Reconstruction of historical abundance and recruitment of red king crab during 1960–2004 around Kodiak, Alaska

Abstract

Gulf of Alaska waters around Kodiak Island once supported the world's largest fishery for red king crab, Paralithodes camtschaticus. Fishery harvests occurred at low levels beginning in the 1930s, but increased rapidly in the 1960s to a peak harvest of 42,800 mt in 1965. However, stock abundance declined dramatically in the late 1960s, and again in the early 1980s. The history of the fishery included a variety of management measures, such as time and area closures and changes to minimum size limits. Despite these efforts, the stock was ultimately recognized as depleted, and a commercial fishery closure since 1983 has not resulted in a stock recovery. We developed a quantitative retrospective analysis to understand the conditions surrounding the rise, collapse, and continued depleted status of the red king crab stock around Kodiak Island, Alaska. Our approach used a population dynamics model to estimate abundance, recruitment, and fishing and natural mortality over time. The model included three male and four female “stages” and incorporated catch composition data from the fishery (1960–1982), a pot survey (1972–1986), and a trawl survey (1986–2004). Male abundance is estimated for 1960 to 2004, but the available data limit analysis of females to the years 1972 to 2004. During a critical time of fishery development in the late 1960s, a chance period of strong recruitment helped promote the capitalization of this fishery. Very high harvest rates in the late 1960s were not sustainable, likely due to reproductive failure associated with sex ratios skewed toward females following a recruit-driven fishing period in the 1970s. Environmental and ecological changes, associated with a climate regime shift, likely exacerbated these problems.