Distribution, feeding behaviour, and condition of Cape horse mackerel early life stages, Trachurus capensis, under different environmental conditions in the northern Benguela upwelling ecosystem

BreMarE (Bremen Marine Ecology), Universityof Bremen, D-28334 Bremen, Germany*Corresponding author: tel: +49 421 238 00 124; fax: +49 421 238 00 30; e-mail: simon.geist@zmt-bremen.deGeist,S.J.,Kunzmann,A.,Verheye,H.M.,Eggert,A.,Schukat,A.,andEkau,W.Distribution,feedingbehaviour,andconditionofCape horse mackerelearly life stages, Trachuruscapensis, under differentenvironmental conditions in the northern Benguelaupwelling ecosystem. – ICES Journal of Marine Science, doi: 10.1093/icesjms/fsu087.Received31 May2013; revised 20 April 2014; accepted 22 April 2014.Earlylifehistory(ELH)traitsarekeytounderstandvariablerecruitmentsuccessandhencethestocksizeofmarinefish.OneofthecurrentlymostpuzzlingecosystemsinthisregardisthenorthernpartoftheBenguelaCurrentupwelling systemoffNamibia.Here,populations oftheformerlydominant pelagic species, sardineand anchovy, failed to recover during the last three decades after a dramatic decline. In contrast, Cape horsemackerel,Trachuruscapensis,maintainedaconstantpopulationsize.Warmingofthesystemandshoalingofhypoxiczonestogetherwithfeedbackloopswithinanalteredfoodwebarediscussedtoberesponsibleforthisregimeshift.Inthisstudy,weaddresstheroleoflarvaltraitsforthesuccessfulperformanceoftheT.capensispopulationunderthepresentenvironmentalconditionswiththefocusonfeedingecology.Weinvestigatedseasonalvariationsofthegeographicaldistribution,growthrate,feedingecology,andnutritionalconditionoftheirELHstagesandexaminedrelationshipswithwatertemperature,dissolvedoxygenconcentration,andmicro-zooplanktoncomposition.T.capensis’ELHstagesshowedawidespatialandseasonaldistribution,apreferenceforhigherwatertemperatures(18–218C)andpresenceoverawiderangeofdissolvedoxygenconcentrations(0.13–6.35 mlO