Environment is determinative for recruitment formation of the NEA cod (Gadus morhua l.) stock

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Complex of reasons on which year-class survival and strength are dependent for most of abundant fish, and particularly for NEA cod, include two basic categories. The first one is connected with environmental influence, in which the eggs drift and incubate, and larvae and young fish develop. The second one is qualitative composition and number (biomass) of spawners on which the quantity of the spawned viable eggs is dependent. Frequency of investigations concerned with the second category, and first of all with spawning stock biomass (SSB) as basis for future recruitment (R) increased especially during the last 1.5-2 decades. The logically expected obligatory availability of SSB→R link and relatively wide accessibility of initial data, which are suitable for including in models, promote a popularity of such investigations. Their results are used as basic biological reference points in the practical fishery management. Nevertheless, the realized analysis of variance enabling us to estimate influence rate of one of the factors (in this case of cod SSB) to the resultant characteristic (in this case surviving 3-year-old cod) showed that it is limited by 4.3-15.9% (reliable variant is 7.5%). The rest of influence falls into the first category of factors, i.e. the environment in which year-classes are forming. The points referred to above cast doubts on the feasibility of traditional fish management based on establishment of Bpa, Blim and the other theoretically derivable indices concerned with them. In practice TAC limitation for support of SSB on the above Bpa level never guaranteed and never may guarantee the appearance of strong recruitment. More fundamental analysis of the known elements and search for new elements affecting the year-class strength is more important for prognosis of future stock dynamics and TAC estimation. In this report, as applied to cod, relationship of R with intensity of Atlantic water flow to the Norwegian and Barents Seas is considered, with the annual and interannual water temperature dynamics and with sun activity tendency evaluated by Wolf's numbers.