EFFECT OF AGE, INJURY, AND PREDATOR ODORS ON SETTLEMENT AND SHELTER SELECTION BY LOBSTER HOMARUS-AMERICANUS POSTLARVAE

The effects of endogenous and exogenous factors on settlement and habitat selection behaviours of Homarus americanus postlarvae were studied under controlled conditions in the laboratory. Light level within shelters, a primary cue used in microhabitat selection by settling lobsters, was manipulated to create 4 microhabitats of different quality (= level of illumination). Preliminary experiments indicated that, when offered separately, low light intensity shelters induced more postlarvae to settle and seek a shelter than microhabitats presenting higher light levels. Choice experiments (all types of shelter offered simultaneously) were designed to test whether (1) delayed settlement, (2) injuries at metamorphosis (loss of one or both chelipeds), and (3) metabolites of the fish predator Tautogolabrus adspersus, influenced settlement rate and selectivity of competent lobsters. Postlarvae settled more quickly and sheltered less selectively as they aged. Similarly, postlarvae released in seawater previously conditioned by T. adspersus tended to exhibit a higher settlement rate and lower degree of selectivity than when tested in control (unconditioned) water. Lobsters which had lost both chelipeds at metamorphosis exhibited a reduced settlement rate compared to normal postlarvae or postlarvae with a single chela. Severely injured postlarvae also appeared less selective than normal or slightly injured postlarvae. Implications of these results for further habitat choice experiments are discussed.