An industry based mark recapture program to provide stock assessment inputs for the Western Rock Lobster Fishery following introduction of quota management
Department of Primary Industries and Regional Development (DPIRD) WA
The recent change to quota management for the Western Rock Lobster fishery has resulted in significant changes in fishing behaviour which has affected the ability to use the long standing empirical catch rate indices that have been a major component of the assessment of lobster stocks (e.g. catch rates of legal, undersize and breeding lobsters). A recent FRDC funded study (2009/019) examined the possibility of using alternative data sources unbiased by effort to monitor biomass levels and exploitation rates using change-in-ratio techniques. The project concluded that: 1. The current data sources available to the fishery had too many unknowns including size and sex specific timing of growth and movement to enable the assessment of exploitation rates using these techniques. 2. A robust tag-recapture study using multiple release periods across different fishing seasons could generate independent assessments of legal biomass and exploitation rates providing an additional baseline level to improve the interpretation of post quota catch rate indices. A comprehensive tag-recapture study would also provide increased resolution of the movement dynamics of lobsters, especially the rate of migration between management zones. Such information is considered vital by industry in their discussions of the potential benefits of voluntarily reducing quotas to generate increased localised catch rates.
1. Determine spatially specific exploitation rates and legal biomass levels
2. Increase precision of estimates for movement rates between management zones
3. Improve understanding of the variability of growth throughout the range of the fishery