Alaskan char adapt to climate change by following food

Chuck Bednar for – Your Universe Online
While climate change has placed many different types of creatures in peril, others – including a species of Alaskan char known as Dolly Varden – have managed to adapt to warming conditions, claims new research published earlier this month in the journal Freshwater Biology.
According to lead author Christopher J. Sergeant of the National Park Service’s Inventory and Monitoring Program in southeastern Alaska and his colleagues, Dolly Varden have adjusted their migratory patterns in order to have continued access to a preferred source of food (salmon eggs), in spite of the fact that climate changes have altered the timing of salmon spawning.
This ability to adapt to climate-driven changes to food and habitat could be a key factor in how resilient different types of creatures are to global warming, the researchers explained. Predators that hunt at times in which their prey are no longer available could completely lose access to food, while others like the Dolly Varden have altered their schedules in order to survive.
Sergeant’s team believes that the key to the Dolly Varden’s success in this field may be that it ignored environmental cues. Instead of determining when it should migrate by variables such as water temperature or stream flow, the species took its cues directly from the presence of the salmon upon with it depends for food.
“Despite warming temperatures and shifting salmon migrations, Dolly Varden do a great job of following their food,” Sergeant explained. “Species that can handle a high degree of variability are the ones that should be most resilient to further changes associated with climate.”
This type of fish gets the bulk of its energy throughout the year by devouring salmon eggs, which are abundant during the summer and are rich in energy thanks to fatty acids, the study authors explained. Salmon eggs can be available during a narrow spawning window lasting two to six weeks, so the Dolly Varden has to keep a close eye on salmon migrations in order to take full advantage of this aquatic buffet.
However, the warming climate has resulted in changes to the migratory patterns of salmon, as previous research has indicated that  pink and coho salmon now travel to their spawning grounds 10 to 17 days earlier, while sockeye salmon migrate eight days earlier.
Dolly Varden living in the Auke Creek region have successfully adjusted their annual migrations from the ocean back to freshwater in order to remain in synch with the salmon, the authors noted. As a result, they have been able to have continued access to their salmon egg feasts.
“In short, the Dolly Varden are shifting their migration to follow their food instead of following temperatures or other environmental cues that, as the climate changes, might otherwise lead them to migrate at a different time than the salmon that provide their most important food,” the NOAA Fisheries West Coast Region explained in a statement.
However, they also caution that it is not clear yet whether or not other salmon predators could make similar adjustments to their schedule, either by watching them as the pass by or detecting the smell of their eggs. Nonetheless, the adaptability of Dolly Varden suggests that at least some creatures are more resilient to climate-induced migration changes than previously believed.
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