Action Statement Flora and Fauna Guarantee Act 1988 No. 201 Freshwater Catfish Tandanus tandanus Preamble The information contained within this Action Statement has been collated from a number of sources (as listed in the reference section of this document). Most of the information, however, has been largely derived from two documents: Freshwater Catfish: A Recovery Plan (Clunie and Koehn 2001a) and Freshwater Catfish: A Resource Document (Clunie and Koehn 2001b). Both of these documents, as well as this Action Statement, have been written to provide background information and a list of achievable goals to natural resource managers with the aim to address the decline in distribution and abundance of this species. Description and distribution Freshwater Catfish (Tandanus tandanus ) The Freshwater Catfish (Tandanus tandanus Mitchell 1838) is a stocky species with a stout tapering body formed by the joining of the second 34 dorsal, caudal and anal fins into a continuous T andanus tandanus median fin. The species has a large head with a D ates of m ost recent records 35 blunt rounded snout. The mouth has thick fleshy B ef ore 1990 A f ter 1989 lips and is surrounded by four pairs of barbels. The skin is scaleless, smooth and tough, and there 36 is a strong, serrated spine in the first dorsal fin and pectoral fins. The pelvic fins are abdominal 37 and rounded (Cadwallader and Backhouse 1983). Although colour varies with age and locality, 38 Freshwater Catfish are usually light to dark greyish to greyish-green dorsally and laterally, and lighter to white ventrally. The body colour continues on 39 141 142 143 144 145 146 147 148 149 150 to the fins. Smaller specimens have darker 5' Grid cell. 10' G rid cell. Source: A tlas of Victorian W ildlif e 02/12/2002 mottling which usually fades as they grow. Larger specimens sometimes have pale yellowish mottling on the posterior half of body. Freshwater Catfish can grow to 900 mm and 6.8 kg, although they Distribution in Victoria usually reach 500 mm and 1.8 kg. From one year of age, the sexes can be distinguished by the shape of the urinogenital papilla, which is cylindrical in males and triangular in females (Cadwallader and Backhouse 1983). Freshwater Catfish are native to the Murray-Darling Davis 1977). In Lake Victoria, however, spawning River system in south-eastern Australia (SA, Vic, was recorded in water temperatures from 21 oC to NSW, Qld), and to coastal drainages in eastern 28.6 oC (Clunie, pers. obs.). Although rising water Australia from central NSW to northern levels may hasten spawning, they are not a Queensland. In Victoria, Freshwater Catfish have necessary trigger (Lake 1967a). Spawning may been recorded from the tributaries of the Murray occur in flooded and shallow areas of large rivers River and associated waters, including the Ovens or quieter backwaters, as well as in farm dams. River, Broken River, Goulburn River, Loddon River Pair formation occurs prior to spawning. The pair and Avoca River (Murray Riverina), as well as from constructs a saucer-shaped depression, 0.5 – 2.0 m the Mallee. Freshwater Catfish have been in diameter, in the substrate, usually in areas of introduced into four other river basins, the coarse sand, gravel or rocks, and occasionally in Wimmera, Richardson, La Trobe and Yarra Rivers mud and silt. If a suitable substrate is not (all outside their natural range), and several lakes, available, material such as sticks and gravel may including Goldfields and Centenary reservoirs, be collected from the surrounding area Lake Victoria in Maryborough, Amphitheatre (Cadwallader and Backhouse, 1983). In Lake Reservoir near Avoca and Lexton reservoir. Victoria, nests have been recorded in water depths Currently there are believed to be only four self- ranging from 0.35 m to 1.6 m (usually <1 m). sustaining populations of Freshwater Catfish in Spawning occurs 1-4 weeks after nest construction, Victoria: the Wimmera River, Richardson River and and is often preceded by elaborate courtship Lake Victoria (all introduced populations) and behaviour. The female then deposits the eggs Cardross Lakes near Mildura (a series of terminal within the nest before leaving. The male remains lakes with an artificially high water level due to by the nest, continually fanning the eggs to remove runoff from irrigation water drainage). Elsewhere, silt and debris, and guarding them against there are now only occasional records of the predation. Several males may use a single nest site species from within its natural range. Reasonable during the breeding season, and males may attract numbers still occur within the lower Murray River multiple females to the one nest (Clunie and (NSW waters) adjacent to Victoria. More detailed Koehn, 2001a). The eggs are spherical, demersal, information on the appearance and distribution of non-adhesive, light green to yellow, and about 3.2 this species can be obtained in Clunie and Koehn, mm in diameter when water-hardened. Up to (2001a). 20,000 eggs are laid, and they hatch after approximately seven days. The larvae are free Habitat swimming by 12-14 days and feeding by 20 days The Freshwater Catfish is a benthic species, found (Lake 1967a). in a range of habitat types such as rivers, creeks, Freshwater Catfish are carnivorous, and feed on a lakes and billabongs (Cadwallader and Backhouse wide variety of organisms including insects 1983). While fish are apparently more abundant in (particularly chironomids), molluscs, worms, lakes and backwaters (Lake 1967b), the species shrimps, yabbies and small fish such as gudgeons does inhabit and spawn in flowing streams (Cadwallader and Backhouse 1983) (Merrick and Schmida 1984). A survey in northern Victoria found that Freshwater Catfish only occurred in standing waters such as lakes if there Conservation status was low turbidity and abundant aquatic plants (Brumley et al. 1987). Other sites where National conservation status populations are known to exist in Victoria (such as The Freshwater Catfish has not been listed under Cardross Lakes and Lake Victoria) also possess the Commonwealth Environment Protection and abundant submerged and emergent aquatic plants. Biodiversity Conservation Act 1999. Habitat in Lake Victoria is shallow, to 1.5-2 m deep, with some deeper holes, and a substrate of stones, Victorian conservation status gravel and silt. The preference of Freshwater Catfish for this habitat structure clearly indicates Freshwater Catfish is listed as threatened under the conditions which must be maintained to the Flora and Fauna Guarantee Act 1988 (FFG Act). provide suitable sites for sustainable Freshwater It is considered endangered in Victoria according Catfish populations. to DSE’s Advisory list of Threatened Vertebrate Fauna in Victoria - 2003 (DSE 2003). Life history and ecology Freshwater Catfish is listed under the FFG Act based on the following criteria: Reproduction Criterion 1.1 The taxon is in a demonstrable state Freshwater Catfish spawn from spring to summer of decline which is likely to result in extinction. in water temperatures above 24 oC (Lake 1967a, 2 Cadwallader and Backhouse (1983) noted that, like Victoria, in recent decades. The reasons for this many of the larger Murray-Darling fish, the decline are not clearly understood as interactions Freshwater Catfish has suffered a marked decline between threatening processes are extremely in natural range and abundance. It has contracted complex. The following threats, however, are largely to the north west of its natural range and is considered to be the most significant in the decline restricted to a small number of sites. Freshwater of this species. It should also be noted that, while Catfish have been introduced at several sites in these threats have been listed in order of most western Victoria and these populations appear to significant to least significant threat, the priority be stable. It was formerly a valuable commercial of these threats may vary for individual species, and has become virtually extinct upstream populations: their importance should be assessed of Lake Mulwala (Cadwallader 1986) on an individual basis for each population. Criterion 1.2 The taxon is significantly prone to Changes to flow regimes/loss of floodplain future threats which are likely to result in habitat extinction . The preference of Freshwater Catfish for slow Alterations in water level affect nest establishment flowing or still water suggests that changes to and breeding success in Freshwater Catfish. these conditions may be detrimental to their Sudden short-term drops in water level may continued survival. In regulated systems, increased expose nests, which are subsequently abandoned. flows for irrigation generally occur during If water levels fluctuate too often, Freshwater summer-autumn periods when natural flow levels Catfish will not spawn (Lake, 1967a). are low. Although the exact effects of this flow Freshwater Catfish require specific temperatures reversal on Freshwater Catfish are not known, for spawning, and so alterations to temperature anecdotal evidence suggests that waters with regimes in rivers and streams may threaten the natural flow regimes (such as the majority of species’ breeding activity. Siltation of waterways, population sites in Queensland) support the as a result of clearing and poor land management largest Freshwater Catfish populations within practices, may also affect spawning success. Australia. Changes to flow regimes generally also reduce the extent and duration of natural flooding, Because Freshwater Catfish maintain populations resulting in a loss of floodplain wetland habitat. without having major upstream spawning Freshwater Catfish have been observed using migrations, localised events such as overfishing, floodplains, but the extent of this usage is largely pollution or destruction of spawning areas by river unknown. Furthermore, high summer irrigation channelisation and desnagging are likely to flows may coincide with Freshwater Catfish seriously depress or destroy local populations spawning, potentially increasing the mortality rate (Reynolds 1983). Interspecific competition with of eggs and larvae by washing them downstream.