Stone Crab Menippe spp. Populations on Louisiana's Nearshore Oil and Gas Platforms: Higher Density and Size at Maturity on a Sand Shoal

Abstract

AbstractOil and gas platforms are common in the northern Gulf of Mexico. Platforms provide substrate for sessile organisms such as barnacles and oysters that enhance habitat for stone crabs Menippe spp. and other fouling‐associated organisms. In recent years, Louisiana's small nearshore platforms (<15 m) have been subjected to a high rate of removal, but little is known about their relative value as artificial reefs. During 2014, we compared stone crab populations at platforms on and off Ship Shoal in order to evaluate habitat conditions in the two areas. We hypothesized that platforms on the shoal would provide higher quality habitat than those in the surrounding area because the shoal supports higher diversity and abundances of benthic organisms. Stone crab populations were characterized by means of visual counts and by removing subsamples for species identification, sexing, and carapace measurements. Of the 378 stone crabs collected, 368 were Gulf stone crabs M. adina and 10 were Cuban stone crabs M. nodifrons. Stone crabs colonized every platform studied, but densities were higher (mean values: 4.0 crabs/m2 on the shoal versus 1.8 crabs/m2 off the shoal), and carapace width at 50% maturity (CW50) was 27.1 mm larger for crabs on than off the shoal. Mean carapace width, size‐class distribution, and sex ratio of crabs on and off the shoal were not significantly different. Platforms provided substrate for barnacles, which enhanced the structural complexity of platforms and were observed to be prey for stone crabs. Nevertheless, higher stone crab density and CW50 on the shoal suggested that shoal platforms are better habitat types for stone crabs.Received February 23, 2016; accepted January 9, 2017 Published online March 15, 2017