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Source: University of Canterbury

02 July 2021

New research into whitebait fishing will address whether whitebait are in decline and assess the impact of commercial and recreational whitebaiting on the long-term sustainability of the species.

The multi-disciplinary project led by University of Canterbury (UC) Research Associate Dr Mike Hickford will be the first to integrate ecological and fishery data to understand whitebait population dynamics.

“There is a general belief that adult populations of most of New Zealand’s whitebait species are declining nationwide, but it is unknown whether overfishing is to blame, or if other factors have disrupted the lifecycle of these fishes,” says Dr Hickford.

“The whitebait fishery is at a crossroads, but there is little basis to select an effective management strategy.”

Dr Hickford says the whitebait fishery is unusual because it targets small, immature fish, so it is difficult to determine the degree to which whitebait fishing has flow-on effects on future populations.

“This new research focuses on whether whitebaiting limits adult populations, and the role that climatic factors and habitat degradation might play in declining adult numbers. It also investigates whether the fishery is actually declining, as there is no reliable catch data to show this is the case, or if a perception of declining catches is due to ever-increasing numbers of fishers after the same resource.

“The major fished species is īnanga, an annual species. They lay their eggs on stream banks, and larvae live in marine waters before returning to freshwater as whitebait in their teeming millions, hence a historically productive fishery. However, within months of whitebait entering waterways, their adult populations are much smaller. This happens naturally but is exacerbated by habitat degradation. The underlying problem is that the effects of whitebaiting are unknown, relative to their high natural mortality.

“Research to date also indicates that some historically unfished streams have more adult fish than nearby fished streams, but the unfished populations have slower growth and produce fewer eggs, so may have no net gain for future populations.”

The new research uses innovative experiments in rivers closed to whitebaiting to isolate fishery and habitat effects on populations, analyses previously unavailable data to reconstruct catch statistics, and develops new methods to assess catch and effort and establish a baseline to determine future changes in the fishery.

The research team includes UC’s Distinguished Professor David Schiel, and Professor Angus McIntosh; Professor George Perry from University of Auckland; Dr Shane Orchard from Waterlink Consulting; and Dr Eimear Egan from National Institute of Water and Atmospheric Research.

“We’ve known for years about the increasing pressures on these iconic taonga species,” says Dr Hickford.

“Our research will provide information urgently needed to support critical decisions on the future of the fishery. Along with our end-user partners and management agencies, we aim for the recovery of whitebait species and their return to ‘non-threatened’ status. Together we plan to overcome the current guesswork approach to the integration of conservation planning and fisheries management, while there is still time to reorient the fishery towards long-term sustainability.”

Where nature and knowledge collide, University of Canterbury researchers are building Sustainable Futures. Throughout July, we are sharing some of the innovative research University of Canterbury academics are creating to grow society’s understanding of the natural world and shape a sustainable future for generations to come. He Kaitiaki tatou katoa – We will enhance and nurture our resources.

See University of Canterbury research building towards a Sustainable Future.

MIL OSI