Climate Change Impact on Alaska Fish

by Bill Hauser and Rachel Hovel

(part one of two)

This FISH TALK is a little different from a usual FISH TALK because it is from a report in an online document, University of Washington, UWTODAY, by Michelle Ma, January 18, 2017, based on a 13-page research report by Rachel Hovel and two co-authors. I am sharing this because it has some interesting information (You do know, of course, “all fish are interesting…etc.”) as well as some other interesting lessons. (I obtained permission from Rachel to do this.) I have done some light editing and periodically added my own comments as: (comments).

One of Alaska’s most abundant freshwater fish species (of 22 strictly freshwater species in Alaska) is altering its breeding patterns in response to climate change. This could impact the ecology of northern lakes, which already acutely feel the effects of a changing climate.

That’s the main finding of a recent University of Washington study published in Global Change Biology that analyzed reproductive patterns of threespine stickleback over half a century in Alaska’s Bristol Bay region. (There are a number of species – or “species-complexes - worldwide but we have only threespine and ninespine sticklebacks in Alaska. Some are freshwater, some are marine, and some are anadromous. ) The data show that threespine stickleback breed earlier and more often each season in response to earlier spring ice breakup and longer ice-free summers.

While several papers have speculated that conditions brought on by a warming climate may allow animals to breed more often in a single year, this has only been empirically (i.e., experimentally) shown in insects. This study is the first to document multiple breeding cycles for fish in a single season because of climate change, said lead author Rachel Hovel, a postdoctoral researcher in the UW’s School of Aquatic and Fishery Sciences.

“The exciting thing about this paper is that it shows, for the first time, the emergence of multiple breeding in a vertebrate as a response to climate change,” Hovel said. “Climate change literature features many predictions and vulnerability assessments, but we don’t have many opportunities to actually observe species’ responses over time, as this is very data-intensive. Our ability to detect multiple breeding in fish is attributed to our comprehensive and high-quality long-term dataset.” 

The data were collected from 1963 to 2015 in Alaska’s Lake Aleknagik, home to one of the UW’s Alaska Salmon Program research stations. The research program has, for decades, recorded the abundance of juvenile sockeye salmon and other fish that live in the region’s freshwater lakes. For 52 years, fish were captured in nets along the lakeshore at 10 different sites every seven days between June and September. All fish were identified and measured. (Freshwater threespine sticklebacks rarely exceed about 4 inches in length.) (This long term dataset is a wonderful legacy of the UW Alaska Salmon Program. A rare dataset such as this is a huge gift for a researcher and allows unique opportunities for this sort of comparison. Think about the Nenana ice classic and the record of timing of spring breakup.)

Read Part II in next month's Flylines. Far before the Nenana breaks....