Is salmonid migration at risk from chemical information disruption?

Good information is the basis for good decisions. For many invaluable salmon species, chemical information is necessary to guide and fine-tune their migrations to and from freshwater mating grounds. A problem is that salmon of the current world are running a gauntlet of toxic chemicals arising from diverse anthropogenic inputs and these chemicals are known to disrupt information. There is sufficient evidence that effluents from cities, mines, agriculture and industry contain chemicals that can rapidly, and sometimes irreversibly, impair the olfactory sense that salmon use to gather information. Some toxic inputs may not only be strong enough to impair migration, but be strong enough to redirect salmon away from their routes. There is also evidence that some synthetic chemicals may serve as the basis for ‘new’ information and be useful in making correct migratory decisions. On the plus side, there are examples of new regulations that limit the input of chemicals of known olfactory toxicity, but on the minus side, increased urbanization and global climate change will likely increase the number and/or severity of some neurotoxic inputs. Here we identify the specific avenues of chemical risks to information disruption and in so doing prioritize and rank the risks to migrating salmon. The data collected here can be used to lay the foundation for modelling the effects of anthropogenic inputs on information disruption in diverse salmonid species from around the world and therefore help secure their longevity in a changing chemical environment.