Fatty acids in eggs of anchoveta Engraulis ringens during two contrasting winter spawning seasons

摘要

ABSTRACT: We assessed the fatty acid (FA) composition of anchoveta eggs collected from the plankton along with female anchoveta reproductive traits and environmental conditions during peak winter spawning in 2005 and 2007. Environmental conditions differed markedly between years at 3 continental shelf stations off Talcahuano, Chile, with a warmer, fresher water column in 2005 and a colder, saltier one in 2007. We confirmed differences in sea surface temperature, measured both at the coastal egg collection stations and using satellite images over a broader area, caused by south winds that induced coastal upwelling in 2007. Winter 2005 was largely dominated by typical small omnivorous and carnivorous copepods (Oncaea and Oithona), whereas in 2007, larger herbivorous calanoid copepods (with high polyunsaturated FA [PUFA] levels that are typical of upwelling conditions) and diatom abundance (indicated by the docosahexaenoic/eicosapentaenoic acids [DHA/EPA] ratio) increased. Although anchoveta eggs were smaller in 2005, batch size and relative fecundity per female were greater in 2007 because of larger ovaries. While relative amounts of saturated (SAFA), monounsaturated (MUFA) FA, and PUFA in anchoveta eggs in 2005 were within the ranges reported for marine fish species, in 2007, PUFA were in the upper and SAFA and MUFA in the lower ranges. Our results suggest that the higher PUFA and lower DHA/EPA values for anchoveta eggs in 2007 may have resulted from increased consumption of larger herbivorous copepods or direct consumption of larger phytoplankton, prey typical of cold upwelling conditions. Conversely, elevated SAFA and MUFA levels in 2005 may have resulted from consumption of smaller omnivorous/carnivorous copepods by adult fish.