Some fish may be evolving to better escape capture from the nets on commercial fishing boats, experts at the University of Glasgow Institute of Biodiversity, Animal Health and Comparative Medicine report in the latest edition of the journal Proceedings of the Royal Society B.
According to Time, the authors of the study demonstrated that fish that swim faster and are more fit overall are less likely to be trapped by trawler nets. This could, over time, lead to long term physiological changes in fish populations that make them harder for fishermen to catch.
“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,” lead investigator Dr. Shaun Killen said in a statement. “But one aspect that is often overlooked is that intense fishing pressure may cause evolutionary changes to remaining the fish that are not captured.”
He and his colleagues believe that this is an example of evolutionary competition between prey and predator, where the creatures that are being hunted make adaptations that make them better at evading capture. They conducted a series of simulations to test out the hypothesis.
Higher anaerobic capacity decreases odds of being caught
Dr. Killen’s team used simulated trawling with schools of wild minnows to see if specific fish were consistently easier to catch than others, and if so, if this increased susceptibility was linked to individual differences in swimming performance and metabolism within the shoal.
They measured the swimming ability and metabolic rate of 43 individual fish, while also keeping tabs on various indicators of aerobic and anaerobic physical fitness. The fish were then placed in a tank with a trawling net where the researchers attempted to catch them several times. The goal was to identify individual that might be more susceptible to capture by the fishing net.
Some fish were indeed more likely to be caught than others, and this likelihood was strongly linked to their ability to engage in intense physical activity for short periods of time (also known as anaerobic capacity). Furthermore, fish that were least likely to be caught also had the fastest aerobic swim speeds and the highest metabolic rates.
“Using simulated trawling, our study provides the first evidence for better swimming fish, and [that] those with higher metabolic rates, are more likely to escape capture,” said Dr. Killen. “Over time, the selective removal of poor-swimming fish could alter the fundamental physiological makeup of descendant populations that avoid fisheries capture.”
(Image credit: Thinkstock)
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