MEPS 576:69-87 (2017)  -  DOI: https://doi.org/10.3354/meps12233

ABSTRACT: The Australasian red (southern) rock lobster, Jasus edwardsii (Hutton, 1875), has a pelagic larval duration (PLD) of 18–20 mo, which may be the longest PLD of any crustacean. This PLD compares with 8–12 mo for 2 other species of rock lobster that occupy overlapping latitudinal ranges in Australia and New Zealand, Sagmariasus verreauxi and Panulirus cygnus. In this article, we examine 2 hypotheses using a Lagrangian individual-based bio-physical model (IBBM). The first hypothesis is that the long PLD of J. edwardsii occurs simply because it is a cool-water species, and its larvae require longer to develop in the cool ocean temperatures around southern Australia and New Zealand. The second hypothesis is that the long PLD of J. edwardsii evolved because some feature in the ocean circulation around Australia and New Zealand led to selection for longer larval duration. We find that potential settlement around Australia shows strong annual cycles with higher settlement in winter, probably caused by stronger onshore Ekman flow in winter. For larvae hatching in spring, those that can delay metamorphosis for 20–21 mo after hatching can take advantage of this higher potential settlement and thereby increase recruitment. Although we cannot exclude temperature as a factor in the evolution of long PLD, we suggest that the long PLD of J. edwardsii may well be an evolutionary response to these strong annual cycles of oceanic circulation that impact potential settlement.

KEY WORDS: Evolution · Larval duration · Numerical simulation · Rock lobster