Peer-reviewed articles 17,970 +



Title: ASSESSING THE PHYSICAL DISTURBANCE ON THE SEABED FROM FISHERIES IN THE BULGARIAN BLACK SEA AREA WITH REFERENCE TO BENTHIC HABITATS STATUS

ASSESSING THE PHYSICAL DISTURBANCE ON THE SEABED FROM FISHERIES IN THE BULGARIAN BLACK SEA AREA WITH REFERENCE TO BENTHIC HABITATS STATUS
V. Todorova; M. Panayotova; V. Doncheva; I. Zlateva
1314-2704
English
21
3.1
• Prof. DSc. Oleksandr Trofymchuk, UKRAINE
• Prof. Dr. hab. oec. Baiba Rivza, LATVIA
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.
conference
21st International Multidisciplinary Scientific GeoConference SGEM 2021
21st International Multidisciplinary Scientific GeoConference SGEM 2021, 16 - 22 August, 2021
Proceedings Paper
STEF92 Technology
SGEM International Multidisciplinary Scientific GeoConference
SWS Scholarly Society; Acad Sci Czech Republ; Latvian Acad Sci; Polish Acad Sci; Serbian Acad Sci & Arts; Natl Acad Sci Ukraine; Natl Acad Sci Armenia; Sci Council Japan; European Acad Sci, Arts & Letters; Acad Fine Arts Zagreb Croatia; Croatian Acad Sci
509-516
16 - 22 August, 2021
website
cdrom
8030
physical disturbance; fisheries; swept area ratio; seabed; benthic habitats; Bulgarian Black Sea