An acoustic survey of orange roughy on the southwest Challenger Plateau (including Westpac Bank) was carried out from 1 to 15 July 2023 by the National Institute of Water and Atmospheric Research Limited (NIWA) onboard research vessel (RV) Tangaroa.
 

Two acoustic instruments used were: the acoustic-optical system; and the dual-frequency towed body. These instruments are towed at depth and operate dual frequencies (38 and 120 kHz), both of which are needed to differentiate orange roughy from other species.
 

Acoustic marks of orange roughy were validated using the NIWA orange roughy bottom trawl. Trawling informs the species composition of the spawning aggregations and provides biological data.
 

RV Tangaroa was used to complete searches for orange roughy around all known areas or features where aggregations have been known to occur on the Challenger Plateau. The searches detected aggregations of orange roughy at Megabrick and Twin Tits (the Pinnacles seamount complex), and Volcano on the Westpac Bank.
 

Despite extensive searches carried out on four separate occasions during the survey, no aggregations of orange roughy were found on the Challenger Flats area.
 

Acoustic surveys (or snapshots) on aggregations of orange roughy carried out on Megabrick produced biomass estimates of 1380 t and 290 t, respectively.

Acoustic surveys on aggregations of orange roughy carried out on Volcano produced biomass estimates between 6461 t and 10 255 t.

Too few fish were caught to determine if spawning of orange roughy was underway during the 2023 acoustic survey.

Document date
Thursday, 27 June 2024

Document type
V 1.3

File format
Adobe PDF

File size
10.0 MB

Reference number
2024/26

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FAR: 2024/26;
AUTHOR: P.C. Escobar-Flores; A. Maurice;
ISBN: 978-1-991285-87-4;
ISSN: 1179-5352;

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