Studies in the biology and reproductive characteristics of Pseudomugil signifer

Howe, EHI

Studies in the biology and reproductive characteristics of Pseudomugil signifer

Howe, EHI

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Publication Type:: Thesis
Issue Date:: 1995

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Field	Value	Language
dc.contributor.author	Howe, EHI
dc.date.accessioned	2009-12-09T04:02:49Z
dc.date.accessioned	2012-12-15T03:52:45Z
dc.date.available	2009-12-09T04:02:49Z
dc.date.available	2012-12-15T03:52:45Z
dc.date.issued	1995
dc.identifier.uri	http://hdl.handle.net/10453/20211
dc.description	University of Technology, Sydney. Faculty of Science.
dc.description.abstract	The aims of this study were firstly to observe the breeding behaviour and embryo ology. and then to identify factors affecting the reproductive biology of the Australian native pseudomtlgilid Pseudomugil signifer (pacific blue-eye) and the impact upon it of the presence of the exotic species Gambusia holbrooki (eastern gambusia). Six species of the genus Pseudomugil, and the related Scaturiginichthys venneilipinnis, are found on the Australian continent. The normal breeding behaviour, egg surface morphology and embryology of four species of Pseudomugil (P. signijer, P. genrudae, P. tenellus and P. mellis) were first investigated, using aquarium and microscopic (light and S.E.M.) studies. The four species were divided into two groups: P. signifer and P. mellis; and P. tenellus and P. gertrudae. The study provided further evidence for the view that the embryology of the genus Pseudomugil differs markedly from that of members of the family Melanotaeniidae, with which the pseudomugilids have previously been grouped. The seasonal pattern of gonadal function in P. signifer, both in the field and in aquariums, was then investigated for populations of P. signifer from the Sydney region. It was found that P. signifer bred over the spring and summer months, commencing breeding as the temperature and daylength increased, and declining in breeding activity as daylength and temperature declined. There was no substantial difference in the pattern of reproductive activity between wild and captive stocks of P. signifer in the populations used. The impact of the presence of the introduced G. holbrooki on P. signifer was then examined, first in open-air tank experiments , and then in the field. In the tank experiments the exotic species profoundly affected the breeding of the native species. When G. holbrooki were in the tanks P. signifer did not gain weight or grow in total length (except for females given supplementary feed); ovarian weight and fecundity was greatly reduced and the ovaries were morphologically undeveloped. No eggs from P. signifer were observed in tanks which also housed G. holbrooki. G. holbrooki were observed to actively hunt and eat young P. signifer and to nip the caudal fins of adult P. signifer. The results indicate clearly, that at least in a captive situation, the presence of the exotic species has a very deleterious effect on breeding and hence possible survival, of a native population. A pilot study conducted at the same time as the harvest of the second tank study did not reveal such drastic consequences. However, even in the less confined field situation, some evidence of an interrelation between water quality, numbers of P. signifer and numbers of G. holbrooki were seen in one disturbed site (Home bush Bay). These findings suggest that a newly designed field experiment based on data collected from the power analysis of the pilot study could clarify whether G. holbrooki adversely affects P. signifer in the wild. The information gained from these studies can be used in the management of P. signifer in the wild, and serve as a model of the possible effects upon other native species.	en
dc.format	Thesis (PhD)	en
dc.language.iso	en	en
dc.relation	https://opus.lib.uts.edu.au/bitstream/10453/20211/217/02whole.pdf
dc.relation.replaces	http://hdl.handle.net/2100/955
dc.rights	info:eu-repo/semantics/openAccess
dc.rights	The author owns the copyright in this thesis including all reproduction and reuse rights for the work. The work may not be altered without the permission of the copyright owner. Attribution is essential when quoting or paraphrasing from this thesis.
dc.rights	au.edu.uts.lib/ppc
dc.subject	Pacific blue-eye.	en
dc.subject	Eastern gambusia.	en
dc.subject	Freshwater fishes.	en
dc.title	Studies in the biology and reproductive characteristics of Pseudomugil signifer	en
dc.type	Thesis
utslib.copyright.status	open_access

Abstract:

The aims of this study were firstly to observe the breeding behaviour and embryo ology. and then to identify factors affecting the reproductive biology of the Australian native pseudomtlgilid Pseudomugil signifer (pacific blue-eye) and the impact upon it of the presence of the exotic species Gambusia holbrooki (eastern gambusia). Six species of the genus Pseudomugil, and the related Scaturiginichthys venneilipinnis, are found on the Australian continent. The normal breeding behaviour, egg surface morphology and embryology of four species of Pseudomugil (P. signijer, P. genrudae, P. tenellus and P. mellis) were first investigated, using aquarium and microscopic (light and S.E.M.) studies. The four species were divided into two groups: P. signifer and P. mellis; and P. tenellus and P. gertrudae. The study provided further evidence for the view that the embryology of the genus Pseudomugil differs markedly from that of members of the family Melanotaeniidae, with which the pseudomugilids have previously been grouped. The seasonal pattern of gonadal function in P. signifer, both in the field and in aquariums, was then investigated for populations of P. signifer from the Sydney region. It was found that P. signifer bred over the spring and summer months, commencing breeding as the temperature and daylength increased, and declining in breeding activity as daylength and temperature declined. There was no substantial difference in the pattern of reproductive activity between wild and captive stocks of P. signifer in the populations used. The impact of the presence of the introduced G. holbrooki on P. signifer was then examined, first in open-air tank experiments , and then in the field. In the tank experiments the exotic species profoundly affected the breeding of the native species. When G. holbrooki were in the tanks P. signifer did not gain weight or grow in total length (except for females given supplementary feed); ovarian weight and fecundity was greatly reduced and the ovaries were morphologically undeveloped. No eggs from P. signifer were observed in tanks which also housed G. holbrooki. G. holbrooki were observed to actively hunt and eat young P. signifer and to nip the caudal fins of adult P. signifer. The results indicate clearly, that at least in a captive situation, the presence of the exotic species has a very deleterious effect on breeding and hence possible survival, of a native population. A pilot study conducted at the same time as the harvest of the second tank study did not reveal such drastic consequences. However, even in the less confined field situation, some evidence of an interrelation between water quality, numbers of P. signifer and numbers of G. holbrooki were seen in one disturbed site (Home bush Bay). These findings suggest that a newly designed field experiment based on data collected from the power analysis of the pilot study could clarify whether G. holbrooki adversely affects P. signifer in the wild. The information gained from these studies can be used in the management of P. signifer in the wild, and serve as a model of the possible effects upon other native species.

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