This results in similar distribution patterns of adults and juveniles, potential for more cannibalism, hence a weak year class. Even when adult and juvenile life stages coincide, stratification of the water column can effectively separate adults from juveniles. Its influence is mainly restricted to the yolk sac larvae and first feeding life stages. Climatic factors, such as atmospheric circulation dynamics that determine frequency and trajectory of storms, wind direction and intensity, ice extent and water temperature, can affect all life stages of pollock. Figure 2 adds evidence supporting our working conceptual model.
Cannibalism is presumed to be the mechanism underlying density dependence.
The spawner-recruit relationship indicates that several points are well above and below the fitted relationship. Warm years are characterized by strong shoreward wind drift, subsequent high spatial separation between adults and juveniles, low rates of cannibalism, and good recruitment. Cold years are characterized by weak shoreward wind drift and subsequent low spatial separation between adults and juveniles, high rates of cannibalism, and poor to average recruitment. In cold years, the cold pool temperature tends to alter distributions of both adult and juveniles tending to enhance coincidence. They also found that the best fit occurred with a one year lag, which suggested that environmental effects were exerted, not in the first few months of life, but rather at later juvenile stages.