Ovarian aging in two species of long-lived rockfish, Sebastes aleutianus and S. alutus

Abstract

Little is known about the ovary during aging in long-lived fish with respect to follicular stages and de novo oogenesis. We examined two species of rockfish, Sebastes aleutianus (rougheye rockfish) and Sebastes alutus (Pacific ocean perch). Fish were sampled offshore of British Columbia, age was estimated by otolith annuli, and the ovaries were examined histologically. In S. aleutianus, age up to 80 yr did not markedly alter the frequency distribution of oocytes, follicles, or their total numbers. Similarly, in a larger sample of S. alutus, the abundance of oocytes and follicles showed little age trend up through 77 yr. However, fish older than 50 yr lacked the largest and smallest oocyte size classes (40-60, >80 microm) and the smallest follicle size class (200-350 microm), which results from the later seasonal developmental state of these older fish. These data provide evidence that oogenesis continues at advanced ages in these two species, in contrast with long-held assumptions about mammals. These species represent an iteroparous extreme in the spectrum of life history strategies and merit investigation to determine the mechanisms for such an extended reproductive life span.