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News Releases 2005
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Reducing bottlenose dolphin entanglements in the South Carolina crab pot fishery may be as simple as keeping the rope tied to the pot in a straight untangled line as it goes into the water, according to NOAA researchers.
The study, prepared for NOAA Fisheries, addresses the highest source of fishery-related dolphin mortality in South Carolina coastal waters which is from entanglement in crab pot lines. NOAA Fisheries funded the study to help address management recommendations from the Bottlenose Dolphin Take Reduction Team a team of stakeholders convened to provide NOAA Fisheries with a framework for a conservation plan to reduce serious injury and mortality of bottlenose dolphins incidental to commercial fisheries.
"We looked at the fishery and found how the gear was deployed may be more important than what type of gear it is,” says Wayne McFee, a wildlife research biologist with NOAA’s National Ocean Service National Center for Coastal Ocean Science Center for Coastal Environmental Health and Biomolecular Research in Charleston, S.C.
“If the fisher puts that pot over the stern, and then makes an arc around the pot, letting the line out smoothly to the end, the line goes straight to the bottom and lies straight on the bottom next to the pot, which would reduce the risk of entanglement,” McFee said, explaining his findings. “If the fisher puts the pot over and picks up the coil of line and just drops the whole thing over, then the line has a tendency to ‘nest’ on the bottom with coiled loops of rope that float upward from the bottom, increasing the risk of entanglement. Neatness counts.”
McFee's dolphin entanglement research is part of a longer-term study a NOAA research team has been conducting looking at causes of marine mammal mortality along the southern United States Coast. Fishing gear of various types can attract the curious marine mammals and is one area of the research focus.
The NOAA research team examined types and lengths of ropes at different tidal stages, current strengths, and water depths. An ideal rope would reduce the risk of entanglement by lying flat and straight on the bottom, possibly by matching the length and type of rope to the water depth and current strength. Particular attention was made during slack tide when it appears dolphins are at a higher risk of entanglement.
Results indicated that lead-core rope of all lengths tended to bend, developing loops that floated off the bottom unless the pots were in a strong current in deep water. Braided nylon ropes, typically used by crab fishers, showed variable results with different rope lengths in varying water depths and currents.
The results of the study are now being reviewed by NOAA Fisheries with the hope that it will produce recommendations to help the crab pot fishery reduce the risk of bottlenose dolphin entanglement. “No matter how the pots are deployed, there is still the chance of entanglement by curious dolphins that may play with the buoy," McFee said,
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