ICES Journal of Marine Science: Journal du Conseil Advance Access originally published online on May 8, 2009
ICES Journal of Marine Science: Journal du Conseil 2009 66(6):1377-1383; doi:10.1093/icesjms/fsp137
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This article appears in the following ICES Journal of Marine Science issue: The Ecosystem Approach with Fisheries Acoustics and Complementary Technologies [View the issue table of contents]
Evaluating the uncertainty of abundance estimates from acoustic surveys using geostatistical simulations
1 Département EMH, IFREMER, rue de l’île d’Yeu, BP 21105, 44311 Nantes Cedex 03, France
2 Mines-ParisTech, Centre de Géosciences/Géostatistique, 35 rue St Honoré, 77300 Fontainebleau, France
3 Marine Laboratory, PO Box 101, 375 Victoria Road, Aberdeen AB11 9DB, UK
Correspondence to M. Woillez: tel: +33 240 374123; fax: +33 240 374075; e-mail: mathieu.woillez{at}ifremer.fr.
Woillez, M., Rivoirard, J., and Fernandes, P. G. 2009. Evaluating the uncertainty of abundance estimates from acoustic surveys using geostatistical simulations. – ICES Journal of Marine Science, 66: 1377–1383.Geostatistical simulations, which can reproduce the spatial variability of a variable, are particularly helpful in estimating the uncertainty associated with the combination of different sources of variability. Acoustic surveys offer an example of such complex situations, where different data (e.g. acoustic backscatter, fish length, and fish age) must be combined to estimate abundance and its associated uncertainty. In this paper, the uncertainty of Scottish herring acoustic-survey estimates is investigated using these techniques. A specific multivariate, geostatistical model is used to describe the structural relationships, which includes highly skewed distributions of the acoustic-backscatter data and incorporates relationships between depth, mean length, and proportions-at-age. Conditional simulations, i.e. geostatistical simulations that honour the data values known at the data points, are used to generate multiple realizations of acoustic backscatter, mean length, and proportions-at-age. These are combined to produce multiple realizations of herring density over the sampled domain. Multiple realizations of total abundance and abundance-at-age are then provided. The uncertainty is assessed using basic statistics to track the significant variations of these values over the period 1989–2005. Higher coefficients of variation (CVs) are found on average for extreme ages (ages 1, 2i, 8, and 9+); otherwise, CVs are mostly around 12% for abundance-at-age and around 10% for total abundance.
Keywords: acoustic survey, conditional simulations, geostatistics, Scottish herring
Received 8 August 2008; accepted 5 February 2009; advance access publication 8 May 2009.
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