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Relation between the hydrographic properties of the northern Adriatic Sea water and sardine (Sardina pilchardus) population schools

Migration of the sardine Sardina pilchardus (Walbaum, 1792) in the northern Adriatic Sea in relation to hydrographic properties of seawater was described. It was observed that seasonal changes in hydrographic properties of seawater (temperature and salinity) could be related to migration pattern of sardine subpopulation in the northern Adriatic Sea. Those changes in properties of marine environment probably have an indirect influence on sardine northward (trophic) migration, but a direct influence on southward migration. Due to fact that in the last 25 years were not published any data on this issue, the objective of this paper is to described sardine migrations in the northern Adriatic Sea, at the same time regarding to the changes in its environment. Hydrographic data used in this paper were collected at five stations in the northern Adriatic sea and one situated in Kvarner Bay. Fleet of commercial mid-water trawlers (10 fishing vessels), searching for the highest concentration of fish schools using echo sounder and sonar (with aim to obtain the biggest possible catch), were used to collect information about the position of the bulk of sardine subpopulation in the northern Adriatic for each month. The information about migrations of the sardine were collected directly on board, 4-5 times a month, in the period from 1995 to 1997. During the spawning season, sardine searched for areas with the highest temperature and salinity values as well as stabile environmental conditions. After spawning, sardine migrated toward the most productive feeding areas.

Sardina pilchardus (Walb.) ; migration ; temperature ; salinity ; Adriatic Sea

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