2014 Assessment of the Pollock Stock in the Aleutian Islands
March 04, 2014
This year the authors’ recommended model is different from last year’s in that we include age 1 pollock. The change in results due to this model adjustment is minimal, but adding the age ones provides consistency among the three pollock stock assessments for the Alaska Region and allows for easier comparisons among different modeling platforms such as Stock Synthesis 3. The 2014 summer bottom trawl survey estimate, 2013 finalized catch estimate, and 2014 fishery catch estimate were included in this year’s assessment. Note that the 2014 summer bottom trawl estimate (85,316 t) was nearly double the 2012 estimate (44,281 t) which was the lowest on record estimated for the area west of 170° w longitude. As in the previous five years there has been no directed fishing for pollock in the Aleutian Islands. As of October 4 there has been only 2,348 t of bycatch, primarily in the arrowtooth flounder and Pacific cod fisheries.
Walleye pollock (Gadus chalcogrammus; Coulson et al. 2006; Carr and Marshall 2008; here after pollock) are distributed throughout the Aleutian Islands (AI) with concentrations in areas and depths dependent on diel and seasonal migration. The population of pollock in the AI incurred an apparent drop in abundance from the mid-1980s to the mid-1990s (1986 bottom trawl survey estimate of 444,000 t to a 1994 bottom trawl survey estimate of 78,000 t). Since 1994 the abundance point estimate has been variable, but considering the variance of the survey estimates the trend appears relatively flat (Fig 1A.1). The 2012 survey abundance was a record low at 44,281 t. The 2014 survey abundance estimate at 85,316t nearly doubled the 2012 estimate. The low 2012 estimate is thought to be anomalous due to the very low temperatures in the region affecting availability of the species to the bottom trawl survey. The precipitous decline between 1986 and 1991 may be in part due to undocumented fishing by foreign vessels claiming
catch from the Central Bering Sea (CBS), as the documented fishing levels alone cannot account for the decline (Table 1A.1). A number of foreign fishing vessels were observed fishing in the AI during this time period (Egan 1988a; Egan 1988b) while claiming catch from the CBS. The most recent surveys show that the AI pollock population is predominantly concentrated in the eastern portion of the Aleutian Island chain, closer to the Eastern Bering Sea shelf. Surveys from the 1980’s and 1990’s estimated higher
proportions of pollock biomass in the central and western Aleutians (Fig 1A.1). This recent spatial change in population abundance may reflect a spatial contraction of the stock in the Eastern Bering Sea after the collapse of the Central Bering Sea population in the early 1990’s, low AI pollock recruitments since the mid 1980’s, documented higher exploitation rate of the AI pollock in the mid- to late 1990’s, and possibly a high undocumented exploitation rate in the late 1980’s by foreign fishers.