EFFECTS OF TEMPERATURE, WIND AND SPAWNING STOCK BIOMASS ON RECRUITMENT OF ARCTO-NORWEGIAN COD

Sea temperature has earlier been shown to have a large influence on th e recruitment of Arcto-Norwegian cod, Gadus morhua. We here hypothesiz e that this linkage is partly due to the direct effect of temperature on larval and juvenile growth. Secondly, temperature acts as a proxy f or both biotic and abiotic factors influencing recruitment. Indices of abundance of early juvenile cod (2-3 months old), O-group cod (4-5 mo nths old) and 3-year old cod are analysed in more detail against the e nvironmental temperature, wind stress components, wind-induced turbule nt energy and the spawning stock biomass. To deal with autocorrelation , non-stationarity and non-normality, which complicate a statistical t ime series analysis, randomization and Box-Jenkins methods are applied . In addition to the important effect of high sea temperature during t he early life stage in forming strong year classes, the results show t hat the spawning stock biomass is nearly as important. Also, alongshor e southerly wind stress anomalies during the period of pelagic drift ( from April through summer) and offshore wind stress anomalies during e gg and early larval stages (in April) act favourably on recruitment. T he beneficial effect of southerly wind anomalies could be linked partl y to high temperature, but the flux of zooplankton-rich water from the Norwegian Sea into the feeding areas of the Barents Sea may also be i ncreased. The favourable influence of offshore winds in April is less predominant and causal links are also less clear; possible explanation s for this might be increased offshore spreading of eggs and early lar vae, resulting in reduced risk of predation, and increased compensatio n inflow of intermediate Norwegian Sea water which, in this restricted period of time, has a high concentration of spawning copepods suitabl e as prey for the developing cod larvae.