Why Size Matters (The One That Got Away)

  • The thing about the road less traveled is, ...it's not really a road...
     ~Jose Wehebe CostaChannelC.com
November 15, 2013

MinuteEarth presents a compelling case for letting big fish get away.

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Interestingly, and worryingly, the Cayman Islands have no law preventing “harvesting” of fish above a certain size. We do have a law banning the taking of non-baitfish below 8 inches (or maybe 9 inches), which seems to make sense.

However, this highlights another one of those areas where common sense breaks down. Of course it makes sense to protect babies and juveniles, right? Right? Wait. Are there more adults or juveniles? Which can we more afford to lose? Which is actually more important to the survival of the species?

Perhaps there is a little be of anthropomorphization going on here. Our children are sacred to us—they’re about the only thing that is anymore—so we assume all young should be sacred.

Thing is, we only make a few young over our lifetime. About the only human who has come close competing with fish in terms of offspring is possibly Genghis Khan, who might be the ancestor of roughly 8% of all Asian males (and presumably quite a few females too). On the other hand the average 1st World citizen only has 2.06 kids. An adult barracuda, to pick a fish at random, can lay up to 300,000 in a single season. Three-hundred thousand. In a year. From one fish. Correction, from one adult fish. A young female only lays about 5,000 eggs. That’s 60 times less. It’s the difference between having your 2.06 kids and having 123 of them running around the house.

It turns out that, counter-intuitively, the adults of some animal species are the most valuable members of the population. Weird I know, but look at it this way, if you have a minimum size restriction on taking fish and those fish reach adult-hood just in time to breed once or twice before we pop them into a dinner pot, you’d need 30-60 of them to equal what one full-grown adult can reproduce. That’s so crazily different that it’s hard to get our heads around the sheer numbers involved.

Actually, different is exactly the word, because animals (especially fish) are in fact very different from us. It’s the old Disney™ problem again. We want attribute our values and biases to the world around us. Of course we pin our hopes to the young of our species. That’s a classically optimistic human perspective. But  the natural world is one of wondrous variety, and not all animals do it like we do.

It turns out that people are bad at much of this common sense stuff. For example, every reasonable adult and parent will tell their child they need an education in order to make a good living. At the same time statistics show that only 20% of college graduates end up with a career in their field of study. However, I hasten to add that they still make a living, still end up with careers. It’s just that while a university education provided something vital for their career, it wasn’t what they or their parents thought it would be. These are the numbers, the statistics, yet year after year parents and freshmen still make the same erroneous assumption about what they’re spending all that money for.

Or take the example of the example of happiness. Who do you think is happier, a recent paraplegic or a recent lottery winner? That’s right: someone who has no use of their limbs and someone who just got given a pile of money. Who is happier. Take your time. After all, it’s just common sense. Right?

Right. Unless you’ve already seen the video (or are a genius), you guessed wrong. After a year they are both equally happy.

This is why actual science with real data is so vital. Without meaningful numbers we would be left at the mercy of our notoriously useless common sense. It is also why our legislation needs to be driven not purely by the whims of the voting public or by the (already suspect) common sense of our politicians, but by actual research and data.

So, to the Cayman Islands Department of Environment, the data is in. Repeal the current (pointless) law and establish a new one that protects the mature, breeding adults of our marine species, for these are truly the future of our waters.

3 Comments

  1. Pingback: Tippets: Letting the Big Ones Go, Unlikely Alliance, Spawning Ethics -

  2. Pingback: Tippets: Letting the Big Ones Go, Unlikely Alliance, Spawning Ethics | MidCurrent

  3. Mike N   November 17, 2013 8:26 pm / Reply

    Check out the laws on Redfish or Black Drum harvest in Louisiana for an example of how to do this right: limits on minimum & maximum length. An angler is permitted five fish, minimum length 16 inches, with no more than one fish over 27 inches. If you want to catch “bull reds” (those over 27 inches), you can have at it, but you’ll be mostly fishing catch & release. It’s a great way to keep people fishing (by letting them keep/eat fish), and keep them engaged in environmental protection (by keeping them fishing), while keeping the fishery stoked with big, productive fish.

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