Interannual variability in growth of larval and juvenile walleye pollock Theragra chalcogramma in the western Gulf of Alaska, 1983–91

Abstract

ABSTRACTInterannual variability in growth of larval walleye pollock Theragra chalcogramma was examined from 1983 to 1991 and of juveniles from 1985 to 1990. ANCOVA was used to assess differences in population growth rates, and an alternate method was developed to examine variations between annual length‐at‐age data and average ‘expected’ values over different age groupings. For larvae, the years 1986, 1987, 1989 and 1990 had higher than average length‐at‐age, and 1988 and 1991 had lower than average values. Relationships between growth and SST and larval density were not clear. A tentative relationship between copepod nauplii abundance and larval length‐at‐age was noted. The consequence of larval growth to larval mortality, late larval abundance or recruitment was not clear. We conclude that larval mortality rates are highly variable and tend to mask effects of moderate variability in growth on later abundance. For juveniles, 1987 had significantly lower than average length‐at‐age and 1988 had higher than average values. Although there are few years of data, they tend to support the importance of juvenile growth in the recruitment process. Conditions for the large 1988 year class are documented and discussed, including warm SST, calm winds, relatively low larval growth rates, low abundances of potential predators on larvae, low larval mortality rates, and high juvenile growth rates.