Fish Trawls

Overview

Subtidal habitats support an abundant and diverse community of animals, including small invertebrate epifauna, larger macroinvertebrates and fishes, and in some regions sea turtles and marine mammals (manatees and dugongs). Larger animals can play important roles in altering habitat structure, community structure, and ecosystem processes, and are key in transporting production from submersed habitats into other habitats. Furthermore, structured habitats like seagrasses serve as a key ‘nursery’ habitats for juveniles of many fish species and can thus support coastal fisheries.

Sampling large, mobile organisms in submersed habitats is challenging because of wide variation among regions in depth, water clarity, and physical setting. This protocol focuses on trawl sampling of deeper subtidal habitats like seagrass meadows and oyster reefs, where beach seines or other methods are not possible. Otter trawls can be non-destructive when done carefully and efficiently, as animals are quickly returned to the water. Thus, otter trawls provide a simple and useful alternative for sampling fishes and mobile macroinvertebrates in a variety of habitat types.

In deeper areas with good visibility, diver visual census provides an alternative to seining.

Measured Parameters

• Mobile fauna abundance and taxonomic composition (individuals)
• Mobile fauna size (length in mm)

Selected Literature

Duffy, J.E., Hughes, A.R., and Moksnes, P.O. (2013). Ecology of seagrass communities. In: Bertness, M.D. et al (editors). Marine community ecology and conservation. Sinauer. Pp.271-297.

Edgar, G. J., & Shaw, C. (1995). The production and trophic ecology of shallow-water fish assemblages in southern Australia I. Species richness, size-structure and production of fishes in Western Port, Victoria. Journal of Experimental Marine Biology and Ecology, 194(1), 53-81.