|Some field observations on usefulness of searchlight sonar during Bluefin tuna (Thunnus thynnus L.) fishing activities in the Adriatic Sea|
Tičina, V.; Kačić, I. (2001). Some field observations on usefulness of searchlight sonar during Bluefin tuna (Thunnus thynnus L.) fishing activities in the Adriatic Sea. Biljes. (Inst. Oceanogr. Ribar. Split) 85: 1-11
In: Biljeske = Notes. Institut za Oceanografiju i Ribarstvo: Split. ISSN 0561-6360, more
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The first field observations regarding to use of a searchlight sonar in the commerciai fisheries, as well as same practicallimitations that could appear are described in this paper. Same problems in sonar use, regarding to bluefin tuna purse-seine fisheries in Adriatic Sea, are presented. The data presented in this paper was collected on board of the commerciai purse-seiner while fishing bluefin tunas during July-August in the Adriatic Sea (Jabuka Pit). This fishing vessei was equipped with FURUNO CH-24 Colour PPI searchlight single-beam sonar system made for commerciai purposes. The importance of proper placement of the transducer on the hull, and disturbances that raised from its improper placement are noticed. The presenee of wakes made by fishing vessels cruising over the fishing ground, were the main limitation for making acoustic observations in the surface laye.r. Also, in comparisan to the ability of fishermen to spot the bluefin tunas c/ose to the sea surface at more than 2000 meters, the effective ranges from 300 to 1200 meters achieved by this sonar was relatively short, and made no significant contribution to the search for fish. Under rough sea conditions (sea state: ~4 Beauforts), it was impossible to use sonar, due to pitching andfolling of the vesseI.