Observations on the spawning distribution and biology of offshore Pacific hake (Merluccius productus)

Two cruises were conducted in February 1990 and 1991 to examine the distribution and biology of spawning offshore Pacific hake. The fish spawned during winter, in the southern portion of their range, i.e., south of Cape Mendocino, and offshore of the shelf break over bottom depths exceeding 1,000 m. In 1990, the schools were 110-167 km (60-90 nmi) offshore in midwater depths ranging from 140 to 240 m, over bottom depths of 3,600 and 4,200 m. In 1991 there were six schools containing spawning hake from 35 degrees to 40.5 degrees N, spanning 720 km (390 nmi). There were more males than females in the spawning schools. In 1991 some schools of predominantly post-spawners were encountered; they tended to be inshore of the spawners and were mainly female. The most surprising of the results was the presence of a north-south dine in biological parameters during spawning similar to the one occurring in summer. We discuss the implications of our results for the present migration hypothesis.