Underwater video surveillance of American lobsters (Homarus americanus) to understand saturation levels in lobster traps

摘要

Estimates of abundance of the American lobster (Homarus americanus) are often based on catch data and are, therefore, potentially influenced by trap saturation (a plateau in catch levels over time). Although aspects of trap saturation in standard lobster traps have been investigated, less is known about the process of saturation in vent-less traps that are currently used for stock assessments. Our goal was to investigate the possible mechanisms leading to trap saturation in ventless and standard lobster traps, by using in situ time-lapse video surveillance. The dynamics of saturation in standard traps were difficult to assess in this study because entry and escape rates were similar throughout each trial, under the conditions tested; therefore, few lobsters accumulated in the standard traps. In contrast, few lobsters escaped from ventless traps used under the same conditions. Lobsters consistently accumulated in ventless traps during the first day of fishing, and then the catch plateaued on the second day as fewer lobsters entered those traps. On the second day of soaking, catch apparently reached a dynamic equilibrium in which the rate of entry declined to the point where it was equal to the rate of escape.