Extensive Aggregations of Wild Fish at Coastal Sea-Cage Fish Farms

By T. Dempster, P. Sanchez‐Jerez, J. B. Sempere, M. Kingsford. Hydrobiologia, 2004

124 citations recorded by the source corpus.

We present evidence of a largely undocumented environmental effect of coastal sea-cage fish farms on wild fish. We estimated the total abundance and biomass of wild fish aggregated in the immediate vicinity of nine fish farms in the Mediterranean Sea and one farm off the east coast of Australia. Estimates of wild fish aggregations ranged from 2000 to 86000 individuals and from 100 kg to 38.5 tons of fish per farm and were always greater than control locations. Particularly large aggregations (>30000 fish, > 12 tons) occurred at half of the farms. Aggregations were temporally stable for weeks to months and most wild fish associated with farms (88%) were of adult size. Potential effects of such large aggregations of wild fish in the immediate vicinity of fish farms include increased vulnerability to fishing and pathogen transfer between caged and wild fish. We suggest specific legislation should be enacted wherever large aggregations of wild fish occur around fish farms to enhance the positive and reduce the negative effects of association.

Subfields: Ecology, Global and Planetary Change

View Paper: https://www.semanticscholar.org/paper/5ef604deaf977e1f292c14713129167eba2a179a

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Citations in the corpus

Vertical variability of wild fish assemblages around sea-cage fish farms: implications for management (2005, background): “Large aggregations of pelagic and/or demersal fish have since been described around seacage fish farms in several temperate and tropical locations, including Greece (Smith et al. 2003, Thetmeyer et al. 2003), the Canary Islands (Boyra et al. 2004, Tuya et al. 2005), Australia (Dempster et al. 2004) ”
Coastal salmon farms attract large and persistent aggregations of wild fish: an ecosystem effect (2009, methodology): “Video counts were scaled up to estimate total abundance and biomass at each farm using a modification of the method of Dempster et al. (2004).”
Impacts of marine and freshwater aquaculture on wildlife: a global meta-analysis (2018, unknown): “…< 0.0001), but this value was strongly influenced by a few outlier studies reporting very large aggregations of wild fish around sea cages (e.g. a mean 13279 increase over three sampling dates at one Australian offshore farm compared to featureless mid-water reference sites: Dempster et al. 2004).”
Changes in demersal wild fish aggregations beneath a sea-cage fish farm after the cessation of farming (2006, background): “…fish farms 63 dramatically increase the presence, abundance and biomass of wild demersal and 64 pelagic fish in their immediate vicinity compared to control nearby areas (Carss, 1990; 65 Dempster et al., 2002; Boyra et al., 2004; Dempster et al., 2004; Dempster et al., 2005; 66 Tuya et al., 2005).”
Seasonal patterns and diets of wild fish assemblages associated with Mediterranean coastal fish farms (2008, background): “, 2004), off Scotland (Carss, 1990) and Norway (Bjordal and Skar, 1992), and around Australia (Dempster et al., 2004) and Indonesia (I.”
Fish aggregation device (FAD) research: gaps in current knowledge and future directions for ecological studies (2004, background): “In the case of fish farms, such effects may be positive, if wild fish receive significant protection (spatial and temporal) from fishing due to their association with fish farms, or negative, if the close association with farms increases the susceptibility of wild stocks to fishing, parasites or dis”
Ecology and conservation of common bottlenose dolphins Tursiops truncatus in the Mediterranean Sea (2009, background): “Increased nutrient levels, complex substrate and provision of fish-feed in the proximity of the cages trigger trophic enrichment and can attract potential bottlenose dolphin prey (Karakassis et al., 2000; Würsig & Gailey, 2002; Kemper et al., 2003; Dempster et al., 2004).”