A new study has ingeniously reconstructed a 103-year record of the Queensland east coast Spanish mackerel spawning fishery, and revealed that catch rates have declined by 70 per cent over the past 80 years.
The research will be presented in Canberra on June 14 2017.
The ARC Centre of Excellence for Coral Reef Studies (Coral CoE) and University of Queensland (UQ) study documented the decline by combining data from historical newspapers with fisher memories.
Lead author and Coral CoE PhD graduate Dr Sarah Buckley, now at the Sea-Fisheries Protection Authority in Ireland, said the decline has had substantial consequences.
“For the past 20 years the Cairns fishery has been commercially extinct and the Townsville spawning aggregations have remained completely offshore,” she said.
Co-author Professor John Pandolfi of Coral CoE and the School of Biological Sciences at UQ said the conservation of spawning aggregations of fish was one of a suite of management tools that could contribute to healthy fish populations.
“Managers need to consider increased protection of Spanish mackerel during this critical time if it is hoped that catch rates can be increased,” Professor Pandolfi said.
Spanish mackerel are large and important recreational and commercial fish found in Queensland and northern New South Wales waters.
Annually they form huge aggregations for breeding purposes at discrete locations for a confined period of time in the Great Barrier Reef.
Although this fishery commenced over 100 years ago, official commercial catch and effort were not recorded by the Government until the 1980s, leaving large gaps in our understanding of long-term changes in the fish spawning aggregations, some of which disappeared undetected.
The scientists interviewed commercial fishers about their memories of changes to catch, gear and technology and locations fished, to reconstruct a valuable and comprehensive record.
Co-author Dr Ruth Thurstan of Deakin University said Spanish mackerel fishers were able to recall fishing from as early as the 1940s, providing a wealth of knowledge that could be used to plug these historical data gaps.
Preventing decline and loss of fish spawning aggregations is a priority for the Great Barrier Marine Park Authority.
These data are currently being used by the Queensland Government to inform stock assessment, demonstrating the valuable knowledge that is held by long-term fishers and in our local archives.
Professor Pandolfi will be presenting on the ‘Subtropical bleaching event along the eastern Australian coastline’ at the Coral Reef Futures Symposium 2017 (15 – 16 June 2017, Shine Dome, Canberra).
A public forum will be hosted by science communicator, Dr Karl Kruszelnicki on Thursday, June 15 2017.
Image caption: Part of a catch of 53 large Spanish mackerel taken on one hook within three hours, pre-1911. Source: D. Stead, The Future of Commercial Fishing in New South Wales, 1911.