Catch Comparisons of Surface Sampling Methods for Age-0 Gizzard and Threadfin Shad

Abstract

Catches in neuston nets were used to estimate abundance and size structure of shad Dorosoma spp. Neuston net catches also were compared with catches in 0.5- and 1.0-m-diameter towed nets and in paired 0.5-m-diameter push nets. At Guist Creek Lake, Kentucky, all sampling methods showed similar abundance trends of gizzard shad D. cepedianum. Catch per unit effort was lower for neuston nets than for 1-m nets but not significantly different from those of other nets through late June. At B. Everett Jordan Lake, North Carolina, neuston and 1-m nets gave similar abundance estimates of Dorosoma spp. on three of five sampling dates; catches in the 1-m net were significant higher on two dates. Precision of abundance estimates was higher at B. Everett Jordan Lake than at Guist Creek Lake, where precision decreased through the sampling season. Mean lengths of shad differed among sampling methods and between tows with the same net, but these differences were rarely large. Neuston, 1-m, and push nets captured gizzard shad that exceeded 80 mm in Guist Creek Lake, and neuston and 1-m nets captured threadfin shad D. petenense that exceeded 60 mm in Jordan Lake. However, catches by any of these methods are unlikely to represent abundance or size structure when mean shad lengths exceed 40 mm. Neuston nets used to sample larval and juvenile shad offer the advantage of neutral gear buoyancy over traditional methods. This feature simplifies operation, minimizes personnel requirements and special rigging, and provides access to shallow water habitats