Estuary electrofishing – a quantum leap for fish surveys

The new electrofishing unit can efficiently capture fish in estuaries whereas previously the technique has been limited to freshwater.

IN a world first, tests on a new electrofishing research boat, called a Grassl electrofisher, have proven very successful.

The new electrofishing unit, designed by Hans Grassl from Germany, can efficiently capture fish in estuaries.

This now opens a wealth of opportunities to carry out fish research in these environments, including demonstrating outcomes from management interventions.

While electrofishing is a key method for sampling fish worldwide, up until now it has been confined to use in freshwater.

This is because it doesn’t work effectively in waters with high electrical conductivities, such as estuaries and brackish environments.

“This electrofisher works in water almost as salty as sea water. It is a real game changer, significantly extending our ability to study fish in estuarine and brackish waters” says Jason Lieschke from the Arthur Rylah Institute (ARI), Department of Environment Land Water and Planning.

Electrofishing involves an electrical current being delivered through the water, which temporarily stuns fish and enables them to be collected, measured and then returned to the water.

There are three types of electrofisher – backpack, bank mounted and boat, and their use depends on the characteristics of the environment.

“We’ve caught large numbers of estuarine fishes, such as mulloway (Argyrosomus japonicus), black bream (Acanthopagrus butcheri) and dusky flathead (Platycephalus fuscus) using the Grassl electrofisher,” Mr Lieschke said.

“Using this research method in estuaries can be cheaper, more efficient and cause less disruption to the fish – so there are plenty of benefits.

“Our laboratory and field tests showed the capabilities of this unit over a wide range of electrical conductivities.  This information is essential for fish ecologists in identifying which local environmental conditions will be ideal for its use.”

The Grassl electrofisher is clearly a viable option to sample fish in estuaries and brackish habitats. This means fish ecologists across the world now have a much better ability to comprehensively assess fish populations in these environments.  

This work was a collaboration between ARI, Hans Grassl from Germany and Jan Dean from Dean Electrofishing LCC in the USA.

The paper, ‘Extending the effectiveness of electrofishing to estuarine habitats: Laboratory and field assessments’ by JA Lieschke, JC Dean and A Pickworth was published in Transactions of the American Fisheries Society and is a feature article. It can be accessed HERE

More information about estuary electrofishing can also b found in the video below.

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