Ziel
The north Atlantic albacore (Thunnus alalunga) has been exploited since the beginning of the century. Spanish and French fisheries are the oldest ones and exploit the juvenile part of the stock during its migration off and inside the Bay of Biscay. Asiatic fisheries have exploited, from the early fifties to the present period, the adult part of the stock on its reproduction and wintering areas in the south and north Atlantic.
Troll, bait boat and longline fisheries have been monitored for a long time. The introduction of 2 fishing techniques (driftnet and pair pelagic trawl), if increased, is going to change the fishing pattern and it appears that new and precise data and parameters are needed for stock assessment (ICCAT, 1990). Among these parameters it appears essential to know mean length at age and its standard deviation for each age group and both sexes as until now approximations of age at length were considered as sufficient. Possibilities of extension of the new gears cannot be monitored with approximated parameters.
The present study is based on existing competency and will intensify, during the above defined period, the research on albacore growth, using adapted sampling methods and image analysis for growth reading on hard parts (mainly dorsal fin rays).
The north Atlantic albacore, is exploited by Spanish and French fleets during its migration off and in the bay of Biscay. Recent trends of changing fishing patterns makes it necessary to develop more precise knowledge of population parameters for stock assessment. Growth is one of the most important parameter. It is expected that an accurate determination of age composition of the catch will increase stock evaluation and assessment. Ageing is based on reading cross sections of hard parts and particularly dorsal fin rays. Samples have been collected during the finishing campaign of the surface fishery, and prepared in order for analysis by automatic reading software to be developed and based on image analysis. Rayon Epineux de la Nageoire Dorsale (REND's) of Thunnus alalunga (north atlantic albacore) have been sampled on the Spanish bait boats and trollers and the French trawlers on landing. 856 slices have been prepared by the Instituto Espanol de Oceanografia (IEO) and the Instituto de investigacion y tecnologia para la oceanografia pesca y alimentacion (AZTI-SIO), for the purpose of this work. An image processing software Traitement Numerique des Pieces Calcifiees (TNPC) has been designed and programmed by IFREMER and used for the reading of the REND's. This interactive software allows the input of biological constraints, such as a growth pattern, in the signal processing. The periodicity of the rings is analyzed under growth constraints and an age length key is proposed. The introduction of a growth pattern in the image processing allows to take into account a dynamic link between the structures and shows that very few rings might be interpreted as doublets after an age of 4. The algorithm allows a better understanding of the periodicity and automates the back calculation operations requested for the adjustment of the first visible ring. Although the software integrates information on a region of interest, an operator is still requested for the reading in 40% to 50% of the cases. The comparison of the results of the image readings with those of the IEO shows the persistence of a difference in the interpretation of the age at the first ring. This lack of biological knowledge shows the need for more research on the larval and juvenile stage development of Thunnus alalunga.
The research work will be divided into 4 phases in which both partners will be engaged.
Phase 1 is perfecting the sampling strategy. This phase will take place before the beginning of the fishing season of the year 1991. The coordinator and other contractor (IEO) will meet and organise a common sampling strategy which will combine length frequency sampling in harbours and subsampling for hard parts for age reading. It will be very important to take note of the different fishing pattern of each fishing gear and, particularly, bait boat and midwater trawl which are known to fish large animals (age equal to or more than 5 years). In respect of the problem of getting a large fish sample, contact will be made with Taiwanese scientists to obtain samples.
Phase 2 is the sampling activity. Each partner will take care of sampling for the above mentioned strategy. Sampling teams will already be active as length frequency data are regularly collected for ICCAT databases. The additional work of sampling hard parts should not intensify greatly the work of the sampling teams.
Phase 3 is preparing samples and developing software. Each laboratory will prepare samples following existing methods. Cross sections of dorsal fin rays will be referred in a file to be exchanged between labs and to be studied by image analysis. Image analysis will be performed in Ifremer laboratory, Brest. Preparation of software for automatic objective reading of the number of rings on dorsal fin ray slices and deducing the age of the fish will be the major part of the work in this study. Reading the age is until now made by eye on a microscopic analogic image. The software will work on a numerised image and will calculate and then validate the age of the fish. This kind of method is working for simple pieces such as otholiths from sole larvae.
Phase 4 is the calculation, application and report. This phase will be an application of the image analysis programme to the various samples collected by the different teams and sent to Brest. Comparisons and calibrations will be made with the different participants involved in the contract. Age computation will be done and compared to different previous age and growth estimations.
Wissenschaftliches Gebiet (EuroSciVoc)
CORDIS klassifiziert Projekte mit EuroSciVoc, einer mehrsprachigen Taxonomie der Wissenschaftsbereiche, durch einen halbautomatischen Prozess, der auf Verfahren der Verarbeitung natürlicher Sprache beruht. Siehe: Das European Science Vocabulary.
CORDIS klassifiziert Projekte mit EuroSciVoc, einer mehrsprachigen Taxonomie der Wissenschaftsbereiche, durch einen halbautomatischen Prozess, der auf Verfahren der Verarbeitung natürlicher Sprache beruht. Siehe: Das European Science Vocabulary.
- Agrarwissenschaften Landwirtschaft, Forstwirtschaft und Fischerei Fischerei
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- Naturwissenschaften Informatik und Informationswissenschaften Datenbank
- Technik und Technologie Elektrotechnik, Elektronik, Informationstechnik Elektrotechnik Signalverarbeitung
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Aufforderungen zur Einreichung von Vorschlägen sind nach Themen gegliedert. Ein Thema definiert einen bestimmten Bereich oder ein Gebiet, zu dem Vorschläge eingereicht werden können. Die Beschreibung eines Themas umfasst seinen spezifischen Umfang und die erwarteten Auswirkungen des finanzierten Projekts.
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Finanzierungsregelung (oder „Art der Maßnahme“) innerhalb eines Programms mit gemeinsamen Merkmalen. Sieht folgendes vor: den Umfang der finanzierten Maßnahmen, den Erstattungssatz, spezifische Bewertungskriterien für die Finanzierung und die Verwendung vereinfachter Kostenformen wie Pauschalbeträge.
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Koordinator
29280 PLOUZANE
Frankreich
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