Environmental influences on daily commercial catch rates of South Australia's southern rock lobster (Jasus edwardsii)

The extent to which catchability of southern rock lobster (Jasus edwardsii) due to short-term environmental factors, rather than abundance, may be affecting legal-size catch rates from the South Australian Southern Zone rock lobster fishery was examined. Multivariate weighted linear regression was applied to daily aggregated commercial catch rates using several environmental covariates in addition to year and month. Model pruning via backward selection identified the following variables as being significantly related to catch rate: wave height and period, lagged wave height, bottom temperature, moon phase, and a spatial block index. These variables explained 7% of the total variance in log-transformed daily catch rates and another 84% was explained by month and year. A negative relationship was found between catch rate and each of bottom temperature and same-day wave height, while the relationships between catch rate and days prior to full moon, and average wave height over the past 3 days were positive.