R. Wager and P. Jackson
Environment Australia, June 1993
ISBN 0 6421 6818 0
Undescribed species and stocks
Currently, several fishes are recognised as distinct taxa, but are yet to be formally described. Many of these taxa are also classified as threatened species and are covered by Species Recovery Outlines. In addition, many freshwater fish families contain unrecognised taxa and distinct stocks (Plotosidae, Percichthyidae and Eleotridae). Several new species or sub-species are likely to be described and some of these will definitely be categorised as threatened.
There is also a need to recognise and conserve unique stocks, or genetically distinct groups, within species. There is considerable evidence that genetically divergent stocks exist within fish species as a result of temporal, spatial or behavioural isolation (Musyl and Keenan 1992). The division of species into stocks is more pronounced in freshwater environments than in marine environments because of the terrestrial barriers that delineate rivers, streams, lakes or springs. Possible interbreeding of stocks needs to be carefully examined prior to re-stocking of natural habitats. Deleterious hybridisation between re-stocked fishes and the original inhabitants could occur.
Most species currently recognised as threatened occur in south eastern Australia. There are no threatened species from the Northern Territory, only one from Western Australia, and one from north Queensland. This may be explained by the fact that threatening processes (habitat degradation, introduced species, over-fishing), and hence threatened species distributions, coincide with the highest human population densities in Australia. However, threatened species distributions also coincide with the largest concentration of fisheries biologists and research institutions in Australia. Perhaps the bias in the threatened species list is in part due to the ecology and threatening processes affecting fish populations being better documented for this region.
There is very little systematic monitoring of fish populations in Australian freshwater systems. Some monitoring may be performed by special interest community groups or individuals. In many cases identification of declining fish populations is accidental and anecdotal. Usually a species becomes threatened before research becomes a priority and management strategies are considered. This limits the options for implementing recovery techniques, especially development of spawning techniques for maintenance of captive populations and restocking. Regular monitoring programs should be established for all threatened species. Monitoring of less threatened species (fishes in the Vulnerable or Poorly Known categories) is essential so that declining fish stocks can be identified and positive actions taken before the species is threatened with extinction.
Habitat management and protection
Threatened fishes recovery plans must identify habitat requirements and conserve any remaining areas of suitable habitat. The protection of habitat, at least for higher vertebrates, is most often achieved through the declaration of parks or reserves. In most cases the condition of upstream areas and catchments directly influences the downstream habitat (see chapter 2) and protection of habitat in an isolated section of stream may be ineffective. Protection of catchment areas is essential. This may be possible in smaller streams but will usually be impractical in larger streams and rivers. In these cases special management practices to reduce downstream impacts must be implemented and will usually involve the combined efforts of several authorities and local land owners. An integrated approach to catchment management is essential. The report of the Murray-Darling Basin Fish Management Committee outlines several aspects of riverine and catchment management (see Lawrence 1991).
Rehabilitation of habitat may be required as part of a threatened species recovery plan. Several techniques are available and include: reconstruction of stream morphology and channel characteristics; replanting of riparian vegetation; stabilisation and replanting of catchment areas; restoration or allocation of stream flows for the in-stream environment; provision of fish ways (fish ladders); provision of artificial habitat structures (Koehn 1987); removal of introduced biota.
This type of management is aimed at protecting species from direct human exploitation. Most states have legislation that allows control of recreational and commercial exploitation of fish stocks. However enforcement of legislation is often difficult. Public education is an essential component of species protection (see below). Chapter 4 outlines legislation available for the protection of fishes.
The value of spending resources on conserving a few threatened species rather than using those resources to protect larger numbers of less threatened species has been questioned. Threatening processes affecting threatened species are generally similar to those affecting other freshwater fishes. Research on threatened species has several benefits; firstly by identifying possible threatening processes that may affect other species, and secondly by drawing attention to fishes in general and the habitats that support them.
Community and ecosystem protection
There is a growing awareness for the need to maintain biodiversity. The draft National Strategy for the Conservation of Australia's Biological Diversity recognises the need to maintain biotic communities. There is currently no recognition of the need to investigate the conservation status of particular assemblages of fishes that characterise unique ecosystems (eg wallum streams and swamps in south east Queensland, subterranean fishes of North West Cape, Western Australia). A community structure may be threatened, whether it contains individual threatened species or not.
There are several unique aquatic communities that contain threatened species for which Recovery Outlines have been prepared. In these cases the Recovery Outlines contain measures that should protect all aspects of the community, including invertebrates and flora. The conservation of other unique communities that may not contain threatened fishes should also be considered.
Control of introduced or feral fishes
Examination of the threats identified in the Species Recovery Outlines (Table 1) clearly indicates that introduced fishes, particularly brown trout, rainbow trout and gambusia, are major threats to native freshwater fishes.
Brown trout and rainbow trout, introduced for their sporting and food qualities, were released into most suitable catchments before 1900 (Tilzey 1976). Reproducing populations are now present in many streams in temperate, upland regions of south eastern Australia. They are still bred in both Goverment and private hatcheries for stocking purposes, particularly in natural lakes and artificial impoundments where reproduction may not occur.
It is impractical to expect eradication of all existing trout populations. It is also undesirable as trout are an important recreational fishing resource. However, specific eradication programs in streams containing threatened fishes is a valid management tool. Furthermore, the distribution of trout must not be further increased by releasing them into new habitats.
Gambusia was first released into Australian waters in 1925, supposedly to control mosquitoes. Reproducing populations are now widespread throughout Australia. Unlike trout, these populations are of no value, but their total removal or control is virtually impossible. However, specific eradication programs to protect threatened fishes are a practical and valid option.
In general the most effective way to control introduced species is to stop their initial release into the wild. This not only requires appropriate legislation and enforcement but must be coupled with a public education campaign. Eradication of new infestations may be possible if detected early and while population densities are low. Once introduced species establish reproducing populations in natural waterways their removal or control is very difficult and costly. Exclusion of introduced fishes may be achieved by erection of barriers to fish movement (eg weirs). In some cases existing impoundments limit invasion of upstream habitat. The effectiveness of these barriers depends on preventing the illegal release of feral species above the barrier.
Re-introduction and re-stocking
The Australian and New Zealand Environment and Conservation Council (ANZECC) have developed a draft policy on the translocation of threatened species for conservation purposes based on the IUCN position statement on translocation (1987).
Re-introduction, defined as the release of individuals into parts of the former range of the species from which it has disappeared, and re-stocking, defined as the release of numbers of individuals into existing populations with the intention of enhancing those populations, can form an important part of a recovery program. Re-introduced and re-stocked populations should become self-sustaining and should not rely on continued input for long term survival. It must be emphasised that altered or degraded habitat will not support viable populations regardless of how many fishes are introduced. Monitoring to gauge the success of new populations must accompany restocking programs.
Fishes are generally highly fecund and many offspring can be obtained from relatively few breeding fish. However loss of genetic diversity, genetic swamping, or inbreeding depression can occur without proper management (Brown 1987).
Establishing new populations
Release of individuals outside the natural distribution of the species can be a useful method of conserving threatened species. Populations established away from threatening processes may thrive and act as a source for restocking natural habitats.
However, indiscriminately introduced species can be detrimental to the receiving ecosystem. Introduced species may have adverse ecological (predation, displacement) and genetic (hybridisation) effects. Adverse effects on the receiving ecosystem should be assessed in terms of the total biota, not just fishes.
Education and community support
Individual fishes rate poorly on the public list of conservation priorities, at least compared to the larger warm blooded mammals. This is partly due to ignorance, and partly to the Australian fish fauna being poorly known. Most people know of a few edible species such as Murray cod or golden perch. Many anglers know a wider variety of larger species although many similar species are lumped together. Fish commonly named black bream or silver perch could account for six or more species. Small fish species found in our streams are often known as 'guppies' or 'minnows'. Conversely introduced exotic species are often well known. Many people extol the angling potential of trout and are aware of the potential impact of redfin, carp and tilapia.
Introduced species, especially popular angling species, must be recognised by the public as feral species. Their impacts on native species should be publicised.
The public understanding of fish habitats is also poor. Most people are aware that fishes require relatively unpolluted water to live in. However they are ignorant of the importance of other habitat features such as the surrounding vegetation, instream features, substrate and water flow requirements.
Public awareness of freshwater fishes is increasing. Several groups, including state fisheries departments, museums, wildlife and conservation organisations, and fishing and aquarist associations such as Native Fish Australia and the Australia New Guinea Fishes Association, are involved with collection and dissemination of information on native fishes. There appears to be an increasing awareness that threatened freshwater fishes (and other less popular animals and plants) are a vital component of the biosphere and need to be saved along with more appealing 'cute and cuddly' animals.
Conservation of threatened species is ultimately achieved with public funds. Community support and political pressure is required to direct the expenditure of these funds to research and management. Public acceptance of the importance of conservation matters can only be achieved through education, and governments should be ultimately responsible for the initiation of education programs. Cooperation from the public is also an essential part of the management of freshwater fishes. For example, the movement of feral fish and the taking of protected species is difficult and costly to control through legislative means alone. Similarly habitat protection or rehabilitation often can not be achieved without the cooperation of private land owners.
The conservation status listing in this report uses categories as defined by the Australian National Parks and Wildlife Service Endangered Species Program and described below. The listing was derived from the Australian Society for Fish Biology (ASFB) list first published in 1987 (Harris 1987), and updated at the ASFB Threatened Fishes Committee meeting during the 1992 National Conference (see Appendix 4). It was decided to develop the Action Plan listing based on the ASFB listing for the following reasons:
- Nomination of species to the ASFB list requires submission of a standard form with specific data. A forum of fish biologists considers the nomination before presentation to the Annual General Meeting of the Society for acceptance. The list is updated annually using the most recent information. Ideally this provides multiple opinions to be expressed and discussed before final categorisations are made. This process also provides the listing with a degree of temporal stability. The nomination process is the only formal process for listing threatened fishes on a national basis.
- Multiple conflicting lists could be confusing to researchers, managers, politicians and the public.
- Currently several conservation listings exist for freshwater fishes. Although the category definitions vary, they are all intrinsically similar. Information used in categorising species for these listings has often been based upon the ASFB listing.
- The ASFB list is generally accepted as useful.
However, it is acknowledged that the ASFB list is based on criteria that are largely subjective, and this may lead to confusion and disagreement over the categorisation of species. Mace and Lande (1991) present a more quantitative scheme using probabilities of extinction within a given time. The applicability of this scheme to Australian freshwater species is discussed in Appendix 5. Where possible this scheme has also been used to categorise species. Although its usefulness is currently limited, it is recommended that it be further developed and considered for adoption by the ASFB.
Initially a draft listing was circulated to ASFB members and other individuals and organisations. Several comments were received and as a result the authors made some changes to the final listing. Consequently, the Action Plan listing differs from the ASFB listing in some aspects.
The comments concerning the altered status of various species will be passed to the ASFB Threatened Species Committee for consideration.
Despite this Action Plan being compiled using the most current information, research may identify new species, subspecies or distinct stocks in the future. Should any of these taxa or stocks be listed as threatened, the preparation of Recovery Outlines must become a priority.
Conservation status categories
Species not definitely located in the wild during the past 50 years or species that have not been found in recent years despite thorough searching.
Species in danger of extinction and whose survival is unlikely if the causal factors continue operating. Included are those species whose numbers have been reduced to a critical level or whose habitats have been so drastically reduced that they are deemed to be in immediate danger of extinction. Also included are the species that are possibly already extinct but have not been subject to recent thorough searching. There is no numerical formula for defining whether a species is endangered or vulnerable: it must be based on the best available scientific judgement.
Species believed likely to move into the 'Endangered' category in the near future if the causal factors continue operating. Included are species of which most or all the populations are decreasing because of over-exploitation, extensive destruction of habitat or other environmental disturbance; species with populations that have been seriously depleted and whose ultimate security has not yet been assured; and species with populations that are still abundant but are under threat from severe adverse factors throughout their range. Also included are species with low or localised populations or which are dependent upon limited habitat that would be vulnerable to new threatening processes.
Species which are suspected, but not definitely known, to be either extinct, endangered or vulnerable. This category covers the many species which have been rarely collected and for which the conservation status cannot be reliably determined until more information is available about them.
Species which are uncommon but which are not currently considered endangered or vulnerable. Such species may be represented by a relatively large population in a very restricted area or by smaller populations thinly spread over a wider range, or some intermediate combination.