Selection of sardine and anchovy catch as a method of conserving the small pelagic fish fond in the adriatic sea

Sitna plava riba pripada među ekološki i ekonomski najznačajnije vrste riba u Jadranskom moru te su izložene velikom ribolovnom pritisku zbog čega je važno provoditi istraživanja u svrhu njihovog očuvanja. U ovom radu istražilo se moguće selektiranje ulova nedoraslih primjeraka sitne plave ribe. Na ribarskom brodu "Galo" prilagodila se veličina promjera rešetke odjeljivača mora/selektora kao dijela ribolovnog alata vakuumske pumpe (FAIVRE 8) koja služi za prijenos ribe iz mreže plivarice u ribarske izotermičke sanduke. Ribolov se vršio tijekom prosinca 2021. i ožujka 2022. na lokaciji sjevernog dijela Dugog otoka. Iz selektiranog ulova izdvojeni su primjerci srdele i inćuna koji su uskladišteni smrzavanjem (-20°C) do obrade. U laboratoriju Zavoda su ribama izmjerene osnovne morfometrijske mjere a makroskopskim i mikroskopskim pregledom gonada utvrdio se spol, njihov omjer, GSI te stupanj gametogeneze. Inćun se lovio u malom udjelu ukupnog ribolova u prosincu '21. (W= 7,26±2,35; TL= 11,22±0,95) a u ožujku se nije uzorkovao. Razudbom se za većinu primjeraka inćuna ustanovila značajna reduciranost tj. potrošenost gonada dok spol nije bilo moguće odrediti. Morfometrijske mjere srdele mužjaka iznosile su (prosinac '21. – W= 14,92±1,92; TL= 12,77±0,37; ožujak '22. W= 14,81±4,23; TL= 12,89±1,03). Morfometrijske mjere srdele ženki iznosile su ( prosinac '21. - W= 17,74±2,2; TL= 13,49±0,52; ožujak '22. - W= 16,49±2,29; TL= 13,33±0,65). U oba ribolova većim dijelom su se selektirali mužjaci srdele (prosinac '21. - M:Ž 1,06:0,7, nedef.= 0,18; ožujak '22. - M:Ž 1,7:0,22, nedef.= 0,13). Daljnjim istraživanjem preporučuje se potvrditi mogući razlog selekcije ulova prema spolu. Prosječni GSI srdele ženki iznosio je (prosinac '21. - 3,75±1,13; ožujak '22. - 5,77±2,15) te mužjaka (prosinac '21. - 2,41±0,79 ; ožujak '22. - 3,76±0,75). Rezultati histoloških presjeka gonada odabranih srdela upućuju na spolno zrelu ribu u različitim stadijima razvoja gonada. Preporučuje se daljnji razvoj selektora ulova sitne plave ribe kako bi se poboljšala njegova izvedba za još bolju selekciju nedoraslih jedinki.Small pelagic fishes are among the most ecologically and economically important fish species in the Adriatic Sea and are subject to high fishing pressure, so it is important to conduct research for their conservation. In this work, the possible selection of catching immature specimens of small pelagic fish was studied. On the fishing boat "Galo", the size of the grid diameter of the selector/sea separator was adjusted as part of the fishing device of the vacuum pump (FAIVRE 8) used to transfer fish from the seine net to the fishing isothermal boxes. Fishing took place during December 2021 and March 2022 in the northern part of Dugi otok. Samples of sardines and anchovies were taken from the selected catches and frozen (-20°C) until processing. Basic morphometric measurements were made in the faculty laboratory, and sex, sex ratio, GSI and degree of gametogenesis were determined by macroscopic and microscopic examination of gonads. Anchovies were caught in a small proportion of the total fishing in December '21 (W= 7.26±2.35; TL= 11.22±0.95) and no sample was collected in March. Dissection of most anchovies revealed that the gonads were severely reduced to the point where sex could not be determined. The morphometric measures of male sardines were (December '21 - W= 14.92±1.92; TL= 12.77±0.37; March '22. W= 14.81±4.23; TL= 12, 89±1.03). The morphometric values of female sardines were (December '21 - W= 17.74±2.2; TL= 13.49±0.52; March '22 - W= 16.49±2.29; TL= 13.33±0.65). In both fisheries, mainly male sardines were selected (December '21 - M:F 1.06:0.7, nondef.= 0.18; March '22 - M:F 1.7:0.22, nondef.= 0.13). Further investigation is recommended to confirm the possible reason for selection of catches by sex. The average GSI of female sardines was (December '21 - 3.75±1.13; March '22 - 5.77±2.15) and of males (December '21 - 2.41±0.79; March '22 - 3.76±0.75). The results of the histological sections of the gonads of the selected sardines indicate sexually mature fish at different stages of gonad development. It is recommended that the catch selector for small bluefish be further developed to improve its performance for even better selection of juvenile fish