Effects of variable mean target strength on estimates of abundance: the case of Atlantic mackerel (Scomber scombrus)

Ben Scoulding, Sven Gastauer, David N. MacLennan, Sascha M. M. Fässler, Philip Copland, Paul G. Fernandes, David Demer (Editor)

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)


Atlantic mackerel Scomber scombrus is a small pelagic, migratory fish which supports commercial fisheries. These fish school and are detectable using echosounders, yet fishery-independent estimates of their abundance in the North East Atlantic do not consider acoustic data. Accurate estimates of mean target strength (TS) are presently limiting echo-integration surveys from providing useful estimates of Atlantic mackerel abundance and distribution. This study provides TS estimates for in situ mackerel from multi-frequency split-beam echosounder measurements. TS equals −52.79 dB at 18 kHz, −59.60 dB at 38 kHz, −55.63 dB at 120 kHz, and −53.58 dB at 200 kHz, for a mean mackerel total length = 33.3 cm. These values differ from those currently assumed for this species in analyses of acoustic survey data. We investigate the sensitivity of acoustically estimated mackerel biomass around the Shetland Islands, Scotland, in 2014, to various estimates of TS. Confidence limits were obtained using geostatistics accounting for coverage and spatial autocorrelation. Stock biomasses, estimated from 38 and 200 kHz data, differed by 10.5%, and stock distributions were similar to each other and to the estimates from an independent stock assessment. Because mackerel backscatter at 38 kHz is dominated by echoes from the flesh and may have similarities to echoes from fish with swimbladders, and backscatter at 200 kHz is dominated by relatively stable echoes from the backbone, we recommend using 200 kHz data for estimates of Atlantic mackerel biomass.
Original languageEnglish
Pages (from-to)822-831
Number of pages10
JournalICES Journal of Marine Science
Issue number3
Early online date26 Dec 2016
Publication statusPublished - Mar 2017

Bibliographical note

This study received funding from the Marine Alliance for Science and Technology for Scotland (MASTS) pooling initiative and their support is gratefully acknowledged. MASTS is funded by the Scottish Funding Council (grant no. HR09011) and contributing institutions.

Thanks to the crew of the MRV Scotia and the technical staff at Marine Scotland Science, United Kingdom. The authors would also like to thank ICES WGFAST for useful discussions and support. Thank you to Dr Pierre Petitgas for his advice on the geostatistics methods. Thank you to the two anonymous reviewers for their constructive comments and to Dr David Demer for providing a detailed review of the paper, leading to substantial improvements.


  • Atlantic mackerel
  • biomass estimation
  • geostatistics
  • scattering properties
  • target strength


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