Graduate Thesis Or Dissertation
 

Recruitment variability in black rockfish (Sebastes melanops): effects of maternal age on offspring quality

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/8336h504b

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  • Black rockfish (Sebastes melanops) is an important marine recreational species throughout the Pacific Northwest. Recent catch data indicate a trend of age-truncation in the black rockfish population off the Oregon coast, with older females rapidly disappearing from the population. In populations with broad age distributions, older fish may contribute disproportionately to larval production through a variety of mechanisms. Thus, the removal of older age classes through fishing may impact the population far beyond the simple loss of biomass. We tested the hypothesis that older females produce higher quality offspring, or offspring otherwise more capable of survival, than those from younger females. Mature female black rockfish of various ages were captured live and held until parturition. Larvae were then reared under identical conditions to compare performance in terms of growth, starvation, and mortality. Results indicate that older females produce offspring that grow faster in both length and weight, survive longer in the absence of an exogenous food supply, and exhibit lower mortality rates than offspring from younger mothers. This difference in larval performance may be explained by the relatively greater amount of endogenous energy reserves present in the oil globules of offspring from older mothers. Larval oil globule volume at parturition was significantly related to all larval performance factors and was strongly correlated with maternal age. Given the difference in larval quality, it is critical for the management of black rockfish, and possibly other species as well, that these older individuals not be addressed solely in terms of biomass, but their relative reproductive contribution and the repercussions of their removal from the population be considered.
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