Reproductive Biology of Pacific Ocean Perch and Northern Rockfish in the Aleutian Islands

Abstract Estimates of maturity (i.e., the proportion of mature individuals at age) play an important role in assessing stock productivity; however, this information has not been published for rockfishes in the Aleutian Islands. Ovary and otolith samples were collected from Pacific Ocean Perch Sebastes alutus and Northern Rockfish S. polyspinis during both fishery-independent and fishery-dependent cruises in 2010 to investigate maturity and other aspects of reproductive biology. Histological examination of ovaries indicated that both species exhibited general parturition in April, while specimens caught in the summer and fall were maturing and generally exhibited progressive stages of vitellogenesis. Histological analysis was more reliable when characterizing ovary condition than were macroscopic or visual assessments during the developing period. Estimates of natural mortality, based on a relationship with the gonadosomatic index, were 0.040 for Pacific Ocean Perch and 0.042 for Northern Rockfish. Mean fecundity estimates calculated for Northern Rockfish (89,320 oocytes) were correlated more with length and weight than age. Estimates of age and length at 50% maturity were 9.1 years at 32.4 cm for Pacific Ocean Perch and 7.6 years at 27.7 cm for Northern Rockfish and indicate maturation at younger ages than do previous studies from the Gulf of Alaska. This information on reproductive biology will improve estimation of fishing mortality reference points and management of these commercially important species in the Aleutian Islands. Received June 22, 2012; accepted December 10, 2012