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Fishermen Contribute Valuable Bluefin Tuna Data

Aug 21, 2013
Summer 2013

Scientists from the University of Maine, Southeast Fisheries Science Center, University of Massachusetts Amherst Large Pelagic Research lab, and GMRI have teamed up with commercial and recreational bluefin tuna fishermen to develop a novel bluefin tuna sampling and data collection program. It is designed to meet critical data needs associated with improving stock assessments for this highly migratory species. Information and samples collected by the fishing community will enable scientists to determine growth rates, catch at age, reproductive biology, and stock mixing rates that more accurately reflect the current state of the bluefin population. The data collection program, now in its third year, has gathered more than 1,300 samples -- the largest yearly collection ever obtained in the region, representing approximately 20% of the commercially landed fish. Sampling rates from the recreational fishery, though lower than commercial rates, have increased year after year.

Prized for their flavor, bluefin tuna have been pursued by several countries across the Atlantic for decades. Stock assessments suggest that the western Atlantic bluefin tuna stock began experiencing a substantial decline in the early 1970s. To keep in line with scientific advice, catch limits have been in place since the 1980s. Since then, the United States has led conservation efforts to rebuild the stocks including maintaining the world's largest commercial minimum size (73 inches), establishing daily retention limits, annual harvest caps, and engaging in extensive collaborative research efforts such as aerial surveys and tagging studies. 

The new sampling program collects otoliths (ear bones), gonads, and morphometric (body shape) measurements from bluefin tuna. Participating commercial fishermen can provide commercial seafood dealers with their samples. The dealers prepare and label individual fish with length, weight, and location information for pick up by biological samplers. Accessing recreationally landed fish is more problematic since these fish do not pass through dealers. To engage recreational participants in the program, freezers are being placed at strategic locations. Anglers are asked to place properly labeled tuna heads into the freezers for biologists to pick up at a later time. In the initial pilot, one freezer was installed at Cape Ann Marina in Gloucester, MA, and scientists are hoping to expand to additional locations in the near future. 

In the coming months, scientists from the University of Maryland will process the otoliths to determine where each fish was spawned (Gulf of Mexico or Mediterranean Sea). Incorporating these new data into the overall stock assessment process will take time. Nevertheless, scientists hope that incorporating this additional data will result in a more robust and comprehensive stock assessment. The data generated from this collaborative effort can produce unprecedented amounts of information, enhancing the scientific understanding of the species and ensuring sustainable management.

 

To learn more and/or if you wish to participate, contact Walt Golet by email at wgolet@gmri.org or at 207-228-1695