In experiments with tagged fish, the researchers go offshore several more times to see which fish they catch again. A gray triggerfish experiencing barotrauma, with intestines pushed out of its anus, is tagged before releasing back to the ocean.
Importantly, they also dive to the sea floor to tag fish that haven’t been brought to the surface, for comparison. Once a fish is caught, they check for any signs of barotrauma, attach a tag or transmitter to the outside of the fish, and then release the fish back into the ocean. “Our work on discard mortality would not have been possible without the knowledge and collaboration of both commercial and recreational fishermen,” noted Rudershausen. Senior research scholar Paul Rudershausen, doctoral candidate Brendan Runde, and others in the Buckel group have conducted experiments with species such as black sea bass, gray triggerfish, scamp, snowy grouper, speckled hind, dolphinfish and cobia. Their experiments begin by catching fish, often hundreds to thousands of them per experiment. Since then, Buckel’s research group has studied discarded fish off the coast of North Carolina to help improve fisheries management. Buckel is on the Scientific and Statistical Committee of the South Atlantic Fishery Management Council, or SAFMC, the agency that sets fishing regulations in waters between three to 200 nautical miles off the shores of North Carolina to Florida.īuckel saw firsthand how uncertainty in survival rates of discarded fish translated into uncertainty in the conservation of these species. This overall increase is probably from a mix of increased fishing effort, such as number of boats and amount of time spent on the water, and changes in regulations that dictate which fish can be kept.Ībout 15 years ago, this increase in discarded black sea bass began to concern Jeff Buckel, a professor at CMAST. In recent years, gray triggerfish discards have been two to three times higher than the number kept. Over the past 20 years, discarded black sea bass in the US Atlantic and Gulf of Mexico fisheries have outnumbered those brought to shore.
Photo: Brendan RundeĪn angler might discard a fish if they don’t want to keep it or if it doesn’t meet regulations, such as a size limit, catch limit or closed season. A black sea bass with a protruding stomach shows signs of barotrauma. That fish might die at the surface or a predator might pick it off. A bloated swim bladder can also act like swim floaties, preventing the fish from returning to deeper water when it’s released. The fish’s eyes may bulge out of its head. The gas inside a fish’s swim bladder, an internal organ that helps them float, expands and can even push other organs out of the fish’s mouth. When fish from about that depth or deeper are brought to the surface, the sudden drop in pressure can lead to injuries called barotrauma.īarotrauma looks extremely uncomfortable. The pressure at 90 feet underwater is almost four times greater than at sea level. They’ve also confirmed that helping a fish get back to deep water, through strategies like venting and recompression, significantly increases a fish’s chance of survival.ĭeepwater fish live under pressure. Over the past few years, they’ve determined discard survival likelihood for several deep fish species. Researchers at North Carolina State University’s Center for Marine Science and Technology, or CMAST, have been studying the fate of released fish, called discards, to more accurately estimate death rates from fishing and to improve survival of discards. Rising numbers of released fish, combined with an uncertain likelihood of their survival, has made it more challenging to estimate how many fish die after release, which is a crucial factor considered when creating fishing regulations. The chance of that fish’s survival is less clear. Photo: Brendan RundeĪfter hooking a fish, reeling it in from the sea floor and posing for a photo, there’s a fairly good chance a recreational fisher might release their catch back into the ocean. Brendan Runde and his grouper tagging crew on the R/V Cape Fear, a UNC Wilmington vessel.
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