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NOAA Technical Memorandum NMFS-AFSC-371

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Age-at-maturity and fecundity of female sablefish sampled in December of 2011 and 2015 in the Gulf of Alaska


We compared published results of the age-at-maturity and relative fecundity of female sablefish Anoplopoma fimbria sampled just prior to the spawning season nearby Kodiak Island in 2011 to results from a study in the same geographic area in 2015. The rate of skip-spawning was higher in 2011 (21%) than in 2015 (6%) and, therefore, in 2011 there were larger effects on the estimates of age-at-maturity when skip-spawning fish were classified as mature or immature than in 2015. When skip-spawning fish were classified as mature, the age-at-50% maturity in 2011 was 0.5 years younger than in 2015. When skip-spawning fish were classified as immature, age-at-50% maturity was 1.9 years older in 2011 than in 2015. Generally, skip-spawning was at ages where a portion of the fish were not yet mature (i.e., the age at which fish were estimated to be <100% mature). For 2011 and 2015 pooled, when including only the age range that included ages where there was skip-spawning, there was a negative relationship between age and skip-spawning, indicating that skip-spawning was more common in younger fish. In addition, relative fecundity by body weight decreased with age (significantly in 2015 and for both years pooled), indicating that as fish age they produce relatively fewer eggs. Although the relationships were diffuse, the estimated decrease in relative fecundity from age 5 to 40 was 21-24%.

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