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MESA: Pacific Ocean Perch Life History

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Rockfish eggs.
Rockfish eggs and larvae under magnification.

There is much uncertainty about the life history of Pacific ocean perch (POP), although generally more is known than for other rockfish species. The species appears to be viviparous (the eggs develop internally and receive at least some nourishment from the mother), with internal fertilization and the release of live young. Insemination occurs in the fall, and sperm are retained within the female until fertilization takes place ~2 months later. The eggs hatch internally and parturition (release of larvae) occurs in April-May.

Information on the early life history of POP is very sparse, especially for the first year of life. Pacific ocean perch larvae are thought to be pelagic and drift with the current. Oceanic conditions may sometimes cause advection to sub-optimal areas, resulting in high recruitment variability. However, larval studies of rockfish have been hindered by difficulties in species identification since many larval rockfish species share the same morphological characteristics. Genetic techniques using allozymes and mitochondrial DNA are capable of identifying larvae and juveniles to species, but are expensive and time-consuming.

Post-larval and early young-of-the-year Pacific ocean perch have been positively identified in offshore surface waters of the GOA, which suggests this may be the preferred habitat of this life stage. Transformation to a demersal existence may take place within the first year. Small juveniles probably reside inshore in very rocky, high-relief areas, and by age 3 begin to migrate to deeper offshore waters of the continental shelf. As they grow, they continue to migrate deeper, eventually reaching the continental slope, where they reach adulthood.

An adult pacific ocean perch.
Young-of-the-year pacific ocean perch.
Adult Pacific ocean perch (left) and young-of-the-year (right).

Dana Hanselman
Auke Bay Laboratories
Alaska Fisheries Science Center, NOAA Fisheries

Ted Stevens Marine Research Institute
17109 Pt Lena Loop Rd
Juneau AK 99801

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