Where have all the big fish gone?
Many countries prohibit fishermen from bagging undersized fish—a strategy intended to ensure the sustainability of fish stocks by allowing young, small fish to grow. But scientists are calling for a rethink, after their findings showed the policy is flawed.
Researchers from Bangor University, the University of East Anglia, the University of the West Indies, and the Max Planck Institute for Developmental Biology say that over-harvesting larger fish not only leads to a population of smaller fish, but ones that are less fertile, too.1,2
In laboratory tests using the Trinidadian guppy, they looked for any changes in the genes of the fish population in response to harvesting of only the larger fish.
Within just a few generations, the researchers observed a dramatic shift in the genetic makeup of harvested fish to smaller, less fertile individuals. They noted that the same phenomenon “has probably already taken place in any number of commercial fishing grounds”, and that this would have “serious global consequences for the environment and for the global fishing industry”.
They are very likely correct on that point, given well-known examples of this occurring, e.g. the ‘crash’ of the cod fishery off Newfoundland in the early 1990s.3
But on one point they are certainly not correct, namely their claim that this is “an evolutionary response to overfishing”. There’s nothing ‘evolutionary’ about it, in that it does not at all support the idea that ‘goo’ became guppies, and fish changed into fishermen, over millions and billions of years. Microbes-to-man evolution requires a gain in information, which is nowhere in evidence here.
Rather, genetic information—the genes that code for large size, and higher fertility—has been lost from the population as a result of human-imposed selection pressure (akin to ‘natural selection’). And it’s likely that other useful characteristics have been lost too, as the researchers themselves rightly surmise: “As well as losing the capacity to produce large-sized and productive fish, specific fish populations may also be at risk of losing other specific adaptations by selective fishing, such as adaptations to particular location characteristics, like colder water or migration routes.”
And this next statement from the researchers is particularly telling: “The loss of these genetic ‘types’ may mean that populations may not be able to recover completely or at all.”
Now what a curious thing, that these evolution-believing scientists should have such little faith in the capacity of evolution! It’s as if they intrinsically realize that the rapid change in genetic makeup they observed in their laboratory fish population is not in the same direction as that needed to create new genetic information. Sadly, however, many in the general public will be duped into thinking that this undisputed example of natural selection is yet more evidence that fish turned into philosophers over millions of years. Beware the bait-and-switch.4
Re-posted on homepage: 18 November 2020
References and notes
- van Wijk, S., and 7 others, Experimental harvesting of fish populations drives genetically based shifts in body size and maturation, Frontiers in Ecology and the Environment 11(4):181–187, 2013. Return to text.
- Big fish catches mean smaller fish—Bangor scientists,bbc.co.uk, 18 March 2013. Return to text.
- Catchpoole, D., Smaller fish to fry, Creation 30(2):48–49, 2008; creation.com/smaller-fish. Return to text.
- Walker, T., Don’t fall for the bait and switch—sloppy language leads to sloppy thinking, Creation 29(4):38–39, 2007; creation.com/baitandswitch. Return to text.