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Research Vessel (research + vessel)

Distribution by Scientific Domains
Earth and Environmental Science80%

Selected Abstracts

A simulation tool for designing nutrient monitoring programmes for eutrophication assessments,

ENVIRONMETRICS, Issue 1 2010
Janet Heffernan
Abstract This paper describes a simulation tool to aid the design of nutrient monitoring programmes in coastal waters. The tool is developed by using time series of water quality data from a Smart Buoy, an in situ monitoring device. The tool models the seasonality and temporal dependence in the data and then filters out these features to leave a white noise series. New data sets are then simulated by sampling from the white noise series and re-introducing the modelled seasonality and temporal dependence. Simulating many independent realisations allows us to study the performance of different monitoring designs and assessment methods. We illustrate the approach using total oxidised nitrogen (TOxN) and chlorophyll data from Liverpool Bay, U.K. We consider assessments of whether the underlying mean concentrations of these water quality variables are sufficiently low; i.e. below specified assessment concentrations. We show that for TOxN, even when mean concentrations are at background, daily data from a Smart Buoy or multi-annual sampling from a research vessel would be needed to obtain adequate power. Copyright © 2009 Crown Copyright [source]

Omnidirectional multibeam sonar monitoring: applications in fisheries science

FISH AND FISHERIES, Issue 3 2006
Patrice Brehmer
Abstract Data exploitation, acquired by medium-frequency omnidirectional multibeam sonar, enables original studies in fisheries research but is seldom used despite the fact that such equipment is found on most fishing vessels and a number of research vessels. This is the only system for real-time monitoring of fish schools within a horizontal omnidirectional plane about a vessel or a buoy. Between 1996 and 2001, we used two standard omnidirectional sonars and developed new methodologies for exploiting their specific acoustic data according to two main sampling schemes: ,prospecting', including fishing and searching operations, and ,drifting', as with an instrumental buoy system or aboard a stationary vessel. We present a complete method for continuous data acquisition from aboard a research vessel or commercial boat, with automated data extraction by picture analysis and a data processing method. Two cases of data analysis are considered: the first on a school-by-school basis, the ,single school' mode; the second taking into account all fish schools detected within the sonar sampling volume, the ,cluster' mode. Elementary sonar information is divided into five categories that comprise 24 survey and sonar parameters and 55 school, cluster and fisher behaviour descriptors. We review the applications of these categories and discuss perspectives for their use in fisheries science. If the sonar system enables the evaluation of the effects of vessel avoidance on fish school biomass assessment, no accurate abundance estimate can be provided by a simple sonar echo-integration process. Omnidirectional sonar data can be used to analyse collectively the fish schools' swimming speed, kinematics in terms of diffusion and migration, aggregative dynamics as school splitting and merging indexes, spatial characteristics of clusters such as school density, 2D structure and fisher behaviour. The prospect of integrating such data into a fish school database, including multifrequency echo-sounder and lateral multibeam (3D) sonar data combined with a species recognition method, will enable a complete view of fish school behaviour and consequently the adoption of accurate fisheries management methods. [source]

Reproductive cycle of female Brazilian codling, Urophycis brasiliensis (Kaup 1858), caught off the Uruguayan coast

JOURNAL OF APPLIED ICHTHYOLOGY, Issue 2 2000
By A. Acuña
Between August 1993 and September 1995, aspects of reproduction of female Urophycis brasiliensis (Phycidae), a euryhaline species found in the Western Atlantic between 23° and 40° S, were studied. A total of 2500 specimens (23,60 cm; 113,2400 g) were obtained from artisanal fishermen at two locations on the Uruguayan coast: Piriápolis, influenced by the discharge of the Río de la Plata, and La Paloma, a marine site. The ovaries of 900 fish, analysed according to standard histological techniques, revealed eight maturity stages, including one virgin ovary obtained from the catch of a research vessel. The gonadosomatic index ranged from 0.13 to 8.7. Its maximum was determined in the autumn in La Paloma, whereas a shift towards the winter was observed in Piriápolis. In both capture areas, resting stage 2 was present in the samples throughout the year, reaching 67% of the total. At no time were hydrated ovaries observed. The histological cycle is described and compared with macroscopic features of the female gonad. Maturity stages determined in the field had to be confirmed by histological analysis in order to avoid erroneous classification. Although the two ports are only 150 km apart, data indicate different and extended reproductive periods, between June and December for Piriápolis, and March to May for La Paloma. Data indicate synchronous group spawning, possibly as a reproductive strategy in a highly variable environment. The results are compared with scarce information available on U. brasiliensis in its distribution area and data on other species of the same genus. [source]

Omnidirectional multibeam sonar monitoring: applications in fisheries science

FISH AND FISHERIES, Issue 3 2006
Patrice Brehmer
Abstract Data exploitation, acquired by medium-frequency omnidirectional multibeam sonar, enables original studies in fisheries research but is seldom used despite the fact that such equipment is found on most fishing vessels and a number of research vessels. This is the only system for real-time monitoring of fish schools within a horizontal omnidirectional plane about a vessel or a buoy. Between 1996 and 2001, we used two standard omnidirectional sonars and developed new methodologies for exploiting their specific acoustic data according to two main sampling schemes: ,prospecting', including fishing and searching operations, and ,drifting', as with an instrumental buoy system or aboard a stationary vessel. We present a complete method for continuous data acquisition from aboard a research vessel or commercial boat, with automated data extraction by picture analysis and a data processing method. Two cases of data analysis are considered: the first on a school-by-school basis, the ,single school' mode; the second taking into account all fish schools detected within the sonar sampling volume, the ,cluster' mode. Elementary sonar information is divided into five categories that comprise 24 survey and sonar parameters and 55 school, cluster and fisher behaviour descriptors. We review the applications of these categories and discuss perspectives for their use in fisheries science. If the sonar system enables the evaluation of the effects of vessel avoidance on fish school biomass assessment, no accurate abundance estimate can be provided by a simple sonar echo-integration process. Omnidirectional sonar data can be used to analyse collectively the fish schools' swimming speed, kinematics in terms of diffusion and migration, aggregative dynamics as school splitting and merging indexes, spatial characteristics of clusters such as school density, 2D structure and fisher behaviour. The prospect of integrating such data into a fish school database, including multifrequency echo-sounder and lateral multibeam (3D) sonar data combined with a species recognition method, will enable a complete view of fish school behaviour and consequently the adoption of accurate fisheries management methods. [source]

An evaluation of the potential influence of SST and currents on the oceanic migration of juvenile and immature chum salmon (Oncorhynchus keta) by a simulation model

FISHERIES OCEANOGRAPHY, Issue 1 2004
Tomonori Azumaya
Abstract Using a salmon migration model based on the assumption that swimming orientation is temperature dependent, we investigated the determining factors of the migration of juvenile and immature chum salmon (Oncorhynchus keta) in the North Pacific. We compared the predictions of the model with catch data of immature and juvenile chum salmon collected by Japanese research vessels from 1972 to 1999. The salmon migration model reproduced the observed distributions of immature chum salmon and indicates that passive transport by wind-driven and geostrophic currents plays an important role in the eastward migration of Asian salmon. These factors result in a non-symmetric distribution of Asian and North American chum salmon in the open ocean. The directional swimming component contributes to the northward migration in summer. The model results indicate that during the first winter Asian chum salmon swim northward against the southward wind-driven currents to stay in the western North Pacific. This suggests that Asian chum salmon require more energy to migrate than other stocks during the first winter of their ocean life. [source]