The native Gaygay (Freshwater catfish – Tandanus tandanus) was once common across the lower Gwydir, but in recent decades, numbers have declined significantly and the species is now considered ‘rare’ in most areas. In 2015, during the Gwydir Long Term Intervention Monitoring (LTIM) sampling, only one gaygay was captured, and no gaygay were detected subsequently in 2016, confirming just how rare the species has become.

Recognising the dire state of the population in the Gwydir, DPI Fisheries made efforts to boost the Gaygay population in the lower Gwydir by relocating adults from Copeton Dam. Gaygay (Freshwater catfish) recovering in the lower Gwydir.

In December 2016, 39 individuals were relocated from Copeton Dam to a number of sites in the lower Gwydir catchment (Gwydir and Mehi rivers). The primary objective of this work was to understand the movement of Gaygay in relation to changes in river flow and therefore individual fish were fitted with acoustic tags. Fish were collected using the two methods, electrofishing and fyke nets.

Fyke nets

A fyke net is a cylindrical fish trap that contains a series of funnel shaped openings which make it easy for fish to enter the trap but very difficult to for them to make their way out. Fyke nets are a passive method of sampling as they rely on fish willingly entering the net.

We were also interested in determining whether any evidence of recruitment could be detected following the relocation through our routine Gwydir LTIM and Gwydir Monitoring Evaluation and Reporting (MER) sampling.

In 2017, the project team detected 23 Gaygay ranging in length from 46–489 mm. In November- December 2018, an additional 62 individuals (435–605 mm) were relocated from Copeton Dam to the lower Gwydir.

Gaygay have been detected each year since the second relocation. Of particular interest, the mean length of individuals collected in the past few years has decreased, which indicates that spawning and recruitment is occurring. In the period 2019– 2021, seven individuals were collected which were 100 mm or less in length.

Detection of juvenile Gaygay in the lower Gwydir over the past few sampling years (2017 – 2022) has been a positive outcome from our relocation efforts.

Further sampling in coming years will provide vital information about the long-term recovery of Gaygay in the lower Gwydir. However, the regular detection of juveniles since 2017 is great news for this culturally, socially and ecologically important species.

Resources

• First published at 2rog

Main photo: A Gaygay (Freshwater catfish -Tandanus tandanus) collected using large-boat electrofishing during routine sampling on the lower Gwydir River.
Source: DPI Fisheries

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