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Providing evidence to improve practice

Action: Use an otter trawl instead of a beam trawl Subtidal Benthic Invertebrate Conservation

Key messages

Read our guidance on Key messages before continuing

  • One study examined the effects of using an otter trawl instead of a beam trawl on subtidal benthic invertebrates. The study was in the North Sea (Germany and Netherlands).

 

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

  • Overall abundance (1 study): One replicated, paired, controlled study in the North Sea found that otter trawls caused similar mortality of invertebrates in the trawl tracks compared to beam trawls in sandy areas but lower mortality in silty areas.

Supporting evidence from individual studies

1 

A replicated, paired, controlled study in 1992–1995 in four areas of sandy or silty seabed in the south-eastern North Sea, Netherlands and Germany (Bergman & Van Santbrink 2000) found that the effects of otter trawls compared to beam trawls on invertebrate mortality varied with the sediment type. Otter trawls caused similar mortality of invertebrates in the trawl tracks compared to beam trawls in sandy areas (otter: 0–41%: beam: 1–53%) but lower mortality in silty areas (otter: 1–65%: beam: 2–82%). In spring-summer 1992–1995 parallel strips (2,000 x 60 m, 300 m apart, number unspecified) in one sandy location and three silty locations were fished with either a commercially used beam trawl with tickler chains or an otter trawl. Prior to trawling, mega-invertebrates (>1 cm) and macro-invertebrates (> 1 mm) were counted from samples taken in each strip using a dredge and a sediment grab. After 24–48 h following trawling, all strips were sampled again using the same methods. Mortality (from trawling) of invertebrates present in the trawl tracks was calculated using the difference between the before and after-trawling abundances (assuming all animals killed by trawling had been eaten by predators).

Referenced papers

Please cite as:

Lemasson, A.J., Pettit, L.R., Smith, R.K., and Sutherland, W.J. (2019) Subtidal Benthic Invertebrate Conservation: Global Evidence for the Effects of Interventions. Synopses of Conservation Evidence Series. University of Cambridge, Cambridge, UK.