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Thursday, 28 November 2013

Written by Laura Glitsos

LOCAL researchers have presented the first quantitative evidence to support the perception that accessibility to ephemeral (transitory) rivers in WA’s north may impact the abundance of some fish species.

Albany-based UWA Centre of Excellence in Natural Resource Management expert Dr Paul Close says while this is preliminary evidence, it suggests there are big gaps in understanding the sustainability of fish stocks in ephemeral rivers and water holes.

The evidence was collected as an ‘off-shoot’ of a study conducted in 2009 in the Kimberley’s Fitzroy River which was part of a federally-funded nation-wide program.

“We collected fantastic data and when we got back to the office we started thinking about the health of the river and realised the sites that we collected fish from, encompassed a gradient of fishing pressure,” Dr Close says.

“So we started looking at the data in terms of how accessible the sites were to both Aboriginal communities and recreational fishers.”

Dr Close says there has long been a perception that fishing reduces the abundance of some species, particularly for Indigenous communities, which rely on these fish for both recreational and customary purposes.

“These fish can become restricted to disconnected habitats and isolated in these river pools, so it would suggest they are predisposed to fishing because they can’t move away,” Dr Close says.

“There was anecdotal evidence, but nobody had ever produced a very good quantitative data set.”

Dr Close emphasises this data is only preliminary evidence, and more than anything, reveals how much more research must be conducted.

“So we need to understand the harvest quantities [how many fish are being pulled out of the system at different times of the year] and what they’re being used for,” he says.

“That part is relatively easy, it would just take investment from relevant agencies to conduct survey of fishing groups.

“However, we really also need to understand [what issues are important].

“For example, barramundi migrate between sea and freshwater so even if you had pulled out all the barramundi from the pool, the following wet season you would have recolonisation in the river pools because they swim back upstream.

“But for things like fork-tail catfish and jenkins grunter, that complete their whole life cycle in the river, it raises a whole lot of ecological questions.”

Notes:

This study was a collaborative effort and was presented at the WA Freshwater Fish Symposium. The Centre of Excellence in Natural Resource Management is based in Albany.

Publishing information:

This story was first published in ScienceNetwork WA on Tuesday 19 November 2013.

Written by Laura Glitsos.

Republished with permission.

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