scholarly journals Physical Oceanographic Influences on Central Benguela Fish Catch

2012 ◽  
Vol 16 (6) ◽  
pp. 1-15 ◽  
Author(s):  
Mark R. Jury
Keyword(s):  
Vertical Motion ◽  
Principal Component ◽  
Ekman Transport ◽  
Commercial Fish ◽  
Benguela Upwelling ◽  
Fish Catch ◽  
Composite Maps ◽  
Catch Rates ◽  
Eggs And Larvae ◽  
High Fish

Abstract Ocean and atmosphere reanalysis fields are used to study environmental conditions and their relation to commercial fish catch in the central Benguela upwelling zone, using both targeted and objective techniques. Composite maps and sections indicate a 10%–20% weakening of southeasterly winds, a 0.5°C warming of sea temperatures over the shelf, and changes in currents and subsurface upwelling associated with higher fish catch. During periods of high fish catch, recirculating gyres form that may aid the retention of eggs and larvae. Offshore winds contribute to poleward Ekman transport in a 50-m-deep layer within 100 km of the coast. In addition to composite analysis, the natural variability is studied by principal component analysis of wind stress, sea level, temperature, salinity, currents, and vertical motion in the period 1970–2007. Comparison of interannual time scores and fisheries data indicate that anomalous poleward winds and warmer temperatures in the Lüderitz plume, driven by an atmospheric trough in the South Atlantic, are associated with higher catch rates.

Relationships among side‐scan sonar classified substrates and fish‐catch rates at multiple spatial scales

2020 ◽  
Vol 36 (8) ◽  
pp. 1579-1587 ◽  
Author(s):  
Jerrod Parker ◽  
Stephen M. Pescitelli ◽  
John Epifanio ◽  
Yong Cao
Keyword(s):  
Spatial Scales ◽  
Side Scan Sonar ◽  
Multiple Spatial Scales ◽  
Fish Catch ◽  
Catch Rates

Use of Oceanographic Forecasts and Echosounders to Guide and Enhance an Inshore Gillnet Fishery for Atlantic Cod (Gadus morhua)

1993 ◽  
Vol 50 (10) ◽  
pp. 2129-2136 ◽  
Author(s):  
G. A. Rose ◽  
W.C. Leggett
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Fishing Effort ◽  
Shallow Waters ◽  
Gill Nets ◽  
Rule Of Thumb ◽  
Combined Use ◽  
Catch Rates ◽  
Depth Ranges ◽  
High Fish

Vessels fishing with gill nets for Atlantic cod (Gadus morhua) in the northern Gulf of St. Lawrence in 1985 and 1986 concentrated their fishing effort in shallow waters (<50 m) where cod densities were highest (to 0.5/m3). In both years, seasonal trends (June–August) in mean daily deployment depths of gill nets were positively correlated with mean depths at which cod were surveyed (1985, r = 0.71; 1986, r = 0.51, Ps < 0.05). Daily catch rate variability of individual vessels was accounted for by fish "flux" adjacent to nets (44%), vessel operator skill (19%), and "flux"–skill interaction (8%; total R2 = 0.71). A guided vessel directed to fish at sites predicted to have high fish flux (located down-current from high-density cod aggregations identified by echosounding within depth ranges forecast to be favorable to cod by "rule of thumb" wind-based oceanographic models) had higher catch rates (mean 1.3 t/d) than the fleet average and its own average fishing without guidance (means 0.4 t/d, P's < 0.05). Directed searches were of shorter duration (mean 0.5 h) than searches conducted at random (1.5 h). Combined use of echosounders and air–sea-based forecasts of cod distribution could help stabilize catch rates, especially at times of poor fish availability inshore.

Climatological annual cycle of Benguela upwelling system using different upwelling indices

2020 ◽  
Author(s):  
Mohammad Hadi Bordbar ◽  
Volker Mohrholz ◽  
Martin Schmidt
Keyword(s):  
Chlorophyll A ◽  
Vertical Velocity ◽  
Annual Cycle ◽  
Ekman Transport ◽  
Spatial And Temporal Variation ◽  
Clear Correlation ◽  
Ekman Pumping ◽  
Chlorophyll A Concentration ◽  
Upwelling System ◽  
Benguela Upwelling

&lt;p&gt;Several long-established upwelling indices derived from the observed wind fields, Chlorophyll-a concentration, sea surface temperature (SST) are used to investigate the climatology annual cycle of Benguela Upwelling System (BUS). Chlorophyll-a concentration is taken as an indicator of ocean primary production. In addition, we analyze a multi-decadal simulation of a state-of-the-art eddy resolving ocean model which was forced by observed atmospheric heat and momentum fluxes. We take the vertically averaged of simulated vertical velocity in water column as a direct measure of upwelling strength.&lt;/p&gt;&lt;p&gt;The Ekman offshore transport tends to have two distinctive upwelling cells near the coast of L&amp;#252;deritz (26.3&amp;#176;S) and Cape Frio (17&amp;#176;S) with large seasonal cycles. The former peaks between September and December. The latter features a biannual cycle with two peaks over April-June and September-December, which is concurrent with meridional migration of Angola-Benguela SST front. The offshore (30-200 km) vertical velocity, primarily induced by Ekman transport divergence, depicts a similar annual cycle, but with smaller magnitude. It becomes broader from south to north with four distinctive upwelling cells located near the coast of Cape Columbine (33&amp;#176;S), Orange River (28&amp;#176;S), Walvis Bay (23&amp;#176;S) and northern part of Cape Frio (16&amp;#176;S). The spatial and temporal variation of Ekman pumping and Chlorophyll-a, as measures of upwelling, show a clear correlation. However, such a correlation is not evident when Ekman coastal transport is taken. SST-based index depicts a very similar spatial pattern. However, the seasonal cycle does not match with other observational and simulated indices. Our finding suggests that the local SST anomalies are strongly influenced by horizontal heat advection and surface heat flux anomaly which can dominate over the anomalies associated with the upwelling; meaning that SST-index alone may not give a realistic estimate of upwelling strength over the region.&lt;/p&gt;

scholarly journals Temporal distribution of ichthyoplankton in the Ivinhema River (Mato Grosso do Sul State/ Brazil): influence of environmental variables

2011 ◽  
Vol 9 (2) ◽  
pp. 427-436 ◽  
Author(s):  
David Augusto Reynalte-Tataje ◽  
Keshiyu Nakatani ◽  
Rodrigo Fernandes ◽  
Angelo Antônio Agostinho ◽  
Andréa Bialetzki
Keyword(s):  
Environmental Variables ◽  
Temporal Distribution ◽  
Principal Component ◽  
Temporal Variations ◽  
Large Species ◽  
Mato Grosso ◽  
Upper Paraná River ◽  
Water Outflow ◽  
Eggs And Larvae ◽  
Mato Grosso Do Sul

Information on ichthyoplankton is an important tool in determining reproduction periods that - if associated to environmental variables - allows for inferences about the factors that regulate their intensity, beginning, and ending. In this context, this study aims to establish (i) ichthyoplankton composition; (ii) temporal variations in the overall density of eggs and larvae and among the most important taxa; and (iii) the influence of some abiotic and biotic variables on these organisms' abundance. Ichthyoplankton sampling was undertaken during the period between April 2005 and March 2006 at the Ivinhema River, upper Paraná River basin (MS/Brazil). Differences in the ichthyoplankton's temporal variation were evaluated using unifactorial ANOVAs. Principal Component Analysis and Pearson's correlation were used for the relationships between eggs and larvae densities and environmental variables. A total of 3,341 eggs and 2,896 larvae were captured during the period studied, and most of them were medium-sized and large species that carried out some type of reproductive migration. The highest densities of eggs and larvae occurred during the months of spring and summer, except for those of Bryconamericus stramineus, which was most abundant during the winter. The density of ichthyoplankton was most positively correlated with the water's outflow and temperature. However, Plagioscion squamosissimus was positively related to the increase in pH and in zooplanktonic organisms, while B. stramineus was inversely correlated with water outflow and temperature. The study concludes that spawning is most intense in the spring and summer, especially between November and January, and is related to the greatest values of water temperature and outflow. Nevertheless, the response and reproductive intensity in relation to the environmental variables vary according to the species.

scholarly journals ON THE QUESTION OF FISHERY REGIME REGULATION IN THE VOLGA-CASPIAN BASSIN (ASTRAKHAN REGION) BY THE EXAMPLE OF NORTH-CASPIAN ROACH

2018 ◽  
pp. 41-48
Author(s):  
Vitaliy Victorovich Barabanov ◽  
Sergey Yurievich Nikiforov
Keyword(s):  
Hydrological Regime ◽  
Fishing Effort ◽  
Major Purpose ◽  
Spawning Grounds ◽  
Commercial Fish ◽  
Factors Affecting ◽  
Fish Catch ◽  
And Gender ◽  
Negative Factors ◽  
Caspian Roach

The article shows the assessment of fishing conditions of roach catches (the number of fishing grounds, fishing gears, catches, catches per unit of fishing effort, fishing intensity, etc.) at the main fishery objects of the Volga delta. There has been made the analysis of structure of size and gender composition of roach from commercial and amateur catches. The results have shown a depression of the population with negative dynamics in future. There have been determined main negative factors affecting the state of roach stock: unfavorable hydrological regime, incoordination in terms of commercial and amateur catches, limits of catch and size. In such circumstances the major purpose is to create a fishing regime, when maximum pass of fish spawners to spawning grounds is provided. The article proposes organizing a special regime of fishing roach with the aim to introduce additional limitations to the commercial fish catch, the main point of which is a transition from fine-meshed seines to medium-meshed seines in the day, when the water level in the Astrakhan region achieves an index mark as 350 cm. This measure will allow assuring a maximum pass of roach spawners to spawning grounds. A similar interdiction must be valid for amateur fishing. It should be noted that this interdiction is a provisional measure allowing to preserve and reproduce roach population.

scholarly journals PeskAAS: A near-real-time, open-source monitoring and analytics system for small-scale fisheries

PLoS ONE ◽  
2020 ◽  
Vol 15 (11) ◽  
pp. e0234760
Author(s):  
Alexander Tilley ◽  
Joctan Dos Reis Lopes ◽  
Shaun P. Wilkinson
Keyword(s):  
Open Source ◽  
Source Monitoring ◽  
R Package ◽  
Small Island ◽  
Small Scale ◽  
Small Scale Fisheries ◽  
Fish Catch ◽  
Catch Rates ◽  
Context Specific ◽  
Species Specific

Small-scale fisheries are responsible for landing half of the world’s fish catch, yet there are very sparse data on these fishing activities and associated fisheries production in time and space. Fisheries-dependent data underpin scientific guidance of management and conservation of fisheries systems, but it is inherently difficult to generate robust and comprehensive data for small-scale fisheries, particularly given their dispersed and diverse nature. In tackling this challenge, we use open source software components including the Shiny R package to build PeskAAS; an adaptable and scalable digital application that enables the collation, classification, analysis and visualisation of small-scale fisheries catch and effort data. We piloted and refined this system in Timor-Leste; a small island developing nation. The features that make PeskAAS fit for purpose are that it is: (i) fully open-source and free to use (ii) component-based, flexible and able to integrate vessel tracking data with catch records; (iii) able to perform spatial and temporal filtering of fishing productivity by fishing method and habitat; (iv) integrated with species-specific length-weight parameters from FishBase; (v) controlled through a click-button dashboard, that was co-designed with fisheries scientists and government managers, that enables easy to read data summaries and interpretation of context-specific fisheries data. With limited training and code adaptation, the PeskAAS workflow has been used as a framework on which to build and adapt systematic, standardised data collection for small-scale fisheries in other contexts. Automated analytics of these data can provide fishers, managers and researchers with insights into a fisher’s experience of fishing efforts, fisheries status, catch rates, economic efficiency and geographic preferences and limits that can potentially guide management and livelihood investments.

Description of the commercial fish catch in Iraqi marine waters

2014 ◽  
Vol 25 (2) ◽  
Author(s):  
K Younis ◽  
A Jabir ◽  
U Yousif ◽  
T Abd-Rassol
Keyword(s):  
Marine Waters ◽  
Commercial Fish ◽  
Fish Catch

scholarly journals Dietary Determinants of Polyunsaturated Fatty Acid (PUFA) Status in a High Fish-Eating Cohort during Pregnancy

Nutrients ◽  
2018 ◽  
Vol 10 (7) ◽  
pp. 927 ◽  
Author(s):  
Marie Conway ◽  
Maria Mulhern ◽  
Emeir McSorley ◽  
Edwin van Wijngaarden ◽  
J. Strain ◽  
...  
Keyword(s):  
Pregnant Women ◽  
Dietary Pattern ◽  
Principal Component ◽  
White Meat ◽  
Fatty Fish ◽  
Total N ◽  
Total Pufa ◽  
High Fish ◽  
Meat And Eggs ◽  
Maternal Status

Polyunsaturated fatty acids (PUFA) are essential for neurodevelopment and the developing foetus depends on an optimal maternal status. Fish is a rich source of PUFA. The current study investigated dietary patterns, and associations with PUFA status in a high-fish consuming cohort of pregnant women in the Seychelles. At 28 weeks’ gestation, pregnant women provided a blood sample, from which serum total PUFA concentrations were measured, A Food Frequency Questionnaire (FFQ) and Fish Use Questionnaire (FUQ) were also completed. Principal component analysis (PCA) of dietary information identified four patterns. Regression analyses found dietary pattern 2, containing foods traditionally eaten in the Seychelles e.g., fish, fruit and vegetables was positively associated with serum docosahexaenoic acid (DHA) (β = 0.134; CI = 0.001, 0.022), and serum total n-3 PUFA (β = 0.139; CI = 0.001, 0.023) concentrations. Dietary pattern 1, high in processed foods, snacks, white meat and eggs, was not significantly associated with any of the serum PUFA concentrations. The FUQ indicated that fatty fish was associated with EPA status (β = 0.180; CI = 0.001, 0.005) in high consumers. The second dietary pattern, consisting of higher consumption of fish and fruit, was positively associated with n-3 PUFA status during pregnancy.

scholarly journals A multivariate statistical analysis to determine catch intention in the pink cusk-eel (Genypterus blacodes) longline fishery in southern Chile

2020 ◽  
Vol 84 (1) ◽  
pp. 17
Author(s):  
Rodrigo Wiff ◽  
Guillermo Martin Gonzalez ◽  
Francisco Contreras ◽  
Marcelo A. San Martín ◽  
T. Mariella Canales
Keyword(s):  
Stock Assessment ◽  
Principal Component ◽  
Sensitivity Analyses ◽  
Commercial Fishing ◽  
Southern Chile ◽  
Multivariate Statistical ◽  
By Catch ◽  
Catch Rates ◽  
Catch Composition ◽  
Over Time

The definition of catch intention in multispecies fisheries is a key step toward building abundance indexes based on commercial fishing data. Previous analysis to determine catch intention in the pink cusk-eel (Genypterus blacodes) has been based on the idea that fishing tactics remain constant over time (static fishing tactics). We propose a statistical procedure to determine the catch intention of each haul in the industrial longline fisheries in southern Chile, where fishing tactics may vary over time. This procedure is based on principal component analysis and agglomerative hierarchical analysis of the catch composition, and relaxes the assumption of static fishing tactics by selecting a subset of data that is informative for fishing intention (target versus by-catch) every year. Sensitivity analyses were conducted to assess the robustness of variable fishing tactics on the nominal catch rates in pink cusk-eel. Targeted and by-catch time series of nominal catch rates showed a different trend, so determining the catch intention became relevant. Sensitivity analyses showed that trends in targeted catch rates are robust to the variations of fishing tactic per year. We recommend the use of variable fishing tactics for further use in effort standardization and stock assessment of the pink cusk-eel fishery in southern Chile.

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