Spawning, egg development, and early life history dynamics of arrowtooth flounder (Atheresthes stomias) in the Gulf of Alaska

摘要

Arrowtooth flounder (Atheresthes stomias) has the highest biomass of any groundfish species in the Gulf of Alaska, is a voracious predator of age 1 walleye pollock (Theragra chalcogramma), and is a major component in the diet of Steller sea lions (Eumetopias jubatus). Owing to its ecological importance in the Gulf of Alaska and the limitedudinformation available on its reproduction, interest has intensified in describing its spawning and early life history.ududA study was undertaken in late January–February 2001–2003 in the Gulf of Alaska to obtain information on adult spawning location, depth distribution, and sexual maturity, and to obtain fertilized eggs for laboratory studies. Adults were found 200–600 m deep east of Kodiak Islandudover the outer continental shelf and upper slope, and southwest along the shelf break to the Shumagin Islands. Most ripe females (oocytes extruded with light pressure)udwere found at 400 m and most ripe males (milt extruded with light pressure) were found at depths ≥450 m. Eggs wereudfertilized and incubated in the laboratory at 3.0°, 4.5°, and 6.0°C. Eggs were reared to hatching, but larvae did not survive long enough to complete yolk absorption and develop pigment. Eggs were staged according to morphological hallmarks and incubation data were used to produce a stage duration table and a regression model to estimate egg age based on water temperature and developmental stage.ududArrowtooth flounder eggs (1.58–1.98 mm in diameter) were collected in ichthyoplankton surveys along the continentaludshelf edge, primarily at depths ≥400 m. Early-stage eggs were found in tows that sampled to depths of ≥450 m. Larvae,udwhich hatch between 3.9 and 4.8 mm standard length, increased in abundance with depth. Observations on arrowtooth flounder eggs and early-stage larvae wereudused to complete the description of the published partial developmental series.(PDF file contains 34 pages.)