Controls of Multiple Stressors on the Black Sea Fishery

Abstract

Black Sea is one of the most severely degraded and exploited large marine ecosystems in the world. For the last 50 years after the depletion of large predatory fish stocks, anchovy (with the partial contribution of sprat) has been acting as the main top predator species and experienced a major stock collapse at the end of 1990s. After the collapse, eastern part of the southern Black Sea became the only region sustaining relatively high anchovy catch (400,000 tons) whereas the total catch within the rest of the sea was reduced to nearly its one-third. The lack of recovery of different fish stocks under a slow ecosystem rehabilitation may be attributed, on the one hand, to inappropriate management measures and the lack of harmonized fishery policy among the riparian countries. On the other hand, impacts of multiple stressors (eutrophication, alien species invasions, natural climatic variations) on the food web may contribute to resilience of the system toward its recovery. The overfishing/recovery problem therefore cannot be isolated from rehabilitation efforts devoted to the long-term chronic degradation of the food web structure, and alternative fishery-related management measures must be adopted as a part of a comprehensive ecosystem-based management strategy. The present study provides a data-driven ecosystem assessment, underlines the key environmental issues and threats, and points to the critical importance of holistic approach to resolve the fishery-ecosystem interactions. It also stresses the transboundary nature of the problem.

First Large-Scale Eastern Mediterranean and Black Sea Stock Assessment Reveals a Dramatic Decline

“…This new economy sought rapid development, and, to encourage this, provided bank credit, subsidies and custom duty exemptions to fishers to quickly develop this sector, which propelled it toward unplanned and uncontrolled growth fueling too much fishing effort (Knudsen et al, 2010). The large marine pelagic predators were first removed from the Black and Marmara Seas in the early 1970s (Oguz, 2017) due to their lucrative value. This was followed by the collapse of demersals in the 1980s namely stingrays, elasmobranchs, flatfish, turbot, and red mullet (Knudsen et al, 2010) when bottom trawling developed in the 1980s, backed by state funding (Can, 2013).…”

Optimal sustainable fishery management of the Black Sea anchovy with food chain modeling framework

“…When estimating the parameters in Table , the constant harvest rate is estimated as 0.48. This constant harvest rate makes sense when we look at the literature (Bilgin, Sumer, Bektas, Satilmis, & Bircan, ; Gucu et al, ; Oguz, ; STECF, ). These studies state that the Black Sea anchovy population has been exploited and the harvest rate must be reduced.…”

“…Now the commercial fishery of the anchovy has almost stopped in most of the northern part of the Black Sea. The size of the anchovy population in the northern part has decreased because of overfishing (Oguz, ; Oguz, Akoglu, & Salihoglu, ), and so the harvesting of the Black Sea anchovy is not profitable anymore in the most of the northern part for commercial purposes. That is why the anchovy fishery now depends mostly on the southern part of the Black Sea (Gucu et al, ), which mainly consists of the Turkish coasts.…”

Use of fish embryo biomarkers for the evaluation of mazut toxicity in marine environment

“…Sewage and hazard chemicals from industrial, agricultural, maritime transport and domestic effluents are the main sources of contamination in the Black Sea ecosystem. Coastal waters are the main recipients of discharges, and combine effects of the various kinds of toxicants result in dramatic ecological consequences such as eutrophication, biodiversity loss, elimination of some species, worsening of their health and decline in the population size (Rudneva and Petzold-Bradley 2001;Oguz 2017). The risk of oil contamination, either through produced water discharges, accidents, or non-point-sources, has increased, and it is accompanied with the negative impact on marine ecosystems, sometimes resulting in extreme consequences for the marine environment, characterizing physical, chemical and biological damage of the water, sediments and impacted natural resources.…”

“…Kovalevski Institute of Marine Biological Research, Russian Academy of Sciences, Sevastopol, Russian Federation e-mail: svg-41@mail.ru straits are located along a heavy oil traffic and the important accidents in recent decades really take place in this region (Ç okacar 2008;Florin et al 2015;Carpenter and Kostianoy 2019). Moreover, the increasing of shipboard transport of petroleum products, consequently, ship operation, oil drilling, pipe cracks and transport of bunker fuel have the risk of oil spills (Patin 2015;Oguz 2017;Sardi et al 2017). In the Black Sea alone, oil production has been increased, it was estimated that annually 80-130,000 tons of oil enters the ecosystem, and 1% of this is associated with the accidents (Leonov and Fashuk 2006).…”