Dynamics of northwestern hawaiian island spiny and slipper lobsters: Spatial heterogeneity and drivers of somatic growth

Sustainable exploitation of valuable species requires accurate estimates of somatic growth and a fundamental understanding of why growth varies spatially.  The Northwestern Hawaiian Islands (NWHI) supported a fishery for Hawaiian spiny lobsters and scaly slipper lobsters until it closed in 2000 because of increasing uncertainty in population models.  This uncertainty stemmed from the disregard of spatial heterogeneity and assumption of synchronous dynamics, regardless of species and location.  To examine NWHI location and species-specific lobster dynamics, a tag/recapture program was conducted from 2002 to 2008.  Results demonstrated that growth rates varied significantly between species, sexes, and locations.  Spiny lobster growth was slower at Necker Island than at Maro Reef while slipper lobster displayed the opposite pattern.  Neither density nor temperature could account for the spatial differences in growth.  Stable isotopes and proximate composition are currently being analyzed to examine the role of diet (prey availability and diversity) in location-specific growth rates.  Recognition of and accounting for the variability in an important life history trait of both lobster species will result in more accurate stock assessments while identification of the drivers of the spatial variability will result in a better understanding of lobster dynamics and the NWHI ecosystem.