During this time they feed and grow to maturity, migrating great distances in the North Pacific Ocean before returning to fresh water to spawn. Alaskan salmon can spend up to seven years at sea, although this varies by species. The results showed that the decreases in body size are primarily due to salmon returning to their spawning grounds at younger ages than they have in the past. This unprecedented dataset enabled them to see patterns of body size changes for four species of salmon - Chinook, chum, coho, and sockeye - across all regions of Alaska. In the new study, published August 19 in Nature Communications, researchers compiled and analyzed data collected over six decades (1957 to 2018) from 12.5 million fish by the Alaska Department of Fish and Game. Smaller salmon provide less food for people who depend on them, less value for commercial fishers, and less fertilizer for terrestrial ecosystems.įor years, people in Alaska have been noticing that wild salmon were getting smaller, but the reasons have been unclear. Salmon are critically important to both people and ecosystems in Alaska, supporting commercial and subsistence fisheries and transporting nutrients from the ocean to inland areas, fertilizing the ecosystems in and around the rivers where they spawn.
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