
TY  - JOUR
A1  - Kloser, RJ 
A1  - Koslow, JA 
A1  - Williams, A 
T1  - Acoustic assessment of the biomass of a spawning aggregation of orange roughy (<I>Hoplostethus atlanticus</I>, Collett) off south-eastern Australia, 1990-93
JF  - Marine and Freshwater Research
JO  - Mar. Freshwater Res.
Y1  - 1996
VL  - 47
IS  - 8
SP  - 1015
EP  - 1024
KW  - 
UR  - https://doi.org/10.1071/MF9961015 
N2  - Orange roughy, which spawn in an aggregation around a seamount off north-eastem Tasmania, were surveyed acoustically with vessel-mounted and deep-tow transducers from 1990 to 1993. Orange roughy dominated at 700-900 m (95% of individuals) and were less numerous both shallower and deeper. Echo integration estimates from the vessel-mounted transducer were consistently lower than those from the deep-tow transducer by a factor of ~1.8, owing to surface bubble attenuation, vessel movement and acoustic beam thresholding among other factors. The absolute estimate from the deep-towed transducer of the prefishery orange roughy biomass (98200 t ; coefficient of variation, 6.7%) compared well with estimates from stock reduction analysis (95000 to 110000 t) and an egg survey (96900 t; CV, 47%). The acoustic surveys had lower sampling error (CV, 7-15%) than that of the egg survey and required less survey time. The present results support the use of initial absolute acoustic biomass estimates to set a management strategy for the fishery. Stock reduction analysis based on the relative acoustic estimates and catch over the four years indicated that orange roughy target strength was -50 dB ± 3 dB, which is consistent with results from models of target strength and from measurements in situ and on dead specimens. 
ER  -

