THE LARGE SCALE SURVEY SYSTEM-LSSS

Acoustic methods are widely used for estimating fish abundance. Currently the Institute of Marine Research (IMR) uses the Bergen Echo Integrator (BEI) to analyse the acoustic data. Development of BEI started in 1987, and although it still fills its purpose it has become increasingly difficult to maintain and expand. An evaluation of existing postprocessing systems for acoustic data concluded that present software systems do not meet the future demands of IMR. Therefore IMR decided to develop a new post-processing system, the Large Scale Survey System (LSSS). LSSS is described here. Correspondence to: Korneliussen, R. J., Institute of Marine Research, P.O. Box 1870 Nordnes, NO-5817 Bergen, NORWAY, email: rolf@imr.no Introduction Acoustic methods are widely used for estimating fish abundance and echo integration at one frequency, supported by biological sampling, is the general method used (MacLennan, 1990). Scrutiny of acoustic data is generally done by analysing and correcting echograms in digital format using a dedicated post-processing system, e.g. BEI (Foote et al., 1991; Korneliussen, 1993, Korneliussen, 2002), BI500 (Anon. 1993a; 1993b), EP500 (Lindem et al., 1993), Echoview (Anon. 1999), Sonar 4, 5, 6, MOVIES+ or ECHO. Within these systems, echogram recordings are subject to manipulation, thresholding, error-checking and noise removal. During the scrutinising process it is possible to rearrange and control new depth layers, within which the fish density is to be estimated. A team of experienced operators interprets acoustic data by drawing lines and encircling schools on the echogram screen. Supported by data from biological and oceanographic measurements this process allows them to separate, isolate, and allocate the different acoustic structures to species and groups of scatterers. In most surveys, identification and separation of one or two targeted species is the main goal, while the rest of the recordings may be of less importance. The work-flow for scrutinising acoustic data at Institute of Marine Research (IMR) shown in Figure 1 is applicable to many other institutions as well. IMR is responsible for research and monitoring marine resources in the large Norwegian waters. In addition to renting vessels for these investigations, IMR runs 4 sea-going research-vessels and 2 coastal vessels. Currently, the system that best fits the needs of IMR for post-processing acoustic data is BEI. These needs are mainly a high quality of the scrutinised data, but also the limited available time to scrutinise the acoustic data to the optimal quality. However, development of BEI started in 1987, and although it still fills its purpose it has become increasingly difficult to maintain and expand. An evaluation of existing post-processing systems for acoustic data concluded that present software systems do not meet the future demands of IMR. Therefore IMR decided to develop a new post-processing system, the Large Scale Survey System (LSSS). Input to ICES WG to recommend quotas Numerical density / age distribution Models Info from other species related sources Scientific studies Echogram interpretation: final decision Postprocessing Real-time processing (filtering, school-detection, data-reduction) Data from external system (trawl, CTD, MOCNESS, .)