How humans shift fish evolution | Things to Know

Humans catch more fish than we ever have before. This ever-growing haul affects the size of the fish population, and over generations, the size of the fish. When fisheries go after mostly large fish, they create evolutionary pressure that favors the survival of smaller ones. Eventually, impacts from intense fishing could lead to food supply issues. In this video, Mikko Heino, a biologist at the University of Bergen, explains how this evolutionary effect works and what we can do to minimize human impacts on fish evolution.

READ MORE: The human hand in fish evolution

Video Transcript:

Knowable:  “Today, humans catch more fish than we ever have before. In 2018, fisheries around the world pulled in 178 million tons of fish, nearly five times the amount caught in 1960. The rise in large-scale fishing involved massive overfishing, which drastically reduced the population of dozens of species. And scientists have found that human fishing has yet another profound impact on fish — specifically, their evolution.

“So how does this happen? Mikko Heino, who’s been studying this exact question for the past two decades, explains.”

Mikko Heino (fisheries biologist, University of Bergen): “We typically like to fish large specimens of a single species, and that means that it becomes kind of dangerous to be a large specimen.”

Knowable:  “So smaller fish will be more likely to survive and pass along their genes to the next generation. This effect on fish size has been shown in tank experiments in the lab. In 2002, a study found that harvesting only the larger fish from a population led to smaller fish in just four generations. Importantly, Heino says, they found that the total yield of fish also got smaller. If the same happens in the wild, this could eventually lead to food-supply issues. So how can we satisfy the huge demand for fish, while minimizing our impact on fish evolution?

“Heino says we have to weigh our options. On one hand, capturing only large fish puts evolutionary pressure on fish to be smaller and reduces our catch. On the other hand, taking too many small fish puts an ecological strain on fish populations since they’re losing members that can grow bigger and reproduce. His suggestion is to target the medium-sized fish, though in practice this could be challenging.

“Fisheries that capture single species could adapt their gear to target a specific size, but for fisheries and tropical areas which catch lots of different species, that wouldn’t work. In any case, Heino says, the best thing fisheries can do is fish less overall. And consumers can help too, by eating smaller-bodied fish like herring and any fish that’s been sustainably harvested — advice that Heino follows himself.”

Mikko Heino: “I’m still happy eating fish that I know comes from a well-managed fishery.