scholarly journals Local overfishing of the Black Sea sprat (Sprattus sprattus: Clupeidae, Pisces) and intraspecies differentiation

2018 ◽  
Vol 3 (1) ◽  
pp. 35-45
Author(s):  
G. V. Zuyev ◽  
V. A. Bondarev ◽  
Iu. V. Samotoi
Keyword(s):  
Black Sea ◽  
Average Length ◽  
The State ◽  
The Black Sea ◽  
Western Region ◽  
Commercial Catch ◽  
Sprattus Sprattus ◽  
The Western Region ◽  
Commercial Stock

The Black Sea sprat (Sprattus sprattus) is known to be one of the most numerous fish species in the Azov – Black Sea basin. It is an object of fishing in all the Black Sea countries, its catch reaches 100 thousand tons. Therefore, the task to monitor the state of the sprat population and identify the risk factors under existing conditions of increasing fishing intensity and climate change is of great importance. The subject of the study is to assess the impact of fishing on the state of the Black Sea sprat population and estimate the prospects of further exploitation of its commercial stock. The article is based on the results of our research and the annual reports of the European Commission’s Scientific, Technical and Economic Committee for Fisheries (STECF). The catch of sprat in both regions was carried out with mid-water trawls, in the shelf zone in the near-bottom layer of water. In all calculations, the standard length (SL) in cm was measured. Long-term (2003–2013) dynamics of integrated characteristics of the size-age structure of sprat population (average length and average age of sprat) and also sprat catch from two geographically similar in climatic conditions regions, the Crimean region and the Western region (the shelf of Bulgaria and Romania), was investigated. Interregional differences in characteristics of the size-age population structure and fishing conditions were identified. In the Crimean region, the average length of sprat varied from 5.57 to 6.85 cm, the average was 6.43 cm. The interannual amplitude of the SL fluctuations was near 20 %. The average sprat age varied from 0.9 to 1.57 year, the average fish age in the population was 1.4 year. The interannual amplitude of sprat age fluctuations was more than 57 %. Negative trends of the average sprat length and its average age have been determined, indicating deterioration of the population state as a whole and of its commercial quality, in particular. The annual commercial catch of sprat varied from 11.4 to 24.78 thousand tons, the average annual catch was 16.09 thousand tons. The interannual amplitude of the catch fluctuations was more than 2.2 time. A close negative correlation between high catches and low average lengths and, as well as low average sprat age in the population for one year forward, was found (r = -0.81, p < 0.01 and r = -0.82, p < 0.01). In the Western region, unlike the Crimean, the sprat was longer, the average length of fish varied from 7.24 to 7.62 cm, average was 7.46 cm. Interannual amplitude of fluctuations less than 5 % indicated a sustainable state of the population. The annual commercial catch of sprat varied from 2.77 to 4.64 thousand tons, with the fishing effort upon the population did not exceed the maximum allowable level. The average annual catch was 3.75 thousand tons, which was 4.3 time lower than that in the Crimean region. There was no significant correlation between the catch and the average length of sprat (r = -0.27, p > 0.15). Local overfishing of sprat in the Crimean region together with long-term progressive deterioration of the sprat population state suggested division of total commercial fish stock into separate commercial unit stocks. This contradicts the concept of total commercial stock (a single population) of the Black Sea sprat. This conclusion is preliminary and further investigations in this area are to be made.

scholarly journals Modern state of the reproductive potential of Black Sea sprat Sprattus sprattus phalericus (Risso, 1826) (Pisces: Clupeidae) in Crimean region and conditions for its formation

2019 ◽  
Vol 4 (4) ◽  
pp. 3-14
Author(s):  
G. V. Zuyev
Keyword(s):  
Black Sea ◽  
Average Length ◽  
Reproductive Potential ◽  
Danube River ◽  
The Black Sea ◽  
Total Catch ◽  
Sprattus Sprattus ◽  
The Absolute ◽  
Individual Fecundity

Black Sea sprat Sprattus sprattus phalericus (Risso, 1826) is one of the abundant species of fish in the Sea of Azov – Black Sea basin. Due to its large number sprat plays an extremely important role in the ecosystem of the sea, being an intermediate link between zooplankton and representatives of the highest trophic level – large predatory fish, dolphins, and birds. At the same time sprat is one of the important commercial fish in all the Black Sea countries, steadily being on the second place of catch volume in recent decades (after anchovy). The total catch reaches 100 thousand tons. Turkey and Ukraine are the main producing countries. Monitoring and forecast of biological state of sprat population with rising fishing intensity and climate changes are urgent tasks. The research subject of this article is the long-term (2000–2016) dynamics of biological (qualitative) parameters determining the population fecundity of Black Sea sprat in Crimean region, the current state of reproductive potential, and the conditions for its formation. The article is based on the results of own research. Parameters determining the population fecundity – the length-age structure of the spawning part population, the absolute individual fecundity, and the sex structure population (ratio between females and males) – were studied. In the long-term plan (in 2011–2016 compared with 2000–2004) the average length of spawning females decreased by 1.22 times (from 7.36 to 6.03 cm). It was accompanied by a decrease in the absolute individual fecundity by 2.39 times (from 13 625 to 5690 eggs). The numerical ratio between females and males decreased by 1.23 times (from 1.95 to 1.59). Simultaneously the sprat stock in the northern part of the Black Sea was reduced by more than 2.5 times (from > 500 thousand tons to < 200 thousand tons). As a result, the population fecundity of sprat in Crimean region decreased by more than 7 times (2.39 × 1.23 × 2.5). The conditions of sprat fishing in the northern part of the Black Sea (from the mouth of the Danube River to the Kerch Strait) were studied. They showed 2-fold decrease (from 251.9 thousand tons in 2000–2004 to 129.1 thousand tons in 2011–2016) in the total catch and more than 2.3-fold decrease (from 50.4 to 21.4 thousand tons) in average annual catch in this region. On the contrary, in the Crimean shelf the total catch at that time increased by 1.2 times (from 76.9 to 92.2 thousand tons), and its average annual value remained constant (15.4 thousand tons). While reducing the stock by 2.5 times, this means that the fishing pressure on the Crimean population increased 2.5 times. This fact suggests considering the factor of fishing as the main cause of its degradation. Validity of this version is confirmed by the fact of conjugacy (inverse connection) of interannual fluctuations between the catch and the length-age parameters of sprat in Crimean region in 2003–2013 previously found: catches over 15–16 thousand tons were accompanied by a next year decrease in the fish average length. Regulation of fishing is a necessary condition for preventing further degradation, for restoring and maintaining sustainable state of sprat population in Crimean region and its reproductive potential. The negative impact of natural (climatic and trophic) factors on the state of the population should be recognized as a secondary one. Local overfishing indicates indirectly the structuring of the commercial stock of Black Sea sprat, its division into a number of geographical aggregations (stock units), i. e. the presence of intraspecific differentiation.

Oithona davisae: naturalization in the Black sea, inter-annual and seasonal dynamics, effect on the structure of the planktonic copepod community

2019 ◽  
Vol 59 (6) ◽  
pp. 1008-1015
Author(s):  
A. D. Gubanova ◽  
O. A. Garbazey ◽  
D. A. Altukhov ◽  
V. S. Mukhanov ◽  
E. V. Popova
Keyword(s):  
Black Sea ◽  
Coastal Waters ◽  
Native Species ◽  
Significant Decline ◽  
Acartia Tonsa ◽  
The Black Sea ◽  
Copepod Community ◽  
Oithona Davisae ◽  
Sevastopol Bay

Long-term (20032014) routine observations of zooplankton in Sevastopol Bay (the Black Sea) have allowed the naturalization of the invasive copepod Oithona davisae to be studied in the Black Sea coastal waters. Inter-annual and seasonal variability of the species and their impact on the native copepod community have been analyzed. The invasion of O. davisae and their undoubted dominance in terms of abundance were shown to alter the community structure but, at the same time, the abundances of the native species did not decrease, excepting the Black Sea earlier invader Acartia tonsa. A significant decline in A. tonsa numbers over the stages of O. davisae establishment and naturalization provided evidence of competition between the species. O. davisae have been demonstrated to gain competitive advantage over A. tonsa, that ensured their fast dispersal in the Black Sea, acclimatization in the new habitat and the successful competition over native species.

scholarly journals Long term trends in the sea surface temperature of the Black Sea

Ocean Science ◽  
2010 ◽  
Vol 6 (2) ◽  
pp. 491-501 ◽  
Author(s):  
G. I. Shapiro ◽  
D. L. Aleynik ◽  
L. D. Mee
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Black Sea ◽  
Sea Surface ◽  
The Black Sea ◽  
The North ◽  
Sst Variability ◽  
Long Term Trends ◽  
Cooling Trend

Abstract. There is growing understanding that recent deterioration of the Black Sea ecosystem was partly due to changes in the marine physical environment. This study uses high resolution 0.25° climatology to analyze sea surface temperature variability over the 20th century in two contrasting regions of the sea. Results show that the deep Black Sea was cooling during the first three quarters of the century and was warming in the last 15–20 years; on aggregate there was a statistically significant cooling trend. The SST variability over the Western shelf was more volatile and it does not show statistically significant trends. The cooling of the deep Black Sea is at variance with the general trend in the North Atlantic and may be related to the decrease of westerly winds over the Black Sea, and a greater influence of the Siberian anticyclone. The timing of the changeover from cooling to warming coincides with the regime shift in the Black Sea ecosystem.

Air recirculation and ventilation in the coastal regions of the Black Sea

2013 ◽  
Vol 5 (2) ◽  
Author(s):  
Galina Surkova
Keyword(s):  
Black Sea ◽  
Eastern Coast ◽  
The Black Sea ◽  
Additional Risk Factor ◽  
Additional Risk ◽  
Sea Breezes ◽  
North Eastern ◽  
Favorable Conditions ◽  
Parameter Values

AbstractAn initial investigation of recirculation is carried out for the coast of the Black Sea. The local mesoscale circulations (land-sea breezes, mountain and valley winds) in coastal areas are shown to be an additional risk factor in creating favorable conditions for air stagnation and accumulation of air pollutants in the surface atmosphere layer. Two types of annual recirculation patterns are revealed for northern and north-eastern coast of the Black Sea. Long-term changes in recirculation are investigated. It is shown that the recirculation parameter values remained quasistable until the mid-1970s. Since 1976–1977, steady intensification of recirculation in both winter and summer is identified.

Long-term ecological changes in Romanian coastal Waters of the Black Sea

1996 ◽  
Vol 32 (1) ◽  
pp. 32-38 ◽  
Author(s):  
Adriana Cociasu ◽  
Liliana Dorogan ◽  
Christoph Humborg ◽  
Luci Popa
Keyword(s):  
Black Sea ◽  
Coastal Waters ◽  
The Black Sea ◽  
Ecological Changes
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