A Bayesian approach to estimating target strength

Currently, conventional models of target strength (TS) vs. fish length, based on empirical measurements, are used to estimate fish density from integrated acoustic data. These models estimate a mean TS, averaged over variables that modulate fish TS (tilt angle, physiology, and morphology); they do n...

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Bibliographic Details
Published in:ICES Journal of Marine Science
Main Authors: Faessler, Sascha M. M., Brierley, Andrew Stuart, Fernandes, Paul G.
Format: Article in Journal/Newspaper
Language:English
Published: 2009
Subjects:
acoustic target strength
Bayesian statistics
herring
survey uncertainty
HERRING CLUPEA-HARENGUS
MALLOTUS-VILLOSUS MULLER
ACOUSTIC SCATTERING
SWIMBLADDER COMPRESSION
SOUND SCATTERING
STOCK ASSESSMENT
ANTARCTIC KRILL
BARENTS SEA
BALTIC SEA
120 KHZ
Antarctic
Barents Sea
Antarc*
Antarctic Krill
Online Access:https://research-portal.st-andrews.ac.uk/en/researchoutput/a-bayesian-approach-to-estimating-target-strength(67d21fe7-f975-4422-b212-e504947623fe).html
https://doi.org/10.1093/icesjms/fsp008
http://www.scopus.com/inward/record.url?scp=84855265408&partnerID=8YFLogxK
Description
Summary:Currently, conventional models of target strength (TS) vs. fish length, based on empirical measurements, are used to estimate fish density from integrated acoustic data. These models estimate a mean TS, averaged over variables that modulate fish TS (tilt angle, physiology, and morphology); they do not include information about the uncertainty of the mean TS, which could be propagated through to estimates of fish abundance. We use Bayesian methods, together with theoretical TS models and in situ TS data, to determine the uncertainty in TS estimates of Atlantic herring (Clupea harengus). Priors for model parameters (surface swimbladder volume, tilt angle, and s.d. of the mean TS) were used to estimate posterior parameter distributions and subsequently build a probabilistic TS model. The sensitivity of herring abundance estimates to variation in the Bayesian TS model was also evaluated. The abundance of North Sea herring from the area covered by the Scottish acoustic survey component was estimated using both the conventional TS-length formula (5.34x10(9) fish) and the Bayesian TS model (mean = 3.17x10(9) fish): this difference was probably because of the particular scattering model employed and the data used in the Bayesian model. The study demonstrates the relative importance of potential bias and precision of TS estimation and how the latter can be so much less important than the former.

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