Action: Cease or prohibit aquaculture activity
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- Two studies examined the effects of ceasing or prohibiting aquaculture activity on subtidal benthic invertebrate populations. Both studies were in the Mediterranean Sea (Italy and Spain).
COMMUNITY RESPONSE (2 STUDIES)
- Overall community composition (1 study): One before-and-after, site comparison study in the Mediterranean Sea found that after ceasing aquaculture activity invertebrate community composition remained different to that of an unfarmed site.
- Worm community composition (1 study): One before-and-after, site comparison study in the Mediterranean Sea found that after ceasing aquaculture activity worm community composition community composition remained different to that of an unfarmed site.
POPULATION RESPONSE (2 STUDIES)
- Overall abundance (1 study): One before-and-after, site comparison study in the Mediterranean Sea found that after ceasing aquaculture activity overall invertebrate abundance was similar to an unfarmed site.
- Worm abundance (1 study): One before-and-after, site comparison study in the Mediterranean Sea found that after ceasing aquaculture activity abundance of health-indicating worms increased, and abundance of pollution-indicating worms decreased.
Aquaculture systems can negatively impact subtidal benthic invertebrate communities through pollution and diminished water quality (Wu et al. 1994). Ceasing or prohibiting aquaculture activity in an area, for instance by decommissioning farms or relocation to a different area, would remove the source of pollution and potentially allow for subtidal benthic invertebrate communities to recover over time (Johannessen et al. 1994). Aquaculture systems also pose serious environment risks by promoting the spread of non-native, invasive, and pest species and diseases.
Evidence for interventions related to non-native, invasive and pest species is summarised in “Threat: Invasive and other problematic species, genes and diseases – Aquaculture”.
Johannessen P., Botnen H. & Tvedten Ø.F. (1994) Macrobenthos: before, during and after a fish farm. Aquaculture Research, 25, 55–66
Wu R.S.S., Lam K.S., MacKay D.W., Lau T.C. & Yam V. (1994) Impact of marine fish farming on water quality and bottom sediment: A case study in the sub-tropical environment. Marine Environmental Research, 38, 115–145.
Supporting evidence from individual studies
A before-and-after, site comparison study in 1997 of two soft seabed sites in the Gulf of Gaeta, Mediterranean Sea, Italy (Mazzola et al. 2000) found that after removing a fish farm, invertebrate abundance appeared similar to that of an unfarmed site after two months, but community composition remained different after four months. Before removal, abundance at the farmed site (850–1,350/10 cm2) appeared different to the unfarmed site (1,250–2,750). This was still true a month after removal (farmed: 1,350; unfarmed: 2,800). After two months, abundances were similar at all sites (farmed: 1,500–2,300; unfarmed: 2,000–2,850). Community composition remained different after four months (data presented as graphical analyses). A fish farm was removed in July 1997. One farmed site and one unfarmed site (1 km north) were surveyed monthly between March and October 1997. Three sediment samples were taken by divers at each site during each survey using a core (3.7 cm diameter, 10 cm depth). Invertebrates (between 37 µm and 1 mm) were identified and counted.
A before-and-after, site comparison study in 2007–2008 in three soft seabed locations 4.8 km off the coast of Murcia, Mediterranean Sea, southeast Spain (Aguado-Giménez et al. 2012) found that eight months after removing a fish farm, the worm community had changed but was still different from that of two nearby unfarmed sites. The similarity in worm community between the farmed and unfarmed sites did not increase after removal (before: 43%; after: 41% similarity). However, abundance of opportunistic (indicating pollution) Capitellidae species decreased, while abundances of Onuphidae and Sabellidae species (indicating good health of sediment) increased at the farmed site after eight months (abundances not reported). A fish farm was dismantled in November 2007. One farmed site and two unfarmed sites (1 km and 1.3 km from the farmed site) were surveyed twice before (January and July 2007) and twice after (January and July 2008) dismantling. Four sediment samples were taken by divers at each site during each survey using a hand grab (20 x 10 x 10 cm). Worms (> 0.5 mm) were identified to family level and counted.
- Mazzola A. (2000) Fish-farming effects on benthic community structure in coastal sediments: analysis of meiofaunal recovery. ICES Journal of Marine Science, 57, 1454-1461
- Aguado-Giménez F., Piedecausa M.A., Gutiérrez J.M., García-Charton J.A., Belmonte A. & García-García B. (2012) Benthic recovery after fish farming cessation: A “beyond-BACI” approach. Marine Pollution Bulletin, 64, 729-738