Catch variation among traps in an American lobster (Homarus americanus) trawl

Most population estimates of American lobster (Homarus americanus) rely on catch data from the commercial fishery. Therefore, it is important to understand the factors that affect the catchability of lobsters and their behavioural response to traps. Commercial fishermen claim that if lobster traps are fished in linked sets, or trawls, that the trap that is adjacent to the surface buoy generally has a lower catch, presumably because of increased trap movement due to more direct exposure to wind influence. For four consecutive weeks during May and June 2007, we recorded the catch of 944 trap hauls to determine if there are differences in lobster catch rates among the four linked traps on a line, and if these differences are related to wind speed. In addition, on the second and fourth week of the study, every second trawl received a gear modification designed to decrease the effect of the wind on catch rates. The study found that there were no significant differences in catch rate among the four traps in a trawl. Although wind and catch rate were expected to be somehow related, no meaningful linear relationship between these variables was found. These results indicate that common assumptions about the effects of gear design on lobster catch rate may not be supported when examined systematically, and that relationships between wind, temperature and catch rate are not always evident.