"Why are sharks, turtles and rays more important than tuna?"

Posted by Willie — 20 March 2014 at 10:32am - Comments
All rights reserved. Credit: Willie Mackenzie / Greenpeace
Is this shark more important than the other fish?

Here’s a question which has cropped up from some supporters about our work on tinned tuna.

‘Why are sharks, turtles and rays more important than tuna?’

There are two answers:

1) They’re not (at least not in the eyes of the tuna, turtle, shark or ray concerned, or in the view of anyone who thinks they matter as much as each other).
2) Because they have more to lose.

Let me expand upon the second answer.

Tuna are bony fish. They lay lots of eggs. Although some tuna species (like bluefin) are big and take a lot of growing, others (like skipjack) are smaller and faster growing. There are lots of skipjack, and they in turn lay lots of eggs, and are eaten by lots of things (including other fish, birds and sharks) other than humans.

In theory tuna can and should be able to rebuild populations, and replace ‘lost tuna’ quite easily, on account of there being lots of tuna making more baby tuna.

Obviously this is not a perfect world, and the very real impact of overfishing (compounded by other threats to the oceans) means that some stocks of tuna species have plummeted. Humanity’s impact in the ocean, unchecked, could be a game-changer for tuna.

But things are immeasurably worse for sharks, turtles and rays.

Sharks and rays are also fish, but they have no bones, only cartilage. They are from ancient lineages and many are thought to have remained in our oceans unchanged for many millennia. Fast forward to today and 1 in 4 species of sharks and rays are threatened with extinction. Many, if not most, of the big sharks and rays have gone from our oceans after decades of destructive fishing. Bycatch in fishing nets as well as direct hunting have been the main causes. Some species, even iconic ones like oceanic whitetips, and hammerheads have seen their numbers tumble a shocking 95 – 99% over the past few decades.

The truth is that sharks, despite a ferocious reputation, and an archaic bloodline, are more vulnerable to us. They breed and grow more slowly, and have fewer babies. Many shark species give birth to live young, like we do - sometimes only one or two at a time. Some live as long as humans (given the chance), and carry their babies for a similar length of time. Some take it even further and have pregnancies that last for a whopping 18months.

So sharks and rays simply can’t bounce back as quickly as tuna, even with a level playing field. And the playing field is far from level at the moment.

The same is true of turtles. Yet again they are ancient creatures, but their chances of survival to adulthood are slim, even without humans in the equation. Female turtles gather on beaches to lay clutches of about 100 eggs, the eggs and young are preyed on by a host of animals before they even reach the sea. Baby turtles also get snacked on – and only about one in a thousand are thought to make it to adulthood, and have a chance of breeding themselves.

Add on the effect of humans – direct hunting, entanglement in fishing gear, pollution, trashing breeding beaches etc. It might not be a huge surprise then that the world’s sea turtles are having a tough time. Six out of the seven species are threatened or endangered with extinction. The single greatest threat to most species is as bycatch in fishing gear.

Call it bycatch, or destructive fishing – the outcome is the same for turtles, sharks and rays (as well as other iconic ocean species like seabirdsporpoises & dolphins). Species that are already ‘adapted’ to growing slowly and having few young that survive are inherently more vulnerable to the methods we use to catch more numerous species.

So, on the issue of tuna fishing, fishing which targets tuna but also ‘accidentally catches’ other species, those other species can be argued to matter more. Not because they are more cute, more worthy, or more innocent – but simply because they are more at risk.

You can make a difference right now, by writing to Tesco stop selling tuna that kills sharks, turtles, and rays. Use this super simple email tool now.

About Willie

Hi, I'm Willie, part of the Greenpeace UK biodiversity team. I work mostly on oceans and fishy issues.

Twitter: @williemackenzie

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