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Pictured above: Unless it’s destined for the fish box, a tuna should not be removed from the water.
It’s a scene from every offshore fisherman’s dreams. You’re standing on the back deck of the boat at first light, watching your lures skip over glassy-calm seas, anxiously awaiting the sound of a screaming drag. Then, it happens. An explosion on the ballyhoo on the long rigger takes the rod down hard. Seconds later, the spreader bar on the short rigger is demolished, followed by the two bars on the flatlines. Amidst the sound of popping outrigger clips and screaming drags, chaos ensues as the crew scrambles into action. When the dust clears, you’ve got seven in the box—all nice 50-pound-class yellows.
On the East Coast, there is probably no large pelagic fish more widely targeted by recreational anglers than yellowfin tuna. Known for their hard-fighting nature, propensity for inciting chaos with multiple simultaneous hookups, and delicious meat, yellowfin drive anglers to travel hundreds of miles and spend thousands on fuel, ice, tackle, and bait in search of the ultimate thrill of a wide-open bite. In fact, each year around 45% of all offshore charterboat trips originating from ports in the U.S. Atlantic target yellowfin, and total annual U.S. recreational yellowfin landings are more than double all other recreational tuna landings combined—that’s bluefin, bigeye, albacore, and skipjack. Add U.S. recreational swordfish and shortfin mako landings to the mix, and you still don’t come close to matching yellowfin landings.
Unfortunately, such demand and popularity comes with consequences. According to the 2016 stock assessment performed by the International Commission for the Conservation of Atlantic Tunas (ICCAT), the Atlantic yellowfin stock is overfished—although the good news is that the stock biomass is only slightly below target levels. To complicate matters, the stock assessment models used by ICCAT scientists have yielded inconsistent results, which cloud our understanding of the true status of the Atlantic stock. In the face of scientific uncertainty and the stock’s overfished status, there is a clear need to better understand the biology and ecology of this valuable species and to find ways to rebuild its depleted population.
In the U.S. Atlantic, yellowfin are managed domestically by the National Marine Fisheries Service Highly Migratory Species (HMS) Branch, a group that is responsible for monitoring commercial and recreational harvest of all HMS including tunas, sharks, and billfishes. Under current federal regulations, recreational anglers may retain three yellowfin tuna measuring greater than 27 inches (curved fork length) per person per trip. When fishing is good, yellowfin limits for crews of even six to eight anglers are obtainable, setting up a scenario in which all yellowfin that are caught in excess of the bag limit must be released. Anglers also must practice catch and release on small yellowfin that are less than the 27-inch minimum size, and some anglers even voluntarily release fish in the 28- to 32-inch class. Believe it or not, data from the National Marine Fisheries Service Large Pelagics Survey suggest that up to 40% of all the recreationally caught yellowfin are released in a given year, with an estimated 4,600 yellowfin being returned to the sea over the past five years—far more releases than have occurred for all other tuna species combined.
Help Scientists Study Tropical Tuna
Despite being captured extensively by commercial and recreational fisheries, we know strikingly little about the life history of tropical tunas like bigeye, skipjack, and yellowfin in the Atlantic Ocean. Data deficiencies on even basic aspects of their biology such as movement patterns/migration, growth rates, size and age at maturity, and spawning dynamics make assessing and managing these species difficult, especially given their highly migratory lifestyle. Fortunately, we are in a great position to gain a better understanding of the life history of these long-distance ocean travelers. Using support awarded to Dr. Golet at the University of Maine by NOAA’s Cooperative Research Program, the NOAA Saltonstall-Kennedy Program, and ICCAT, he and his colleagues will start filling in these data gaps. However, to do this, we need your help! One component of this project relies on the collection of otoliths (fish earbones that can be used to estimate age), stomach, and reproductive organs of tuna—basically, pieces of the tuna that you would otherwise throw overboard! If you want to help us collect important samples, simply hold onto your carcasses after you remove the good parts and we will arrange to pick them up. In addition, this summer we will begin a large conventional and electronic tagging project on bigeye, skipjack, and yellowfin tuna throughout the western north Atlantic. This project aims to deploy these tags from Canada to Venezuela, including the Gulf of Mexico and the Caribbean, and we can provide any interested volunteer taggers with free conventional tags to deploy on these species during your normal fishing trips. If you are interested in helping us collect these valuable biological samples or participating in our volunteer conventional tagging program, please reach out to Dr. Walt Golet (walter.golet@maine.edu) or Dr. Jeff Kneebone (jkneebone@neaq.org) and we can provide you with more information on how to become involved in our research.
For many popular recreational fish species like largemouth bass and striped bass, catch and release is an effective method for mitigating fishing mortality, as long as released fish are captured and handled appropriately. But, what about post-release survival rates in large pelagic fish such as sharks, billfish, and tuna, which fight hard, take a long time to land—sometimes completely exhausting themselves in the process—and are difficult to handle at boatside? Well, research has shown that post-release survival rates for these fish varies considerably among species and are impacted by factors like a species’ physiology, the tackle/gear used, fight time, and how released fish are handled.
For example, research out of the Virginia Institute for Marine Science (VIMS) has shown that Atlantic bluefin tuna caught with trolling gear and light-tackle spinning rods exhibit 100% survival even when fought for periods up to 78 minutes. On the other hand, data from the Pfleger Institute of Environmental Research in Oceanside, California, have demonstrated that prolonged fight times over 200 minutes can be lethal for Pacific bluefin tuna when caught on similar fishing gear. Handling method can also have a large effect on survival, as evidenced by a recent VIMS study showing that white marlin removed from the water prior to release are ten times more likely to die than those released without being removed from the water. Even a simple thing like hook type has a big impact on survival rates, with several studies demonstrating that species such as white marlin, sailfish, and shortfin mako exhibit higher survival rates when caught on circle hooks rather than traditional J-hooks.
However, no previous studies have thoroughly examined the effects of rod-and-reel capture on the post-release survival of yellowfin tuna, even though it is one of the most frequently-released large pelagic species. Seeing the opportunity to expand our knowledge and generate best-practice capture and handling recommendations for recreational anglers, our research group (led by Dr. Walt Golet at the University of Maine) received funding from the NOAA Saltonstall-Kennedy Program to estimate the survival rate of yellowfin following release in the recreational troll fishery using pop-up satellite tags. Since yellowfin are primarily targeted over the broad region from Cape Hatteras, North Carolina, to the southern New England canyons, we decided to focus our study in this region and to use the gear and techniques most commonly used in the troll fishery, including 30- to 80-pound-class stand-up rods, 12- to 80-pound-class reels, and a variety of popular lures including skirted ballyhoo, green machines, and spreader bars.
Oregon Inlet Madness And Southern New England Struggles
Armed with 50 pop-up satellite tags, our research kicked off in June 2016 with three solid days of fishing aboard Captain Rom Whitaker’s Release out of Oregon Inlet, North Carolina, in which 18 yellows were tagged and released. Returning in June 2017, another 21 fish couldn’t resist Captain Rom’s offerings, bringing our total to 39 fish tagged over six days. Unfortunately, as is often the case with tuna fishing, our productivity slowed dramatically when we tried to deploy the remaining tags in the southern New England canyons in summer 2016 and 2017. As many of you may have experienced, the yellowfin fishing in this area was hardly up to snuff over the past two seasons and we were only able to get tags on five fish during six trips to the edge. While our work is not yet done, the good news is that 44 of our 50 tags have been deployed on fish ranging from 30 to 47.5 inches curved fork length (about 20 to 50 pounds), and this summer we plan to deploy our remaining tags on yellowfin in the southern New England region.
For each tagged fish, we recorded the fight time, the gear (rod/reel type and class), lure type, hook type and size, hooking location, fish condition, and handling time. To ensure proper placement of the pop-up tag at the base of the second dorsal fin, all fish were brought onboard for unhooking and tagging. Larger fish were lip-gaffed and slid the through the tuna door, while smaller fish were swung through the door or over the rail by the leader. While on deck, fish were placed on a wet rubber mat with a wet towel over their eyes, a proven technique for keeping tuna calm on deck, and then released head first out the tuna door (larger fish) or over the rail (smaller fish). Previous studies showed that most post-release mortality usually occurs within 72 hours of release, thus, the fate of each tagged fish was inferred three days after release based on temperature, depth, and light level data transmitted from the pop-up tag.
Early Results
Tagged yellowfin were fought for periods of 3 to 20 minutes and kept out of water for no more than 2 minutes for unhooking, measurement, and tagging. All fish were hooked in the mouth with J-hooks and appeared to be in good condition at release. Examination of the available data from 41 reporting tags (three tags failed to report via satellite) that remained on the fish for periods of 3 to 60 days indicated that 40 fish were alive after three days, a survival rate of over 97%. Three surviving fish were even recaptured—two by recreational anglers and one by a pelagic longline vessel—as quickly as ten days after release! However, despite this high survival rate, four fish were not so lucky in the long run and appeared to have been eaten by sharks 8 to 30 days after release. It’s hard to say for certain whether tagging influenced these predation events, however, given the number of days between release and the predation event, and the fact that many a yellowfin has fallen victim to sharks off North Carolina over the past years, it seems these may have been natural occurrences.
Nonetheless, our preliminary data suggest that yellowfin are a resilient species capable of recovering from and surviving capture on typical trolling gear when fought for up to 20 minutes and handled properly. However, it is important to note that although all fish monitored in our study were brought onboard for tagging, under current U.S. federal law it is illegal to remove yellowfin, or any HMS (tunas, sharks, billfish) for that matter, from the water before release. Given this law, any yellowfin that you intend to release must be kept in the water during de-hooking. Many good de-hooking devices are on the market today and should be effective at removing the J-hooks typically used in trolling lures from the mouths of yellowfin. If in-water de-hooking is difficult due to the sea conditions, or if the fish just doesn’t want to behave, we recommend cutting the leader as close to the hook as possible, again, while the fish is in the water. Following these simple and logical guidelines will ensure you remain in compliance with federal laws, and will maximize the chance that yellowfin and other HMS that recreational anglers love to target survive to fight another day.
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References:
French, R.P., Lyle, J., Tracey, S., Currie, S. and Semmens, J.M., 2015. High survivorship after catch-and-release fishing suggests physiological resilience in the endothermic shortfin mako shark (Isurus oxyrinchus). Conservation physiology, 3(1), p.cov044.
Goldsmith, W.M., Scheld, A.M. and Graves, J.E., 2017. Performance of a low-cost, solar-powered pop-up satellite archival tag for assessing post-release mortality of Atlantic bluefin tuna (Thunnus thynnus) caught in the US East Coast light-tackle recreational fishery. Animal Biotelemetry, 5(1), p.29.
Horodysky, A.Z. and Graves, J.E., 2005. Application of pop-up satellite archival tag technology to estimate postrelease survival of white marlin (Tetrapturus albidus) caught on circle and straight-shank (“J”) hooks in the western North Atlantic recreational fishery. Fishery Bulletin, 103(1), pp.84-96.
Marcek, B.J. and Graves, J.E., 2014. An Estimate of Postrelease Mortality of School-Size Bluefin Tuna in the US Recreational Troll Fishery. North American Journal of Fisheries Management, 34(3), pp.602-608.
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