dc.contributor.author | Øvredal, Jan Tore | |
dc.contributor.author | Huse, Ingvar | |
dc.date.accessioned | 2012-10-12T19:23:39Z | |
dc.date.available | 2012-10-12T19:23:39Z | |
dc.date.issued | 1999 | |
dc.identifier.citation | This report is not to be cited without prior reference to the authors | no_NO |
dc.identifier.uri | http://hdl.handle.net/11250/105935 | |
dc.description.abstract | Detailed acoustic observations of fish behaviour, distribution and density in the trawl area are
necessary in order to establish quantitative relationships between trawl samples and fish density.
Acoustic observation close to the bottom may reduce the near bottom acoustic dead zone. A
transducer deployed dose to the bottom may resolve deep targets and avoid effects of the bottom
acoustic dead zone associated with deep recordings. Ship avoidance is also a well known
problem related to acoustic fish abundance surveying.
This paper describes a system consisting of a Simrad EY500 echo sounder built into an
aluminium underwater bottle and a portable PC. Two different split-beam transducers can be
connected to the bottle. The system is remotely controlled and can be used down to 400 m depth,
either powered from a battery bottle or from an external 220/110 V AC supply. All Iogged data
are stored on an intemal disk or sent via Ethemet through fibre optical cables to a shipboard
device, depending on the application.
The system is used for different purposes. Mounted on the trawl headline, with the transducer
pointing upwards, it is used to monitor the escape of fish over the trawl headline. The system can
also be mounted on a towed, remotely controlled vehicle (FOCUS 400), to constitute a deeptowed
acoustic system to improve precision of acoustic surveys on bathypelagic and deep
dwelling demersal fish, or to record fish in the near bottom acoustic dead zone. The vehicle-mounted
system is also used to observe fish behaviour relative to trawl and vessel, e. g.
abundance variation in areas around the trawl and between the trawl and vessel to facilitate
establishing of the catchability of survey trawls. Deployed as a free floating buoy it is also used
to quantitatively determine fish avoidance to a surveying vessel. | no_NO |
dc.language.iso | eng | no_NO |
dc.publisher | ICES | no_NO |
dc.relation.ispartofseries | ICES CM Documents;1999/J:9 | |
dc.subject | fish behaviour | no_NO |
dc.subject | fiskeatferd | no_NO |
dc.subject | distribution | no_NO |
dc.subject | utbredelse | no_NO |
dc.subject | acoustics | no_NO |
dc.subject | akustikk | no_NO |
dc.subject | sampling | no_NO |
dc.subject | prøvetaking | no_NO |
dc.title | Observation of fish behaviour, density and distribution around a surveying vessel by means of a deployable echo sounder system | no_NO |
dc.type | Working paper | no_NO |
dc.subject.nsi | VDP::Mathematics and natural science: 400::Zoology and botany: 480::Ethology: 485 | no_NO |
dc.subject.nsi | VDP::Mathematics and natural science: 400::Geosciences: 450::Oceanography: 452 | no_NO |
dc.subject.nsi | VDP::Agriculture and fishery disciplines: 900::Fisheries science: 920::Fisheries technology: 924 | no_NO |
dc.source.pagenumber | 15 s. | no_NO |