Using an oceanographic model to investigate the mystery of the missing puerulus

[摘要] Dynamics of ocean boundary currents and associated shelfprocesses can influence onshore and offshore water transport, criticallyimpacting marine organisms that release long-lived pelagic larvae into thewater column. The western rock lobster, Panulirus cygnus , endemic to Western Australia, isthe basis of Australia's most valuable wild-caught commercial fishery. Afterhatching, western rock lobster larvae (phyllosoma) spend up to 11 months inoffshore waters before ocean currents and their ability to swim transportsthem back to the coast. The abundance of western rock lobster post-larvae(puerulus) provides a puerulus index used by fishery managers as apredictor of lobster abundance 3–4 years later. This index has historicallybeen positively correlated with the strength of the Leeuwin Current. In 2008and 2009, the Leeuwin Current was strong, yet a settlement failure occurredthroughout the fishery, prompting management changes and a rethinking ofenvironmental factors associated with their settlement. Thus, understandingfactors that may have been responsible for the settlement failure isessential for fishery management. Oceanographic parameters likely toinfluence puerulus settlement were derived for 17 years to investigatecorrelations. Analysis indicated that puerulus settlement at adjacentmonitoring sites has similar oceanographic forcing, with kinetic energy inthe offshore and the strength of the Leeuwin Current being key factors.Settlement failure years were synonymous with “hiatus” conditions in thesoutheast Indian Ocean and periods of sustained cooler water presentoffshore. Post-2009, there has been an unusual but consistent increase inthe Leeuwin Current during the early summer months, with a matching decreasein the Capes Current, which may explain an observed settlement timingmismatch compared to historical data. Our study has revealed that aculmination of these conditions likely led to the recruitment failure andsubsequent changes in puerulus settlement patterns.

[学科分类] 大气科学