Can rockfish keep producing eggs when they are nearly 80 years old?

Details

Little is known about how ovaries age in long-lived fish, particularly about follicular stages and the formation of new egg cells, or de novo oogenesis.

This observational study examined two rockfish species: Sebastes aleutianus (rougheye rockfish) and Sebastes alutus (Pacific ocean perch). Fish were sampled offshore of British Columbia. Researchers estimated their ages using otolith annuli, the rings in their ear stones, and examined their ovaries histologically, by studying tissue sections.

In S. aleutianus, age up to 80 years did not markedly alter the frequency distributions or total numbers of oocytes and follicles. In a larger sample of S. alutus, oocyte and follicle abundance likewise showed little age trend through 77 years.

However, fish older than 50 years lacked the smallest and largest oocyte size classes (40–60 and >80 micrometers) and the smallest follicle size class (200–350 micrometers). The abstract attributes these absences to the older fish being at a later seasonal developmental stage.

These findings provide evidence that oogenesis continues at advanced ages in both species, in contrast with long-held assumptions about mammals. The researchers describe these species as an extreme example of iteroparity—reproducing repeatedly over a lifetime—within the spectrum of life-history strategies. They call for investigation of the mechanisms behind such an extended reproductive lifespan.