Is there really just one species of Western Minnow?

The freshwater fish fauna of the south west of Western Australia is highly endemic, with 80% of species found nowhere else in the world. Unfortunately, it is also in grave danger of extinction, with many species having their ranges impacted by threats such as climate change, salinisation, river regulation and the introduction of exotic aquatic species.

Recent molecular genetic studies in our laboratory have suggested that the extent of biodiversity loss in our freshwater fish fauna may be even greater than expected, because morphologically described species may actually consist of a number of genetically differentiated cryptic species. This project will use DNA sequencing to investigate the occurrence of cryptic species in the relatively common and widespread western minnow, Galaxias occidentalis. A preliminary study has already identified extensive genetic diversity in western minnow and the project will build upon these preliminary results to map genetic diversity against geographic distribution and determine whether we actually have more than one species in the south west. If we do, then this will have major implications for the management of fish populations.

How well do fish swim?

River barriers, such as dams and weirs, are a major threat to the unique freshwater fish fauna of Western Australia, because they prevent feeding and spawning migrations and may lead to disconnected, genetically depauperate populations. Fishways are structures which may enable fishes to negotiate these barriers and we are involved in a number of projects to design and construct fishways throughout the state. Effective fishway design, however, requires knowledge of the swimming performance of the target fishes and this information is currently very limited for native freshwater fishes in Western Australia.

This study will utilise a swim tunnel, recently installed in our laboratory, to measure the swimming performance of freshwater fishes and to relate swimming performance to parameters such as fish age, size and sex, water temperature and parasitic infection. The data that are obtained will then be related to water flow measurements obtained from current fishways and used to design improved fishways in the future.

Do freshwater mussels improve water quality and fish health?

The freshwater mussel Westralunio carteri occurs in freshwater rivers of the south-west. The mussel is classified as Vulnerable on the IUCN Red List of threatened species and a Priority 4 species under the Wildlife Conservation Act 1950. We have evidence, from a current PhD project being undertaken by Michael Klunzinger, that the distribution of W. carteri has severely contracted in recent years because of their vulnerability to secondary salinisation and the loss of host fish species, which are essential to complete the parasitic phase of the mussel’s life cycle.

Mussels play important roles in the functioning of freshwater ecosystems throughout the world, particularly because their filter feeding activities influence water chemistry and clarity, and the amount and kind of suspended particles in the water. Nothing is known, however, of the extent to which W. carteri influences water quality in Western Australian rivers. Mussel densities can be very high (³ 100 m^-2) in pools which form over summer in many of the ephemeral rivers in the south-west. These pools are important refuge sites for native freshwater fishes and we hypothesise that mussels contribute to the survival of fishes in the pools through their filter feeding activities, which may reduce algal density, enhance water quality and prevent lethal deoxygenation. The aim of this study is to test this hypothesis using a combination of field observations and manipulation of mussel and fish densities in experimental ponds.

Can zoonotic pathogens be detected in mussels?

Water is increasingly recognized as an important vehicle for the transmission of many important zoonotic protozoan parasites, such as Cryptosporidium, Giardia and Toxoplasma. Filter-feeding bivalves, such as mussels, may bioaccumulate these pathogens and thereby serve as both sentinel organisms and as potential sources of infection if they are eaten by people or by other animals.

Freshwater and estuarine mussels are abundant throughout the Swan-Canning and other catchments in close proximity to urban populations in Western Australia. They also occur in a range of habitats, from relatively pristine to highly degraded waterways. Despite this, we know almost nothing about the prevalence of zoonotic parasites within them.

The objectives of this study are to: (a) use PCR and sequencing techniques to analyse the prevalence and genotypes of protozoan parasites in mussels captured from a range of environments in the Swan-Canning River; and (b) use experimental infections of mussels to determine their suitability as sentinel organisms to monitor parasite contamination of waterways. This study will therefore provide important information on the epidemiology of water-borne zoonotic parasites and on the potential of utilizing mussels in future monitoring programs.

Is river health linked to tree health?

South-western Australia is a global biodiversity hot-spot, with an exceptionally large concentration of endemic species in both terrestrial and freshwater ecosystems. Both terrestrial and aquatic biodiversity in the south-west are threatened by processes such as land clearing, salinisation, introduced species (including infectious diseases) and climate change. Riparian zones, at the interface between terrestrial and aquatic environments, are not only important centres of biodiversity, they are also one of the ecosystems most disturbed by human activity and most in need of restoration to maintain ecological integrity.

There are important linkages, mediated by riparian zones, between the health of terrestrial and freshwater ecosystems. For example, streams and rivers depend on riparian plants for bank stability, shade to reduce water temperatures, the input of carbon to support aquatic food webs and woody material which provides important aquatic habitat. Conversely, streams and rivers may provide a source of nutrients and a means of seed dispersal for riparian plants, habitat for the larval stages of many riparian invertebrates and corridors for the transport of infectious disease. Despite these linkages, confirmed by a number of studies in Australia and throughout the world, there has been no large scale mapping of the correlation between riparian tree health and aquatic ecosystem health in the south west, and no detailed investigation of the causal pathways which may be responsible for this correlation. This project will use a combination of existing databases, remote sensing data and on-ground fieldwork to establish correlations between riparian tree health and river health in south-western Australia.

Western Minnow (Galaxias occidentalis). Photo: D. Morgan 

Goodga River Fishway, Two Peoples Bay 

Carter's Freshwater Mussel (Westralunio carteri) 

Giardia duodenalis trophozoites. Photo: R. Hobbs

S. Beatty and T. Fazeldean in the Donnelly River