PHYSICAL TRANSPORT OF YOUNG POLLOCK LARVAE (THERAGRA-CHALCOGRAMMA) NEAR SHELIKOF-STRAIT - AS INFERRED FROM A HYDRODYNAMIC MODEL

An advective model was used to simulate the drift of larval walleye po llock (Theragra chalcogramma) over a 40-day period (late April through early lune) near Shelikof Strait, Alaska. This model was used: (i) to assess how much of the observed change in larval positions during tha t period can be explained by transport at fixed depth; (ii) to demonst rate that observed change can he related to mean large-scale meteorolo gical forcing; and (iii) to investigate accumulation of larvae in spec ific areas near the coast. Based on availability of larval and circula tion data, three years were studied: 1988, 1989 and 1991. Velocity fie lds generated from a hydrodynamic model driven by winds and runoff wer e used to advect particles seeded in accordance with observed larval d istributions in late April of each year. The modelled larvae were trac ked at 40 m depth, corresponding to the mean depth of sampled larvae a nd the depth of neutrally buoyant drifters employed in field studies. Specific features observed in late May larval surveys were reproduced by the model, such as the accumulation of larvae in a shoal area downs tream of the strait. Differences among the modelled years include exte nsive flushing of larvae to the south-west in 1988 and 1991, vs. limit ed flushing in 1989. These differences appear related to the mean larg e-scale atmospheric pressure patterns for April-May of those years.