Catch comparison between otter and rollerframe trawls: Implications for sampling in seagrass beds

Abstract

The use of otter trawls as a sampling gear in habitats with shallow, submerged aquatic vegetation (SAV) has been criticized due to its variable and low capture efficiency. Moreover, the area swept by otter trawls is dynamic both between and within tows; capture of fauna associated with seagrass can be strongly influenced by gear-induced turbulence, and animals are able to escape under the net that often rides on top of the SAV. We compared catch from the commonly-used otter trawl with that from the rollerframe trawl, which has not been previously evaluated for fishery-independent research purposes. We found that the rollerframe trawls had higher catch rates and caught more species of fauna in seagrass beds across the northeastern Gulf of Mexico. Among the species captured, 72% were more abundant in the rollerframe trawls compared to 11% more abundant in otter trawls (17% of species were captured at equal abundances). These results were consistent across sites and for a wide range of taxa. Additionally, the rollerframe trawls captured 25% more species than the otter trawls. Our findings suggest that rollerframe trawls generally have a higher capture efficiency than otter trawls in seagrass beds. We therefore recommend that the rollerframe trawl be used as an alternative or supplemental gear for ecologists and fisheries scientists working in seagrass beds.