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Flyfishing in Saltwaters, May/June 2010
THE TRUTH ABOUT ďCATCH AND RELEASEĒ MORTALITY
And what we can do to help
By Capt. John McMurray
Saltwater flyfishers are perhaps the most conservation-minded users of marine resources out there. The catch-and-release ethic is certainly more prevalent with us than anywhere else. Indeed, thatís a good thing, but ďrelease discardsĒ (those fish that donít survive the battle) are a considerable source of motility in many fisheries. Flyfishers could arguably be more responsible than other users for ďcryptic mortalityĒ because of the inefficient gear we use. Bringing those large fish boat-side inevitably takes longer than it would if we were using traditional saltwater gear, and itís become fairly well known that the longer the fight, the less chance that fish has of surviving. Thus, I thought it was worthy of addressing here.
Letís take a look at bonefish first. While there isnít really any science out there showing that the species is overfished, or that overfishing is occurring, there are concerns over the sustainability of some localized bonefish populations given expanding recreational fishing. There is mounting evidence that at least some populations are experiencing negative shifts in both abundance and size. Given that very few folks keep bonefish, itís widely believed that such changes are the result of increasing recreational discard mortality.
A 1998 study in which post-release bonefish were held and observed in an artificial lagoon with no predators, showed a low release mortality rate - only 4.1% despite the fact that some fish were released as many as 10 times. In a 2002 study conducted in the Bahamas, scientists assessed mortality following bonefish releases in two regions of the Bahamas, each with differing shark abundances. All observed mortality was from fish being killed by sharks within 30 minutes of capture. In the low shark abundance areas there was no mortality, whereas in the high shark abundance areas, almost 40% release mortality was documented.
So, release mortality is probably quite substantial in real-world marine ecosystems. Minimizing the fight and releasing fish in suitable conditions away from predators is pretty important if we want bonefish populations to remain healthy. But itís hard to argue that angles releasing bonefish donít have an impact on the stock.
While Tarpon are vastly different creatures, the same sort of predation mortality exists after release. During a recent study in Boca Grand Pass, a confirmed 10% of fish released were killed by sharks, but the scientists conducting the study acknowledged that the unobserved shark related mortality was probably much higher.
Yet even in the absence of sharks, tarpon are so large and fight so hard that they can and often do seriously compromise their survival systems. A long fight may spell the end of a tarpon and there have been studies that show such a correlation. Even if a tarpon survives the fight, it may not get back to normal. In time, the resulting changes reduce growth and maturation rates and as well as reproductive success.
Fishing pressure tarpon is heaviest during peak spawning season - May to July. And those larger tarpon that flyfishers tend to target on the flats are ripe females. During this time of year tarpon put more energy into reproduction and their lower energy reserves can result in difficulty recovering from the stress of a fight. Warmer water temperatures have also been shown to cause more stress. That said, studies indicate that large adult tarpon can recover well from if not attacked by sharks and handled with care. However, smaller adult tarpon may be more likely to die after release due to being easier to handle and lift, thus keeping them out of the water longer.
Obviously tarpon are generally not kept, at least not in the states, and thus there isnít a lot of info out there on the state of tarpon stocks. But folks have been expressing concern over declining opportunities to target them for decades. Without a doubt catch and release angling has an impact. The extent of that impact isnít really known though, but Bonefish and Tarpon Trust is currently working on a study that seeks to address this.
Moving on to snook, because snook support one of the largest recreational fisheries in Florida and because of their complex biology and susceptibility to low water temperature events, managers have put in effect strict regulations that emphasize low bag limits, closed seasons, while putting a lot of emphasis on catch-and-release. But even with a low assumed release mortality rate of 2.13% the magnitude and consequences of release mortality are great. According to the Florida Fish and Wildlife Conservation Commission 43% of the total number of snook harvested were lost to cryptic mortality. But this estimate assumes a single snook is caught only one time in the year. Studies have shown that snook may be caught as many as 4 times a year. This means that the real loss to release mortality is not the 2.13% but is may be much higher. It is fair odds that perhaps half of the total harvest of snook die each year from the trauma of release.
A similar problem exists with the Red Drum fishery. Since 1982 recreational fishing has accounted for about 87% of all red drum fishing. The assumed recreational release mortality is 8%. The percentage of fish that are caught and released has increased from about 4% in 1982 to more than 83% in 2008. Furthermore red drum appear to recover more slowly during the spawning season and may be subjected to higher predation or decreased spawning success after a catch-and-release event.
Because the frequency of catch-and release has increased dramatically for this species in the past two decades, the associated release mortality has increased with it.
Up North, striped bass is no exception. Like red drum the assumed release mortality rate is 8% (Generally, Iíd peg it quite a bit higher based on just what I see in my neck of the woods). The problem manifests itself when you consider the pure volume of the recreational fishery. The last benchmark assessment revealed that recreational dead discards compromise 34% of all the mortality in the fishery. Thatís actually double the total commercial catch during the time period. As I noted in the prior column here, while striped bass appear to be in good shape on paper, many perceive the fishery to be declining significantly, and those fish we release and die later are most certainly part of the problem.
Release mortality is even more relevant when you consider a species such as weakfish, which is in terrible shape. Thereís currently a one fish bag-limit (although there should be moratorium) but certainly itís possible for a saltwater flyfisher to encounter several weakfish during any given fishing trip and weakfish are not what Iíd call sturdy fish. Any mortality associated with a stressed population such as weakfish is likely to cause negative consequences.
And then thereís the fast growing light-tackle/saltwater-flyfishing bluefin tuna fishery. As Iíve detailed more than once in this column, bluefin, is in critical shape. These fish are incredibly strong and fast and the big ones require long drawn-out fights. Not only are these fish frequently stuck in places (eye, nose etc.) that cause excessive bleeding, such fish often fight themselves to the death or close to it. Those flyfishers that target them, myself included, are most certainly responsible for a significant amount of mortality in the bluefin fishery. To claim that is not the case would be to simply overlook what is an obvious reality in a growing fishery.
The take home message is this. Given the growing recreational fishing population and the very real release mortality issues, itís becoming harder and harder to point the finger at other folks for the mounting problems in popular recreational fisheries. I would certainly encourage readers to continue their release practices, but to be ever more diligent in insuring the fish you carefully put back in the water has the best possible chance of survival.
You can find release methods for each fishery by doing an internet search, but the bottom line is to use common sense. That means using the appropriate gear for the job, minimizing the fight and keeping fish in the water. Stay away from Boga Grips, as they have been shown to tear a larger fishís inner organs when used improperly. Likewise, nets are never a good idea, but if you must use one use the rubber kind. Numerous studies that show that cryptic mortality increases dramatically once the water warms, so be even more diligent during those hi-temp times of the year. Lastly, avoid targeting fish during their spawning season. Not only can releasing fish disrupt the reproductive process, but most fish become greatly weekend and susceptible prior during and post spawn.