Use a smaller beam trawl

Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 1
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How is the evidence assessed?

Effectiveness

30%
Certainty

35%
Harms

0%

Calculating overall effectiveness category

Background information and definitions

Trawling is a method of fishing that involves pulling a fishing net (trawl) through the water behind one or more boats. A beam trawl is a type of trawl where the mouth of the net is held open by a wooden or metal beam, which can be up to 14 m long. Beam trawls can negatively impact subtidal benthic invertebrates through direct physical damage, bycatch, and alterations to the seabed (Bergman & Van Santbrink 2000). A smaller beam could be used, which may potentially limit impact on subtidal benthic invertebrates through reduced damage to the seabed. Evidence related to the use of other fishing gear instead of a beam trawl is summarised under “Threat: Biological resource use – Use a pulse trawl instead of a beam trawl” and “Use an otter trawl instead of a beam trawl”.

_{Bergman M.J.N. & Van Santbrink J.W. (2000) Mortality in megafaunal benthic populations caused by trawl fisheries on the Dutch continental shelf in the North Sea in 1994. ICES Journal of Marine Science, 57, 1321–1331.}

Study locations

Key messages

One study examined the effects of using a smaller 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 a smaller beam trawl caused similar mortality of invertebrates in the trawl tracks compared to a larger beam trawl.

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

A replicated, paired, controlled study in 1992-1995 in four areas of silty or sandy seabed in the south-eastern North Sea, Netherlands and Germany (Bergman & Van Santbrink 2000) found that using a smaller beam trawl caused similar mortality of invertebrates in the trawl tracks compared to using a larger beam trawl. Mortality using a 4-m beam trawl varied between 2 to 80% depending on species, similar to a 12-m beam trawl (1–82% mortality). Mortality did not differ across sediment type (sandy or silty). 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 12-m (commercially used) or 4-m beam trawl (both with tickler chains). Prior to trawling, mega-invertebrates (>1 cm) and macro-invertebrates (>1 mm) were counted from samples taken from 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).
Study and other actions tested
Referenced paper
Bergman M. & Van Santbrink J.W. (2000) Mortality in megafaunal benthic populations caused by trawl fisheries on the Dutch continental shelf in the North Sea in 1994. ICES Journal of Marine Science, 57, 1321-1331.

Please cite as:

Lemasson, A.J., Pettit, L.R., Smith, R.K. & Sutherland, W.J. (2020) Subtidal Benthic Invertebrate Conservation. Pages 635-732 in: W.J. Sutherland, L.V. Dicks, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2020. Open Book Publishers, Cambridge, UK.

Where has this evidence come from?

List of journals searched by synopsis

All the journals searched for all synopses

This Action forms part of the Action Synopsis:

Subtidal Benthic Invertebrate Conservation

Related Actions

Actions	Effectiveness	Studies	Category
Use traps instead of fishing nets Action Link	Unknown effectiveness (limited evidence)	1	Synopsis Link
Fit one or more soft, semi-rigid, or rigid grids or frames to trawl nets Action Link	Likely to be beneficial	2	Synopsis Link
Outfit trawls with a raised footrope Action Link	No evidence found (no assessment)	0	Synopsis Link