Marlin madness

The 1431 lb marlin caught at Lady Musgrave Island (image: Scott Mitchell).

A group of anglers fishing east of Lady Musgrave Island on the southern Great Barrier Reef made history in early December 2018 with their capture of the second largest black marlin (Istiompax indica) ever taken in Australia (and possibly one of the top 5 or 10 largest black marlins ever captured), which weighed a whopping 649.8 kg (1,431 lb). Weighed as it was over a day after it was taken, the fish was somewhat dehydrated and if weighed straight away clearly would have bested the largest black marlin captured in Australia (654 kg/1441 lb), while the tale of the tape suggests it was not too far off the dimensions of the long reigning all tackle world record black marlin of 1560 lb (707.6 kg) taken by Alfred Glassell way back in 1953 off Cabo Blanco, Peru.

The Lady Musgrave fish was weighed due to the fact that it died during the final stages of the fight, and the anglers did not want to waste the specimen and were keen to donate it to science and see how big and old it actually was. But even if it was healthy and could be released, the lucky anglers were quite entitled to take the fish anyway, if only to advance scientific knowledge for the species, because of the extraordinary circumstances of the encounter. Given the fact it was caught off Lady Musgrave Island, nearly 1500 km south of the only known east coast spawning grounds for this species off Cairns in far north QLD, scientifically it is important to measure the gonad staging of the fish to determine if spawning was actually taking place. Yes, these days over 95% of marlin captured by recreational anglers are released, and rightly so, but extraordinary fish invoke extraordinary circumstances. From a scientific perspective the only way to get this vital information is to kill the fish for closer examination – in other words, you can’t make the scientific omelette without breaking a few eggs from time to time.

The reality is, recreational fishing for marlin has generated the majority of scientific information that is available on these elusive fish. Without help from recreational angler tag and release programs (The NSW gamefish tagging program alone has tagged around 140,000 billfish, see HERE), we would know very little about the movements or life history of black marlin. Why? Black marlin are a highly mobile species that are here today, gone tomorrow. Tagging has shown they migrate enormous distances relatively quickly – for example, one 700 lb black marlin tagged with a popup tag off Cairns in November 2015, was found to have travelled 4393 nautical miles (8320 km) after only 240 days. From the point of view of scientific researchers, these fish are very hard to find, very expensive to access, and almost impossible to study without the help of citizen scientists in the form of recreational anglers. The outcomes from this sort of research are then used to inform management of marlin stocks, and it is widely known that recreational anglers worldwide have been at the forefront of marlin conservation. The strongest advocates for limiting commercial marlin take in all the worlds oceans have been recreational fishers who are active through groups such as the Billfish Foundation, the International Game Fishing Association (IGFA), Game Fishing Association of Australia (GFAA) and others. Why? Because recreational anglers require healthy marlin populations in order to have a quality fishing experience.

Unfortunately, what will probably be most remembered about this capture, is not its biological uniqueness or scientific value, but more likely the fact that anglers sharing the capture with their friends on social media suffered a huge outcry and abuse from all directions. Sadly, given the rise of social media, this sort of misinformed commentary after the taking of a large fish (or indeed any fish nowadays in some social circles) now appears the norm. Social research has found these attitudes originate from increasingly urbanised westernised societies which are losing touch with nature, natural processes, and where their food comes from. The previous public outcry after the weighing of a grander marlin taken off Exmouth on 1 January 2018 was a case in point. In that case, responding to a similar social media furore, Jim Harnwell wrote a mainstream media piece in which he pointed out that while the vast majority of marlin these days are caught and released, the economic potential of the Exmouth blue as a genuine “grander” was a factor behind the anglers decision to bring it into port to be weighed. Jim’s article is still worth a read, and is available HERE.

Social media like Facebook is not renowned for civil, fact based discussion, and this was again evident in the case of the Lady Musgrave fish. A lot of the social media noise came from people who questioned why the fish was taken (answer, it died) and whether most other released marlin survive. These sorts of conservation oriented comments disclose a huge amount of ignorance from the general public on such issues. Natural mortality rates of black marlin are very high, but how a marlin naturally dies is seldom discussed (for large fish death from pack shark attack is their most likely fate when the end finally comes). Marlins are also targeted by commercial fisheries in most parts of the world, but remember, it has been recreational anglers worldwide who have been most active in the field of marlin research and conservation. The survival rates of released marlin are also well known, because the topic is one of the most intensively studied research questions about these species. Many studies have shown that post-release survival rates of marlin taken by recreational anglers are high, usually around 90%, and can approach 100% when experienced anglers use lures (or circle hooks when using baits) and utilise best practice in fighting and handling the fish (tagging and releasing the fish beside the boat, no air exposure etc.). Examples of marlin that were tagged, released, then recaptured again in under 10 minutes during tournaments off Port Stephens show that, besides marlin having voracious appetites, properly captured and released marlin have excellent survival rates and no significant impairments (for more, see

Other responses on social media questioned the activity of catch and release angling itself, let’s call these the “welfare and rights” oriented concerns. Catch and release angling has a long history, and is mandatory in some form or another in all jurisdictions where fisheries management regulations such as minimum and maximum size limits and bag limits are enforced (i.e. regulatory catch and release). However, the act of voluntary catch and release of many fish species, including marlin, has also risen in popularity in recent decades as a means of further reducing recreational fishing related impacts on fish populations, while maintaining the associated social and economic benefits to anglers and society. If catch and release angling is conducted using best practice methods (as outlined in Australia’s National Recreational Fishing Code of Practice ), many scientific studies have shown the released fish generally has a very high chance of survival with little to no measurable impacts on fitness, meaning that the fish welfare impact of the catch and release event is likely to be trivial, or negligible. Thus catch and release is proven to provide substantial positive benefits to fish populations, ecosystems, anglers and wider society. Despite this, in some European countries (e.g. Germany and Switzerland), the practice of voluntary catch and release angling has been outlawed due to cultural, moral, and political reasons based on “feelings based” fish welfare and animal rights philosophies. It is these sorts of animal rights undertones that populated many of the social media opinions against catch and release marlin fishing.

The problem with animal rights philosophies when they are applied to wild fish is that a healthy aquatic environment is a food chain where huge numbers of fishes die each day as food for other predatory fishes. This natural mortality is a situation to which fish are well adapted via natural selection that in many cases has favoured development of their ability to produce many thousands (or even millions) of offspring each spawning, provided the fish remain in a clean, healthy environment where human threats from pollution and overfishing are well managed and critical processes like natural selection are allowed to remain unimpeded1 . In fact, because of the unique biological and ecological characteristics of fishes and their environment, many of the traditional “feelings based” welfare concepts originally devised to protect the welfare of domesticated birds and mammals are simply not appropriate for wild fish1,2. This is because the animal rights and welfare theories behind the “feelings based” approach cannot adequately explain why we should, for example, stop human predation on fishes on one hand, but on the other hand, not attempt to intervene to stop the suffering (or “rights violations”) of other fishes in terms of their predation upon each other3.

Indeed, a literal interpretation of animal rights philosophy is that one acceptable solution to predation is to “humanely eliminate all predators”, and because humans alone can determine what is morally right or wrong, we are therefore obliged to act and protect the so-called rights of prey species3. Like other billfish, black marlin are apex predators that grow extremely rapidly by feeding mostly on small tunas, but also other fishes, squids, cuttlefishes, octopods, and even large crustaceans. Black marlin reach around 15 kg in their first year, 50 kg in their third year, and given sufficient food supply, a “grander” female black around 450 kg (1000 lb) is possibly as little as 10-12 years old. The secret to black marlin growing so fast is the fact they eat a huge volume of food, and being an apex predator this means they kill and eat many thousands of other fish during their lifetime. So if the animal rights logic is applied, one could argue that by taking a marlin out of the ecosystem, you are actually “saving the lives” of thousands of other fish. So in this way, killing marlin is actually consistent with animal rights philosophy. Go figure.

Philosophers have noted that the same fundamental flaws in animal rights philosophy can also theoretically lead to conclusions that all wild animals should be domesticated and predatory native animals should be replaced with less predatory invasive species, which would clearly decimate biodiversity in natural systems and disrupt natural selection and other natural processes critical to ecosystem function and ongoing survival of fish populations3. Clearly, animal rights philosophies and feelings based welfare concepts developed for domesticated animals are fundamentally flawed when dealing with environmentally critical natural processes such as predation and natural selection that underpin the basic function and integrity of natural aquatic ecosystems. In effect, animal rights theories recognize all of the individual dots (animals), but are unable to join the dots together into a coherent ecosystem3. This is why more pragmatic functional and “nature based” approaches to fish welfare are required in wild fisheries1,2, as these can be accommodated within a framework of human interaction with the aquatic environment that maintains ecosystem integrity3.

A few of the social media rants against marlin fishing claimed the capture process was painful, however the available scientific evidence actually suggests that fish do not feel pain when hooked. Indeed, studies of Atlantic cod found that fish with hooks in the mouth showed no “pain behaviour”, only head shaking4. Furthermore, the angling process is actually equivalent to the control manipulations in those disputed studies that claim to have found evidence of “pain behaviour” in fish injected with acids and venoms. Of course, the control manipulations in these experiments (injecting fish with saline via needles) were not found to cause “pain behaviours”, and hooking is equivalent to penetrating with the needle, but without injecting the saline. The upshot is that angling does not cause pain by the definitions used by fish pain researchers, because anglers do not tip their hooks with acids or venoms. This scientific reality is a very different to that portrayed by animal rights groups, who do not want people to know these facts as they try to force their anti-fishing views on the wider public and generate controversy, emotive arguments and through that gain the funding they need from the public to operate.

As an aside, black marlin not only live hard, they die young – the oldest fish reliably aged is only around 15 years, and while time will tell, there is a good chance that researchers will find the Lady Musgrave fish may be between 15 and 20 years old (i.e. about the same age as a 40 cm black bream, which seem to attract little attention when they are killed by anglers). All the really big black marlin are females with an age at first maturity of 4-5 years old, and each fish spawns many millions of eggs (up to 40 million each spawning season), so its likely the Lady Musgrave fish had spawned hundreds of millions of baby marlin during the previous decade of her lifetime. Sure, most of those larvae would have been eaten by other fish, but in doing so she has done her job to contribute to the future of her species. Such is the staggering reproductive output of black marlin, portraying them as equivalent to a whale, an African elephant, rhino or tiger (as is often done on social media) is completely and utterly misleading….

Its also worth remembering that marlin fishing has social and societal benefits as well as economic benefits. The economic benefits of marlin fishing are well known, and were explained to a wider audience in Jim Harnwells article about the grander marlin taken in Exmouth on 1 January 2018. What is less well explained is that recreational fishing of all types, including for marlin, is not solely a biological or predatory process involving use of fish. Fishing is an activity that exists within broader human dimensions that include socio-economic factors as well as complex interactions between the fishing activity itself, ecosystem functions, development of urban and rural communities and human health and welfare. Numerous studies5,6,7 have investigated the human health and welfare benefits generated from recreational fishing, including:

physiological benefits such as improved cardiovascular health resulting from reduced blood pressure, heart rate and cholesterol

improvements in general health and well-being for children, troubled or disadvantaged youths, the elderly and disabled

reductions in antisocial behaviour and crime rates from troubled youths engaged in fishing

reduction of stress, improvements in mental health, improved recovery from post traumatic stress disorders, and alleviation of symptoms of anxiety and depression

improved immunity and resilience to stressful life events

improved recovery from breast cancer surgery in women,

improved relationships with family and friends,

maintaining connection and a sense of place within the natural world, and more.

In other words, the interactions between recreational fishers, fish and their environment generate multiple benefits to human health and welfare, and the economy, which is why some State governments in Australia (like Victoria) are actively working to increase recreational fishing participation within their jurisdictions8. Because most types of fishing can be undertaken with minimal financial cost (marlin fishing being a notable except here), these benefits are potentially attainable to everyone, irrespective of their age, physical ability or socio-economic status. However all of these economic and societal benefits cannot be obtained if recreational fishers cannot catch a fish, or are prevented from catching fish.

Fortunately, it seems this time the mainstream media ran a reasonably balanced article on the viral story of the Lady Musgrave capture, including an article which included a lot of information from biologists who actually study marlins and fisheries science. For more, click HEREOnly by this sort of education and scientific information extension will the wider community become more informed on these topics. Of course, if they had asked less qualified persons from certain other universities, and/or had asked marine conservation or animal rights groups to comment instead, a very different storyline may have emerged…

1 Diggles BK et al. (2011). Ecology and welfare of aquatic animals in wild capture fisheries. Reviews in Fish Biology and Fisheries 21: 739-765.

2 Arlinghaus R et al. (2007a). Fish welfare: a challenge of the feelings-based approach, with implications for recreational fishing. Fish and Fisheries 8: 57–71.

3 Fox W (2006). Human Relationships, Nature, and the Built Environment: Problems That Any General Ethics Must Be Able to Address. The MIT Press.—Probs-for-GE.pdf

4 Eckroth JR et al. (2014). Physiological and behavioural responses to noxious stimuli in Atlantic cod (Gadus morhua). PLOS One

5 Schirmer, J, ( 2012). Understanding the social dimensions of recreational fishing in South Australia.

6 McManus A et al. (2014). Investigating the health and well being benefits of recreational fishing in Western Australia.

7 Hunt W, McManus A (2016). Recreational fishing supports health and wellbeing in Western Australia. Australian and New Zealand Journal of Public Health 40: 292.


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