Larval and juvenile distribution and growth of Patagonian toothfish around South Georgia

Abstract

Early stages of toothfish are reported from cruises between 1978 and 2001. South Georgia was regularly sampled, Shag Rocks was briefly sampled in three summers, and Burdwood Bank was sampled in 1997. Most samples were using 8 m2 and 1 m2 nets in the upper 250 m and upper 3 m, respectively. Forty-three pelagic larval/early juvenile stages between 18.2 and 63 mm standard length (Ls) were taken between December and March. Four specimens were taken at Burdwood Bank, one at Shag Rocks, and 38 at South Georgia. Forty fish were from the upper 250 m, and 23 from the upper 3 m. They occurred onshelf and offshore over water depths between 10 and 3000 m. Estimated growth rate, at South Georgia from 11 cohorts (including published data), is c. 1% Ls, d−1 (n = 39). From this and a hatch size of 15 mm Ls, the predicted hatching season is November to mid-December. From seven trawl surveys during summer at South Georgia and Shag Rocks between 1986 and 2000, the mean depth of the smaller demersal juveniles 13–25 cm total length (LT) was < 140 m, indicating that early juveniles probably migrate inshore.