Please use this identifier to cite or link to this item: http://hdl.handle.net/1893/7404
Appears in Collections:Aquaculture Journal Articles
Peer Review Status: Refereed
Title: Inhibition of spawning and associated suppression of sex steroid levels during confinement in the substrate-spawning Tilapia zillii
Authors: Coward, Kevin
Little, David Colin
Bromage, Niall R
Contact Email: dcl1@stir.ac.uk
Keywords: Tilapia zillii
crowding
sex steroids
spawning inhibition
ovarian development
Issue Date: Jan-1998
Publisher: Wiley-Blackwell
Citation: Coward K, Little DC & Bromage NR (1998) Inhibition of spawning and associated suppression of sex steroid levels during confinement in the substrate-spawning Tilapia zillii, Journal of Fish Biology, 52 (1), pp. 152-165.
Abstract: Substrate-spawning Tilapia zillii failed to spawn in crowded holding tanks but exhibited a marked tendency to spawn soon after transfer to individually partitioned aquaria. Confined conditions suppressed the levels of serum 17β- oestradiol (E2) and testosterone (T) in females, which remained low throughout the period of confinement. Levels of both steroids rose significantly following transfer of fish to individual aquaria and were maintained at consistently higher levels than those of fish which remained confined. Proportions of stage 3 (late perinucleolar) oocytes were significantly lower (P less than 0.001) in individual fish 21–30 days after transfer, coincident with significantly higher (P less than 0.01) proportions of stage 6 or 7 oocytes (late vitellogenic or maturing oocytes). However, no significant differences (P≥0.05) were detected between individual or confined groups of fish in the relative proportions of stage 2 (early perinucleolar), stage 4 (cortical alveolar) or stage 5 (early vitellogenic) oocytes. Atresia increased as the period of confinement increased. Following return of individual fish to confined conditions, blood steroids fell rapidly to levels seen in fish that had remained confined throughout. It is suggested that the reduced sex steroid levels detected during confinement were insufficient to allow developing oocytes to complete oocyte growth and maturation. The detection of significantly lower proportions of stage 3 and significantly higher proportions of stage 6/7 oocytes soon after transfer suggest that fish were preparing one batch of oocytes for spawning (stage 6/ 7 oocytes) whilst recruiting from a pool of previtellogenic oocytes (stage 3) for the ensuing spawning c
Type: Journal Article
URI: http://hdl.handle.net/1893/7404
DOI Link: http://dx.doi.org/10.1111/j.1095-8649.1998.tb01560.x
Rights: The publisher does not allow this work to be made publicly available in this Repository. Please use the Request a Copy feature at the foot of the Repository record to request a copy directly from the author. You can only request a copy if you wish to use this work for your own research or private study.
Affiliation: University of Stirling
Aquaculture
University of Stirling

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