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Monday 21 January 2019

Feeding frenzy

When Japan announced it was resuming commercial whaling, the rest of the world was horrified. Yet we eat vast quantities of big fish like tuna. Are we hypocrites?

By Ella Hill

Late last year, Japan announced it was withdrawing from the International Whaling Convention (IWC) and planned to resume commercial whaling. Conservation groups were dismayed. Yet most of us condone the large-scale harvesting of big fish such as tuna. Is gobbling vast quantities of tuna really better than eating whales?

Tuna have quite long lifespans. The bluefin tuna, the largest of tuna-kind, can live for up to 40 years. Other species more commonly eaten in the West such as the Albacore tuna, can survive until they are about 10 or 15. In the animal kingdom, long-lived often means slow to reach maturity, which is a problem if a species is endangered yet still hunted for food. It is difficult for stocks to recover if tuna are fished before they have had a chance to breed.

The bluefin is a case in point. The fish is critically endangered and yet, a few years ago, a study by Pew Environment Group found that 90 per cent of the bluefins caught were juveniles. In the UK, bluefin is not eaten – there is a ban on commercial fishing – but they are eaten in Japan.

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Caged bluefin tuna are being fattened for the sushi market.

Other species of tuna are more abundant and fairly well managed (Skipjack is the most sustainable), the only caveat is that it does matter how it was caught – ideally with a short line. You can continue eating your Salade Niçoise guilt free, just do some research first. (Greenpeace have a helpful Tuna league table which ranks supermarket brands).

Now for the whales. Like tuna, whales live for a very long time indeed. They also reach maturity late. Blue whales can live for up to century. Many other species survive into their seventies. Whales therefore face many of the same problems as the bluefins, except with one further issue – whales have only one baby at a time. Tuna, by comparison, lay up to ten million eggs a year. Granted, only a fraction of the hatchlings survive into adulthood, but that is prolific in comparison to whales. However, Japan has no qualms about picking off young whales and pregnant females. In the first half of 2018, Japan hunted 333 whales, 36 per cent of them were pregnant, 34 per cent were juveniles.

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Bowhead whales in the Vrangel Bay.

Although the minke whales that Japan favours are not endangered – their conservation status is determined as “of least concern” – there is not really enough data for us to know how many there are out there. So even if Japan is taking just a few hundred a year, we cannot be sure of the effect. But there is plenty of evidence to suggest that it might be bad.

That is because whales are critical to the life cycle of the sea. They are extremely large, the very definition of “big-boned”. When a whale dies it is an ecological event that creates an entire ecosystem. The whale carcass gradually sinks to the bottom of the ocean where it is eaten up by scavengers – sharks and fish which can munch through the tough skin and blubber. Once they are done eating (a whale carcass can provide up to two years of food for them) it is the turn of smaller creatures such as starfish and crabs to eat up the residual meat.

The feeding frenzy does not end there. When only the skeleton remains, bacteria get to work digesting the bones, releasing nutrients which attract molluscs and worms. All told, a dead whale can feed a whole community of animals for decades. Slaughtering whales and removing their carcasses from the ocean takes away this opportunity. The body of an aged tuna, although likely to be large, makes for slimmer pickings.

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Humpback whale and calf

Whales provide a lot of nutrients to other fish throughout their lives, not just in death. Euphemistically called “whale pump,” whales excrete large clouds of faeces at the surface of the sea. Although whales can feed at great depths, where nutrient rich zooplankton, fish and squid are found, the pressure on their digestive systems means that they prefer to relieve themselves up top. In so doing, whales bring all of these nutrients to the surface. Whereas other fish make “marine snow” – faeces that sinks to the bottom of the sea – whale poo floats, so it serves an important role in fertilising the surface plant plankton that form the first link in countless ocean food chains.

The bottom line is this: whales are such valuable ecosystem engineers that even their waste is gold dust. Let’s not eat them.