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.

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.

scholarly journals Characterizing uncertainty in target-strength measurements of a deepwater fish: orange roughy (Hoplostethus atlanticus)

2003 ◽  
Vol 60 (3) ◽  
pp. 516-523 ◽  
Author(s):  
R.J Kloser ◽  
J.K Horne
Keyword(s):  
Active Avoidance ◽  
Target Selection ◽  
Target Strength ◽  
Wax Ester ◽  
Fish Length ◽  
Orange Roughy ◽  
Single Target ◽  
Species Specific ◽  
Hoplostethus Atlanticus

Abstract The variability of ensemble 38 kHz, target-strength (TS38) estimates for orange roughy (Hoplostethus atlanticus) (4.9 dB, factor of 3.1) in deep water (>600 m) limits the use of echo integration for absolute-biomass estimates. Orange roughy are high in oil content, have a wax-ester swimbladder, and show an active-avoidance response to sampling gear. The interpretations of ensemble, in situ target strengths of orange roughy (range 〈TS38〉=−52.9 to −51.0 dB for standard fish length 〈SL〉 = 35 cm) are lower than previous model and surface-based measurements (〈TS38〉 = −48 dB, SL = 35 cm). In situ TS measurements from individuals on the periphery of dense schools were processed to minimize uncertainties from single-target selection criteria, species composition, and active avoidance. Video and acoustic-tracking data quantified the variability in TS measurements arising from the variability in fish orientation. Multi-frequency acoustics and fish tracking are used to quantify in situ TS variability due to species identification and fish density. The Kirchhoff-ray-mode backscatter model was used to illustrate the sensitivity of species-specific backscatter to assumptions of tilt-angle and material properties (density and sound-speed contrasts). We conclude that a remaining source of uncertainty for in situ TS measurements is the assumption that dispersed targets are representative of the survey population.

scholarly journals Validation of modeled snow properties in Afghanistan, Pakistan, and Tajikistan

2019 ◽  
Author(s):  
Edward H. Bair ◽  
Karl Rittger ◽  
Jawairia A. Ahmad ◽  
Doug Chabot
Keyword(s):  
Snow Depth ◽  
Snow Water Equivalent ◽  
Median Number ◽  
In Situ Measurements ◽  
Snow Properties ◽  
Wide Range ◽  
Spatial Estimates ◽  
Snow Water ◽  
Critical Layers

Abstract. Ice and snowmelt feed the Indus and Amu Darya rivers, yet there are limited in situ measurements of these resources. Previous work in the region has shown promise using snow water equivalent (SWE) reconstruction, which requires no in situ measurements, but validation has been a problem until recently when we were provided with daily manual snow depth measurements from Afghanistan, Tajikistan, and Pakistan by the Aga Khan Agency for Habitat (AKAH). For each station, accumulated precipitation and SWE were derived from snow depth using the SNOWPACK model. High-resolution (500 m) reconstructed SWE estimates from the ParBal model were then compared to the modeled SWE at the stations. The Alpine3D model was then used to create spatial estimates at 25 km to compare with estimates from other snow models. Additionally, the coupled SNOWPACK and Alpine3D system has the advantage of simulating snow profiles, which provide stability information. Following previous work, the median number of critical layers and percentage of facets across all of the pixels containing the AKAH stations was computed. For SWE at the point scale, the reconstructed estimates showed a bias of −42 mm (−19 %) at the peak. For the coarser spatial SWE estimates, the various models showed a wide range, with reconstruction being on the lower end. For stratigraphy, a heavily faceted snowpack is observed in both years, but 2018, a dry year, according to most of the models, showed more critical layers that persisted for a longer period.

Enzyme variation in orange roughy, Hoplostethus atlanticus (Teleostei: Trachichthyidae), from southern Australian and New Zealand waters

1992 ◽  
Vol 43 (6) ◽  
pp. 1561 ◽  
Author(s):  
NG Elliott ◽  
RD Ward
Keyword(s):  
Genetic Diversity ◽  
New Zealand ◽  
Sampling Error ◽  
Genetic Homogeneity ◽  
Gene Frequencies ◽  
Orange Roughy ◽  
Enzyme Variation ◽  
Enzyme Loci ◽  
Total Genetic Diversity ◽  
Hoplostethus Atlanticus

Orange roughy from six localities around the southern coasts of Australia showed no evidence of genetic subdivision when the products of 11 polymorphic enzyme loci were analysed electrophoretically. Samples ranged in size from 84 to 171 per locality. Gene frequencies were very similar in samples taken from New Zealand. The amount of total genetic diversity attributable to subdivision among samples is estimated at 0.55 to 0.22%, but bootstrapping procedures showed that much of this diversity could arise from sampling error. A minimum of around 200 migrants per locality per generation would be sufficient to maintain the observed genetic homogeneity, although actual numbers migrating are likely to be greater than this.

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

Use of Risk Analysis to Assess Fishery Management Strategies: A Case Study using Orange Roughy (Hoplostethus atlanticus) on the Chatham Rise, New Zealand

1992 ◽  
Vol 49 (5) ◽  
pp. 922-930 ◽  
Author(s):  
R. I C. C. Francis
Keyword(s):  
New Zealand ◽  
Risk Analysis ◽  
Fishery Management ◽  
Management Strategies ◽  
Scientific Advice ◽  
Orange Roughy ◽  
Biological Risk ◽  
Stock Assessments ◽  
Hoplostethus Atlanticus

Risk analysis can enhance the value of scientific advice to fishery managers by expressing the uncertainty inherent in stock assessments in terms of biological risk. I present a case study involving an overexploited population of orange roughy (Hoplostethus atlanticus) on the Chatham Rise, New Zealand. This analysis quantifies the risk to the fishery and shows how this decreases as the rate of reduction in total allowble catch increases. The technique helps fishery managers balance biological risk against economic risk. Ways of generalizing the technique are discussed.

scholarly journals In situ target strength estimates of optically verified southern blue whiting (Micromesistius australis)

2012 ◽  
Vol 70 (2) ◽  
pp. 431-439 ◽  
Author(s):  
Richard L. O'Driscoll ◽  
Johannes Oeffner ◽  
Adam J. Dunford
Keyword(s):  
New Zealand ◽  
Confidence Interval ◽  
Fork Length ◽  
Target Strength ◽  
Blue Whiting ◽  
Acoustic Target ◽  
The Mean ◽  
The Relationship ◽  
Immature Fish

Abstract O'Driscoll, R. L., Oeffner, J., and Dunford, A. J. 2013. In situ target strength estimates of optically verified southern blue whiting (Micromesistius australis) – ICES Journal of Marine Science, 70: 431–439. Estimates of the acoustic target strength (TS) of southern blue whiting (Micromesistius australis) at 38 kHz were obtained using an autonomous acoustic–optical system (AOS) mounted on a demersal trawl. Data were collected from aggregations of spawning adult [mean fork length (FL) 34.4 cm] and immature (mean FL 24.6 cm) southern blue whiting south of New Zealand. Mean TS was estimated from 162 tracks containing 695 echoes from targets identified from video as southern blue whiting. The mean TS was –37.9 dB with a 95% confidence interval (CI) of –39.7 to –36.6 dB for 21 immature fish and –34.6 dB (95% CI –35.4 to –34.0 dB) for 141 adults. A logarithmic fit through the mean TS values produced a TS–fork length (FL) relationship from optically verified targets of TS = 22.06 log10FL – 68.54. This new relationship gives TS values within 1 dB of those estimated using the relationship recently adopted by ICES for blue whiting (Micromesistius poutassou) of TS = 20 log10TL – 65.2 (where TL is total length) obtained from in situ measurements, but higher values than those estimated from the previous relationship for southern blue whiting of TS = 38 log10FL – 97, which was based on swimbladder modelling.

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