Detecting ecological-economic effects of marine spatial plans from displacing the bottom fishing pressure

Abstract

Bottom fishing is expected to have significant effects on benthic fauna, while these impacts are likely to vary according to gear type, fishing intensity and between seafloor habitats. We tested spatial scenarios for mitigating benthic fauna depletion caused by fishing, while evaluating likely effects on the economy of local fisheries. We first identified and mapped gradients of fishing pressure (FP, swept area. y-1) and evaluated the sensitivity of functional fauna groups (deposit feeders and suspension feeders) related to different FP within predefined habitat types. Functional relationships were obtained from the coupling of vesselbased VMS data, logbooks and core sampling of benthic fauna within the Kattegat (ICESIIIas) over the period 2008-2012. We then applied the previously published DISPLACE model (Bastardie et al., 2014) , to provide fishery policy makers and sector-specific stakeholders with an evaluation of likely effects of spatial planning when FP is displaced to different fishing grounds and thereby impact other areas and habitats. This empirical study showed that response to FP is more pronounced for both deposit and suspension feeders associated with muddy substrate compared to harder substrates. Areas with lower fishing pressure had a significantly higher abundance of benthic fauna. Fleet modelling showed that a FP restriction of 60% in the most sensitive habitat results in 4% increase in overall profit (due to change in fuel costs, underlying stock developments, and landing composition). Offshore wind farm development in Kattegat also potentially increases the overall fishery profit by 5%. Interestingly, the scenarios led to positive or negative individual profit depending on the type of vessels and fishing activities. By looking back at our empirical study of benthic fauna, we found that the displaced spatial closure in Scenario 1 will lead to an 1% increase in overall benthic fauna abundance ( +3 % in the sensitive habitat), while wind farm implementation in Kattegat could likely reduce overall benthic fauna abundance by 2%. Modelling approaches are required to anticipate potential adverse effects on fisheries and underlying habitats from effort displacement. Further development of modelling framework that includes the dynamics of both the fisheries and benthic fauna community are essential to meet public demands for ecosystem based fisheries management.