Size selectivity of sampling gears targeting red snapper in the northern Gulf of Mexico

The ability to estimate fish abundance accurately over a particular habitat is contingent upon the use of appropriate sampling methods. The objectives of this study were to compare the catch per unit area (A), length-specific bias, and relative catchability (q-ratio) of four different gear types for sampling red snapper (Lutjanus campechanus) over natural low-relief reef habitats on the inner continental shelf of the northern Gulf of Mexico. Specifically, our goal was to assess the overall performance of a standard otter trawl, a small fish trap, a chevron trap, and a stationary 4-camera underwater video array during six quarterly sampling cruises performed in 2004 and 2005. The sizes of snapper captured by trawls ranged from 30 to 250 mm total length (TL) (ages 0 and 1 yr). Trawls captured the most red snapper per unit area and had q-ratios of 3:1 to 5:1 relative to small fish traps for juvenile red snapper. The chevron trap collected the second highest number of red snapper and proved most useful at collecting red snapper from 150 to 440 mm TL (ages 1–5 yr). The q-ratio of the chevron trap relative to the underwater video array was approximately 3:1. Our comparison demonstrated the chevron trap is most effective for sampling adults, while trawls were the most effective gear for sampling age-0 yr fish.