OPINION: Understanding Alaska Peninsula fisheries’ impact on Yukon-Kuskokwim salmon

Central to the question of Arctic-Yukon-Kuskokwim (AYK) chum salmon conservation is identifying at what stage salmon fail to survive in their life cycle — at the egg-to-smolt stage, their first month in saltwater, the periods in the Bering Sea and Gulf of Alaska, bycatch at the sub-adult stage, or finally as adults harvested in mixed stock fisheries as they migrate home. This final stage draws much of the attention, specifically when AYK chum passes through the 1,200-mile Aleutian chain. The June Alaska Peninsula fisheries around south Unimak Island represent a very small geographic piece of the AYK chum migration. As we look at these phases of life, National Oceanic and Atmospheric Administration and the Alaska Department of Fish and Game research provide important data on health and mortality for these chums throughout their lifecycle.

Salmon survival at the adult migration phase of their lifecycle — key to so many communities throughout Alaska — depends on an understanding of a few scientific terms. This jargon of “stock composition” and “harvest rate” — as used in mixed-stock fisheries genetic analysis — can cause folks’ eyes to glaze over. So, in the simplest of terms: The harvest rate demonstrates the effect of a particular fishery on the total run, whereas stock composition is a snapshot confined by a specific time and area and does not represent the percentage of the total run.

The AYK region and adjacent Bristol Bay and Norton Sound chum stocks are identified as a single genetic stock: the Coastal Western Alaska (CWAK) stock group. From 2007 to 2009, the Western Alaska Salmon Stock Identification Program (WASSIP) used innovative genetic techniques to uniquely identify stock groups stretching from Korea to Oregon. This research informed stock composition and harvest rate analyses in those years, but it also continues to be critical to identifying prohibited species trawl bycatch and informing ongoing ocean salmon research.

The WASSIP years showed median harvest rates of 2.1%, 3.6% and 6.9% for the CWAK stock in South Alaska Peninsula June salmon fisheries. Harvest rates are equivalent to the proportion of the run. The total population for CWAK stock is determined by adding the estimated escapement of each river system from Bristol Bay to Norton Sound, plus harvests in Bristol Bay, the North Peninsula, and Area M. The population (catch + escapement) for 2007 was close to 8.5 million chums. By dividing the 2007 June chum harvest in Area M by 8.5 million chums, the resulting harvest rate or percent of the run is 2.1%.

Stock composition, by contrast, is the percent of harvest during a given timeframe and area. To put this all in more concrete terms, a weeklong fishery with 20,000 chums harvested, which consists of 11,400 CWAK stock, would have a composition of 57% CWAK. Yet this one component does not define the percentage of the total run. The AYK chums run were strong in the years 2007-2009 and Asian chum stocks were relatively low, unlike in recent years, when the Asian stocks are quite high.

All this being said: Harvest rates in Area M are not the culprit, even if we assume the most liberal harvest numbers of salmon passing through Area M to AYK from available data. Mortality factors such as poor ocean-rearing environments, low prey abundance and low energy reserves, as observed by scientists, are far greater factors contributing to the low CWAK chum salmon productivity than Alaska Peninsula harvest rates. While it can be tempting to blame one region’s fishery harvests for another region’s poor returns, the science simply doesn’t support that argument, and the biologists at NOAA and Fish and Game maintain that conclusion as well.

Steve Reifenstuhl is a retired salmon biologist with 45 years of experience in Alaska. He continues to study salmon harvest data and ocean research in Alaska statewide.

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