Movements and activity levels of juvenile American lobsters Homarus americanus in nature quantified using ultrasonic telemetry

In this study we expand the size range of American lobsters Homarus americanus tracked in nature by quantifying for the first time the movements and activity levels of juveniles using ultrasonic telemetry. Ten individuals 20-47 mm carapace length (approximate to 1-4 yr old) were tracked for 21 d in August 2010 on a shallow nursery ground in southwest Bay of Fundy, Canada, using the Vemco VRAP tracking system. Many of our results are consistent with the literature on juvenile lobster ecology, which is largely based on laboratory experiments and short-term field observations. For example, the juvenile lobsters were significantly more active at night (71% of all activity) than during the day (29%), and they behaved as central place foragers, displaying movements that greatly limited their dispersal from the nursery habitat. However, the average amount of time individuals spent outside of shelter (approximate to 2.2-32.7% of each day, or 0.5-7.8 h) and the average size of their daily home ranges (approximate to 27.4-111.6 m(2)) did not increase with increasing body size, as was predicted based upon the literature. We also report for the first time evidence of a tidal (12.4 h) cycle of activity in juvenile lobsters, which was displayed more consistently at night than during the day. This study advances our understanding of the behavioural ecology of juvenile lobster on nursery grounds, and it suggests that these young individuals spend more time outside of shelters than might currently be concluded from the literature.