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Pacific Bluefin Tuna, Overfishing, and the Anthropocene Defaunation


Failure to Protect the Pacific Bluefin Tuna

A magnificent creature is going extinct before our eyes because it ranges far and wide across the Pacific Ocean, because it takes too long to grow up before it begins to reproduce, because it tastes far too good, and most of all because we are selfish, unwilling to relinquish the taste sensation or the buckets of money to be made in catching it. It is the Pacific bluefin tuna, Thunnus orientalis. IUCN listed it as ‘Least Concern’ in 2011, and have not yet seen fit to change their view. FAO reports it to be ‘Fully Exploited’ but otherwise scarcely mentions it in the 2014 State of World Fisheries and Aquaculture. The Inter American Tropical Tuna Commission (IATTC), which is supposed to be managing the catch in the Eastern Pacific, met in Lima, Peru, in July, and decided to punt until October, despite a clear recommendation from its scientific staff to reduce the catch in 2014 to no more than the tonnage caught in 2013 (3154 tonnes). (This compares to catches from the Eastern Pacific averaging about 10,000 tonnes per year in the period since 2000.)

PacificBlueTuna5918 CAS MacDonald

Pacific bluefin tuna, Thunnus orientalis, a high-speed, long-distance swimming machine.
Photo © CAS MacDonald

Across the Pacific, abundance of bluefin has fallen to about 4% of pre-fished state, and spawning stock biomass (literally the tonnage of adult fish) is at all-time lows. Recruitment of juveniles also seems to be bouncing along close to the minimum. About 90% of the fish taken are not yet mature – never the best way to harvest a population that is at very low numbers. But, of course, the science can always be questioned, and number of recruits is notoriously variable from one year to the next, so why should the catch be reduced until we are sure there is a problem? Then too, the numbers taken in the East Pacific are just a small part of the total and if catch is reduced there while fishing continues in the West Pacific all that has happened is the East Pacific fishers have lost money.
This is how we fish species to oblivion. By delaying action until we are absolutely certain that there is a problem. By assuming that the behavior of others (in the West Pacific) is the real cause of the problem. By being unwilling to step forward and do the right thing, because we do not want to lose even a tiny bit of income. By holding endless meetings in which we discuss but never reach a conclusion. The Pacific bluefin tuna is simply too tasty, and therefore, pound for pound too valuable to be allowed to continue to exist.

In the 1990 comedy, The Freshman, starring Marlon Brando and Matthew Broderick, the plot revolves around the clandestine Fabulous Gourmet Club, which meets in out-of-the-way venues to serve endangered species to wealthy guests. For a million dollars, you get to eat the last individual of a species going extinct. I remember watching, and thinking, this is not that far from reality! We value rarity, and willingly pay to possess it, whether it be fine art, fast cars, or bits and pieces stripped from the carcasses of rare animals – tiger whiskers, bear gall bladders, dried seahorses ground to a fine dust, rhino horn (also ground), shark fin, or a couple of slices of kuro- or hon-maguro sushi. Unfortunately, no matter how rare each species becomes, there is always somebody willing to acquire one more meal, one more fur, one more medicinal powder, and eventually another species bites the dust.


Matthew Broderick delivers a Komodo dragon to the Fabulous Gourmet Club.
Image © The Freshman, Tristar Pictures

In December 2012, I wrote of the plight of the Atlantic bluefin tuna, which is, if anything, closer to extinction than the Pacific species. What I wrote then about the sheer magnificence of this beast is true also of the Pacific Bluefin, and worth re-reading. So beautifully adapted to living on the high seas, a magnificent swimming machine, an engineering marvel that leaves me in total awe of the power of evolutionary change to sometimes achieve perfection, these are really the ultimate fishes. We are so privileged to share this planet with them that I find it hard to believe we are capable of willingly watching ourselves fish them to extinction. And yet we are. Because they taste too wonderful.

There had been outside pressure on IATTC to act. The Pew Charitable Trust had called upon members, prior to their July meeting, to act decisively on Pacific bluefin tuna because of its perilous status. Predictably, the failure of IATTC to act was met with considerable outrage and high dudgeon. The EU representative was annoyed that nothing much happened at the meeting, but reports suggested the annoyance was more with failure to act on a whole host of items (such as election of a new Director) that the EU favored, rather than specifically at the lack of action on bluefin. The WWF was critical of the failure to act, and has said it will call for a cessation of the fishery if IATTC fails to act in October, and Amanda Nickson, director of global tuna conservation work by the Pew Charitable Trust, was quoted as saying after the meeting,

“Once again, fishing nations have ignored the scientific evidence before them and will allow this decimated population to continue to be overfished, despite dire warnings that it is on the edge of collapse. Pacific bluefin tuna needs an oceanwide recovery plan. This lack of action shows that a suspension of the Pacific bluefin tuna fishery may be the only way to save this species.”

I do not see a suspension of the fishery occurring any time soon. Not until a far greater proportion of humans begins acting ethically instead of selfishly. Nor do I see this case as an isolated instance. We are currently causing an unprecedented thinning out of biodiversity across the planet.

The Anthropocene Defaunation

In the 25th July issue of Science, Rodolfo Dirzo of Stanford University, and five colleagues from the USA, Brazil, Mexico, and UK, published a chilling article, Defaunation in the Anthropocene. In it, they review anthropogenically driven loss in biodiversity since 1500, choosing that year as the start of the Anthropocene, that period in Earth history in which humanity is a major force for planetary change. Their results are not surprising, but they should be concerning. In the past 500 years, humanity has triggered a wave of reduction in abundance, extirpations of populations, and extinction of species that may rival anything seen in any of the five great mass extinction events in Earth’s history. Since 1500, 322 species of terrestrial vertebrates have become extinct, and populations of the remaining species show 25% average decline in abundance.

Invertebrate patterns are equally dire: 67% of monitored populations show 45% decline in mean abundance. (Not mentioned in their article, our impacts on the ocean have been just as severe, with a 90% reduction in biomass of marine fishes commonly cited as the result of our over-enthusiastic fishing.)

As Dirzo and colleagues make clear, while the extinctions, particularly of large, charismatic species, capture the attention, it is the pervasive losses in abundance and reductions of range of individual species that are the most important consequence ecologically. Fewer individuals are available, in fewer places, to play the ecological roles they used to play.

In fact, if we think carefully, most of us can remember a time when there was more life on this planet (and I am not referring to the 1960’s, although they were lively). I particularly remember that back in the days when all gas stations were full service, part of that service was getting your windshield washed. A capable attendant could get the nozzle going, filling your gas tank, and then have time to wash and squeegee your windshield clean before he had to get back to close the tank, hang up the hose and collect your money. Sometimes you got additional cleaning of headlamps and so on. What I particularly remember, back in the day, was that travel in the country, rather than the city, sometimes made it necessary to stop at a gas station before you needed fuel, because you needed your windshield cleaned.

1959 LVC Lambda La Verne Chevron Service

Gas station attendants gave personalized service back in the day. Image © Old Towne Laverne Blog

Flying insects, particularly the big ones that managed to go splat right in front of your steering wheel, were so abundant that the windshield cleaning courtesy was far more than a courtesy. It was a necessity for safe travel. Today, I can drive for hours through farming country and pick up no more than two or three modest little bugs. People of a certain age who watch birds, and particularly those who watch and keep a journal, can tell numerous tales of birds that used to be common but are now seldom seen. In my part of the world, I find the question, ‘have you heard a whip-poor-will lately?’ an effective way to get people thinking about the losses that have taken place. Because this iconic call, that always told a much younger me it was summertime in Ontario, is a call I have not heard for years. The bird is not extinct in Ontario, but it is completely absent from large swaths of former territory.

Dirzo et al Fig 1 large

Four examples from the article by Dirzo and colleagues show the losses in biodiversity being caused by humanity worldwide. A) Large fractions of all the insect species monitored by IUCN are currently declining in abundance. B) Records for British insects of four Orders show from 30 to 60% of species are becoming less widely distributed. C) Globally, an index based on invertebrate species abundance shows that moths and butterflies have declined less severely than other types of invertebrate. D) A meta-analysis of studies of moth and butterfly diversity show the overwhelming majority of disturbed areas hold a reduced biodiversity of these insects. Figure 1 © R. Dirzo, Science

Dirzo and colleagues make the important point that while deforestation is a well-understood term, and an event that is readily apparent and quantifiable in aerial photos of landscapes, defaunation is a far less familiar process to people, and essentially invisible until detailed monitoring studies are undertaken. (Or until someone asks if one has heard a whip-poor-will.) Yet both defaunation and deforestation are vitally important ecologically. They discuss the patterns in defaunation, noting that species are differentially susceptible, and that extent of defaunation varies geographically as well. Among vertebrates, the amphibia have proven particularly susceptible, perhaps because of their dependence on water in the landscape and their sensitivity to chemical pollution. Among mammals, the larger species tend to be most impacted; indeed, mammal faunas show a clear pattern in which the largest-bodied species became extinct by the end of the Pleistocene, a next-largest cohort became extinct in recent years, a next-largest cohort of species is currently threatened and in reduced numbers, and the smallest-bodied cohort seems relatively less affected by us. In general, defaunation has also proceeded more rapidly in the tropics, partly because this is where most species occur, but also because this is where human activities have had the most profound impacts on natural habitats.

Dirzo et al Fig 3 large

Distribution of adult body size varies among mammal species that became extinct during the Pleistocene, became extinct more recently, are currently considered as threatened with extinction, or are currently considered not to be threatened.  Anthropocene defaunation is making mammalian faunas smaller in stature. Figure 3 © G. Dirzo, Science

The main strength of their article, however, is not in how it enumerates the losses of species or reductions in population range or abundance. Dirzo and colleagues summarize the several ecological consequences of this simplification of the biosphere. These include pollination, pest control, nutrient cycling and decomposition, maintenance of water quality, impacts on human health, and the distinct possibility that our defaunation is shaping the evolution of ecological systems in ways that may or may not be to our advantage.

I commented on pollination issues in this blog in April 2013, and attention to the declining abundance of bees has, if anything, grown since then. Neonicotinoid pesticides are among the new weapons we are attacking bees with, and the seed and pesticide agribusinesses are playing the ‘evidence does not absolutely confirm neonicotinoids are to blame’ game used by every business on the planet that wants to continue with practices that obviously damage the biosphere. Dirzo and colleagues simply state that 75% of all our crop plants require insect pollinators, and that the pollination service is estimated to be worth 10% of the economic value of our global food supply. They then report that pollinators appear to be declining strongly, both in abundance and diversity, across the globe.

Small vertebrates play a major role in controlling the abundance of smaller, usually insect or other invertebrate, pests. Experimental or observational studies have found that removal of small vertebrates from a site leads to a broad range of adjustments to the composition of the animal community as prey species become more common, and inflect more damage on plants or their own prey organisms. Such ‘trophic cascades’ are a feature of any ecological system that is disturbed by removing an important predator. Dirzo and colleagues report that arthropod (mainly insect) pests are typically responsible for destroying 8 to 15% of crop yields, and that reduced abundance of small vertebrates could see this damage rise to 37%. In North America alone, they peg the value of pest control by small native vertebrates at $4.5 billion annually.

Comments in the article on effects on human health were particularly chilling. Defaunation, by reducing diversity, reduces the provision of numerous goods and services, including sources of pharmaceutical compounds, biocontrol agents, food resources, and disease regulation. Between 23 and 36% of all birds, mammals, and amphibians used for food or medicine are now threatened with extinction. In addition, wildlife provides important food resources in many societies, and loss of abundance deprives people of needed food. One estimate suggests loss of wildlife in Madagascar will lead to a 30% increase in anemia with resultant increases in mortality, morbidity and learning difficulties. While Dirzo and colleagues stuck to terrestrial fauna, the collapse of coastal artisanal fisheries is increasing the challenges for the very poor in many tropical countries, yet current trends suggest we are proving inept at preventing this degradation.

Dirzo and colleagues end their review with a warning that “cumulatively, systematic defaunation clearly threatens to fundamentally alter basic ecological functions and is contributing to push us toward global-scale ‘tipping points’ from which we may not be able to return.” Then, they plead for a more meaningfully attack on “immediate drivers of defaunation” stating that

“mitigation of animal overexploitation and land-use change are two feasible, immediate actions that can be taken. These actions can also buy necessary time to address the other critical driver, anthropogenic climate disruption. However, we must also address the often nonlinear impacts of continued human population growth and increasingly uneven per capita consumption, which ultimately drive all these threats (while still fostering poverty alleviation efforts). Ultimately, both reduced and more evenly distributed global resource consumption will be necessary to sustainably change ongoing trends in defaunation and, hopefully, eventually open the door to refaunation.”

I came away feeling that their recommendations for action were unlikely to achieve very much, and that until people realize the true extent of the 6th mass extinction, we are unlikely to change our ways. But then, that is true for virtually every aspect of the global environmental crisis we face. Until a sufficient number of us wake up and look around, nothing much is going to get done and the problems will continue getting worse. Surely that sufficient number must be just around the corner?

forest fish bee reef

We will find our way once we comprehend that the trees are worth more than the timber, the bluefin are worth more than the sushi, the bees are worth more than the honey, and the reefs are worth more than the limestone.