| Popis: |
Large variations in abundance, distribution, and size composition of planktonic Parophrys vetulus larvae were observed in late winter-early spring over a 4-year period 1972–1975, off the Oregon coast. Mean larval abundance was much greater in 1973 and 1975 than in 1972 and 1974. In 1973, P. vetulus larvae occurred more frequently, were more widely distributed, made up a greater proportion of the larval catch, and were larger and older than in the other three years. Weather conditions in the winter of 1973 were unseasonably mild, precipitation was less, winds were lighter and more variable, and sky cover was reduced compared to the other years studied. The observed fluctuations may have been related to variations in spawning time and differences in food availability. Unusual wind and weather conditions may have affected the timing and intensity of the winter phytoplankton bloom producing optimal larval fish feeding conditions and good larval survival in 1973. Differences in water circulation patterns and larval growth rates probably were less important. Distribution and abundance of larvae of three other pleuronectids common in the samples, Isopsetta isolepis, Platichthys stellatus, and Psettichthys melanostictus did not fluctuate as widely as did P. vetulus. |
