent to their migration, the rock lobsters have a reduced catchability, and are distributed in deeper off-shore waters.
KeywordsFishing Effort Carapace Length Depth Zone Fishing Season Moult Stage
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