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Providing evidence to improve practice

Action: Install physical barriers to prevent trawling Subtidal Benthic Invertebrate Conservation

Key messages

Read our guidance on Key messages before continuing

  • One study examined the effects of installing physical barriers to prevent trawling on subtidal benthic invertebrate populations. The study was in the Bay of Biscay (Spain).

 

COMMUNITY RESPONSE (1 STUDY)

  • Overall community composition (1 study): One before-and-after study in the Bay of Biscay found that one to four years after installing artificial reefs as physical barriers to prevent trawling invertebrate community composition changed.

POPULATION RESPONSE (1 STUDY)

  • Overall abundance (1 study): One before-and-after study in the Bay of Biscay found that one to four years after installing artificial reefs as physical barriers to prevent trawling overall invertebrate biomass increased.
  • Echinoderm abundance (1 study): One before-and-after study in the Bay of Biscay found that one to four years after installing artificial reefs as physical barriers to prevent trawling the biomass of sea urchins and starfish increased.
  • Molluscs abundance (1 study): One before-and-after study in the Bay of Biscay found that one to four years after installing artificial reefs as physical barriers to prevent trawling the biomass of gastropods (sea snails), of one species of cuttlefish, and of two species of octopus increased.

Supporting evidence from individual studies

1 

A before-and-after study in 1998–2007 in one area of soft seabed in the Cantabrian Sea, southern Bay of Biscay, Spain (Serrano et al. 2011) found that one to four years after installing barriers to prevent illegal trawling the biomass of invertebrates increased, and species community composition changed. Total invertebrate biomass was higher after one (3 kg/ha) and four years (7 kg/ha), compared to before installation (0–1 kg/ha). There were increases in the biomass of sea urchins (before: 12; after: 3,150 g/ha), common octopus Octopus vulgaris (before: 222; after: 920 g/ha), starfish (before: 9; after: 78 g/ha), gastropods (before: 18; after: 50 g/ha), cuttlefish Sepia spp. (before: 56; after: 131 g/ha), and curled octopus Eledone cirrhosa (before: 9; after: 18 g/ha). Invertebrate community composition was different before and after deployment (results presented as graphical analyses). Bottom trawling in the area was prohibited at depths <100 m by local legislation, but illegal trawling was common. To prevent it, artificial reefs (groups of concrete blocks 2 km apart; numbers not specified) were deployed in 2003 at 80–85 m depth. One sampling station near each group of blocks (sandy seabed without blocks) was surveyed annually in October in 1998–2007 (survey methods not specified).

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.