Perhaps ANGFA should purchase a copy of the floowing proceedings for its
library. It has a rather large number of papers dealing with some of the
material we have been discussing here. They are like $25 from the
Australian Society for fish Biology.
Harris, J.H. and S.C. Battaglene, 1989. The introduction and
translocation of native freshwater fishes in south-eastern Australia. In
Pollard, D.A. (Ed). Introduced and translocated fishes and their
ecological effects. Proceedings of the Australian Society for Fish
Biology Workshop No. 8. Bureau of Rural Resources. Australian Government
Printing Office, Canberra.
Langdon, J.S., 1989b. Disease risks of fish introductions and
translocations. In Pollard, D.A. (Ed). Introduced and translocated fishes
and their ecological effects. Proceedings of the Australian
Society for Fish Biology Workshop No. 8. Bureau of Rural Resources.
Australian Government Printing Office, Canberra.
And also, from Wager and Jackson's Action Plan for Australian Freshwater
Fish a "short" piece on fish and disease problems. While not specific to
aquarium type problems I thought it may be of general interest.
Introduced Exotic and Native Species
Introduced exotic species
Between 20 (McKay 1989) and 24 (Allen 1989) exotic species have been
recorded from Australian waters and 19 or 20 of these are likely to breed
in the wild (Arthington, pers. comm.). Several of these have been
implicated in the decline of native species although it is difficult to
distinguish this from other threatening processes. Predation, utilisation
of similar resources, aggressive behaviour, introduction of exotic
pathogens, and habitat modification have been suggested as detrimental
factors associated with introduced exotic (and introduced native) species.
The effect of salmonids on some native species has been documented
(Jackson and Williams 1980, Jackson 1981). Brown trout (Salmo trutta)
has been implicated in the decline of several species including Swan
galaxias (Galaxias fontanus) (Fulton 1978) and mountain galaxias
(Galaxias olidus) (Tilzey 1976). This decline is usually due to
predation by brown trout. See Fletcher (1986) for a review of the
impacts of trout.
The effect of common carp (Cyprinus carpio) has not been conclusively
demonstrated. Carp utilise a variety of food resources required by some
native fish species and larger invertebrates (which are preyed upon by
several native fish species). Modification of habitat due to feeding and
spawning behaviour of carp may also occur, although this is not clearly
documented. Carp have been strongly implicated in the reduction of
shallow rooted and soft leaved species of aquatic vegetation (Fletcher et
al. 1985). In some areas Murray cod and golden perch may feed on carp.
Gambusia (Gambusia holbrooki), also known as mosquitofish, is a small,
aggressive, predatory species widespread in mainland Australia. It has
been actively introduced by governments and military institutions for the
control of mosquitoes. This species has been implicated in the
extinction of small fishes in Asia and Africa and in the reduction in
abundance or range of 25 species worldwide (Arthington and Lloyd 1989).
In Australia Gambusia has been implicated in the decline of species of
Ambassis, Chlamydogobius, Craterocephalus, Galaxias, Melanotaenia, Mogurnda,
Pseudomugil, Retropinna and Scaturiginichthys. Causal factors include
utilisation of similar food resources, utilisation of the same habitat,
predation on eggs or fry and aggressive interactions (fin nipping).
Exotic cichlids have been introduced to waters of Queensland, Victoria
and Western Australia. Interaction between cichlids and native fishes
are poorly known mainly due to the scarcity of scientific studies.
Bludhorn, Arthington and Mather (1990) demonstrated limited overlap in
the diet of adult tilapia (Oreochromis mossambicus), spangled perch
(Leiopotherapon unicolor) and eel-tailed catfish (Tandanus tandanus) in
a Queensland impoundment. They suggested that resource partitioning may
not occur among juveniles of these species.
Occurrence of cichlids in Victoria is restricted to the Hazelwood
Pondage, a waterway artificially heated by the effluent cooling water of
a power generating station. Due to low water temperatures downstream, it
is unlikely that the species will spread from this location (Cadwallader
et al. 1980).
It is significant that 10 of the 24 Species Recovery Outlines presented
in this Action Plan nominate exotic fishes as the major threat. Five
list brown trout as the threat, and five list gambusia.
Introduced native species
Introduction of native species to areas outside their natural
distribution, can have a detrimental impact. For example, the climbing
galaxias (Galaxias brevipinnis), not previously recorded in Lake Pedder
prior to its flooding, may be implicated in the decline of the Pedder
galaxias (Galaxias pedderensis) (see Species Recovery Outlines).
Barlow et al. (1987) documented the role of introduced native species in the
extinction in the wild of rainbowfish from Lake Eacham, North Queensland.
The effects of introduced native species on the environment and
ecosystems are similar and perhaps more severe than those of introduced
exotic species. These include: introduction of disease organisms;
disturbance of ecosystems; and loss of biogeographic information. In
addition introduction may result in loss of genetic diversity when
separate stocks of the same species are mixed. Harris and Battaglene
(1989) provide more details on the effects of native species translocation.
The ecological effects of introduced exotic and native fishes were the
subject of an Australian Society for Fish Biology Workshop (see Pollard
1990).
Disease and Parasites
Diseases or parasites have frequently been spread throughout the world
by the translocation of fishes. Pathogens not endemic to a particular
region are frequently more dangerous to the new hosts (the endemic
fishes) than the original carrier. Even the translocation of native
species within their natural range poses the risk of spreading taxon
specific pathogens (Langdon 1989b). Supposedly taxon specific
(species specific) diseases have been shown to be capable of infecting
other non-related species. Redfin perch (Perca fluviatilis) carries a
pathenogenic virus (epizootic haematopoietic necrosis) which has been
shown to be highly pathenogenic for silver perch, mountain galaxias,
Macquarie perch, and to a lesser extent, Murray cod (Langdon
1989b). Many other fishes are likely to be susceptible. Several additional
pathogens have been introduced to native species from exotic species. In
the Tambo River (Victoria), some Australian grayling (Prototroctes
maraena) have been found to be infected with anchor worm (Learnea
cyprinacea) which depletes fish populations overseas (Hall 1988). Anchor
worm was probably introduced with salmonids or redfin perch and is known
to infect other native species including river blackfish and Murray
cod (Langdon 1988).
For detailed information on the ecological and genetic impacts of
introduced and translocated species, see Arthington (1991).
Tootles
Peter Unmack