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- Title
Measuring herring densities with one real and several phantom research vessels.
- Authors
Patel, Ruben; Ona, Egil
- Abstract
Patel, R., and Ona, E. 2009. Measuring herring densities with one real and several phantom research vessels. – ICES Journal of Marine Science 66: 1264–1269.Vessel-induced avoidance can potentially cause a large bias in acoustic estimates of schooling, pelagic-fish biomass. This paper presents a method for quantifying this uncertainty. Volume-backscattering strength (Sv) from a horizontally projecting, multibeam sonar (Simrad MS70) is resampled to form synthetic, vertical, echosounder beams to the side of the survey vessel. These data are analysed as if they were collected from phantom vessels surveying parallel transects at fixed ranges from the real vessel. The nautical-area-backscattering coefficients (sA) from the synthetic echograms are compared with those measured by conventional 70 and 120 kHz echosounders (Simrad EK60) on the real vessel. Data collected in 2006 from schools of Norwegian spring-spawning herring are used to illustrate the method and explore its limitations. Potential effects of vessel-induced avoidance are evaluated by comparing the mean sA values observed from the phantom vessels with those observed from the real vessel. The technique also allows direct estimates of the mean lateral-aspect target strength of in situ herring.
- Subjects
FISH sounds; PACIFIC herring fisheries; BIOMASS; FISH spawning; IN Situ (Poem); SONAR in fishing
- Publication
ICES Journal of Marine Science / Journal du Conseil, 2009, Vol 66, Issue 6, p1264
- ISSN
1054-3139
- Publication type
Article
- DOI
10.1093/icesjms/fsp128