Meeting Abstract

1.6  Sunday, Jan. 4  Defensive Strategies of Caribbean Spiny Lobsters: Effects of Lobster and Predator Group Size LAVALLI, K.L.*; HERRNKIND, W.F.; Boston University, Boston, MA; Florida State University, Tallahassee, FL klavalli@bu.edu

Migrating queues of Caribbean spiny lobsters Panulirus argus can potentially suffer attacks during daylight by variable numbers of piscine predators, particularly triggerfish that are found on reefs and open terrain that lobsters use. When attacked, queued lobsters assemble into outward facing radial groups, remain coherent, and defend against attack by parrying with ther antennae. The studies presented here summarize both field tethering trials and mesocosm free-ranging trials. In 1-hour long field tethering trials, solitary lobsters were subdued 44% of the time while lobster groups of five suffered only minor bites; triggerfish present numbered from 4-23. In a series of experiments in large seawater enclosures, we pitted 1, 3, 5, 10 or 20 free moving lobsters against 2, or 5 gray triggerfish, Balistes capriscus, all of which had previously killed lobsters. We hypothesized that larger fish numbers would be more effective in subduing the prey independent of lobster group size, but that lobsters in larger groups would benefit by a higher per capita survival rate, as compared to smaller groups. We found that per capita mortality declined with lobster group size, but remained the same statistically whether there were two or five triggerfish, due to interactions between the triggerfish that reduced the effectiveness of attacks. Additional survival advantages arise with increasing lobster group size, such that individuals may potentially have to expend less energy in defensive behaviors. These results suggest that the communal defense of spiny lobsters is primarily a selfish action of individuals, rather than true cooperation.