Target strength of an oily deep-water fish, orange roughy (Hoplostethus atlanticus) I. Experiments

1999 ◽  
Vol 106 (1) ◽  
pp. 131-142 ◽  
Author(s):  
Sam McClatchie ◽  
Gavin Macaulay ◽  
Roger F. Coombs ◽  
Paul Grimes ◽  
Alan Hart
Keyword(s):  
Deep Water ◽  
Target Strength ◽  
Orange Roughy ◽  
Water Fish ◽  
Hoplostethus Atlanticus

scholarly journals Measurement and visual verification of fish target strength using an acoustic-optical system attached to a trawlnet

2009 ◽  
Vol 66 (6) ◽  
pp. 1238-1244 ◽  
Author(s):  
Tim E. Ryan ◽  
Rudy J. Kloser ◽  
Gavin J. Macaulay
Keyword(s):  
Optical System ◽  
Deep Water ◽  
Video Camera ◽  
Target Strength ◽  
Dual Frequency ◽  
Low Light ◽  
Orange Roughy ◽  
Video Images ◽  
Acoustic Target ◽  
Frequency Split

Abstract Ryan, T. E., Kloser, R. J., and Macaulay, G. J. 2009. Measurement and visual verification of fish target strength using an acoustic-optical system attached to a trawlnet. – ICES Journal of Marine Science, 66: 1238–1244. It is difficult to make acoustic target-strength (TS) measurements of fish behaving naturally in deep-water habitats. The fish may avoid the acoustic instrumentation, and, if measured, there is uncertainty about their species and their orientation relative to the incident sound. To address these issues, a novel acoustic-optical system (AOS) has been developed, which combines a battery-powered, dual-frequency, split-beam acoustic system with a low-light video camera. The AOS attaches to the headline of a commercial deep-water demersal trawlnet that herds fish past the AOS and to the codend. This paper describes initial trials of the AOS to measure calibrated TS of New Zealand orange roughy, validated with video images. The fish species were visually identified, and their behaviour and orientation were approximated. The trawl catch provided associated samples for species identification and measurements of their length and other biological metrics. The combination of acoustics and optics in a net-mountable system constitutes a powerful sampling tool with broader applications in fishery research and ecosystem investigations.

Acoustic assessment of the biomass of a spawning aggregation of orange roughy (Hoplostethus atlanticus, Collett) off south-eastern Australia, 1990-93

1996 ◽  
Vol 47 (8) ◽  
pp. 1015 ◽  
Author(s):  
RJ Kloser ◽  
JA Koslow ◽  
A Williams
Keyword(s):  
Management Strategy ◽  
Sampling Error ◽  
Target Strength ◽  
Acoustic Beam ◽  
Orange Roughy ◽  
Eastern Australia ◽  
Acoustic Surveys ◽  
Surface Bubble ◽  
Hoplostethus Atlanticus

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.

Species identification in deep water using multiple acoustic frequencies

2002 ◽  
Vol 59 (6) ◽  
pp. 1065-1077 ◽  
Author(s):  
R J Kloser ◽  
T Ryan ◽  
P Sakov ◽  
A Williams ◽  
J A Koslow
Keyword(s):  
Simple Model ◽  
Species Identification ◽  
Deep Water ◽  
Standard Length ◽  
Positive Bias ◽  
Orange Roughy ◽  
Uncertainty Factor ◽  
Spawning Site ◽  
Dominant Fish ◽  
Hoplostethus Atlanticus

Multifrequency 12, 38, and 120 kHz acoustics were used to identify the dominant fish groups around a deepwater (>600 m) seamount (a known spawning site for orange roughy, Hoplostethus atlanticus) by amplitude mixing of the frequencies. This method showed three distinct acoustic groupings that corresponded to three groups of fishes based on size and swimbladder type: myctophids of total length less than 10 cm, morids and macrourids with lengths >30 cm, and orange roughy with a mean standard length of 36 cm. These three groups were the dominant groups caught in the demersal and pelagic trawls in the study area. A simple model of swimbladder resonance at depth of large and small gas-filled bladder fish groups is in agreement with our experimental observations. Traditionally, demersal and pelagic trawling is used to identify fish species in acoustic records. However, orange roughy are rarely caught in mid-water owing to net avoidance. Using three frequencies, these groups could be distinguished directly over their entire vertical extent from the acoustic records. This reduces a major source of positive bias uncertainty (factor range of 2.0–6.4) in the orange roughy biomass estimates.

In situ measurements of orange roughy (Hoplostethus atlanticus) target strength

2007 ◽  
Vol 64 (6) ◽  
pp. 1220-1234 ◽  
Author(s):  
Roger F. Coombs ◽  
Richard Barr
Keyword(s):  
New Zealand ◽  
Standard Length ◽  
In Situ Measurements ◽  
Rate Of Change ◽  
Target Strength ◽  
Commercial Fisheries ◽  
Orange Roughy ◽  
Wide Range ◽  
Hoplostethus Atlanticus

Abstract Coombs, R. F., and Barr, R. 2007. In situ measurements of orange roughy (Hoplostethus atlanticus) target strength. – ICES Journal of Marine Science, 64: 1220–1234. Orange roughy (Hoplostethus atlanticus) support one of New Zealand's most valuable commercial fisheries, and its assessment poses many problems. Acoustic estimation using echo integration has become one of the main sources of biomass information, and for this an estimate of orange roughy target strength (TS) is needed. Its schooling characteristics together with patterns in the rate of change of phase vs. TS plots are used to identify ensembles of orange roughy targets from in situ TS data collected from a wide range of fishing areas off eastern New Zealand. The results suggest a TS of −49.3 dB for an orange roughy of 35 cm standard length.

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