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More Undersize Catches Can Survive With “Venting” Method

Cindy Spence
John Stevely (941) 722-4524, ext. 239

SARASOTA—Imagine you’re the captain of a charter vessel taking a bunch of anglers to sea for a day of fishing. They catch a beautiful grouper, but it’s a few inches undersize, so you have to take the fish off the line and throw it back.

After all, it’s the law. Now imagine that the fish floats away on the waves, unable to descend to its normal depth, and is snapped up by a bird looking for dinner.

The fishermen are irritated, you’ve lost any word-of-mouth business and fisheries laws look pretty silly.

That’s the scenario the University of Florida and the Florida Sea Grant College program are trying to prevent. Frank Lawlor and John Stevely, marine extension agents for Sea Grant and UF’s Institute of Food and Agricultural Sciences, are teaching charter captains and fishermen a technique to help undersize reef fish survive after they are tossed back into the water.

The problem is with the creature’s swim bladder, an organ the fish uses to regulate its buoyancy, Stevely says. When a reef fish like snapper or grouper is hooked in deep water and reeled to the surface quickly, its swim bladder does not have time to adjust to the change in water pressure.

The swim bladder ruptures and swim bladder gas fills the gut cavity. An undersize fish with air in its gut cavity has no chance for survival when tossed back into the sea because it can’t descend or right itself to swim.

“An 18-inch grouper is a beautiful fish,” says Stevely. “It could be the largest fish someone has ever caught, and then if the captain throws it back and the fish floats away on the surface of the water it really irritates them.

“Sea Grant got involved when charter captains asked for help. They were returning more undersize fish to the water, but many clients were distressed about throwing back fish that looked like they were going to die anyway,” Stevely said. “Coming up with a means of increasing survival of the released fish was important, because if the fish returned to the water don’t survive, then fisheries management laws will not be very effective.”

Frustrated charter captains had been trying to deflate fish, but were using techniques that injured the fish further. Some fishermen were jabbing the fish with a knife or ice pick and cutting internal organs. Others were just squeezing the fish until the gut cavity popped.

Sea Grant stepped in and designed a venting method that deflates the gut cavity and gives fish the best chance for survival. A tool made of a hollow steel cylinder is inserted underneath a scale behind the base of the pectoral fin to release trapped air. The tools that will work include a sharpened sports ball inflating pin or a veterinarian’s cannula. The point is that it is hollow and allows gas to escape.

“By giving the fishermen a means of venting, we’re promoting voluntary compliance with fisheries laws,” Stevely said. “It’s important to return the smaller catches so the fish have a chance to grow, reproduce, replenish the stock and perhaps be caught another day, when they are bigger.”

The small puncture wound inflicted by the venting tool has a good chance to heal because the cut is small and covered by muscle and scales. The swim bladder itself heals in about four days. And fish that are vented at least have a chance for survival, unlike a fish with an inflated gut cavity.

Mote Marine Laboratory in Sarasota has collaborated with Sea Grant on evaluating venting methods, and Karen Burns, Mote fisheries biology program manager, said venting increases the survival of undersize catches that are thrown back.

“If the minimum size regulation is to work, then we need to make sure that undersize fish that are thrown back survive,” Burns said. “This is an easy, shipboard method to enhance the survival of undersize fish.”

Fishermen don’t mind following laws that force them to throw back undersize reef fish, Stevely said. They just get frustrated throwing back a fish that is going to die anyway. Most fishermen are conservation-minded and understand that the minimum-size laws are designed to allow fish to spawn, replenishing populations and making for good fishing for generations to come.

“Venting is an important part of the fisheries management process,” Stevely said. “We can put down rules about returning undersize catches to the water, but we need to take the next step and try to ensure that they survive. It’s a great stride forward, and that’s why this work is so important.”