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The biology of the Sandy Sprat Hyperlophus Vittatus in coastal waters along the West Coast of Australia

Goh, Jason (1992) The biology of the Sandy Sprat Hyperlophus Vittatus in coastal waters along the West Coast of Australia. Honours thesis, Murdoch University.

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Abstract

Samples of the commercially important Hyperlophus vittatus were obtained from commercial purse seine and beach seine catches at six regions, between Perth and Bunbury, in the period from November 1991 to September 1992.

Macroscopic and histological examination of ovaries indicated that H. vittatus is a multiple spawner and has a very protracted spawning season. Oocytes develop in batches, with two or three distinct modal size classes of oocytes present in the ovaries of mature H. vittatus. Spermatozoa were found in testes throughout the spawning season. In both sexes, sexual maturity is first attained at a body length of 60 mm. The proportion of mature fish at lengths > 60 mm increased in inshore regions from January to June. Large fish (~ 60 mm) from offshore waters had mature gonads in November 1991, ,January, May and September 1992.

Dietary studies showed H. vittatus to be an omnivorous rnicrophagist, feeding predominantly on copepods and other holozooplanktonic crustaceans. Feeding was opportunistic and significant dietary differences were found amongst seasons and regions. Morphological adaptations to a zooplanktivorous diet in H. vittatus included relatively short and widely spaced gill rakers, and a comparatively short alimentary tract with few digestive caeca. A dietary shift towards the consumption of larger prey species with increasing fish size, associated with the ontogenetic development of the gill rakers, is exhibited by H. vittatus.

Age determination of Hyperlophus vittatus using scales and otoli ths was unsuccessful. The restricted number of larger offshore fish obtained in this study meant that growth rings present on these fish could not be validated as occurring annually. Length-frequency histograms indicated that H. vittatus < 90 mm utilise the shallow inshore regions but subsequently migrate to deeper offshore waters with increasing size. The mean annual commercial CPUE for Hyperlophus vittatus increased during recent years, probably reflecting the increasing use of purse seines rather than the less efficient beach seines. Mean monthly CPUE for the purse seine fishery with H. vittatus catches peaked during January and July1 probably due to the off shore migration of this species during those months.

Publication Type: Thesis (Honours)
Murdoch Affiliation: Centre for Fish and Fisheries Research
Notes: Note to the author: If you would like to make your thesis openly available on Murdoch University Library's Research Repository, please contact: repository@murdoch.edu.au. Thank you.
Supervisor: Potter, Ian
URI: http://researchrepository.murdoch.edu.au/id/eprint/40935
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