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K’gari Fish Health

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In April 2021, as part of the federal government’s Wildlife and Habitat Bushfire Recovery Program, rapid on-ground ecological surveys of the distribution and abundance of priority threatened species were undertaken to determine the extent and severity of threats to habitats and populations.

The wetlands field team consisted of staff from the Butchulla Aboriginal Corporation (BAC), Griffith University’s Australian Rivers Institute (ARI), Mary River Catchment Coordinating Committee (MRCCC) and the Burnett Mary Regional Group (BMRG).

BAC’s Butchulla Land and Sea Rangers assist with fish sampling in K’gari’s wetlands (Photo: ARI)

Field sampling focussed on the acid wetlands (freshwater streams, lakes and swamps) in coastal wallum and dune systems of south-eastern Queensland and northern New South Wales. Wetland sampling was conducted within known fire-affected and neighbouring areas within Great Sandy Strait Ramsar Wetland, Noosa National Parks, areas near Peregian Beach township, coastal dune islands (K’gari, Mulgumpin and Minjerribah) and in coastal northern New South Wales.

Northern K’gari areas burnt in October 2020 were also sampled to allow the team to investigate the post-burn recovery of these systems over time. Unburnt area samples and historic data were also included in the study for comparison.

Griffith University wetland sampling sites on K’gari (Photo: ARI)

Of the 26 species of freshwater fish known to occur on K’gari, 19 species were recorded. All three threatened fish species targeted by this study – Oxleyan pygmy perch (Nanoperca oxleyana), honey blue-eye (Pseudomugil mellis) and ornate rainbowfish (Rhadinocentrus ornatus) were sampled at multiple sites and while no site sampled contained all three species, several contained two.

Ornate rainbowfish were found 6 km south of their previously recorded southernmost range. Two invasive species were also sampled on K’gari: mosquitofish and platy. Honey blue-eyes were not sampled at three previously recorded sites (Yidney Creek, Lake Allom and Deep Lake), and one site for each ornate rainbowfish (Deep Lake) and Oxleyan pygmy perch (Yidney Creek). Mosquitofish were sampled at Yidney Creek, which did not contain honey blue-eyes and Oxleyan pygmy perch.

Species were absent from only a small number of previously recorded sites, without any strong trend between fire affected and non-fire affected sites. While native species were present mostly across both fire affected and non-fire affected sites, invasive species were only present at fire-affected sites. While fire disturbance may negatively affect native fish species, it is unlikely to do so to the extent of causing localised extinctions, whereas invasive species may be more likely to proliferate at sites impacted by fire disturbance. At fire-affected sites such as Deep Lake and Yidney Creek, invasive species may have a competitive edge over native species in persisting or recolonising after a fire disturbance.

The relatively minor overall differences in fish species composition and abundances between fire affected and non-fire affected sites may be attributable to a number of factors including (a) fire-affected wetland habitats and their fish communities may have partially recovered in the months since the occurrence of the fires, and (b) wallum wetlands and their fish communities may be inherently resistant and resilient to fire disturbances, although this likely depends on wetland size, depth, riparian zone characteristics, contributing catchment size, and a range of other factors.

Article contributed by the Butchulla Aboriginal Corporation

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