The environment under which fish are maintained as broodstock before
reproduction is often stressful; however, the impact of stress on broodstock and gamete
quality is not well known. We investigated the effects of stress over the final stages (i.e.
the 3 months preceding ovulation) of sexual maturation of female rainbow trout,
Oncorhynchus mykiss, on their reproductive performance and physiology and that of their
progeny. Stress was administered over the period of early vitellogenesis (one and a half
months), late vitellogenesis-final maturation (one and a half months), or during both
periods (three months). Each stress treatment and control was triplicated with eight
females in each replicate (n=24 fish per treatment). The eggs and progeny of each female
were kept separate and observations made for four months after transfer to rearing tanks.
Cortisol levels were measured in plasma, ovarian fluid and eggs by radioimmunoassay.
Fish that experienced stress during final maturation and those that were under stress
during the whole experiment spawned on average two weeks earlier than the control
group. In contrast, fish stressed during the period of early vitellogenesis spawned at the
same time as the controls. Absolute fecundity and fertilization were not significantly
affected in any treatment group; however, significant differences were found in relative
fecundity. Stress applied early in vitellogenesis resulted in smaller eggs and swim-up fry;
but, these differences were not found in juveniles 8 weeks after hatching. Furthermore,
we found no differences in survival of the progeny or resistance to the fish pathogen
Vibrio anguillarum. Circulating levels of cortisol were high at ovulation in all groups,
but significantly less cortisol was observed in the ovarian fluid and eggs. Sex hormone
concentrations were high in plasma; however, they were several orders of magnitude
lower in the ovarian fluid. These differences were not as extreme as those observed for
cortisol. Lower levels of cortisol and sex steroids in ovarian fluid and eggs compared to
that which is available from plasma suggests that there is a mechanism by which the
female protects the eggs from potentially deleterious effects of prolonged exposure to
elevated concentrations of steroids. / Graduation date: 1996
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/34905 |
| Date | 24 October 1995 |
| Creators | Contreras S��nches, Wilfrido M. |
| Contributors | Schreck, Carl B., Fitzpatrick, Martin S. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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