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June 27, 2011

Proper Fish Venting

Doing it right is an easy and effective way to release bottomfish

This story is my “ace of fins,” the card I play when anyone suggests that venting a fish does more harm than good.

As the facts go, we were bottomfishing near Bimini, Bahamas, in 70 feet of water when I landed a 12-pound red grouper. The fish’s swim bladder had expanded, virtually guaranteeing the grouper’s death if it was released as is. Minus a venting tool (this was 15 years ago), I laid the fish upon a wet towel placed on the gunwale. I slightly punctured the rise in the flesh just aft of its pectoral fin with the end of the point of a thin fillet knife, expelled the trapped gasses from its swim bladder and released the fish. It swam slowly for bottom, seemingly none the worse for wear. This was confirmed by the underwater videographer, who was shooting the action for a bottomfishing video.

Four months later, we returned to the same numbers and caught the same grouper, easily identifiable by the light venting scar. I repeated the procedure and returned the fish to the ocean. And if that wasn’t coincidence enough, I caught the same fish the next time I fished that spot. Once again I vented and released it.

After that, I never saw that red grouper again, leaving me to wonder if it ultimately ended up in someone’s cooler, moved from that section of reef or died. Yet the bottom line remains the same: That fish had three opportunities to thrive and spawn over the course of eight months due to my venting it. There is little doubt about its fate had it not been vented: It would have wallowed at the surface and become an easy meal for a predator or died and floated away with the current.

To Poke or Not to Poke?

Whether venting a fish is beneficial or harmful stirs much debate. There’s no denying that it can be stressful and sometimes fatal to a fish if done incorrectly. That’s why, after you acquire enough fish for a few dinners, it’s always sound practice to leave a bottomfishing spot or alter your tactics to catch fish at or near the surface. Yet even when food fishing, you are likely to catch undersize, undesirable or protected bottom species, which must be returned to the sea, before you limit out. And when these fish are reeled up from depths greater than 50 feet, the likelihood of swim bladder expansion and rupture — referred to as rapid decompression — is high. This is when venting becomes a viable option.

It should be noted that venting is required by law in Gulf of Mexico waters should an unwanted bottomfish come up bloated or have difficulty swimming back down. Though it is yet to be law along the rest of the coastal United States, it is often a sound choice. Off the West Coast, recompression is the preferred tactic. This involves returning a fish safely to the depths via weights so the increasing pressures recompress the gasses in the expanded bladder.

The Good Doctor
Dr. Karen Burns, Gulf of Mexico Fishery Management Council ecosystems management specialist, says reef fish rapidly brought up from depths of 50 feet or more are vulnerable to the expansion of the gasses within their swim bladders. Many times these swim bladders burst, and the escaping and expanding gasses fill the fish’s body cavities. Burns explains that reef fish such as red grouper, red snapper and vermilion snapper can experience swim bladder rupture beginning at 33 feet (the equivalent of one atmosphere). When a fish is on the bottom, the pressures associated with depth compress the gasses so they fit in its swim bladder. As a bottomfish is rapidly brought up from the deep, the decrease in pressure allows the gasses to expand. As Burns points out, decompression when a fish is coming up leads to swim bladder expansion and rupturing. Rapid decompression is evidenced by the stomach protruding from a fish’s mouth, the intestines protruding from a fish’s anus or the bloating of the area behind a fish’s pectoral fins.

Venting is especially effective on reef fish, like groupers, snappers and sea bass, which have large swim bladders. These are true bottom dwellers and the most vulnerable to bladder expansion. Other species with smaller, thicker swim bladders can traverse the water column with less threat of barotrauma, and others with no swim bladders at all, like sharks, swordfish, cobia and mackerel, are immune to the problem. This is why they can dive deep during a fight and swim back to the surface with no apparent ill effects.