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Dianne M. Tracey - One of the best experts on this subject based on the ideXlab platform.
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lead radium dating of orange roughy Hoplostethus atlanticus validation of a centenarian life span
Canadian Journal of Fisheries and Aquatic Sciences, 2009Co-Authors: Allen H. Andrews, Dianne M. Tracey, Matthew Dunnm R R DunnAbstract:Life-span estimates for orange roughy (Hoplostethus atlanticus) range from ~20 years to well over 100 years. In this study, an improved lead–radium dating technique provided independent age estimat...
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Lead–radium dating of orange roughy (Hoplostethus atlanticus): validation of a centenarian life span
Canadian Journal of Fisheries and Aquatic Sciences, 2009Co-Authors: Allen H. Andrews, Dianne M. Tracey, Matthew R. Dunnm.r. DunnAbstract:Life-span estimates for orange roughy (Hoplostethus atlanticus) range from ~20 years to well over 100 years. In this study, an improved lead–radium dating technique provided independent age estimat...
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diel variation in spawning orange roughy Hoplostethus atlanticus trachichthyidae abundance over a seamount feature on the north west chatham rise
New Zealand Journal of Marine and Freshwater Research, 2001Co-Authors: B. Bull, Dianne M. Tracey, Ian J. Doonan, Alan HartAbstract:Abstract The diel variation in abundance of an orange roughy (Hoplostethus atlanticus Collett) spawning aggregation on a deepsea seamount on the Chatham Rise known as “Graveyard” was studied using acoustics. A 4‐day survey was carried out using a Latin cube statistical design. The acoustic data was echo‐integrated and analysis of variance was carried out to estimate the effects of day, time of day, and transect path. The estimated biomass of the spawning aggregation did not display any significant diel variation. We conclude that this result validates the current practice of acoustically surveying orange roughy on this seamount without considering diel effects. The aggregation fluctuated in abundance over the survey period, suggesting that turnover offish was occurring. Differences in roughy biomass with transect orientation indicate the importance of randomised radial transects for these surveys.
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Diel variation in spawning orange roughy (Hoplostethus atlanticus, Trachichthyidae) abundance over a seamount feature on the north‐west Chatham Rise
New Zealand Journal of Marine and Freshwater Research, 2001Co-Authors: B. Bull, Dianne M. Tracey, Ian J. Doonan, Alan C. HartAbstract:Abstract The diel variation in abundance of an orange roughy (Hoplostethus atlanticus Collett) spawning aggregation on a deepsea seamount on the Chatham Rise known as “Graveyard” was studied using acoustics. A 4‐day survey was carried out using a Latin cube statistical design. The acoustic data was echo‐integrated and analysis of variance was carried out to estimate the effects of day, time of day, and transect path. The estimated biomass of the spawning aggregation did not display any significant diel variation. We conclude that this result validates the current practice of acoustically surveying orange roughy on this seamount without considering diel effects. The aggregation fluctuated in abundance over the survey period, suggesting that turnover offish was occurring. Differences in roughy biomass with transect orientation indicate the importance of randomised radial transects for these surveys.
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The effects of commercial exploitation on orange roughy (Hoplostethus atlanticus) from the continental slope of the Chatham Rise, New Zealand, from 1979 to 1997
Fisheries Research, 2000Co-Authors: Malcolm R. Clark, Owen F. Anderson, R. I. C. Chris Francis, Dianne M. TraceyAbstract:Abstract Orange roughy ( Hoplostethus atlanticus ) is a recently exploited species, fished by trawling at depths of 700–1200 m on the continental slope around New Zealand. In this paper, changes in the major New Zealand orange roughy fishery on the Chatham Rise during a 19-year period are examined. Data from research trawl surveys and commercial fishing returns from 1979 to 1997 were analysed, and changes in the population described. The distribution of orange roughy showed a marked contraction, and aggregations became largely centred around seamounts or very localised areas of the slope. The biomass of orange roughy, measured by trawl survey and commercial catch-per-unit-effort indices, declined substantially, and in 1997 was estimated to be about 20% of virgin levels. Most bycatch species also declined in abundance, with no indication of species replacement. Size structure of the population did not change markedly over the period. Timing of spawning in July, and the pattern of gonad development, were also consistent over the years. There was no change in size or age at maturity. Prey composition remained similar. Biological changes may not have been apparent because orange roughy is a long-lived, slow-growing species, with low productivity. There could be a long response time of the population to fishing pressure.
Rudy J. Kloser - One of the best experts on this subject based on the ideXlab platform.
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In situ target strength estimates of visually verified orange roughy
ICES Journal of Marine Science, 2012Co-Authors: Gavin J. Macaulay, Rudy J. Kloser, Tim E. RyanAbstract:The first estimates of orange roughy ( Hoplostethus atlanticus ) target strength at 38 and 120 kHz with visual verification were obtained from a self-contained echosounder and video camera system affixed to a demersal trawl towed through dense aggregations of spawning orange roughy. Mean target strength estimates were obtained from 24 tracks of orange roughy containing 83 echoes. The mean target strength at 38 kHz was –52.0 dB with a 95% confidence interval of –53.3 to –50.9 dB for fish with a mean length of 33.9 cm. At 120 kHz the mean target strength was –47.9 dB (confidence interval of –48.8 to –46.4 dB). This work makes two significant advances: in situ TS measurements have been made that can be confidently attributed to orange roughy, and using a trawl to herd orange roughy past the system resolved the previously intractable problem of fish avoidance.
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Characterizing uncertainty in target-strength measurements of a deepwater fish: orange roughy (Hoplostethus atlanticus)
ICES Journal of Marine Science, 2003Co-Authors: Rudy J. Kloser, John K. HorneAbstract: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 (>600m) 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 hTS38i 1⁄4 52:9 to 51.0 dB for standard fish length hSLi 1⁄4 35 cm) are lower than previous model and surface-based measurements (hTS38i 1⁄4 48 dB, SL 1⁄4 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 speciesspecific backscatter to assumptions of tilt-angle and material properties (density and soundspeed 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.
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Species identification in deep water using multiple acoustic frequencies
Canadian Journal of Fisheries and Aquatic Sciences, 2002Co-Authors: Rudy J. Kloser, Tim E. Ryan, Pavel Sakov, Alan Williams, J. A. KoslowAbstract: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) b...
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Avoidance of a camera system by a deepwater fish, the orange roughy (Hoplostethus atlanticus)
Deep Sea Research Part I: Oceanographic Research Papers, 1995Co-Authors: J. Anthony Koslow, Rudy J. Kloser, C.a. StanleyAbstract:Abstract The response of the benthopelagic fish, orange roughy ( Hoplostethus atlanticus ), to lowering an underwater camera was monitored acoustically. Acoustic layers of the fish at 660–790 m depth dispersed rapidly at least 30–40 m when the camera was ∼130 m above them. The reaction occurred day and night and prior to activation of the strobe lights, so it was presumably mediated by the low-frequency sound of the system being lowered rather than visually. Orange roughy contain a pronounced lateral line and extensive frontal sensory canal system that may be used to sense low-frequency sound. Our observations indicate that some marine species are highly sensitive even to non-capture sampling gears, so use of non-remote methods of sampling may lead to highly biased estimates of density. The avoidance response is consistent with the relatively high metabolic levels that have been reported for this species, as well as with their very low estimated rates of natural mortality. We speculate that the response has evolved to facilitate escape from large, highly mobile predators.
Tim E. Ryan - One of the best experts on this subject based on the ideXlab platform.
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In situ target strength estimates of visually verified orange roughy
ICES Journal of Marine Science, 2012Co-Authors: Gavin J. Macaulay, Rudy J. Kloser, Tim E. RyanAbstract:The first estimates of orange roughy ( Hoplostethus atlanticus ) target strength at 38 and 120 kHz with visual verification were obtained from a self-contained echosounder and video camera system affixed to a demersal trawl towed through dense aggregations of spawning orange roughy. Mean target strength estimates were obtained from 24 tracks of orange roughy containing 83 echoes. The mean target strength at 38 kHz was –52.0 dB with a 95% confidence interval of –53.3 to –50.9 dB for fish with a mean length of 33.9 cm. At 120 kHz the mean target strength was –47.9 dB (confidence interval of –48.8 to –46.4 dB). This work makes two significant advances: in situ TS measurements have been made that can be confidently attributed to orange roughy, and using a trawl to herd orange roughy past the system resolved the previously intractable problem of fish avoidance.
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Species identification in deep water using multiple acoustic frequencies
Canadian Journal of Fisheries and Aquatic Sciences, 2002Co-Authors: Rudy J. Kloser, Tim E. Ryan, Pavel Sakov, Alan Williams, J. A. KoslowAbstract: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) b...
R. I. C. C. Francis - One of the best experts on this subject based on the ideXlab platform.
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Inferring spawning migrations of orange roughy (Hoplostethus atlanticus) from spawning ogives
Marine and Freshwater Research, 1998Co-Authors: R. I. C. C. Francis, M. R. ClarkAbstract:Orange roughy (Hoplostethus atlanticus) occurs throughout New Zealand waters at depths between 700 and 1500 m. Most spawning occurs in a few localized aggregations in winter and it appears that fish migrate substantial distances (hundreds of kilometres) to and from these aggregations. However, there is no direct evidence of migration. Indirect evidence of migration of females is presented in the form of trends in L50, the mid point of the spawning ogive (i.e. the length at which 50% of mature females are spawners). Data from 21 research surveys carried out between March and August over an eleven-year period show consistent geographical trends in L50 on the east coast and the Chatham Rise. L50 was consistently low (28–32 cm) near major spawning grounds and increased to high values (>34 cm) far from these grounds. These trends increase the knowledge of orange roughy spawning migrations in two important fishing areas.
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Transition zone in otoliths of orange roughy (Hoplostethus atlanticus) and its relationship to the onset of maturity
Marine Biology, 1997Co-Authors: R. I. C. C. Francis, P. L. HornAbstract:A transition zone in the otoliths of orange roughy (Hoplostethus atlanticus) is described where annulus width decreases markedly. For fish sampled at spawning time, the relationship between gonad stage and the presence or absence of a transition zone is consistent with the hypothesis that this zone marks the onset of maturity, if allowance is made for some error in gonad staging and identification of the zone. Another data set from a non-spawning area after the spawning season is not consistent with the hypothesis. However, these latter data are considered less reliable because of the small size of the fish in the sample and difficulties in determining, outside the spawning season, whether a fish has been reproductively active. This hypothesis was used to provide estimates of the median age (30 yr) and length (31 cm) at the onset of maturity for the Chatham Rise, New Zealand population. These estimates are unaffected by the biases associated with the usual ogive method of estimation.
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Mean length, age, and otolith weight as potential indicators of biomass depletion for orange roughy, Hoplostethus atlanticus
New Zealand Journal of Marine and Freshwater Research, 1995Co-Authors: R. I. C. C. Francis, David C. SmithAbstract:Abstract It is a common observation that the mean length in a fish population progressively decreases as the biomass is reduced by fishing. However, this has not happened with the population of orange roughy (Hoplostethus atlanticus) on the Chatham Rise, New Zealand, even though the biomass is estimated to have declined by almost 80%. Because orange roughy are slow growing it might be expected that mean age (or its proxy, mean otolith weight) would be a more sensitive indicator of biomass decline than mean length. A simulation study shows that this is not true. With equal sample sizes, all three indicators are equally sensitive; on an equal cost basis, mean length is more sensitive than the others. A log transformation increases the sensitivity of age and otolith weight, but it is not clear whether this increase is sufficient to outweigh the much greater costs of measuring age and otolith weight, compared to length. Under the assumption of constant recruitment, it is more likely than not (P = 0.55–0.8) th...
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Use of Risk Analysis to Assess Fishery Management Strategies: A Case Study using Orange Roughy (Hoplostethus atlanticus) on the Chatham Rise, New Zealand
Canadian Journal of Fisheries and Aquatic Sciences, 1992Co-Authors: R. I. C. C. FrancisAbstract: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.
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Loss of genetic diversity due to fishing pressure
Fisheries Research, 1991Co-Authors: P. J. Smith, R. I. C. C. Francis, M. McveaghAbstract:Loss of genetic diversity in the orange roughy, Hoplostethus atlanticus, caught off New Zealand, was measured by gel electrophoresis of nine polymorphic enzyme loci. There has been a significant reduction in genetic diversity on three spawning sites over the past 6 years, during which time the virgin biomass has been reduced by ∼ 70%. It is suggested that fishing activities which concentrate on spawning populations differentially remove the older and more heterozygous individuals from the virgin stock. Commercial fishing activities may have had significant genetic effects on fish stocks without reducing them to near-extinction levels.
Peter J. Smith - One of the best experts on this subject based on the ideXlab platform.
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Global genetic population structure in the commercially exploited deep-sea teleost orange roughy (Hoplostethus atlanticus) based on microsatellite DNA analyses
Fisheries Research, 2013Co-Authors: Andrea I. Varela, Peter A. Ritchie, Peter J. SmithAbstract:Abstract The widely distributed teleost orange roughy, Hoplostethus atlanticus , has been one of the main species targeted in deep-sea fisheries. While morphometric, parasite and otolith analyses have generally found differentiation among populations within ocean basins, genetic techniques have shown contradictory results at different geographical scales. Here, we used nine microsatellite DNA loci to study genetic diversity and differentiation in orange roughy at a global scale using samples from New Zealand, Australia, Namibia, Chile, and the Northeast Atlantic Ocean. Additionally, temporal genetic variation was assessed for eight sites in Northern New Zealand sampled in two different years. The expected heterozygosity was high in all the sites, suggesting high levels of genetic diversity in orange roughy. Overall, we detected low but significant differentiation at the global scale: across the Southern hemisphere and between the Southern hemisphere regions and the Northeast Atlantic Ocean. However, genetic homogeneity was found between New Zealand and Australia. The present data does not showed temporal variation in orange roughy from Northern New Zealand. A pattern of isolation by distance at the global scale suggests stepping-stone migration, which is likely the result of active adult dispersal. This study revealed levels of genetic differentiation at the global scale that were undetected with mitochondrial DNA sequences analyses.
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Low levels of global genetic differentiation and population expansion in the deep-sea teleost Hoplostethus atlanticus revealed by mitochondrial DNA sequences
Marine Biology, 2012Co-Authors: Andrea I. Varela, Peter A. Ritchie, Peter J. SmithAbstract:The orange roughy Hoplostethus atlanticus is a well-known commercial species with a global distribution. There is no consensus about levels of connectivity among populations despite a range of techniques having been applied. We used cytochrome c oxidase subunit I (COI) and cytochrome b sequences to study genetic connectivity at a global scale. Pairwise ΦST analyses revealed a lack of significant differentiation among samples from New Zealand, Australia, Namibia, and Chile. However, low but significant differentiation (ΦST = 0.02–0.13, P < 0.05) was found between two Northeast Atlantic sites and all the other sites with COI. AMOVA and the haplotype genealogy confirmed these results. The prevalent lack of genetic differentiation is probably due to active adult dispersal under the stepping-stone model. Demographic analyses suggested the occurrence of two expansion events during the Pleistocene period.
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Genetically isolated stocks of orange roughy (Hoplostethus atlanticus), but not of hoki (Macruronus novaezelandiae), in the Tasman Sea and Southwest Pacific Ocean around New Zealand
Marine Biology, 1996Co-Authors: Peter J. Smith, S. M. Mcveagh, A. EdeAbstract:Restriction fragment-length polymorphisms of mitochondrial (mt) DNA, generated by six-base restriction enzymes, were used to examine the stock structure of the two major commercial species in New Zealand fisheries, orange roughy (Hoplostethus atlanticus Collett) and hoki (Macruronus novaezelandiae Hector). Samples of orange roughy from six spawning sites around New Zealand and one site off Tasmania show significant genetic heterogeneity. Samples from two sites around the south of New Zealand were genetically similar to each other, but dissimilar to samples from all other sites. The common haplotype observed in northern sites was absent from the two southern sites. Low numbers of unique haplotypes were restricted to the Challenger Plateau in the Tasman Sea. There was no significant genetic heterogeneity in five samples of hoki from two spawning sites off New Zealand and one site off Tasmania.