Growth, Mortality, and Yield‐per‐Recruit Models for Speckled Hind and Snowy Grouper from the United States South Atlantic Bight

Opaque rings on cross‐sectioned otoliths from speckled hind Epinephelus drummondhayi and snowy grouper E. niveatus, taken off North Carolina and South Carolina, were determined to be annuli. Annulus formation occurred primarily between April and June for speckled hind, and from May through July for snowy grouper. The length‐weight relationship for speckled hind was W = 1.1 × 10 −8 L 3.073 and for the snowy grouper was W = 7.0 × 10 −8 L 2.755 , where W = weight in kilograms and L = total length in millimeters. Back‐calculated mean lengths (mm) of speckled hind from ages 1 to 15 were 186, 317, 408, 475, 528, 572, 613, 645, 678, 709, 739, 774, 804, 839, and 861. For snowy grouper ages 1 to 17, they were 210, 328, 403, 462, 514, 562, 605, 647, 686, 721, 762, 798, 832, 874, 900, 924, and 958. The maximum age of both species was at least 25 years. The von Bertalanffy growth equations for speckled hind and snowy grouper (t = age in years) are L t = 967{1 ‐ exp[‐0.13(t + 1.01)]} and L t = 1,255{1 ‐ exp[‐0.074(t + 1.92)]}. Instantaneous annual mortality rates for speckled hind, determined from catch curves, increased from 0.26 to 0.40 in the headboat fishery between 1975 and 1979, and fluctuated between 0.23 and 0.32 in the commercial hook‐and‐line fishery. Snowy grouper mortality increased from 0.19 to 0.57 in the headboat fishery between 1972 and 1978, but remained stable at 0.24 to 0.25 in the commercial fishery from 1977 to 1979. Yield‐per‐recruit models for both species indicated that the headboat and commercial fisheries are harvesting between 60% and 80% of the maximum available yield per recruit. Received June 13, 1983 Accepted May 11, 1984