Biologia

Aquaculture
ELSEVIER

Aquaculture

138 (1995)

331-347

Effects of selected hormones and male cohorts on final oocyte maturation, ovulation, and steroid production in walleye (Stizostedion vitreum)
Terence P. Barry *, Jeffrey A. Malison, Anita F. Lapp, Lynne
S. Procarione
University

cf Wisconsin

Aquaculture

Program.

Department
53706,

Accepted

@Food

Science,

123 Babcock

Hall,

Madison,

WI

USA

15 June 1995

Abstract
A series of in vivo and in vitro experiments were conducted to evaluate the effects of selected hormones and male cohorts on oocyte maturation and ovulation in walleye captured from the wild.
In one experiment conducted 2 weeks prior to the normal spawning season, single intramuscular injections of human chorionic gonadotropin (hCG, 500 IU kg- ‘) and des-Gly”’ [D-Ala”] LHRHethylamide ( LHRHa, 100 pg kg ’ ) stimulated final oocyte maturation and ovulation. LHRHa induced oocyte maturation faster than hCG. The presence of spermiating males had a slight stimulatory effect on oocyte maturation in non-injected fish, but did not potentiate the effects of LHRHa. In a second experiment conducted 3 weeks prior to normal spawning, hCG (500 IU kg-‘), LHRHa ( 100 pg kg ’ ), and 17,20-P ( 100 pg kg- ’ ) all induced final oocyte maturation. In this experiment, however, hCG was more effective than LHRHa, and there was no male cohort effect. In maturing females, oestradiol-17P levels declined, and testosterone levels increased transiently prior to final oocyte maturation and ovulation. Levels of 17cu,20P-dihydroxy-4-pregnen-3-one
( 17.20-P) were significantly elevated 2 and 3 days prior to ovulation. Cortisol levels were high (50-l 00 ng ml ’ ) in newly captured fish and remained elevated during the experimental period. No control fish in either experiment underwent final oocyte maturation. These findings suggest that capture and confinement stress may inhibit oocyte maturation in walleye.
In vitro,