Fishways Passage


	Why is Fish Passage Important? Fish passage is the process where fish move within their environment. Forty-two species of essentially freshwater fish have been described for Victoria, all of which need to undertake some form of movement within their habitat.		Fish passage is critical in allowing: • adult fish access to and from spawning habitats, • dispersal of juvenile fish to new habitats, • access to feeding habitats, • re-colonisation of new habitats, • exploratory movements and habitat selection, and • access to and from refuge areas during droughts or floods.
Electrofishing in Dight's Falls, Yarra River
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	Types of Migrations and Movements Freshwater fish movements and migrations can vary in distance from small localised movements (<1 km) up to 1000 km depending on both the species and the purpose of the movement. There are two main classifications of migrations: 1. Potamodromous: fish that migrate wholly within freshwater 2. Diadromous: fish that migrate between freshwater and the sea *(2a)* Anadromous – diadromous fish that spend most of their life in the sea and migrate to freshwater to breed		*(2b)* Catadromous – diadromous fish that spend most of their life in freshwater and migrate to the sea to breed *(2c)* Amphidromous – diadromous fish that migrate between the sea and freshwater, but not for the purpose of breeding and occurs regularly at some other stage of the life cycle. Fish are stimulated to migrate by a variety of environmental cues, including seasonal or diurnal cycles and changes in water flow and temperature.

	Coastal Fish Species Seventy percent of native fish species in Victoria’s coastal drainages need to migrate at some stage of their life cycle. In south-eastern coastal drainages, approximately 50 % of the available aquatic habitat has been obstructed by barriers.		This has had dramatic effects on many coastal native species, particularly those species that require access to both fresh and sea water to complete their life cycle. For fish that have these large scale migrations, restricted fish passage can lead to localised extinctions of these species above the barrier, particularly with large structures such as dams.

	Australian grayling (Prototroctes Maraena) Victorian FFG Act Listing: Vulnerable, National EPBC Act Listing: Vulnerable. Australian grayling occur in coastal rivers and streams from as far north as Grose River in NSW to Hopkins River western Victoria and in Tasmania. As adults the species prefers large and small coastal rivers with gravel substrates and moderate flows. Adult grayling are known to reach 330 mm but are more commonly 170-190mm at 3 years of age. Australian grayling are a shoaling, amphidromous species, where the young migrate upstream from the sea to complete its life cycle. Spawning occurs in the adult freshwater habitat during late summer, and the hatched larvae drift downstream to the estuary or sea. Around six months later, the juvenile fish then return to upstream freshwater habitats. Grayling have undergone severe declines throughout most of its former range and are now listed as vulnerable at a State and National level. The main cause of its decline is thought to be due to barriers preventing its dispersal downstream and recolonisation of upstream habitats. Other causes of decline are loss of suitable gravel habitats through increased siltation, and predation and competition by exotic species such as trout. *Australian Grayling (Prototroctes Maraena) © ARI*
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	Murray-Darling Fish Species Potamodromous fish species can undertake either small or large scale movements, however the purpose behind their movements is largely unknown. Some studies have suggested that adult Murray cod and golden perch undergo upstream migrations specifically to access favourable spawning locations.	Additionally juvenile golden and silver perch are known to migrate in large numbers upstream probably to disperse into new habitats. Recent work has also suggested that adult golden perch can undergo downstream migrations.
	Golden perch (Macquaria Ambigua) Part of Murray River endangered ecological community in Victoria and NSW. Golden perch occur throughout most of the Murray-Darling Basin, except at higher altitudes, and also in the Lake Eyre, Bulloo River and Dawson-Fitzroy River systems. They are found in a range of habitats from clear, rocky, headwater streams to turbid, lowland rivers. Adults have been recorded up to 76 cm and 23 kg, but are more commonly at sizes less than 5 kg. Golden perch are a migratory species that are thought to move upstream following increases in flow during spring and summer. The adult upstream movements are widely speculated to be linked to pre-spawning migrations. Whilst some studies have shown that adult golden perch are capable of undertaking large scale movements of up to 1000 km upstream and 900 km downstream, other studies have found that most golden perch generally undergo small scale localised movements. The role of short-term localised movements and sporadic large-scale movements by golden perch has not been evaluated. In a study at Torrumbarry weir fishway on the Murray River, large numbers of juvenile golden perch were found to move upstream after small rises in water level. Although golden perch are still relatively common throughout most of their range and are regularly caught by anglers, the species is thought to have undergone dramatic declines in abundance. The main causes for its decline are thought to include the effects of river regulation, obstruction of adult and juvenile movements by barriers, thermal pollution and habitat alteration. *Golden perch (Macquaria Ambigua)* Drawing by Dave Crook, © ARI


	Further Reading Allen, G.R., Midgley, S.H., Allen, M. (2002). Field guide to the freshwater fishes of Australia. Western Australian Museum, Perth, Australia. p. 394. Koehn, J.D. and O’Connor, W.G. (1990). Biological information for management of native freshwater fish in Victoria. Department of Conservation and Environment. Melbourne, Australia. p165. Mallen-Cooper, M. (1994). How high can a fish jump? New Scientist, 142 (1921), 32-7. McDowall, R.M. (Ed.) (1996). Freshwater fishes of South-Eastern Australia. Reed Books, Chatswood, NSW, Australia. p. 247. O’Connor, J., O’Mahoney, D., and O’Mahoney, J. (2002). Downstream Migration of Adult Murray-Darling Fish Species. Freshwater Ecology Section, Department of Sustainability and Environment.