THREATENED SCIENTIFIC COMMITTEE Established under the Environment Protection and Biodiversity Conservation Act 1999

The Minister’s delegate approved this Conservation Advice on 16/12/2016.

Conservation Advice mariensis

Mary River cod

Conservation Status Maccullochella mariensis () is listed as Endangered under the Environment Protection and Biodiversity Conservation Act 1999 (Cwlth) (EPBC Act) effective from 16 July 2000. The species was eligible for listing under the EPBC Act as it was listed as Endangered under Schedule 1 of the preceding Act, the Endangered Species Protection Act 1992 (Cwlth).

The main factors that are the cause of the species being eligible for listing in the Endangered category are its very restricted extant of occurrence, small population size and fragmented habitat that is subject to continuing to decline in quality of habitat due to degraded riparian lands.

Description The Mary River cod is an elongate, percoid with concave head profile and protruding lower jaw. Back colouration varies from golden-yellow to green to dark brown, overlaid with a black to dark green mottling which sometimes extends onto the grey or whitish ventral surface. Dorsal, pectoral, caudal and anal fins are clear to dark, with dark mottling on their bases. The soft dorsal, anal and caudal fins have thin, whitish margins, and the whitish pelvic fin has white filaments (Simpson & Jackson 1996).

The Mary River cod do not grow as large as the related (Maccullochella peelii). Merrick and Schmida (1984) note the largest known Mary River cod at 23.5 kg, anecdotal reports from local residents suggest that specimens to 38 kg have been observed from the (McKay and Johnson 1990 cited in Simpson & Jackson 1996). The Department of Environment and Heritage Protection (DEHP) (2016) state that it is uncommon for the Mary River cod to grow over 70 cm and 5 kg.

Distribution The Mary River cod occurs in southeast in the Mary River system. Historically the Mary River cod was more wide spread occurring across the Brisbane-Stanley, Albert-Logan and systems (Wager and Jackson 1993 cited in Simpson & Jackson 1996).

There are three areas within the Mary River system where cod are present. These are Tinana- Coondoo Creek upstream from Tinana Barrage, Six Mile Creek downstream from Lake Macdonald, and upper Obi Obi Creek (Simpson 1994, and personal observation, R. Simpson in Simpson & Jackson 1996). Mary River cod have also been reported from Widgee, Glastonbury, , and Yabba Creeks, and other parts of the Mary River since 1990. However, surveys conducted by DPI Fisheries in 1996 suggested that numbers are very low (personal observations, R. Simpson cited in Simpson & Jackson 1996).

Mary River cod have been stocked in impoundments, both within and outside the Mary River system, since 1983 (Simpson & Jackson 1996). Stocking activities outside the Mary system have been into areas where the Mary River cod were historically present (Simpson & Jackson 1996). There are no data available to determine if the releases have resulted in any self- sustaining populations but stocking has not reduced the gene pool of the natural population (Huey et al. 2013).

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Relevant Biology/Ecology The present knowledge of reproduction and early life history of the Mary River cod is based on experience with captive fish in hatcheries (Simpson & Jackson 1996).

Mary River cod form pairs and spawn annually around spring. The male selects and guards the nest site, which in hatchery ponds is a hollow pipe or purpose-built nesting box. It is therefore presumed that hollow logs are used as nests in the wild (Simpson & Jackson 1996). Spawning takes place soon after the water temperature rises to 20 degrees Celsius, and may involve considerable aggression between the spawning pair (Simpson & Jackson 1996). The female is frequently injured before she can escape the guarding male. The eggs are deposited as a layer inside the nest where they adhere to the hard surface of the pipe or log, although they are sometimes scattered around the nest site following fighting. The opaque eggs, which measure 3.0 - 3.5 mm in diameter, are guarded by the male (Simpson & Jackson 1996). Hatching commences towards the end of the fourth day at 21 degrees Celsius, and is usually completed by the end of the seventh day. Newly hatched cod larvae are 5 - 7 mm long. The male continues to guard the brood until they disperse to search for food around seven to nine days after hatching.

The fecundity of wild Mary River cod is not well known, but experience suggests that around 2000 eggs per kilogram of the females weight can be expected (Simpson & Jackson 1996). Some females may spawn more than once in a season. Mary River cod fry may grow to 50 mm in less than 10 weeks in plankton-rich hatchery ponds (Simpson & Jackson 1996). They are harvested for stocking at 30 to 50 mm, by which time they are aggressive predators.

The Mary River cod inhabits from high gradient, rocky, upland streams, to large, slow-flowing pools in lowland areas. Anecdotal accounts by anglers and landowners often describe the ideal cod habitat as comprising deep, shaded, slow flowing pools with plenty of snags and log-piles. Similar habitat types are utilised by the closely related Murray cod and (Maccullochella macquariensis) in the Murray River system (Cadwallader and Backhouse 1983; Douglas et al., 1994).

The Mary River cod is known to migrate into smaller tributaries from the main river in late winter (Simpson & Jackson 1996). Depending on flows and time of year the Mary River cod may move over 30 km up or down stream (Simpson & Jackson 1996). The species is also known to have a home range where fish may stay for large proportion of time. Some Mary River cod have returned to a home range after long absences (Simpson & Jackson 1996).

Threats The main threats to the Mary River cod are impoundment of streams, loss of riparian vegetation and invasive fish are listed in the table below in approximate order of severity. These threats are addressed in the conservation management actions.

Table 1 – Threats impacting the Mary River cod in approximate order of severity of risk, based on available evidence.

Threat factor Threat Evidence base type and status Habitat loss and fragmentation Impoundment known Streams that are impounded and prevent Mary River cod from of streams current travelling both in and out of home ranges may result in further and changes fragmentation of the species and population decline. in flow Ineffective fish ways may also impact the species ability to regimes move. Altered hydrology such as the removal of water for irrigation and urban use may change flow regimes that effect macrophyte beds, riffle and pool zones, and create

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Threat factor Threat Evidence base type and status temperature changes that in turn effect breeding conditions for the Mary River cod. Loss of known Removal of riparian vegetation (e.g. clearing for agricultural riparian current land use) may result in the loss of shaded deep pools which vegetation the Mary River cod inhabits (Simpson 1994 in Simpson & and in-stream Jackson 1996). Removal of riparian vegetation also allows timber and erosion which in turn deposits large amounts of sediment into vegetation stream channels (Simpson & Jackson 1996). The combination of deposited sediment and removal of riparian vegetation degrades the quality of habitat. In addition the reduction or removal of in-stream structure and debris such as timber and vegetation may impact on a number of variables that enable a suitable habitat for the Mary River cod (Simpson & Jackson 1996). Invasive species Grazing and known Grazing and disturbance of banks by cattle (Bos taurus) disturbance current inhibits the natural regeneration of native vegetation (Simpson of banks by & Jackson 1996), which provides cover along stream channels cattle which is habitat for the Mary River cod. Introduced known Exotic previously recorded in the Mary River system fishes past and include the guppy (Poecilia reticulata), swordtail (Xiphophorus current helleri), and mosquito-fish (Gambusia holbrooki) (Pusey et al., 1993) and are likely to compete with Mary River cod larva for resources. The mosquito-fish has been implicated in the decline of many freshwater fishes in and worldwide (Arthington and Lloyd 1989; Lloyd 1990; Arthington 1991 cited in Simpson & Jackson 1996). Introduced known Native fish ( ambigua), silver perch non - past and (Bidyanus bidyanus) and saratoga (Scleropages leichardtii) indigenous current are known (Simpson & Jackson 1996) to have been Australian translocated in to Mary River cod habitat. In particular the fishes golden perch is likely to compete with Mary River cod for resources as their feeding and habitat preferences are similar. In addition to the golden perch, (Macquaria novemaculeata) occurs naturally in the lower Mary River and Simpson & Jackson (1996) noted that it was more abundant in the upstream reaches following stocking. Over fishing Over fishing suspected Mary River cod are a popular target for recreational fishers current (Simpson & Jackson 1996). In 2016, this species was listed as and past a no take species in areas that have not been restocked (DEHP 2016). In areas where the species has been restocked, this species may be caught and taken but is subject to strict limits under the Queensland Fisheries Act 1994. Take which exceeds this limit in approved areas and in areas where at no take limit applies could further reduce the population. During the 1800s and early 1900s large numbers of Mary River cod were fished for both human and food (Simpson & Jackson 1996).

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Conservation Actions

Conservation and Management priorities Habitat loss, degradation and modification

o Ensure that appropriately designed fishways are installed at barriers to Mary River Cod movements.

o Protect existing riparian vegetation and restore riparian vegetation by replanting known endemic riparian species that provide shade cover to pools along the stream channels.

o Improve the management of stream flows, water quality and riparian environments throughout catchments which are known and potential habitat for the Mary River cod by monitoring and mitigating erosion.

o Control livestock access to riparian zones along rivers that contain suitable habitat such as deep shaded pools in catchments which are known and potential habitat for the Mary River cod.

o Ensure land managers are aware of the species’ occurrence and the key and potential threats including removal of riparian vegetation and the impacts of cattle grazing along stream channels. Invasive species

o Avoid translocation of invasive fish species within the known and potential range of the Mary River cod. Maintain guidelines for translocation of fish in south-eastern Queensland in consultation with local angling clubs and fish management groups. Fishing

o Maintain a no-take policy on this species in river systems where the species is not stocked. Breeding and restocking of river systems

o Continue to restock the Mary River cod throughout is historic distribution. Stakeholder Engagement

o Engage stakeholders in improving management of riparian vegetation on private land, avoiding take of Mary River cod by fishers and ensuring scientific knowledge is incorporated into management of the species and its habitat.

Survey and Monitoring priorities • Design and implement a monitoring program or, if appropriate, support and enhance existing programs for restocking in known historic distribution. • Monitor the genetic fitness of Mary River cod (including Tinana Creek) populations and manage threat of failed recruitment where appropriate. • Monitor the progress of recovery, including the effectiveness of management actions and the need to adapt them if necessary • Enhance citizen science monitoring (e.g. by recreational fishers) to ensure that data are robust and can be used for population monitoring.

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Information and research priorities • Undertake research on the life history of the Mary River cod in situ. • Undertake surveys suitable and potential habitat across the Mary River cod’s historical distribution to locate any additional occurrences and more precisely assess current population size and distribution. • Investigate and prioritise options for linking, enhancing or establishing additional populations through effective fishways and riparian vegetation restoration. • Investigate the use of citizen science research programs, such as tag and release to record demographic information.

References cited in the advice

Simpson, R., & Jackson, P. (1996), The Mary River Cod research and recovery plan. Mary River Cod recovery team, Queensland Department of Primary Industries – Fisheries group, Queensland. Available on the internet at: http://www.environment.gov.au/system/files/resources/1450d9f6-8d17-4354-8e6b- dd51169edf8f/files/mary-river-cod.pdf

Huey, J.A., Espinoza, T. and Hughes, J. 2013. Natural and Anthropogenic Drivers of Genetic Structure and Low Genetic Variation in the Endangered Freshwater Cod, Maccullochella Mariensis. Conservation Genetics. 14:5 -997-1008.

Other sources cited in the advice

ALA (2016) Atlas of Living Australia, Maccullochella peeli marinsis profile,

Viewed 26 April 2016, Available on the internet at http://bie.ala.org.au/species/MACCULLOCHELLA+MARIENSIS

DEHP (2016) Mary River cod – Maccullochella mariensis, WetlandInfo, Department of Environment and Heritage Protection, Queensland,

Viewed 26 April 2016, Available on the internet at http://wetlandinfo.ehp.qld.gov.au/wetlands/ecology/components/species/?maccullochella- mariensis

DPI (2016) Department of Primary Industries, Species Identification, Mary River Cod, .

Viewed 26 April 2016 Available on the internet at https://www.daf.qld.gov.au/fisheries/species-identification/freshwater-fish/mary-river-cod

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