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Providing evidence to improve practice

Action: Translocate habitat-forming (biogenic) species - Translocate reef- or bed-forming molluscs Subtidal Benthic Invertebrate Conservation

Key messages

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  • Two studies examined the effects of translocating habitat-forming molluscs on associated subtidal benthic invertebrate populations. Both were in Strangford Lough (UK).

 

COMMUNITY RESPONSE (2 STUDIES)

  • Overall community composition (2 studies): One replicated, site comparison study in Strangford Lough found that plots with translocated mussels had different associated invertebrate communities to plots without mussels, but also to natural mussel beds. One replicated, controlled study in Strangford Lough found that translocating mussels onto scallop shells or directly onto the seabed led to similar associated invertebrate communities.
  • Overall richness/diversity (2 studies): One replicated, site comparison study in Strangford Lough found that plots with translocated mussels had higher richness and diversity of associated invertebrates to plots without mussels, and similar to natural mussel beds. One replicated, controlled study in Strangford Lough found that translocating mussels onto scallop shells or directly onto the seabed led to similar richness and diversity of associated invertebrates.

POPULATION RESPONSE (2 STUDIES)

  • Overall abundance (2 studies): One replicated, site comparison study in Strangford Lough presented unclear abundance results. One replicated, controlled study in Strangford Lough found that translocating mussels onto scallop shells or directly onto the seabed led to higher abundance of associated invertebrates in one of two comparisons.

Supporting evidence from individual studies

1 

A replicated, site comparison study in 20102011 of 10 plots in Strangford Lough, Northern Ireland, UK (Fariñas-Franco et al. 2013 - same experimental set-up as Fariñas-Franco & Roberts 2014) found that over a year after translocating habitat-forming horse mussel Modiolus modiolus, invertebrate species richness and diversity were higher in plots with translocated mussels than those without, and similar to those of nearby natural reefs. Species richness and diversity were reported as indices. All plots had different community composition from one another (community data presented as graphical analyses). The effect of translocation on invertebrate abundance was unclearly reported (see original paper). In 2010, divers translocated live adult horse mussels from nearby natural mussel patches within the Lough to four plots (1,000 mussels/plot). After 12 months, two quadrats (0.25 × 0.25 m) were deployed at each plot with translocated mussels and at four adjacent plots without translocated mussels. Sediment and shell were sampled in each quadrat to 10 cm depth. Organisms > 1 mm were identified and recorded as either counts or presence/absence. Natural horse mussel communities from two nearby horse mussel reefs within the lough were sampled in December 2010 using the same sampling methodology.

2 

A replicated, controlled study in 2010–2011 of 12 plots in Strangford Lough, Northern Ireland, UK (Fariñas-Franco & Roberts 2014 – same experimental set-up as Fariñas-Franco et al. 2013) found that over a year after translocating habitat-forming horse mussel Modiolus modiolus, overall invertebrate species richness and diversity increased, and invertebrate community composition changed, but with no differences between mussels translocated onto scallop shells or onto natural seabed. In plots where scallop shells had been added, either as elevated or flattened piles, and in plots where no shells were added, species richness and diversity (presented as indices) increased following translocation of horse mussels, but without differences between treatments. Community composition changed over time, but after a year was similar across treatments (data presented as graphical analyses). In addition, total abundance of invertebrates increased for the first six months but decreased between six and 12 months in all treatments. Over a year, abundance was higher in plots with elevated scallop shells (5–2,350 individuals) than in plots with flattened shells (2–1,370 individuals) or without shells (3–780 individuals). In November 2009–March 2010, sixteen tonnes of king scallop Pecten maximus shells were deployed in bags at four sites (17–19 m depth) to recreate suitable habitat for horse mussel reefs. Each site was divided into an elevated plot (8 m2; shell rising 1 m above seabed) and a flattened plot (4 m2; 0.5 m above seabed). Divers translocated live adult horse mussels from nearby natural mussel patches within the Lough into each plot and at four adjacent natural seabed plots without scallop shells (500 mussels/plot). One, six and 12 months after translocation, animals were identified and counted from one 0.5 × 0.5 m quadrat/plot. Strangford Lough is a marine protected area where fishing is prohibited.

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.