Scholarly record
ASSESSING THE PHYSICAL DISTURBANCE ON THE SEABED FROM FISHERIES IN THE BULGARIAN BLACK SEA AREA WITH REFERENCE TO BENTHIC HABITATS STATUS
Abstract
The Marine Strategy Framework Directive (MSFD) requires that biodiversity, structure and function of benthic ecosystems are safeguarded against adverse effects from various human activities. Bottom-trawl fisheries have been identified as a major cause of sea-floor abrasion and it is legally required to evaluate the pressure and its impact. The present study provides a pilot assessment of the physical disturbance on the seabed by mobile bottom-contacting gears and links the pressure intensity to benthic habitats status in the Bulgarian Black Sea shelf in 2017. Vessel Monitoring System (VMS) data were analysed to reconstruct the trawling lines from fishing gear towed on/near the bottom. The fishing pressure extent and intensity were estimated using the swept-area ratio (SAR) calculated in grids with cell sizes 0.5x0.5 km, 1x1 km, 2x2 km and 5x5 km. Grid resolution had a significant effect on the assessment results: the spatial extent of the physical disturbance was overestimated, while the intensity was underestimated as the cell size increased. Benthic habitats (macrofauna) condition was assessed at 73 sampling locations (147 samples) using the normalized multivariate marine biotic index M-AMBI(n). Based on “good” and “not good” status of seabed biota, SAR was categorised in two corresponding classes of “low” and “high” pressure intensity. ROC curve analysis on those classes derived an ecologically relevant low/high pressure threshold at SAR ? 0.2. Significant difference of macrofauna status was demonstrated at low and high physical disturbance. Areas with absent, low and high fishing pressure were mapped and their extent was estimated. Overall, nearly 60 % of the Bulgarian Black Sea shelf was trawled in 2017. However, only 12 % of the sea-floor was subjected to high physical disturbance pressure from fisheries. The fishing pressure was unevenly distributed among the MSFD benthic broad habitat types: the most extensive disturbance occurred in the circalittoral mud (82 %), circalittoral mixed sediments (71 %) and offshore circalittoral mixed sediments (61 %). The respective proportion of intensive disturbance (SAR ? 0.2) was 21% for both circalittoral habitats and only 5 %for the offshore sediments. The proportion of infralittoral sand that was physically disturbed was 31 %, while 12 % was intensively disturbed. The latter estimates are probably underrated due to the lack of VMS data for small boats that operate in the shallow coastal area. The pressure and impact evaluations derived from the present study contribute to fulfilling the national reporting obligations under MSFD. The methodological advancement, in particular the established low/high pressure threshold, facilitates the assessment of the extent of habitats at risk to be adversely affected by physical disturbance from fisheries. The identification of core fishing grounds provides management options for fishing effort optimization to achieve habitat protection at minimal cost to the fishing industry.
Publication Impact Profile
- Citations
- Scopus - Citation Indexes: 5
- Captures
- Mendeley - Readers: 4
Publication details
References8
EU. 2008. Directive (EU) 2008/56 of the European Parliament and of the Council of 17 June 2008 establishing a framework for community action in the field of marine environmental policy (Marine Strategy Framework Directive). 22 pp.
EU. 2017. Decision (EU) 2017/848 of the European Parliament and of the Council of 17 May 2017 laying down criteria and methodological standards on good environmental status of marine waters and specifications and standardised methods for monitoring and assessment, and repealing Decision 2010/477/EU. 32 pp.
ICES 2017. EU request on indicators of the pressure and impact of bottom-contacting fishing gear on the seabed, and of trade-offs in the catch and the value of landings. ICES Special Request Advice, eu.2017.13. 27 pp.
ICES 2018. Interim Report of the Working Group on the Effects of Extraction of Marine Sediments on the Marine Ecosystem (WGEXT), 16–19 April 2018, Copenhagen, Denmark. ICES CM 2018/HAPISG:05. 49 pp.
ICES 2019a. EU request to advise on a seafloor assessment process for physical loss (D6C1, D6C4) and physical disturbance (D6C2) on benthic habitats. ICES Special Request Advice, sr.2019.25. 42 pp.
ICES. 2019b. Technical guideline document for assessing fishing impact from mobile bottom-contacting fishing gears (version 1; 7 February 2019) within: 2018 Report of the Working Group on Fisheries Benthic Impact and Trade-offs (WGFBIT).
Hiddink, J. G., Jennings, S., Sciberras, M., Bolam, S. G., Cambi?, G., McConnaughey, R. A., Mazor, T., et al. 2019 Assessing bottom-trawling impacts based on the longevity of benthic invertebrates. Journal of Applied Ecology, 56: 1075–1083.
Todorova V., Abaza V., Dumitrache C., Todorov E., Wolfram G., Salas Herrero F., 2018. Coastal and Transitional waters Black Sea Geographic Intercalibration Group. Benthic invertebrate fauna ecological assessment methods, EUR 29555, Publications Office of the European Union, Luxembourg, 2018, ISBN 978-92-79-98333-7, DOI: 10.2760/31396, JRC114342
View or Download full articleAccess options
SWS access login
Login as SWS Scientific CommitteeLogin as SWS Scientific PartnerLogin as SWS AuthorAuthors and approved SWS contributors will read and export their own linked papers after identity matching by SWS profile, email and SGEM GlobalID.
For librarian assistance: [email protected]
Purchase Instant Access
- Article can be downloaded after successful payment.
- Article may be used according to SWS library access terms.
- Article cannot be redistributed.