Chemical prints finger fish

Chemical prints finger fish

A technique that collects chemical ‘fingerprints’ from the ear bones of fish to help scientists identify which estuaries they originated from could have important implications for the management of New Zealand’s local fisheries, said a report published today by the National Institute of Water & Atmospheric Research (NIWA).

Estuaries are vital nursery areas for many of New Zealand’s valuable coastal fish, including snapper. Unfortunately, estuaries are very vulnerable to human activities, and few, if any, in New Zealand remain in a pristine state, said NIWA fisheries scientist Mark Morrison. “Sedimentation, chemical runoff, pollution, and foreshore reclamation all have negative effects on our estuaries. Their effects on important juvenile fish habitats can be devastating, and may lead to a drop in adult fish populations.”

NIWA’s National Centre for Fisheries & Aquaculture is developing techniques to trace the links between fish nursery habitats in estuaries and adult fish habitats in the open coast. One technique showing great potential for a wide range of fish species and habitats is the identification of chemical ‘signatures’ of particular estuaries in fish ear bones (otoliths).

“Juvenile fish that have spent their whole life in a single estuary will take up chemicals from their environment through food or directly from the water. The amount of chemicals in the estuary is reflected in the fish’s ear bones or tissues, and it’s these chemical fingerprints that we hope will help us to establish chemical signatures for different estuaries,” said Dr Morrison.

NIWA is currently sampling snapper less than 1 year old by this method from estuaries in the west coast of the North Island. If this technique is successful, scientists will be able to find out how different estuaries contribute to adult fish populations, assess the movement of fish from estuaries over time along the open coast, and possibly investigate the homing behaviour of fish over larger areas.

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