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from the themightybuzzard-ain't-gonna-like-this dept.
Intensive fishing prompts much concern and debate over sustainability of fish stocks, but could it also be driving evolutionary changes that render fish of the future less catchable?
There are many examples of an evolutionary 'arms race' between predator and prey, where adaptations that help hunted animals avoid capture prompt changes in hunters that help them become more deadly.
Scientists at the University of Glasgow investigating whether commercial trawling is similarly driving evolutionary change in fish have found fitter fish are better at evading capture. They speculate that, over time, this could lead to physiological changes in future fish populations.
Dr Shaun Killen of the Institute of Biodiversity, Animal Health and Comparative Medicine, said: "There is a lot of concern on how overfishing is affecting the abundance of wild fish, consequences for the economy, employment and the ecosystem as a whole.
"But one aspect that is often overlooked is that intense fishing pressure may cause evolutionary changes to remaining the fish that are not captured."
A study led by Dr Killen, published in the journal Proceedings of the Royal Society B, used simulated trawling with schools of wild minnows to investigate two key questions around fisheries-induced evolution.
The researchers wanted to know whether some individuals within a fish shoal were consistently more susceptible to capture by trawling than others, and if so, was susceptibility related to individual differences in swimming performance and metabolism?
The researchers measured the swimming ability, metabolic rate, and indicators of aerobic and anaerobic physical fitness of 43 individual fish. They then placed them in a tank with a trawling net in a simulation that was repeated several times, enabling the identification of individuals which were more susceptible to capture.
Dr Killen said: "Fish being trawled will try to swim at a steady pace ahead of the mouth of the net for as long as possible, but a proportion will eventually tire and fall back into the net.
"Fish that escape trawling are those that can propel themselves ahead of the net or move around the outside of the net. The key question is whether those that escape are somehow physiologically or behaviourally different than those that are captured. Most trawlers travel at the about same speed as the upper limit of the swim speed of the species they are targeting.
(Score: 1, Interesting) by Anonymous Coward on Sunday August 09 2015, @02:03PM
The normal scenario for most fish and other sea creatures is a far higher death rate for the small young ones and a significantly lower death rate for the big adult ones.
Normally more of the small ones get eaten up. We're the weird creatures that eat the big ones that produce the young and avoid eating the "babies" because "Oh Noes, we musn't eat the babies".
But eating baby fish instead of the adults is what we should be doing (as long as we don't eat all of them). Despite what our hormones and other stuff (instincts, culture etc)[1] lead most of us to be believe, two babies are worth significantly less to a species than a breeding pair of adults. That applies to humans too- beware though - such truths can get you unfriended on facebook or in real life. The babies have a lower probability of survival, and they might not live to breed successfully and even if they do it might take them a while to reach maturity and breed successfully. Whereas the adults have proven their ability to breed and thus they are far more likely to be able to produce young the next breeding season, and the next and so on.
[1] Yes those hormones and stuff are useful encouraging parents to value their young. But the truth is if the species survival is at stake, and you had to choose between one or the other - let the parents live and let their babies die. Of course I'm talking about fertile productive parents, not the sterile ones.
(Score: 2) by jcross on Sunday August 09 2015, @02:30PM
Excellent point. At least part of this bias toward larger fish might be unintentional, though. After all, it's difficult to construct a net that catches small fish but allows larger ones to pass through. With today's technology, it becomes possible to imagine a "smart net" that could do this, but it would be damned expensive thing to drag through salt water behind a trawler.
There's a fungus called Dactylaria that forms little nooses that it uses to catch and eat nematode worms. Somehow it knows when it's got a worm in there and is very hard to fool with non-worm objects; a net that worked like that would be pretty neat, and could potentially select for species as well as size.
(Score: 3, Insightful) by gnuman on Sunday August 09 2015, @02:57PM
You are forgetting 1 thing - we are already fishing out the stocks faster than they can reproduce. 80% of fish stocks are in decline and almost all larger ones are fished out by us.
http://news.nationalgeographic.com/news/2003/05/0515_030515_fishdecline.html [nationalgeographic.com]
But eating baby fish instead of the adults is what we should be doing (as long as we don't eat all of them). Despite what our hormones and other stuff (instincts, culture etc)[1]
And despite brain too?
Fishing nets with larger openings that allow some larger things to escape is the best we can do at this time. If you can make better fishing nets, including those that don't catch whales or turtles and nest that disintegrate when lost, then go ahead. Make a net like that. So far, AFAIK, these nets are not exactly found on the market.
(Score: 0) by Anonymous Coward on Sunday August 09 2015, @05:10PM
You are forgetting 1 thing - we are already fishing out the stocks faster than they can reproduce. 80% of fish stocks are in decline and almost all larger ones are fished out by us.
I think that post's point is in theory if you eat say 80% of the babies instead of 80% of the adults they wouldn't be declining at such a rate.
It's true there's currently no easy way to do that with current commercial fishing nets and methods. But there's already a really huge problem with the existing commercial fishing methods - read this and weep: https://en.wikipedia.org/wiki/Bycatch [wikipedia.org]
The sad thing is there's plenty of scientific evidence that humans do better on a diet that includes oceanic fish. I guess in the future we might have to get our omega-3 and other goodies from other sources.
(Score: 1) by Ethanol-fueled on Monday August 10 2015, @04:02AM
Baby fish aren't worth eating. To get a decent meal you'd have to catch much more, clean them, and after all that hassle and depriving babies breeding be left with maybe a small sardine tin worth of meat and an equivalent volume of chum.
If you're that desperate for food you might as well hang out by the rocks and catch crabs all day like the Tijuana beach homeless do.
(Score: 1) by Ethanol-fueled on Monday August 10 2015, @04:14AM
In some places people catch small fish for bait to catch bigger fish.