Finding lobsters: investigating a period of unusually low settlement of

Abstract

Context Spiny lobsters are critically affected by ocean current movements over their long journey from hatching to swimming post-larvae (puerulus). Methods Isolating three different larval stages of the Western rock lobster (Panulirus cygnus), we have applied three-dimensional larval-dispersal modelling techniques Aims To better understand a period of unusually low puerulus settlement in the late 2000s. Key results Model results showed that transport mechanisms assisting pueruli in reaching nearshore habitats may have been inhibited by a strengthening of the southward-flowing Leeuwin Current over the austral summer at the settlement stage. As a result, modelled pueruli were transported significantly less northward, in some cases southward, during and after the period of unusually low settlement. Hatching-stage trajectories also suggest increased dispersal off the coast during 2007 and 2008, transporting modelled larvae further offshore and possibly contributing to decreased recruits into the fishery. Conclusions Our study distinguishes the influence that ocean circulation patterns off Western Australia have on three different larval stages. Implications Larval dispersal modelling of pueruli, therefore, provides a possible explanation for the changes in puerulus settlement over the past two decades and future considerations.