Finland’s wild salmon reduction is ‘evolution in action’

We may tend to think of evolution as something that happens slowly over millions of years, but that’s not always the case. When a population of a particular species changes, there can be a variety of possible causes, including climate change or human pressures on a particular ecosystem, such as overfishing.

When a species changes faster than traditional views of natural selection historically allowed, it is called “rapid evolution” or “evolution in action.” These accelerated evolutionary processes are due to “the interaction of ecology and evolution as a dynamic interaction in both directions and on contemporary timescales”, which “confirms the paradigm that demographic and are ultimately entangled,” according to a 2014 study published in Frontiers in Ecology and Evolution.

A new study examines the case of shrinkage of wild Atlantic salmon in the Teno River in northern Finland, where overfishing has been seen as a possible cause of the noticeable change in salmon size. However, the study demonstrated that the shrinking of this particular fish population could have another, more indirect cause.

The study, “Rapidly changing life history of salmon induced by direct and indirect effects of fishing“, was published last month in the journal Science.

“Our previous research had shown that the age at which salmon matured in this river was getting younger and as a result the size of spawning salmon was decreasing, showing ‘evolution in action’. Important in demonstrating rapid evolution, there also had changes in their DNA at a gene known to be linked to height and age of maturation,” said Craig Primmer, professor in the Organisms and Evolutionary Biology Research Program. at the Biotechnology Institute of the Helsinki Institute of Sustainability Science, as reported by the Natural Resources Institute Finland.

The shrinkage of wild salmon in the Teno River is thought to be the result of the commercial capelin fishery (Mallotus villosus), a small fish found in the Atlantic and Arctic oceans.

Using genetic methods, Finnish scientists have discovered how changes in salmon fishing, in addition to commercial fishing for capelin – one of wild salmon’s favorite foods – could be linked to declining salmon populations Wild Atlantic.

Some of the capelin caught by commercial fishermen is used as fishmeal to feed aquaculture salmon, and overfishing of capelin could indirectly affect wild salmon, according to the study.

“The aquaculture industry has made significant progress in finding alternative protein sources for aquaculture fish feed, and our study suggests that these efforts have not been wasted, as it appears that harvesting capelin could affect wild salmon populations,” Primmer said, as reported by Finnish Natural Resources Institute.

Alternative sources of protein and the use of fish cuts from processing plants that would normally be wasted help to reduce the use of wild fish for fish feed.

“Different types of vegetable proteins are increasingly used. Waste from other types of fish processing is also used to reduce the amount of wild fish used in aquaculture (and other pet food),” Primmer told EcoWatch in an email.

The researchers found that another more direct cause of the increase in small salmon is likely the use of salmon weirs by local fishermen.

“We discovered that a special type of net, a salmon weir, which represents [the] majority of netting catches mainly catches smaller fish, although netting is often assumed to catch larger fish,” said Jaakko Erkinaro, research professor at the Institute of Natural Resources of Finland (Luke), reported the Institute of Natural Resources of Finland.

Indigenous Sami fishermen told researchers that the smaller mesh size of the salmon weir, which is used in shallower waters later in the season, increases the catch of small fish.

And spawning populations of small, early-maturing fish have increased as weir fishing has declined.

The decrease in weir fishing is mainly due to restrictions imposed by the Norwegian and Finnish governments, Primmer told EcoWatch.

In order to determine which of these influences was responsible for the rapid evolutionary changes occurring in the population of wild salmon in the Teno River, the study’s lead author, Dr. Yann Czorlich, said researchers needed to connect the differences annuals in the variation of salmon DNA to the annual environment. human-caused changes and influences.

“We’ve literally collected millions of data points on factors including annual water temperature, salmon fishing effort, and commercial catches of the fish that salmon eat in the ocean, and compared them with our data on DNA changes in our 40-year time series,” Yann said, as reported by the Natural Resources Institute Finland.

To do this, the scientists examined samples of salmon scales over a 40-year period and found that genetic variation for the size and spawning age of salmon was influenced by various fishing methods. They used the scales to obtain DNA and determine the age distribution of the salmon population. Managed by the Natural Resources Institute Finland, the archive contains more than 150,000 scale samples from individual salmon collected since the 1970s.

The decrease in salmon population size could be taken as an indicator that fish would be less resilient to environmental changes in the future, but it could also be taken as evidence that salmon are adapting.

“Variation in age at maturity is one of the main life history traits that drives variation in life history strategy in the population. Thus, a generally smaller size probably means there will be fewer life history variation in general meaning there may be less buffer to deal with future environmental changes Another way of saying this more generally is that reducing life history strategy variation probably results in less biological resilience of the population,” Primmer told EcoWatch. “On the other hand, we were able to show that this change is likely due to evolutionary adaptation, indicating that the change is in line with management strategies. life histories that are more optimal for current environmental conditions, so in some ways the change can be seen as a good thing in that the popu tion adapts.

However, the size of Teno River salmon appears to have stabilized in the 1990s.

“The largest decline occurred earlier in the time series, particularly among males…. But starting in the 90s, men’s height stabilized (but remained small),” Primmer said.

The shrinking population of wild salmon in the Teno River, rather than the shrinking size, is currently affecting a traditional food source for the indigenous Sámi people.

“Food source issues are a combination of size and abundance. Size itself is not necessarily a problem if fish are abundant, but currently they are not, affecting the availability of traditional food. native Sami people of the Teno River Valley,” Primmer told EcoWatch. “Also, salmon fishing is a source of income for some Sami and other locals through fishing tourism (people travel very far in this remote area to try to catch large salmon, and the locals act as guides), so reductions in the frequency of large salmon will have a negative effect on that.

Primmer said that since fishing regulations have not improved the number or size of Teno River salmon, solutions must extend beyond the salmon, the river and even Finland itself. .

“The fishing regulations in place seem to have reduced selection pressure over the last few decades, i.e. they have done what they are supposed to do, but as neither abundance nor size have improved, this suggests that more needs to be done.Our results show that the solutions can be quite difficult and complex, as regulating salmon fishing in the river seems to be only part of the problem: the fishing of “Other species at sea, by a range of other countries, also appears to be affecting Teno salmon size. But at least we now know that it’s also necessary to focus on what’s happening in the ocean,” said Primer said.

An approach that takes into consideration the traditional fishing of the indigenous Sami people, fishing tourism-based enterprises and restrictions designed to protect fish populations is a difficult balancing act.

“What’s best for people will depend on who you ask – as a researcher I could say ‘stop all fishing’ is the safest way, but these stocks have been fished for millennia by Indigenous Sami people, who are now struggling to pass on their knowledge of traditional fishing methods to the next generation because of the heavy restrictions, and then there are others whose fishing tourism businesses are struggling, so that’s a very complex question to answer,” Primmer told EcoWatch. “Ideally, targeted, well-targeted restrictions that still allow fishing that causes the least damage would be the best strategy, and hopefully our research results can do that. to confirm.”

About Patricia Kilgore

Check Also

Catfishing, then and now – Waxahachie Daily Light

Luke Clayton Daily Light Contributor I’ve always loved catching catfish and…eating them! I guess my …