The Substantial First Impact of Bottom Fishing on Rare Biodiversity Hotspots: A Dilemma for Evidence-Based Conservation

Abstract

This study describes the impact of the first passage of two types of bottom-towed fishing gear on rare protected shellfish-reefs formed by the horse mussel Modiolus modiolus (L.). One of the study sites was trawled and the other was scallop-dredged. Divers collected HD video imagery of epifauna from quadrats at the two study sites and directed infaunal samples from one site.The total number of epifaunal organisms was significantly reduced following a single pass of a trawl (90%) or scallop dredge (59%), as was the diversity of the associated community and the total number of M. modiolus at the trawled site. At both sites declines in anthozoans, hydrozoans, bivalves, echinoderms and ascidians accounted for most of the change. A year later, no recovery was evident at the trawled site and significantly fewer infaunal taxa (polychaetes, malacostracans, bivalves and ophuroids) were recorded in the trawl track.The severity of the two types of impact reflected the undisturbed status of the habitats compared to previous studies. As a ‘priority habitat’ the nature of the impacts described on M. modiolus communities are important to the development of conservation management policy and indicators of condition in Marine Protected Areas (EU Habitats Directive) as well as indicators of ‘Good Environmental Status’ under the European Union Marine Strategy Framework Directive.Conservation managers are under pressure to support decisions with good quality evidence. Elsewhere, indirect studies have shown declines of M. modiolus biogenic communities in fishing grounds. However, given the protected status of the rare habitat, premeditated demonstration of direct impact is unethical or illegal in Marine Protected Areas. This study therefore provides a unique opportunity to investigate the impact from fishing gear whilst at the same time reflecting on the dilemma of evidence-based conservation management.

Mediation of macronutrients and carbon by post-disturbance shelf sea sediment communities

“…In particular, bottom fishingthe use of towed nets and dredges-causes surface and sub-surface physical disturbance that results in a range of morphological and biogeochemical changes in continental shelf and slope systems Puig et al 2012;Sciberras et al 2016) depending on fishing type and frequency (Oberle et al 2016), including sub-lethal injury or mortality of benthic invertebrates and the destruction of specific biogenic habitats (Kaiser et al 2006;Cook et al 2013). Bottom fishing practices may remove surficial sediments and mix organic matter into subsurface sediment layers where they can become buried (Duplisea et al 2001;Warnken et al 2003;O'Neill and Summerbell 2011).…”

Spatial scale and geographic context in benthic habitat mapping: review and future directions

“…Research on nearbottom environments and their associated biota has become essential to support effective monitoring and management strategies (Thrush & Dayton 2002, Ramirez-Llodra et al 2011. Anthropogenic impacts on the seafloor alter benthic biodiversity (Cook et al 2013, Grabowski et al 2014, habitats (Jones 1992, Puig et al 2012, and modify ecosystem structures and functions (Koslow et al 2000, Olsgard et al 2008. Ramirez-Llodra et al (2011) noted that exploration, scientific research, monitoring, and conservation measures are essential to ensure that ex ploitation of resources does not lead to massive destruction of ecosystems.…”

New Technological Interventions in Conservation Conflicts: Countering Emotions and Contested Knowledge

“…Here, therefore, technologies such as sonar, GPS, and RTK devices were deployed by some actors to produce precise, accurate, and valuable data under challenging marine conditions, and were thus an important means of addressing the ‘evidence trap’ situation documented by Cook et al (2013), where lack of evidence of impact is perceived as evidence that there is no impact.…”