Abstract:

The Mid-Atlantic coast sees phenomenal inshore juvenile bluefin and yellowfin tuna fishing during the summer months. More and more recreational fishing boats combined with information flowing over the internet and social media has certainly turned some days into an all out circus out there.  Have you ever experienced a hot scallop boat bite with 20 boats releasing upwards of 15-20 plus small bluefin in a few hours? In that frenzy of an epic day while high-fiving all your buddies do you ever stop to think how many of your released fish are actually surviving?  I highly doubt it – and to be perfectly honest with you, I caught my first tuna in the 1980s and it’s only somewhat recently that this question really started to cross my own mind. So I decided it was about time to reach out to some experts and gather perspective on dynamic factors that affect post-release mortality. My first conversation was with Molly Lutcavage, Ph.D – Director of Large Pelagics Research Center (LPRC) and Research Professor at The University of Massachusetts, Boston.  We spoke at length about many aspects of the tuna fishery and she gave me perspective on the subject. Dr. Lutcavage then lead me to two other experts: 1) Rich Brill, Ph.D – Physiologist at Virginia Institute of Marine Science (VIMS) who shared with me some of his in depth research on stress physiology and post-release mortality in large pelagics; and 2) Captain Nat Moody – Night Heron Fishing, Gloucester, Massachusetts – an expert in catch and release since 2000 with hundreds of released bluefin leading to recovered tags to his credit.  Lastly, I had a conversation with Sami Ghandour (Shimano Pro Staff) – Owner, SaltyWater Tackle, Sayreville, New Jersey to get some perspective on how this topic relates to modern spinning gear fishing. The goal of my research was to grow personally as a fisherman as well as better inform other recreational anglers how important their actions on board a vessel actually are to the survival of a released pelagic fish. The discussion will center around the Atlantic Bluefin Tuna but most of what is documented is applicable to all Highly Migratory Species across the board.

Introduction:

According Dr. Lutcavage, the current stock of the Atlantic Bluefin Tuna in all categories has “rebuilt beautifully” over the last few decades.  She adds that “I don’t think that with the low quotas that were enforced between Canada and the U.S. and based on what we saw from aerial surveys in the 90’s – I never felt that the stock assessment represented what the real population was because all they were doing was tracking catch and there were strict quotas.”  More recently – tagging and recovery data on over 800 fish by LPRC has demonstrated that there is extensive gene flow occurring across the entire Atlantic Ocean. The hypothesis that our Mid-Atlantic Bluefin make pilgrimages from the Gulf of Mexico up to the Gulf of Maine and PEI has been disproven. Accurate population size estimates remain a daunting task without time and proper funding simply because the Atlantic Bluefin Tuna is one giant interbreeding population of fish that move constantly and rarely hang with the same pack for long. Capt. Nat Moody shared that one day a few years ago he tagged and released 3 fish all in the 65” class out of Gloucester and in 2017 around the same time period all 3 tags came back. One was 400nm south of Iceland in the Central Atlantic, one was in the Bay of Biscay (Spain) and the other was off Sicily in the Mediterranean. So much for any hypotheses suggesting that schools remain together long periods of time and that these fish follow specific migratory routes.

 

What about the smaller fish?  Dr. Lutcavage shared that a study done in conjunction with VIMS (Virginia Institute of Marine Science) on 1-2 year old juvenile bluefin tuna off the Mid-Atlantic found high levels of PCBs in the fish. PCBs are banned in the US and therefore, not in the concentrations in our waters needed to bioaccumulate to the levels found in the young bluefin. The only plausible explanation was that these little tuna had been born in and foraged in the Eastern Mediterranean Sea where PCB levels are still high enough to cause significant bioaccumulation.  So here are recreational anglers off the coast of Virginia catching 1-2 year old bluefin from all the way across the Atlantic that are high in PCBs. Now we know not just giant bluefin tuna but even juvenile fish are exhibiting this tendency to travel extensively reinforcing Dr. Lutcavage’s assertion that “every bluefin we have tagged is highly mobile”.

Survivorship – the Evidence:

Dr. Lutcavage asserts that when it comes to survivorship, “It’s all about how the fish was caught, its state when it was caught, and how you handled it.”  She adds, “You could have 100% survivorship with the best methods – or pretty darn close – and you could kill every fish you catch if you handle it wrong.”   Of all the tuna species she states “Bluefin are the toughest and we know that yellowfin are more susceptible to post release mortality than bluefin.”  Dr. Lutcavage reports that longliner survivorship for Bluefin Tuna is among some of the highest. Much of what she knows about survivorship has come from long lasting partnerships with commercial fishermen and feedback from tagged fish. She said, “Every fish the Eagle Eye II tagged for us in the Atlantic – both bigeye and bluefin – we didn’t have a single case of mortality. Most likely it’s because the fish are able to swim and breathe better, unless a poor hookset or damage to the palate, and this aides tremendously in survivorship.”  

As far as handling fish, stress physiology, and mortality, Dr. Lutcavage defers to Dr. Rich Brill as someone “who has done most of the work on tuna physiology in the U.S. primarily raising captive yellowfin tuna in Hawaii and observing stress physiologies in tunas.”  She explained “When we first started tracking Bluefin here Rich and I collaborated extensively.” I asked if there was enough research conducted to make “stress physiology on tuna” a well documented field of study and her response was an emphatic “Oh yes. There are many papers, particularly Rich’s work which is very detailed on blood gas properties and really honing in on survivorship of the fish after it’s been stressed.”  A direct quote from published research in which Dr. Brill participated (with Lela Schlenker, Robert Latour, and John Graves) states: “Researchers examining the physiological response to exhaustive exercise (e.g. Iwama et al., 2006) have analysed blood samples taken from fish in the field (Moyes et al., 2006; Heberer et al., 2010; Danylchuk et al., 2014) and laboratory (Mazeaud et al., 1977; Cicia et al., 2012) to quantify levels of capture stress for species that are frequently released by recreational and commercial fisheries. The response to capture and handling typically initiates a suite of reactions that include the following: an accumulation of lactate in white muscle, a decrease in intracellular and extracellular pH, internal fluid shifts, splenic contractions releasing red blood cells into the general circulation, and red blood cell swelling, the latter two driving elevations in haematocrit (Wood, 1991; Kieffer et al., 1995; Brill et al., 2008; Skomal and Mandelman, 2012).”  The research goes on to state “physiological disturbances resulting from exhaustive exercise may be of great enough severity to cause death (Wood et al., 1983), but the identification of physiological predictors of post-release mortality has remained elusive.” Interestingly, Dr. Brill and colleagues did find that shorter fight times led to greater post-release mortality than longer and add “we suggest that short, intense angling events may represent a ‘sprint’ …(i.e. involve a high proportion of anaerobic muscle activity), whereas longer angling events are a ‘jog’ (i.e. involve a high proportion of aerobic muscle activity). This hypothesis is further corroborated by the significant inverse relationship we observed between [K+], a predictor for mortality, and angling time.” The data shows that, in general, large pelagic species “have a high white muscle buffering capacity (Abe et al., 1985; Dobson et al., 1986, Dickson, 1995), which allows these fish rapidly to generate high levels of white muscle lactate, and short angling events involving intense activity and anaerobic metabolism in the white muscle are likely to result in a much greater oxygen debt than longer angling events that primarily involve aerobic metabolism.”  

Proper angling technique is essential when using light tackle spinning gear where experience knows it’s best to just “settle in” and use big muscles.  You can do so knowing that research shows longer duration fights are better for survivorship. Photo: C. Falicon

When asked about duration of fight, Dr. Lutcavage replied, “That’s a tough one.”  Most of the giant bluefin they tagged and released in the Gulf of Maine when they developed their release techniques were landed in under 30 minutes and had extremely high survivorship when proper release and resuscitation techniques were used. She also noted that plenty of fish in her career of tagging have gone as long as 90 minutes on the rod and with proper resuscitation techniques those fish all did “just fine – pointing to the fact that if the fish is hooked properly and oxygenating it’s body systems during the fight it doesn’t appear that fight time versus mortality is a significant issue”.  Capt. Moody adds, “On a short fight there is high lactic acid buildup and very low blood oxygen content. Couple that with removing a fish from the water for any length of time you are going to do some serious damage to that fish and even if it looks like it kicks away pretty good it’s not going to survive for long.” He adds, “Based on years of commercial fishing we know that a short fight is bad for the market and that fish need to swim to clear the lactic acid.  The ideal fight time seems to be about 50 minutes but there have been plenty longer and the fish is in good shape.” Data suggests survivorship increases with size.  This becomes increasingly significant to anglers in the Mid-Atlantic targeting juvenile bluefin tuna where it is even more imperative that proper release techniques are used.  Every single professional I spoke with in researching this piece emphatically agrees on the fact that, at all costs, fish shall not be removed from water if being released.  Dr. Lutcavage said, “Rich Brill was the first to teach me about the damage done to a fish’s spinal column when the fish is handled by its tail – they were not designed to be handled this way.”  When asked about this Dr. Brill simply says, “Fishermen should never pick up fish by the tail. Their spinal column is very weak when being stretched.” So it is critical for any crew that is planning to release a large pelagic to not to handle the tail.

On the topic of hooks Dr. Luctavage and Capt. Moody state that circle hooks are by far the best for survivorship.  J hooks are fine as long as they don’t penetrate the upper palate or get deep in the throat. Treble hooks should be avoided at all times when catch and release fishing.  Saltywater Tackle (Sayreville, New Jersey) Owners Sami Ghandour and Paul Chua do not recommend using treble hooks when topwater tuna fishing and stated ONLY do so if you are harvesting bluefin tuna.  Once you have your harvest limit immediately switch over to inline J hooks. Sami adds that inline hooks “actually generate better hooksets on topwater fish.” He says, “You may get tight more on trebles but you will also drop more fish due to mediocre hook sets and you have, in turn, left these fish wounded.  With inline J hooks you will have more swings and misses but the good strikes will equal good hook sets and landed fish.” They also note that treble hooks on poppers seem to be the most detrimental since the “strikes on poppers tend to be so violent the hooksets can be very damaging to the fish.” Sami even adds that often when exclusively catch and release fishing (especially far offshore or in remote areas) he will remove the barb from the hook. This serves two purposes – safety if the angler or crew are hooked and easier release of healthy fish. Dr. Lutcavage says, “Ultimately the main problem is where the hookset occurs – with the upper part of the palate being the worst as it leads to excessive blood loss and internal bleeding which could be significant enough to lead to a delayed mortality.” Obviously, we cannot control hooksets but we can be vigilant when we know we are finished harvesting and do our part in minimizing wounding to the fish during the catch and release part of our pelagic fishing.

How to Perform a Proper Release of a Large Pelagic:

When asked about release techniques, it didn’t take long for Dr. Lutcavage to put me in touch with Captain Nat.  We ended up having a great conversation about release and many other interesting aspects of the bluefin fishery (some mentioned above).  Capt. Nat comes off as a super humble guy who is as passionate as all of us about tuna fishing with a deep rooted interest in the well being of the fishery.  When it came down to release techniques the instructions were extremely simple.

Step 1:  Take your time!!!  No need to wrench a catch and release pelagic species to the side of boat in record time when at this point you are not fishing for harvest anyway.  The research clearly shows the longer and slower duration the battle the better the fish can keep its blood oxygenated (aerobic), minimize lactate accumulation (anaerobic) and minimize stress to critical organs such as the spleen.  

Step 2:  Do not release a green fish!!  If you are performing step one properly the fish should be tired and very willing to lay laterally alongside the boat.  NEVER bring a catch and release fish on deck and NEVER handle a fish by its tail.

Step 3:  With the fish laying on its side along the gunnel leave the hook in and begin to swim the fish via the leader at 4 to 6 knots.  Alternatively a narrow 2” lip gaff may be used by experienced hands and as long as the crew is very careful not to hit the upper palate or do significant damage to the lower jaw.  If fishing topwater baits it may be necessary to carefully lip gaff the fish first then remove the stickbait prior to beginning the swim. But when circle or J hook fishing best practice always is to drag by the leader.  

Step 4:  This is the critical step!!!!  Continue swimming the fish until FULLY resuscitated or, on average, for 8-10 minutes with 3-4 minutes being the absolute minimum.  Specifically, Capt. Nat says to look at the lateral fins and watch for them to really start to flutter. Shortly after this point the fish should start trying to turn itself upright as it should be uncomfortable laying on its side.  DO NOT release a tuna that is still laying on it’s side as that is the #1 sign it is not properly resuscitated yet.

Step 5:  Once the fish is lively and working to get properly oriented in the water carefully either 1) reach down and remove the hook, 2) use a dehooker to remove the hook or 3) carefully remove the lip gaff and allow the fish to swim away.

Caught on a topwater popper this photo is immediately after the crew removed both hooks and carefully placed a narrow lip gaff in the lower lip avoiding damage to the soft palate.  From here here boat speed is increased to 4-6 knots to begin the swim and move copious amounts of oxygen rich seawater into its mouth and across its gills. Photo: C. Falicon

Conclusion:

According to Capt. Nat, one of the big misconceptions among anglers is “just because a fish gives a good kick and swims away from the boat means nothing about the chances of that fishes survival.”  Most fishermen fall into the category where they catch the fish, handle it, release it, see it give a good kick and assume high survivorship. It’s the exact opposite! That being said – Capt. Nat believes so strongly in the simple process outlined above stating “there have been multiple occasions in which I wrote 0% chance of survival on a tag card because the fish was hooked deep in the throat or losing a lot of blood from the gills and I was sure that fish had no chance but we swam the fish and properly resuscitated it and, believe it or not, the tag pops up off the Canary Islands or somewhere long after release in Gloucester.”  Bottom line is if you and I use these simple resuscitation techniques, we are doing our part to significantly increase the likelihood that our released juvenile Mid-Atlantic tuna will survive. We will also be educating other anglers every time they step aboard our vessel – which is what it’s all about. Tight Lines!

About the Author:
Captain Doug Phillips is the owner/operator of Openbow Charters and Openbow.Org.  He fishes his 30 foot North Rip out of Barnegat Light, New Jersey.
When he's not fishing, skiing or surfing you can find Captain Doug teaching Advanced Placement Biological Sciences at Colts Neck High School.