Species composition and acoustic signatures of mesopelagic organisms in a subtropical convergence zone, the New Zealand Chatham Rise

Abstract

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 503:23-40 (2014) - DOI: https://doi.org/10.3354/meps10731 Species composition and acoustic signatures of mesopelagic organisms in a subtropical convergence zone, the New Zealand Chatham Rise Stéphane Gauthier1,2,*, Johannes Oeffner1, Richard L. O’Driscoll1 1National Institute of Water and Atmospheric Research, Private Bag 14-901, Kilbirnie, Wellington, New Zealand 2Fisheries and Oceans Canada, Institute of Ocean Sciences, PO Box 6000, Sidney, British Columbia V8L 4B2, Canada *Corresponding author: stephane.gauthier@dfo-mpo.gc.ca ABSTRACT: The Chatham Rise is a submarine ridge east of New Zealand. The subtropical convergence occurs over this ridge and it is an area of high productivity, associated with important deepwater fisheries. Acoustic recordings suggest that there is a relatively high biomass of mesopelagic fish over the Chatham Rise, but little is known about the species composition, distribution, and spatio-temporal dynamics of the organisms responsible for the acoustic scattering layers. Two research trawl and acoustic surveys were carried out in May and June 2008 and November 2011 to assess the distribution and acoustic signatures of mesopelagic animals on the Chatham Rise. A total of 171 species or species groups were caught in 86 midwater trawls to a maximum depth of 1000 m. Seven species assemblages were described corresponding to different acoustic mark types. These 7 assemblages were dominated by euphausiids, Maurolicus australis (Stomiiformes), Lampanyctodes hectoris, Symbolophorus boops, Electrona carlsbergi, Diaphus danae and Gymnoscopelus piabilis (all Myctophiformes). Euphausiids could be separated from mesopelagic fish species based on their multi-frequency acoustic response, but the 6 fish groups could not be separated based on their frequency response alone. These different fish assemblages were distinguished based on their unique acoustic mark characteristics (amplitude and dimension features of the volume backscatter), vertical distribution and ancillary information. Classification results were synthesised in a decision model. M. australis and L. hectoris were associated with shallower water on the central and western Chatham Rise, D. danae occurred mainly in deeper water on the north side of the Rise, and E. carlsbergi was associated with cooler water on the south Rise. KEY WORDS: Mesopelagic fish · Acoustics · Myctophids · Deep scattering layer · Spatial distribution Full text in pdf format Supplementary material PreviousNextCite this article as: Gauthier S, Oeffner J, O’Driscoll RL (2014) Species composition and acoustic signatures of mesopelagic organisms in a subtropical convergence zone, the New Zealand Chatham Rise. Mar Ecol Prog Ser 503:23-40. https://doi.org/10.3354/meps10731 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 503. Online publication date: April 29, 2014 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2014 Inter-Research.