Ecological and biological features in the dynamics of recruitment and spawning stock biomass of gadids (Gadiformes: Gadidae) in the North Atlantic

Regional and trans-Atlantic statistical relationships among multi-year variations of recruitment abundance and spawning biomass of 11 cod stocks, 5 haddock stocks, and 4 saithe stocks from different areas in the North Atlantic Ocean for the period of 1946–2020 have been identified. To study the patterns of spatial and temporal variability of the identified relationships, the peculiarities of biology and population structure of the species under study, as well as anthropogenic impact (fishing) on stock structure were analyzed. Coincidences in variations of recruitment abundance were noted among those gadid stocks that were distributed in areas with a similar range of mean annual near-bottom water temperature, regardless of their geographical remoteness. The lack of reproductive isolation between stocks contributes to the synchronization of their recruitment dynamics. With increasing time shift from 0 to 5 years, an increase in the absolute values of correlation coefficients between spawning stock biomass was observed for all three studied species. Overexploitation leads to changes in the structure of spawning stocks. An increase in the proportion of younger fish and in the rate of sexual maturation results in decrease in the quality of producers, affecting significantly the recruitment abundance and spawning biomass of gadid stocks.