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. / Graduation date: 2004
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/30050 |
| Date | 27 May 2003 |
| Creators | Chapman, Colin G. |
| Contributors | Berkeley, Steven A. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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