Tuna: Majestic oceanic wanderers, renowned for their muscularity, speed and elegance, now often end up in cans sold with “dolphin-safe” labels. It is crucial to look beyond these labels and ensure sustainable fishing practices have been applied and the species in question is not endangered. Daniel Brinckmann reports.
Tuna swirling inside a tuna pen
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Tunas are oceanic creatures that travel thousands of kilometres across the oceans in shoals. They are packs of muscle with the ability to keep their body temperature above that of the water. Unfortunately, they are so popular as food that a simple Google search for their species will inevitably return their average nutritional value, even on the main page. Whether canned, grilled, fried or served as sushi, sashimi or tartare, tunas are highly prized around the world for their firm flesh. In fact, they account for almost half of the biomass of all seafood caught worldwide.
According to estimates from the UN Food and Agriculture Organization (FAO), the global tuna catches increased fourfold from approximately 400,000 tonnes in 1955 to over two million tonnes in 1997. This level has been consistently maintained with little fluctuation ever since. It is not surprising that tuna, among other species, have seen their populations plummet to a tenth of their original size over the past 70 years.
If the remaining giant females had not released millions of larvae in their spawning grounds off the coasts of Africa, Mexico and the Mediterranean, the bluefin tuna species would probably have been driven to regional extinction long ago due to the desirability of its meat. Archaeologists have found evidence of chamber net systems dating back more than 2,000 years in North Africa. Additionally, in the 18th century, traders from Tyrol not only brought lemons but also salted tuna from Italy across the Alps to Central Europe.
Misleading labels?
The average consumer reaching for the usual canned food in the supermarket may only take a brief look at the “caught dolphin-safe” label but not give any thought to who the actual supplier is. The label typically depicts an inconspicuous silver fish with widely spread fins, far from the endearing image of a character like Nemo. But just because the fishing industry puts sustainability labels on its products does not necessarily mean it aligns with marine conservation efforts.
Imagine witnessing these massive swimmers, which can weigh up to half a ton and grow up to four metres long, in their natural habitat. If more people had the chance to see them in the water, they might think twice before reaching for tuna at the supermarket. Anyone who has snorkelled or dived among a school of tuna will never forget the experience. Swimming among a living wall of enormous, gleaming metallic bodies with eyes the size of fists feels like being in the midst of a tornado. It is a synchronized ballet, where each fish is much stronger than a human and can noticeably affect the water pressure with just a small change in direction.
This ancient ritual, which has occurred in every ocean for countless years, has become increasingly uncommon. Up until the end of the post-war era, tuna was even spotted off the coast of the Danish North Sea and occasionally in the western Baltic Sea. However, due to the rapid rise in marine pollution and a few record years of industrial fishing, the tuna population was nearly wiped out in the 1960s. Less than two decades later, the first stocks in the inland seas, particularly in the Mediterranean, also collapsed.
Tourist attraction
The last commercially operated tuna traps off Western Sardinia were maintained as a tourist attraction until the early 2000s despite declining fish populations. In 1954, there was a significant migration of tuna into the fjord-like bays of the northern Adriatic near Trieste, which led fishermen from various communities to quickly take to their boats for a major fishing trip. The few remaining photo and film documents from this time appear to be relics from a long-forgotten era when “tourists” were still a new phenomenon and were protected from sharks, as well as humans, by shark nets at seaside resorts such as Opatija.
When people refer to “the” tuna, they are usually talking about the bluefin tuna—a massive fish found in the temperate Atlantic. Its habitat ranges from Canada and Mexico in the west to Norway and West Africa in the east and even extends into tropical waters. During spawning, some of the population migrates to the Mediterranean, while others migrate to the Gulf of Mexico.
In subtropical marine regions with temperatures above 21°C, the largest and most sought-after species, which is considered critically endangered, can be found alongside the second largest representative of the family, the yellowfin tuna (potentially endangered), the albacore (or white tuna, potentially endangered) and the bigeye tuna, which is currently on the verge of being classified as critically endangered by the International Commission for the Conservation of Atlantic Tunas (ICCAT).
The economic relevance of the remaining five species, apart from the larger tuna and the smaller bonito (or “skipjack”), has been inadequately researched. This lack of attention is due in part to the fact that these smaller tropical species have become increasingly rare, as the industry has prioritized them less than the larger ones.
Easily spotted
The visibility of tuna has been a major factor contributing to their decline. Shoals of these large fish can be easily seen from exposed capes, even without binoculars, when they swim in shallow waters. Their hunting behaviour also makes them easy to track, as it causes a visible disturbance on the sea surface.
The Phoenicians developed a cage-like system of net chambers to catch tuna as they spawned in the Mediterranean Sea, beyond the Strait of Gibraltar. This fishing method has survived for an incredible 2,000 years. During their migration to the Mediterranean in May and June, tunas were lured into the “death chamber” at bottlenecks in their migration routes along net walls. The net was then pulled to the surface on command by the “mestre” (master or leader overseeing the fishing operation – ed.) for the final catch at the end of the season when no more fish arrive.
At the turn of the millennium, these almadrabas (Spain) and mattanzas (Italy) were increasingly replaced by several hundred tuna-fattening farms between the coasts of Andalusia and Cyprus. This approach makes sense from an economic perspective. Fewer animals need to be utilised more efficiently. After all, the almost complete collapse of the Mediterranean bluefin tuna around ten years ago could only be averted at the last minute with rigorously reduced catch quotas and strict controls.
Monitoring
EU fisheries observers have been monitoring every trawler and farm to ensure compliance with fishing quotas. Severe penalties are imposed whenever the specified number of fish is exceeded by a double-digit percentage. Both fisheries inspectors and fishing co-operatives are familiar with the laws and loopholes, resulting in a daily battle at sea between economic interests and environmental sustainability. As a result, fattening farms operate legally with young wild-caught tuna, which are not recorded in any statistics as live animals. These tunas are then sold at high prices through middlemen, starting at a varying minimum size.
The Mediterranean tuna, especially the ones that are exported to Japan, are known for their high quality. In gourmet wholesale markets like those in Tokyo, these tunas, which are caught as young fish and then fattened to become fat-rich, command astronomical prices in the millions.
Extensive bycatch
In the Western Pacific and the southern Indian Ocean, as well as anywhere with dense shoals that justify the operating and maintenance costs of trawler fleets, tunas are caught using drift and purse seine nets. Unfortunately, this method leads to the unintentional capture of fish, marine mammals and reptiles, including manta rays, sharks, swordfish and turtles. This unintentional capture, known as “bycatch,” is so extensive that it poses a serious threat to the survival of some species due to the impact of tuna fishing.
Sustainable practices are crucial. If destructive practices go unnoticed or are concealed to keep prices low, stocks are depleted until wild catches are significantly reduced, and farmed animals become luxury items. Even the organic sections of Michelin-starred chefs and self-proclaimed soul-food icons often only highlight the evolutionary traits that give tuna its firm, deep red flesh.
No information is mentioned about the endangered status of fish and the need for moderation. There is also no reference to the significant contamination of meat with heavy metals like mercury, microplastics and other toxins, particularly in tinned tuna. While the health benefits of fish oil, proteins and omega-3 fatty acids are not in question, the current reality is that the higher a fish is in the food chain, the more detrimental it is to health.
If you are looking forward to enjoying a delicious tuna fillet, it is important to know that the fish may contain harmful microplastics and substances that it accumulated while growing up, eating other fish and so on. Enjoy your meal! ■
