Seasonal Abundance, Density and Distribution of Cetaceans in the Bulgarian Black Sea Shelf in 2017

Popov, Dimitar; Panayotova, Marinela; Bekova, Radoslava; Dimitrov, Hristo; Meshkova, Galina Vladimirovna

doi:10.3390/d15020229

Cited by 3 publications

(4 citation statements)

References 9 publications

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“…Elsewhere, acoustic approaches such as ADDs (pingers) have been used (Dawson et al, 2013). A few models have been tested in Türkiye, Romania and Bulgaria, some showing good results while others not (Gönener and Bilgin, 2009;Popov et al, 2020). In the current study, use of PAL pingers showed promising results.…”

Section: Discussionmentioning

confidence: 63%

“…Three models of pingers have been tested: Future Oceans 10 kHz, Future Oceans 70 kHz and Porpoise Alerting Devices (PAL), frequency 10 kHz. Observed differences in bycatch levels in strings fitted with Future Oceans pingers and those without pingers were not significant in 2019 (Popov et al, 2020). The only model which showed significant decrease in bycatch (86%, p<0.05) was the PAL pinger deployed on six strings.…”

Section: Discussionmentioning

confidence: 87%

“…During the current study, cetacean stranding data were collected as supplementary evidence for the occurrence of bycaught cetaceans ashore during the seasons of observations. Surveys were conducted by some of the authors and information from existing databases was used (Bulgaria: Popov and Meshkova, 2022;Ukraine: Vishnyakova et al, 2021;Romania: Paiu et al, 2022;Türkiye: Paiu et al, 2021b and I ̇Ü-TUDAV, unpubl. data).…”

Section: Cetacean Stranding Surveysmentioning

confidence: 99%

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Assessment of the bycatch level for the Black Sea harbour porpoise in the light of new data on population abundance

Popov

Meshkova²,

Vishnyakova

et al. 2023

Front. Mar. Sci.

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Incidental catch in fishing gear (often known as bycatch) is a major mortality factor for the Black Sea harbour porpoise (Phocoena phocoena relicta), an endemic subspecies listed as Endangered in the IUCN Red List. The primary gear, responsible for porpoise bycatch in the Black Sea are bottom gillnets and trammel nets targeting turbot (Scophthalmus spp.), the most valuable commercial fish species in the Black Sea. From 2019 to 2021, a study was conducted in Bulgaria, Romania, Türkiye and Ukraine, to estimate the bycatch level in light of new information on porpoise distribution and abundance obtained from aerial surveys (CeNoBS) undertaken in 2019 as part of ACCOBAMS Survey Initiative (ASI). Bycatch data were collected by independent observers onboard turbot fishing boats (Bulgaria and Romania), complemented by questionnaire surveys and examination of stranded carcasses (in all countries). Some 48 monitoring trips took place (63 hauls by 11 different vessels). Cetaceans were caught on just over half of the trips (55%): 182 harbour porpoises, 4 bottlenose dolphins and 3 common dolphins. The median number of porpoises bycaught per trip was 1 (maximum 41) and the number of porpoises per km of net varied between 0 and 3.66 (median 0.1). Bycatch rates showed seasonal variation with marked increase in summer, compared to spring. The total annual bycatch of harbour porpoises in the Black Sea was roughly estimated as between 11 826 and 16 200 individuals. These numbers were the product of median values for effort (days/trips and vessels) and bycatch rate. Given the new estimates of porpoise abundance based on the CeNoBS survey of 2019 and reconciling abundance and bycatch estimates, harbour porpoise bycatch in the Black Sea represents between 4.6% - 17.2% of the estimated total population, depending on assumptions used. Even the most conservative estimate is among the highest worldwide and far exceeds the probable sustainable levels of around 1.0-1.7%. This study confirms that bycatch poses the most serious threat to the Black Sea harbour porpoises and that all riparian countries engaged in turbot fisheries must implement urgent measures to reduce it immediately, if the population is to survive in the long-term.

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Section: Discussionmentioning

confidence: 63%

Section: Discussionmentioning

confidence: 87%

Section: Cetacean Stranding Surveysmentioning

confidence: 99%

See 1 more Smart Citation

Assessment of the bycatch level for the Black Sea harbour porpoise in the light of new data on population abundance

Popov

Meshkova²,

Vishnyakova

et al. 2023

Front. Mar. Sci.

View full text Add to dashboard Cite

show abstract

“…Monitoring surveys in the Black Sea have been limited, with most large-scale surveys conducted prior to 1987. Recent efforts have focused on local surveys in coastal areas (Birkun et al, 2004, Birkun et al, 2004Dede and Tonay, 2010;Birkun et al, 2014Kopaliani et al, 2015Panayotova and Todorova, 2015;Gladilina and Gol'din, 2016;Gladilina et al, 2017;Popov et al, 2017;Baș et al, 2019;Paiu et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Shipping noise assessment in the Black Sea: insights from large-scale ASI CeNoBS survey data

Frassà,

Prospathopoulos,

Maglio

et al. 2023

Front. Mar. Sci.

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Sighting data deriving from the ACCOBAMS1 Survey Initiative (ASI), conducted through the CeNoBS2 project, enabled the investigation of the habitat preferences for three different cetacean subspecies occurring in the Black Sea waters: the bottlenose dolphins (Tursiops truncatus), the common dolphins (Delphinus delphis) and the harbour porpoise (Phocoena phocoena). ASI aerial surveys, aiming at assessing the distribution and abundance of cetacean populations, were conducted during summer of 2019 in waters in front of Romania, Georgia, Bulgaria, Turkey and Ukraine. The surveys allowed recording of 1716 sightings: 117 bottlenose dolphins, 715 common dolphins and 884 harbour porpoises. The aim of this study was twofold: (i) to develop habitat models, using physical characteristics, such as depth and slope, as covariates, in order to estimate the presence probability of the three cetacean species in the Black Sea; (ii) to demonstrate the usefulness of the habitat models in support of environmental status assessments on marine mammals where the stressor is the shipping noise. The results of this study show the reliability of physical covariates as predictors of the probability of occurrence for the three species of interest in the Black Sea, providing additional knowledge, complementary to abundance estimates, which may support the assessment of the vulnerability of marine areas to different pressures, including noise.

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Cetacean Strandings along the Bulgarian Coast of the Black Sea in 2010–2022

Popov,

Meshkova

2024

Oceans

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Cetacean strandings are valuable sources of data about their life history, health status, population trends, and impact of threats. We examined the strandings along the Bulgarian coast of the Black Sea for a period of 13 years from 2010 to 2022. A total of 1528 cetacean strandings of all three species inhabiting the basin were recorded: 1031 harbour porpoises Phocoena phocoena, 199 bottlenose dolphins Tursiops truncatus, 97 common dolphins Delphinus delphis, 19 delphinids and 182 unidentified. The highest numbers were observed in 2016 and 2022. Monthly peaks for harbour porpoise and bottlenose dolphin were in July and August and for common dolphin in May. An unusually high mortality of porpoise neonates was recorded in 2015 and 2016. The overall sex ratio showed a slightly higher share of males at 120:100. This bias was the most pronounced for males of common dolphins. Spatial distribution varied interspecifically but was predominantly along the southern coast. Bycatch signs were detected in 80 animals including during the turbot fishing ban period, suggesting the existence of illegal fishing operations. All of this highlights the need for better reinforcement and control to ensure both the conservation of endangered cetaceans and the sustainability of fisheries. Improvement in data collection is needed to improve the quality of information.

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Seasonal Abundance, Density and Distribution of Cetaceans in the Bulgarian Black Sea Shelf in 2017

Cited by 3 publications

References 9 publications

Assessment of the bycatch level for the Black Sea harbour porpoise in the light of new data on population abundance

Assessment of the bycatch level for the Black Sea harbour porpoise in the light of new data on population abundance

Shipping noise assessment in the Black Sea: insights from large-scale ASI CeNoBS survey data

Cetacean Strandings along the Bulgarian Coast of the Black Sea in 2010–2022

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