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In many ways, fish are the forgotten component of Victoria's vertebrate fauna. Unlike most other vertebrates, fish remain largely unseen and to the uninitiated, their life histories and habitat requirements remain a complete mystery. The naive view is perhaps that a minimal quantity of water supplies all that a fish requires, an attitude that would explain the treatment, until very recently, of Victoria's river systems, as on one hand a source of water and on the other a convenient drain.
The low level of appreciation both of the diversity of our freshwater fish fauna and their habitat requirements has undoubtedly led to a lack of interest in the conservation of native fishes. Rarely have fishes been included in general fauna surveys or management plans.
Although there are obvious differences between the environments occupied by the aquatic and terrestrial vertebrate faunas, there are also many parallels. As with terrestrial fauna, fish are dependent on structural habitat, the removal or alteration of which can result either in the loss of species or a decline in their abundance. While the health and well-being of terrestrial fauna is influenced by the properties of the surrounding air, fish are equally dependent on the properties of their surrounding medium - water. Unlike many terrestrial fauna however, fish remain largely confined within their aquatic habitat, unable to escape any detrimental changes in water quality that are imposed upon them. Aquatic habitats are distinguished from their terrestrial counterparts in that negative impacts affecting one part of the aquatic ecosystem can be transferred through downstream flow to other parts of the system. Stream systems interact continuously with their local environs and catchments, and the consequences of unsympathetic management within the catchment may therefore have profound effects on the riverine environment and on fish populations.
Because angling is one of the most important recreational activities in Victoria, much of the interest that does exist in freshwater fish management tends to be focussed on the larger angling species, in particular those of the Murray-Darling system. While these species are of course important, the smaller less familiar species should not be overlooked. These species must be recognised as a faunal component of high conservation value, occupying important niches within aquatic communities.
Although the artificial propagation and release of fish may supplement populations, the rehabilitation and long term survival of species will ultimately depend on the maintenance of self-sustaining populations, which in turn relies on the availability of suitable habitat. Most of the decline in distribution and abundance documented for Victoria's freshwater fish species can be directly attributed to alteration and destruction of their environments. To halt and reverse these trends, remaining high quality habitat must be maintained and a start must be made on the restoration of degraded areas.
Despite being hidden beneath the water's surface; fish, their habitats and aquatic systems in general require appropriate management strategies that are no more difficult to develop and apply than those for terrestrial ecosystems. The same principles and approaches apply.
Whilst significant gaps exist in our understanding of the precise habitat requirements for many native freshwater fish species, the need for appropriate management plans for aquatic ecosystems is urgent. The survival of Victoria's freshwater fish depends on a greater appreciation and understanding of these systems, and the use of all available biological information in making decisions on the management of our catchments, rivers and streams.
VicFishInfo: Biological Information for Management of Native Freshwater Fish in Victoria