The spatial ecology and resource selection of juvenile Lemon sharks (Negaprion brevirostris) in their primary nursery areas

Abstract

Shark nursery areas have been well studied but information on long-term, finescale movements within nurseries and between nursery areas is lacking. I tracked 47 neonate and juvenile lemon sharks (Negaprion brevirostris) at Bimini, Bahamas (25°44¢ North, 79°16¢ West) over three years (2003-2005) within two nursery areas. Using both manual and automated telemetry, I examined the movement patterns and habitat selection of juvenile sharks in the waters surrounding Bimini. Sharks consistently showed a high degree of site fidelity to their natal nursery areas and there was no detectable immigration or emigration between nurseries. Juvenile lemon sharks had small home ranges showing a high degree of reuse of certain areas and there was a positive relationship between home range size and distance from shore with body size. However, sharks from the nursery area that was known to be more environmentally stable showed a stronger relationship between body size and movement patterns. There were consistent differences in movement parameters when comparing similar aged sharks from the two nursery areas. Sharks from the more stable nursery had smaller home ranges were found closer to the mangrove shoreline when compared to the other nursery. Resource selection functions calculated during both the wet and dry seasons from 2003 to 2005 showed that shark locations were most correlated with increased prey biomass and decreased distance to the shoreline.Examining both movement patterns and habitat selection from two distinct nurseries over a long time period demonstrated that juvenile lemon sharks in Bimini utilized the habitat in their natal nursery seemingly to minimize predation risks while maximizing prey availability. Integrated approaches using a variety of long-term data to understand how juvenile sharks utilize nursery areas can significantly improve how essential fish habitat is defined and thereby strengthen conservation and management plans for these species.%%%%Ph.D., Environmental Science – Drexel University, 2007