Аннотация:Recent studies have shown that by 1991 the sandbar shark (Carcharhinus plumbeus) population along the Atlantic coast of the United States had declined in abundance to approximately 20% of its level in the late 1970s. This phenomenon allowed us to test the hypothesis that compensatory (density-dependent) growth occurred after severe population reduction. Age and growth of sandbar sharks were investigated by counting rings and back-calculating lengths at previous ages from vertebral samples collected in 1980-1981 and 1991-1992. The collections included 188 sharks from 1980-1981 and 412 sharks from 1990-1991 ranging in length from 51-172 cm precaudal length (PCL). All sharks were mature at lengths > 136 cm PCL. Minimum and maximum ring counts, which included a birth mark, were 1 and 25. Age at maturity was 15-16 years for both sample periods and both sexes. For sexes combined, the von Bertalanffy growth parameters were L,. = 199 cm PCL, K = 0.057, to = -4.9 years for the 1980-1981 sample and L,. = 164 cm PCL, K = 0.089, to = -3.8 years for the 1991-1992 sample. Statistical tests found significant differences between the two growth models. Significant differences in size at age and annual incremental growth of juveniles suggest a small increase in juvenile sandbar shark growth rate between the two sampling periods. However, age at maturity was unchanged between samples suggesting that any biological significance of a growth rate increase has not been realized.
