Otolith biochronology reveals factors underlying dynamics in marine fish larvae

Abstract

Study of the dynamics in marine fish larvae is notoriously difficult, given their minute size in a vast, complex and variable marine environment. We demonstrate a novel statistical approach, utilizing a panel of 19 annual hatchdate distributions, to unravel environmental and potential harvesting effects on the spawning, hatching and survival processes for walleye pollock in the Gulf of Alaska. Hatchdates are determined from counting daily increments on otoliths of larvae. The hatchdate frequency distribution determined from sampling a population of larvae depends on factors influencing birth and death processes, i.e. spawning times and survival rates. Using a nonlinear and partly parametric statistical model, temperature, strong winds, and the age frequency of spawning adults were found to strongly influence hatchdates. Moreover, the interaction of both a climate regime shift and the 'Exxon Valdez' oil spill in 1989 suppressed pollock larval abundance in 1989, with geometrically diminishing after-effects lasting until around 1992. The novel method presented here provides a general framework for unlocking the rich information hidden in hatchdate data about environmental and/or intervention effects on dynamics in marine fishes. Head of a walleye pollock Theragra chalcogramma larva showing otoliths (small dark spots within green circle).

Interannual variation in the coastal distribution of a juvenile gadid in the northeast Pacific Ocean: The relevance of wind and effect on recruitment

“…The enduring relevance of wind to GOA walleye pollock recruitment is demonstrated by its explanation of significant variance over long time series (1961–1995) (Lee et al., 2009) and over our more recent study period. We focus here on the direct mechanisms of turbulent mixing and transport (Chan, Zhang, & Bailey, 2010), but recognize that possible wind effects on primary production and zooplankton are also relevant to walleye pollock recruitment. First, wind‐driven turbulence was associated with low survival of larvae (Bailey & Macklin, 1994).…”