By Allison Sayer for Seward City News –
Prince William Sound pink salmon fishermen are glad to have this season, described by one captain as “biblically bad” behind them. The salmon harvest was less than 30% of the expected harvest for this year. Prince William Sound was not alone; Kodiak, Cook Inlet, and Chignik all had pink salmon harvests that were a fraction of their usual size. Southeast Alaska showed slightly better salmon returns but the numbers were still far short of projections. While fishermen try to pick up the pieces of an unprofitable summer, a lot of people have the same question: “What happened?”
Deputy Director of ADF&G Commercial Fisheries Forrest Bowers believes “there are issues related to survival in the North Pacific. We can control freshwater quality, and the freshwater habitat is generally pristine.” The fishery is also managed for “escapement goals.” Every year the first priority of management is to ensure that enough fish return to their natal streams to create the generation of fish that will return two years later. There were no problems with freshwater habitat or escapement two years ago.
Joe Orsi, a Research Fishery Biologist for NOAA fisheries, agrees that pink salmon encountered a serious issue in their marine habitat. Salmon runs “usually don’t all come in good or all come in bad. This year they all came in bad. This points to something in the ocean basin that affected them all.” He also went on to explain that NOAA predictions for pink salmon fisheries are typically within 10 percent of the actual harvest, but this year the salmon returns were much lower than predicted. NOAA makes predictions by making computer models of the population that incorporate data from marine surveys and physical ocean data. The scientists are now searching for the missing parameter- the factor that was not included in the model but that affected the population.
Both Bowers and Orsi think recent unusually warm temperatures in the Pacific could have had a negative impact on pink salmon, although it is not possible to be sure without definitive research. Alaskan people enjoy swimming in warm water, so it is somewhat counterintuitive that warm water could be harmful to the Alaskan ecosystem. However, a mass of warm water known as “The Blob” has been associated with widespread deaths of marine mammals, invertebrates, and seabirds throughout the Pacific.
Harmful algal blooms occur more frequently in warm water than they do in cold water. NOAA scientists are exploring the hypothesis that they could have affected pink salmon. Samples of pink salmon tissue from this year and from past years are currently being analyzed to determine whether the fish were carrying higher than normal loads of toxins from harmful algal blooms. The results from these tests will be back later in the winter.
What are some other ways in which increasing temperatures change Alaska pink salmon habitat? Pink salmon mostly eat plankton, and water temperature affects the timing and composition of plankton blooms. Increased temperature also has an effect on the metabolism of the salmon themselves, causing an increase both in the fish’s growth rate and the demand their bodies have for food. This could be a problem if there is not enough food available. Once it reaches too high a temperature, warm water can form a barrier to pink salmon migration, shrinking the size of their available habitat. Fish from south of Alaska that ordinarily can not survive in cold temperatures can also come farther north, and compete with or predate upon pink salmon.
According to NOAA research, pink salmon are currently compensating for changes in plankton timing, and Orsi expects they are generalistic enough in their diets to be able to survive changes in plankton composition. Other factors have not yet been explored with direct research. It is also possible that either a combination of factors worked perfectly together to harm the salmon population this year, or that something completely different but not yet discovered was responsible. In general, the farther salmon are from shore, the less is known about what is happening in their lives.
What does all this mean for the future? Both Bowers and Orsi remain cautiously optimistic for the fisheries, despite the terrible returns from 2016. The situation in the Pacific Ocean is complex; whatever occurred last year may not play out the same way this year. The population of one year old salmon that was surveyed this summer appears to be strong, and escapement and freshwater habitat continue to be managed well. Researchers clearly need more information, and many questions may be answered after the International Year of the Salmon in 2019. Canada, Japan, Russia, South Korea, and the United States will work together on a wide range of projects, including research questions relating to climate change and studies of salmon in international waters (more than 200 miles offshore). In the meantime, fishermen, managers, and scientists will continue to do their best with what they have.