Haddock

Mining and processing of minerals produce large quantities of tailings as waste. Some countries, including Norway, allow disposal of mine tailings in the sea. In this study we investigated the impacts of tailings from a calcium carbonate (CaCO3) processing plant on early live stages of haddock (Melanogrammus aeglefinus) and Atlantic cod (Gadus morhua). Fish eggs (3 days post fertilisation; dpf) were exposed for 48 h to three concentrations of tailings, nominally 1 mg L-1 (low, L); 10 mg L-1 (medium, M) and 100 mg L-1 (high, H); with L and M representing concentrations occurring at tailing release points. Results show that tailings rapidly adhered to eggs of both species, causing negative buoyancy (sinking of eggs) in M and H exposures. While tailings remained on egg surfaces in both species also after exposure termination, adhesion seemed more pronounced in cod, leading to larger impacts on buoyancy even after exposure. Tailing exposure further induced early hatching and significantly reduced survival in M and H exposed embryos in both fish species, and in cod from the L exposure group. Moreover, tailing exposure caused reduced survival and malformations in larvae, potentially related to premature hatching. This study shows that mineral particles adhere to haddock and cod eggs, affecting egg buoyancy, survival and development.

Nature conservation and fisheries management often focus on particular seabed features that are considered vulnerable or important to commercial species. As a result, individual seabed types are protected in isolation, without any understanding of what effect the mixture of seabed types within the landscape has on ecosystem functions. Here we undertook predictive seabed modelling within a coastal marine protected area using observations from underwater stereo-video camera deployments and environmental information (depth, wave fetch, maximum tidal speeds, distance from coast and underlying geology). The effect of the predicted substratum type, extent and heterogeneity or the diversity of substrata, within a radius of 1500 m around each camera deployment of juvenile gadoid relative abundance was analysed. The predicted substratum model performed well with wave fetch and depth being the most influential predictor variables. Gadus morhua (Atlantic cod) were associated with relatively more rugose substrata (Algal-gravel-pebble and seagrass) and heterogeneous landscapes, than Melanogrammus aeglefinus (haddock) or Merlangius merlangus (whiting) (sand and mud). An increase in M. merlangus relative abundance was observed with increasing substratum extent. These results reveal that landscape effects should be considered when protecting the seabed for fish and not just individual seabed types. The landscape approach used in this study therefore has important implications for marine protected area, fisheries management and monitoring advice concerning demersal fish populations.