DATA LIMITED STOCK ASSESSMENT OF POPULATION DYNAMICS BY CMSY MODEL ON THE EXAMPLE OF BLACK SEA SPRAT IN THE RUSSIAN WATERS

This study performs approbation of trend CMSY model on the example of Black sea sprat fishing unit, localized in Russian waters. Data sources has been reduced to the level of data limited modeling for indicator and trend models approach. CMSY population model results were compared with previously performed estimations by more powerful cohort model - XSA. CMSY results shows no significant deviations from the XSA results. Forecast scenarios and conclusions based on CMSY model fitting leads to the same statements with previously published results by XSA. CMSY model shows next results: stock biomass in 2019 B2019 = 63,9 ths. t, fishing mortality – F2019 = 0,29. Stock biomass in 2019 was significant below the target reference point BMSY = 105 ths. t and higher then limit reference point Blim = 52,7 ths. t. Some uncertain overexploitation in 2019 was underlined, F2019/FMSY = 1,12. Investigation of forecast scenarios with different total allowed catch levels indicates that there are no features for increasing the catch capacity in short-term projection. CMSY model fitting have passed the necessary stability tests and confirm previously founded results. In summary of this study, we can recommend to use CMSY model for stock assessment procedure in terms of data-limited information background.

Propebela bogdanovi sp. nov. (Gastropoda, Conoidea, Mangeliidae) - a new species from Chukchi Sea and East Kamchatka

In 1990 I.P. Bogdanov provided the new localities for Propebela fidicula - off the Wrangel Island in the Chukchi Sea and off the eastern coast of Kamchatka [Bogdanov, 1990]. These locations were far beyond the known range of this species - from Puget Sound Bay to the Aleutian Islands [Oldroyd, 1927]. Verification of material from the ZIN collection showed that the real Propebela fidicula in Russian waters is found only near the Commander Islands. The shells that Bogdanov identified as Propebela fidicula, belong to a new species. It differs from Propebela fidicula both in sculpture and radular morphology.

PRELIMINARY STUDY OF IMPACT WARMING EFFECT TO SPRAT QUALITY CHARACTERISTICS IN RUSSIAN WATERS OF THE BLACK SEA (1951–2019)

Preliminary study of impact of temperature factor to sprat quality characteristics in Russian waters of the Black sea in period 1951–2019 was performed. In this research statistical hyphothesis about relationship between indicator sea surface temperature factor near to Chernomorskoe, Yalta, Feodosia and long-term sprat mean weight fishery statistics was done. Linear relationship hyphothesis performed by Pearson correlation test. Preliminary cross-correlation test results shows significant moderate relationship between temperature factor average and mean sprat weights (r = –0,60). After preliminary diagnostics input data was smoothed by polynomial regression to reduce interannual fluctuations and cross-correlation test to smoothed data was repeated. Correlation test by smoothed data indicate strong negative (r = –0,75) relationship between long-term sea surface temperature in all indicator points and mean sprat weights and high powerful relationship between sea surface temperature and oldest sprat classess (r = –0,86). Performed study underline the primary part of temperature factor and warming effect to degradation result in Black sprat fishery quality characteristcs. Global warming effect starting from 1990 made significant negative impact into sprat environment in the Black sea

Hull shape peculiarities of conventional and model icebreakers: analysis

This paper discusses hull shapes of conventional and modern icebreakers to analyse the peculiarities of their bows, sterns and parallel midbodies. It discusses main performance parameters, main dimensions and hull shape details of conventional and modern icebreakers. The data base generated in this study includes hull shape details for bow, parallel midbody and stern ice belt areas of conventional and modern icebreakers. This work also yielded mean statistical data making it possible to judge how waterline slope and side slope depend on the position of design section. This study summarizes and generalizes overall design data for the majority of icebreakers operating in freezing Russian waters, including the Arctic. Depending on hull shape, displacement and ice class, this paper identifies three representative groups of icebreakers. The results of this study were further used to analyse the loads on ice belt structures of icebreakers, as well as to develop a system of relationships intended to obtain design ice loads as per RS Rules.

STOCK ASSESSMENT AND LONG-TERM DYNAMICS OF AZOV SEA ROACH (RUSSIAN WATERS), BASED ON CMSY MODEL FOR DATA-LIMITED MODELLING IN PERIOD (1999-2019)

Stock assessment of Azov sea roach Rutilus rutilus (Linnaeus, 1758) has been performed by CMSY model in period 1999-2019 by data-limited modelling in R. The current population status – in biological safe zone for stock biomass and no overfishing signals (B2019/BMSY = 1,32, F2019/FMSY = 0,53). Perhaps, current paper results can be a slightly incomplete in background that there is no relevant data about IUU fishery ever exists, which can lead to fishing mortality underestimation. Azov sea roach population continue to be in “depleted” status after river flow regulation in 1950’s. Joined continuous biomass estimates time series over whole fishing his-tory 1932–2019 showed at least 2 population collapses: in 1940’s and 1980’s years. According to model re-sults TAC (total allowed catch) should be accepted at level 516.9 t. If the recommendation is followed stock biomass will stay at safety in level 1828.1 t. Data limited modelling shows a good performance for sea roach in background of data lucking and in this reason still the best choose against cohor or surplus production models.