Mollusk Shell Debris Accumulation in the Seabed Derived from Coastal Fish Farming

• Main Authors: Pablo Sanchez-Jerez, Lotte Krüger, Nuria Casado-Coy, Carlos Valle, Carlos Sanz-Lazaro
• Format: Article
• Language: English
• Published: MDPI AG 2019-09-01
• Series: Journal of Marine Science and Engineering
• Subjects: aquaculture; benthos; mitigation; environmental impact
• Online Access: https://www.mdpi.com/2077-1312/7/10/335

Fish farm facilities become colonized by biofouling, and in situ cleaning activities may increase the accumulation of biofouling, mostly shell-hash, on the sediment. However, there is a lack of knowledge about the effect of fish farming on this process. We evaluated the effect of fish farming on shell-hash accumulation on sediments in three fish farms in the Western Mediterranean in Spain. On the one hand, coverage of non-degraded shell on the seabed was estimated using an underwater camera attached to a frame of 1 × 1 m. On the other hand, superficial sediment samples were taken by a Van-Veen grab, and from a subsample, shell-hash was sorted at the laboratory, dried, and weighted. A significant increase of shells on sediment was detected under fish farms compared with the other treatments, with average values of 53 g kg-1, and 1.12% of cover. Shell-hash at zones close to the fish farm cages (Zone of Influence located between 40 to 60 m from the closest cage) did not show statistical differences compared to the reference zones, 300–500 m away from the concession limits, but the shell cover showed statistical differences. Fish farming activities produce a local increase in the sedimentation rate of shells under the cages. The derived ecological consequences of this accumulation need to be further studied.