Gm. Weber et al., Morpho-physiological predictors of ovulatory success in captive striped bass (Morone saxatilis), AQUACULTURE, 188(1-2), 2000, pp. 133-146
This study evaluates morpho-physiological characters as predictors of ovula
tory success in cultured striped bass, Morone saxatilis, that could be used
by farmers to select females for induced spawning. Diameter, size homogene
ity and growth of ovarian follicles; blood plasma levels of testosterone (T
), oestradiol-17 beta (E-2) and vitellogenin (VTG); and in vitro maturation
of oocytes, in response to a combination of insulin-like growth factor-I (
IGF-I, 100 nM) and 17,20 beta,21-trihydroxy-4-pregnen-3-one (20 beta-S, 290
nM) were examined for females prior to spawning induction and compared wit
h their subsequent ovulatory response. Fish spawning within 8 days of impla
ntation with pelleted analogue of mammalian gonadotropin-releasing hormone
analogue (GnRHa; [D-Ala(6)-des-Gly(10)-NEt]-LHRH) were considered to have g
iven a satisfactory maturational response. The in vitro assay was the most
reliable predictor for ovulatory success. All fish whose oocytes completed
final oocyte maturation (FOM) in vitro in response to the combination of IG
F-I and 20 beta-S spawned, whereas, 12 out of 13 fish, whose oocytes did no
t complete FOM in vitro, failed to spawn within 8 days of GnRHa treatment.
The in vitro assay was field-tested on commercial farms, and correctly iden
tified all four females that spawned out of the eight females that were giv
en hormone treatment. Among the other measurements, follicle diameter best
differentiated between fish that later spawned and those that did not spawn
. Plasma T concentrations were greater on average in fish that spawned, but
the technical complexity of the assay and overlap in T concentrations betw
een fish that spawned and those that did not limits the value of this measu
rement to farmers. There was no significant difference in follicle size hom
ogeneity, follicle growth over the 2-week period prior to hormone treatment
, or plasma levels of E-2 and VTG between fish that spawned and those that
did not. (C) 2000 Elsevier Science B.V. All rights reserved.