scholarly journals Metodologia para a monitorização e gestão da pesca de arrasto em Portugal. O exemplo do SIG GEOCRUST 1.0

Finisterra ◽  
2012 ◽  
Vol 38 (76) ◽  
Author(s):  
Joana Simões ◽  
Carlos Pinto ◽  
Manuel Afonso-Dias
Keyword(s):  
Fishing Effort ◽  
Geographical Information ◽  
Catch Per Unit Effort ◽  
Trawl Fishery ◽  
Single Vessel ◽  
External Software ◽  
Directorate General ◽  
Exploratory Data ◽  
The University ◽  
Trawl Fisheries

A METHODOLOGY FOR THE MONITORING AND MANAGEMENT OF TRAWL FISHERIES IN PORTUGAL. THE SIG EXAMPLE OF GEOCRUST 1.0. This paper aims to present the Geographical Information System GEOCRUST 1.0, a computer programme developed within the fishery research project DGXIV 99/059, Use of Satellite GPS data to map effort and landings of the Portuguese crustacean fleet (GEOCRUST), in the University of Algarve. This stand-alone application was developed essentially to map fishing effort and catch per unit effort (CPUE) information for the Portuguese crustacean trawl fleet, operating off the Southwest and South coasts of Portugal. The data available for this study included GPS vessels’ geographical positions and speed, transmitted via satellite to the Portuguese fisheries inspection authorities, and their catch reported to the Portuguese Directorate-General of Fisheries. GEOCRUST 1.0 was developed in ®VISUAL BASIC 6.0 using two ActiveX control: ADODB, to connect with the ®MSACCESS 2000 database and ®MAPOBJECTS 2.0 PRO, to communicate with the maps and provide GIS facilities. The application includes seven modules with the following objectives: Module 1 – to map and edit the original VMS data for a single vessel or group of vessels, for different periods of time; Module 2 – to analyse the trawl speed of each vessel; Module 3 – to define the boundaries of all fishing trips performed by vessel along the year; Module 4 – to identify and define the trawl hauls, within each fishing trip; Module 5 – to issue maps of fishing effort and CPUE; Module 6 – for exploratory data analysis and to extract data from the DB for further use in other computer packages and Module 7 – to recreate the activity of a single vessel, group of vessels or the total fleet, for a fixed period of time. This GIS application, fully developed by programming, has the advantage of being able to be used on its own without any need for external software support. The system developed is a methodological proposal to implement in Portugal, to monitor and manage the trawl fisheries, in particular, the crustacean trawl fishery.

scholarly journals Combining in-trawl video with observer coverage improves understanding of protected and vulnerable species by-catch in trawl fisheries

2014 ◽  
Vol 65 (9) ◽  
pp. 830 ◽  
Author(s):  
Vanessa F. Jaiteh ◽  
Simon J. Allen ◽  
Jessica J. Meeuwig ◽  
Neil R. Loneragan
Keyword(s):  
Video Camera ◽  
Fishing Effort ◽  
Vulnerable Species ◽  
Independent Observer ◽  
Video Footage ◽  
Trawl Fishery ◽  
Scalloped Hammerhead ◽  
Sea Snakes ◽  
By Catch ◽  
Trawl Fisheries

Assessments of incidental wildlife mortality resulting from fishing rarely account for unobserved by-catch. We assessed by-catch of protected and vulnerable wildlife species in an Australian trawl fishery by comparing in-trawl video footage with data collected by an on-board observer. Data were obtained from 44 commercial trawls with two different by-catch reduction devices (BRDs). Eighty-six individuals from six major taxa (dolphins, sharks, rays, sea snakes, turtles and sygnathids) were documented from video analysis, including the endangered scalloped hammerhead shark (Sphyrna lewini) and the critically endangered green sawfish (Pristis zijsron). On the basis of the 2008–2009 fishing effort of 4149 trawls and scaling from these results, we estimated the annual catch of protected and vulnerable species (± 1 s.e.) at 8109 ± 910 individuals. Only 34% of by-catch was expelled through the BRDs. Independent observer data for the 44 trawls showed that 77% of the landed by-catch from these taxa were dead when discarded. The results indicate that unaccounted by-catch in trawl fisheries can be substantial, and that current methods of recording by-catch on-board vessels are likely to underestimate total fishing mortality. We recommend gear modifications and their validation through dedicated observer coverage, combined with in-trawl video camera deployments to improve current approaches to by-catch mitigation.

Multispecies spatial assessment models for the British Columbia groundfish trawl fishery

1999 ◽  
Vol 56 (4) ◽  
pp. 601-628 ◽  
Author(s):  
Carl J Walters ◽  
Ramón Bonfil
Keyword(s):  
British Columbia ◽  
Protected Areas ◽  
Gravity Model ◽  
Marine Protected Areas ◽  
Management Strategies ◽  
Fishing Effort ◽  
Catch Per Unit Effort ◽  
Trawl Fishery ◽  
Spatial Redistribution ◽  
Quota Management

A multispecies spatial model is proposed for evaluation of trawl management strategies and tested with data from British Columbia groundfish. Minimum stock sizes are estimated for 16 species using spatial catch per unit effort data; these data indicate that only small proportions of most stocks are exposed to fishing at any time and that exchange rates of fish between the grounds and other habitats are rapid. A gravity model for spatial effort allocation predicts substantial side effects of marine protected areas or discarding of particular species on nontarget species/grounds due to redistribution of fishing effort. Multispecies, multiground delay-difference models are used in conjunction with the gravity model for spatial effort distribution to predict long-term population responses to various regulatory strategies. This simulation suggests that species composition and spatial structure of the fishery are changing slowly due to reduction in abundance of long-lived species, but rapid collapses of target stocks are unlikely due to spatial redistribution of effort in response to local declines. We question whether quota management (individual vessel quotas) can be safely implemented due to extreme uncertainty about current stock sizes and suggest that a better strategy may be to simply denominate fishing rights as individual effort quotas while providing protection for sensitive stocks through carefully placed marine protected areas.

scholarly journals A framework for mapping small-scale coastal fisheries using fishers' knowledge

2014 ◽  
Vol 71 (7) ◽  
pp. 1781-1792 ◽  
Author(s):  
Marc Léopold ◽  
Nicolas Guillemot ◽  
Delphine Rocklin ◽  
Cheryl Chen
Keyword(s):  
Spatial Information ◽  
New Caledonia ◽  
Fishing Effort ◽  
Marine Conservation ◽  
Geographical Information ◽  
Small Scale ◽  
Catch Per Unit Effort ◽  
Distributed Resources ◽  
Coastal Fisheries ◽  
Promising Source

Abstract Collecting spatial information on fisheries catch and effort is essential to understanding the spatial processes of exploited population dynamics and to manage heterogeneously distributed resources and uses. The use of fishers' knowledge through geographical information systems (GISs) is increasingly considered as a promising source of local information on small-scale coastal fisheries. In this paper we describe the first framework for mapping entire small-scale coastal fisheries using fishers' knowledge on catch size and fishing effort. Four mangrove and coral reef fisheries targeting invertebrates or finfish in New Caledonia (southwest Pacific) were mapped following a five-step framework: (i) stratified random sampling of regular fishers; (ii) collection of fishers' knowledge of fishing areas, fishing effort, and catch size through map-based interviews; (iii) data integration into a spatial geodatabase; (iv) statistical extrapolation of fisher data to the fishery scale; and (v) mapping of catch, effort, and catch per unit effort (CPUE) for each fishery using a GIS overlay procedure. We found evidence that fishers' knowledge supplied precise and accurate quantitative and spatial information on catch size, fishing effort and CPUE for entire fisheries. Fisheries maps captured the fine-scale spatial distribution of fishing activities in a variety of ways according to target taxa, gear type, and home ports. Applications include area-based marine conservation planning and fishery monitoring, management, and governance. This integrated framework can be generalized to a large range of data-poor coastal and inland small-scale fisheries.

scholarly journals Technology-enhanced Learning for Promoting Technical and Social Competences in Hydrological Science

2021 ◽  
Author(s):  
Feliciana Licciardello ◽  
Simona Consoli ◽  
Giuseppe Cirelli ◽  
Carlos Castillo ◽  
Elvira Fernández-Ahumada ◽  
...  
Keyword(s):  
Geographical Information Systems ◽  
English Language ◽  
Teaching Experience ◽  
Geographical Information ◽  
Technology Enhanced Learning ◽  
Technical Knowledge ◽  
Academic Calendar ◽  
The University ◽  
Social Competences ◽  
Enhanced Learning

AbstractThis paper explains and analyses a virtual gamification experience developed by a teaching group from the University of Catania (Italy) and the University of Cordoba (Spain). A competition based on professional tasks about hydrological planning was implemented in two subjects on Hydrological Sciences. The teaching experience was designed to improve the acquisition of technical knowledge and skills needed for hydrological studies, promote the management of ICT and increase international cooperation between different universities; all aimed at making students more employable. The experience is transferable to different academic levels. Following the philosophy of soccer leagues, the students solved and presented the exercise by teams of two students. Through videoconference, the presentation and the explanation were done so the fans in each country supported their teams. The students found it a very challenging experience but at the same time, some of them were aware of their needs of improving technical knowledge, particularly Geographical Information Systems, and English language skills. Updating of tools and the schedule within the different academic calendar were their main organization handicaps. The main outcome of the presented experience is that social energy and enthusiasm associated to popular activities such as soccer led to improve the interest and the motivation of the students in challenging technical contents as well as teamwork and language transversal competences.

scholarly journals Factors affecting relative abundance of low-mobility fishing resources: spiny lobster in the Galapagos Marine Reserve

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e7278 ◽  
Author(s):  
Juan Carlos Murillo-Posada ◽  
Silvia Salas ◽  
Iván Velázquez-Abunader
Keyword(s):  
Monitoring System ◽  
Relative Abundance ◽  
Spatial Scales ◽  
Marine Reserve ◽  
Spiny Lobster ◽  
Fishing Effort ◽  
Additive Models ◽  
Catch Per Unit Effort ◽  
Monthly Basis ◽  
Galapagos Marine Reserve

Management of low-mobility or benthic fisheries is a difficult task because variation in the spatial distribution and population dynamics of the resources make the monitoring and assessment of these fisheries challenging. We assumed that environmental, spatial, and temporal factors can contribute to the variability of the relative abundance of such species; we used Generalized Additive Models for Location Scale and Shape (GAMLSS) to test this hypothesis using as a case study the lobster fishery (targeting two species) in the Galapagos Marine Reserve, Ecuador. We gathered data on each of the two species of lobster on a monthly basis over seven years, including: (a) onboard observers’ records of catch data, fishing effort, and ground location by trip, and (b) data from interviews undertaken with fishers at their arrival to port, recording the same type of information as obtained from onboard observers. We use this information to analyze the effect of the measured variables and to standardize the Catch per Unit Effort (CPUE) in each case, using the GAMLSS. For both species, the temperature, region, fishing schedule, month, distance, and the monitoring system were significant variables of the selected models associated with the variability of the catch rate. ForPanulirus penicillatus, CPUE was higher at night than during the day, and forPanulirus gracilisit was higher during the day. Increased temperature resulted in a decrease of CPUE values. It was evident that temporal, spatial scales and monitoring system can influence the variability of this indicator. We contend that the identification of drivers of change of relative abundance in low-mobility species can help to support the development of monitoring and assessment programs for this type of fisheries.

Fishing on floating objects (FOBs): how French tropical tuna purse seiners split fishing effort between GPS-monitored and unmonitored FOBs

2018 ◽  
Vol 75 (11) ◽  
pp. 1849-1858 ◽  
Author(s):  
Julia E. Snouck-Hurgronje ◽  
David M. Kaplan ◽  
Emmanuel Chassot ◽  
Alexandra Maufroy ◽  
Daniel Gaertner
Keyword(s):  
Search Time ◽  
Fishing Effort ◽  
Purse Seine ◽  
Trajectory Data ◽  
Catch Per Unit Effort ◽  
Position Information ◽  
Foreign Objects ◽  
Tropical Tuna ◽  
Floating Objects ◽  
Over Time

Fishing on floating objects (FOBs) dominates catch in tropical tuna purse seine fisheries. One frequently cited advantage of deploying GPS-monitored FOBs is that the position information can be used for directed fishing to reduce search time for tuna. However, purse seiners also fish on foreign objects for which position information is not available. It is critical to quantify the prevalence of fishing on GPS-monitored versus unmonitored FOBs to understand how they impact fishing effort and catch per unit effort. We analyzed French commercial, observer, and FOB trajectory data in the Atlantic and Indian oceans to determine how often purse seine vessels fish on GPS-monitored FOBs. Only 2.7%–20.4% of French FOB fishing sets over 2007–2013 in both oceans were made on GPS-monitored FOBs. Though increasing over time, the low percentage suggests that French vessels do not primarily use GPS-monitored FOBs to reduce search time for tuna. We hypothesize that fishery-wide FOB deployments have important collective consequences for overall fishing effort and recommend that future effort metrics should be based on fishery-wide FOB activities.

scholarly journals Use of avoidance behaviours to reduce the economic impacts of the EU Landing Obligation: the case study of a mixed trawl fishery

2019 ◽  
Vol 76 (6) ◽  
pp. 1554-1566
Author(s):  
Fabien Pointin ◽  
Fabienne Daurès ◽  
Marie-Joëlle Rochet
Keyword(s):  
Temporal Distribution ◽  
Grid Method ◽  
Fishing Effort ◽  
Economic Losses ◽  
Otter Trawl ◽  
Trawl Fishery ◽  
Nested Grid ◽  
Fishing Practices ◽  
The Eu

Abstract The EU Landing Obligation (LO) is designed to reduce bycatch (i.e. unwanted catch) through more selective fishing practices, such as avoidance behaviours which consist in allocating fishing effort to other species, fishing grounds or seasons. Incentives for fishers to change their behaviours depend on their economic performances as well as their ability to avoid bycatch. Changes in economic performances under the LO are evaluated based on cost and revenue equations. The nested grid method is then used to explore the spatial and temporal distribution of landings and discards, and to suggest alternative effort allocation to avoid bycatch. This article is focussed specifically on the French otter trawl fishery in the eastern English Channel and southern North Sea. Results suggest that under the LO the choke species problem will curtail fishing activities earlier in the year, leading to significant economic losses. In the absence of significant quota top-ups (at least 75%), a change in fishing practices consisting in reducing overall bycatch by 30% is insufficient to reduce losses. With a particular attention to choke species, more economically efficient avoidance strategies can be found thanks to the nested grid method.

Population Dynamics of the Arcto-Norwegian Cod

1967 ◽  
Vol 24 (1) ◽  
pp. 145-190 ◽  
Author(s):  
D. J. Garrod
Keyword(s):  
Gadus Morhua ◽  
Barents Sea ◽  
Fishing Effort ◽  
Catch Per Unit Effort ◽  
Group Iii ◽  
Spawning Stock ◽  
Stock Recruitment ◽  
Post War ◽  
The One ◽  
Definition Of

By reason of its geographical distribution, the Arcto-Norwegian cod (Gadus morhua) supports three distinct fisheries, two feeding fisheries in the Barents Sea and at Bear Island–Spitsbergen, and a spawning fishery off the Norway coast. In the past this diversity of fishing on the one stock has made it difficult to unify all the data to give an overall description of post-war changes in the stock. In this contribution three modifications of conventional procedures are introduced which enable this to be done. These are: (i) a system of weighting the catch per unit effort data from each fishery to a level of comparability; (ii) a more rigorous definition of the effective fishing effort on each age-group; (iii) a method of estimation of the effective fishing effort on partially recruited age-groups.Using these methods the analysis presents the effects of fishing on each fishery in the context of its effect on the total stock, and at the same time it indicates ways in which factors other than fishing may have influenced the apparent abundance of the stock. The treatment of the data is also used to derive estimates of spawning stock and recruitment of 3-year-old cod for subsequent analysis of stock–recruitment relationships.

Relative effects of trap versus trawl fisheries on population dynamics of the northern cod (Gadus morhua) stock

1998 ◽  
Vol 55 (1) ◽  
pp. 76-85 ◽  
Author(s):  
L Fahrig ◽  
S E Pope ◽  
K M Henein ◽  
G A Rose
Keyword(s):  
Population Dynamics ◽  
Gadus Morhua ◽  
Simulation Modelling ◽  
Trawl Fishery ◽  
Trawl Catch ◽  
Stock Biomass ◽  
Northern Cod ◽  
Trap Fishery ◽  
Using Data ◽  
Trawl Fisheries

We compared the effects of the inshore trap and the offshore trawl fisheries on the population dynamics of the northern cod (Gadus morhua) stock using data analyses and simulation modelling. We first statistically characterized the catch versus stock biomass relationships for the two fisheries (1977-1986). We found a significant (P < 0.0001) relationship between the trawl catch at time t and the stock biomass at time t - 2. No temporal lag was evident in the trap catch versus stock biomass relationship. The variability in these two relationships was similar. We then modelled the catch and stock biomass dynamics of the two fisheries in parallel, incorporating the observed catch versus stock biomass relationships, but assuming equal mean catches, to examine the effects on cod population dynamics of the temporal lag and variability in the catch versus stock biomass relationships. The results suggest that, for the same amount of fish taken, a quota-based trawl fishery presents a much greater risk of collapse to the cod stock than does an inshore trap fishery. Current management methods overestimate the "safe" catch for the trawl fishery because they do not incorporate the consequences of the lag in the relationship between stock biomass and trawl catch.

An empirical model of fleet dynamics in New England trawl fisheries

1999 ◽  
Vol 56 (2) ◽  
pp. 253-264 ◽  
Author(s):  
Daniel S Holland ◽  
Jon G Sutinen
Keyword(s):  
New England ◽  
Empirical Model ◽  
Ideal Free Distribution ◽  
Species Group ◽  
Fishing Effort ◽  
Past Behavior ◽  
The Individual ◽  
Choice Of Species ◽  
Fleet Dynamics ◽  
Trawl Fisheries

Regulations and changes in market and environmental conditions that change the profitability of one fishery or area will result in a redistribution of fishing effort among alternative fisheries or areas. The magnitude of this effort displacement will depend on the relative profitability of the alternatives for the individual fishers affected. When fishing areas and fishers are heterogeneous, simple aggregate effort models such as those based on ideal free distribution theory may provide inaccurate predictions. We present an empirical model of individual vessel fishery and location choice based on trip data for a group of over 400 large trawlers fishing in New England. The model uses lagged average revenue rates for different alternatives and the individual vessel's past behavior to predict choice of species group and fishing location on a trip-by-trip basis. This model is used to predict aggregate effort levels in different fisheries and areas over time.

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