Poor resolution makes it necessary to lump several taxa together. Sample area tends to be small and variable due to changes in visibility. Limitations of trawl Lack of exact information on where animals came from. Only get an average over the total area sampled. Difficult to follow a prior trawl track with a trawl in seabed impact studies.
Trawl is ineffective at sampling the benthos.
Dredge gear may be more suitable for this purpose. Resolution still good at very low speeds. Use of high speed video as an alternative to digital video to address problems with low resolution at low speeds.