Rays in bottom trawling and trammel nets in south western European waters: discards, survivability and implications for the application of the landing obligation
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1
Oceanographic Center of Vigo, Spanish Institute of Oceanography, Spain
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2
Other, Spain
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3
Department of Sea, Regional Government of Galicia, Spain
We present the results of a study to investigate the survivability of rays caught by bottom trawlers and trammel nets in northern Spanish waters. Trials were carried out to evaluate the survival rates of rays that would be discarded since they are too small or not the target of the fishery. The trials consisted of: (a) an assessment of the vitality of the individuals brought on board and (b) a long-term study of survival after capture in the lab (to where the animals caught were transported).
Our results indicate that ca 93.5% and 100%, respectively, of the sampled rays captured by bottom trawlers and trammel nets survive the fishing operation and handling onboard. For bottom trawls, 62.8% of the thornback rays (Raja clavata) and 80% of the cuckoo rays (Leucoraja naevus) were recorded as in 'Poor' health condition. Estimated survival at medium term was 58% (47.7-69.9) and 17% (10.1-27.4) at the end of the observed period (one month). Trammel nets captured four species: the thornback ray, the spotted ray (Raja montagui), the small-eye skate (Raja microocellata) and the undulate ray (Raja undulata). 12.9% of rays were recorded as in 'Poor' health condition. Estimated survival at medium term was 100% and it was 73% (56.3-93.9) at the end of the observed period (one month). Thornback ray scored the lower survivability (33.3%), spotted ray intermediate (83.3%) and all undulate ray survived the trial without mortality events.
Our trials represent the first study of this type in the area and by, helping to quantify the survivability of the ray species analysed, support the granting of the discard exemption to these fisheries, as included in Article 15 of the Common Fisheries Policy (the so called Landing Obligation).
Acknowledgements
We would like to thank scientist, skippers and crew of RV Miguel Oliver, FV Ensenada de Bueu, FV Chapeliño and FV Portosanto for kindly collaborate during IEO samplings by observers onboard. Thanks to OPROMAR, Federación Galega de Confrarías de Pesca, Dirección Xeral de Pesca, Acuicultura e Innovación Tecnolóxica and Dirección Xeral de Desenvolvemento Pesqueiro (Xunta de Galicia). This work was made within the DESCARSEL Project financed by and European Maritime and Fisheries Funds (EMFF).
Keywords:
Fisheries,
Rays (Fish),
landing obligation,
discards management,
Survivability analysis
Conference:
XX Iberian Symposium on Marine Biology Studies (SIEBM XX) , Braga, Portugal, 9 Sep - 12 Sep, 2019.
Presentation Type:
Poster Presentation
Topic:
Fisheries, Aquaculture and Biotechnology
Citation:
Valeiras
J,
Álvarez-Blázquez
B,
Velasco
E,
Abad
E,
Barreiro
M,
Lluch
N,
Cordeiro
G,
Neira
JA,
Otero
A and
Santos
MB
(2019). Rays in bottom trawling and trammel nets in south western European waters: discards, survivability and implications for the application of the landing obligation.
Front. Mar. Sci.
Conference Abstract:
XX Iberian Symposium on Marine Biology Studies (SIEBM XX) .
doi: 10.3389/conf.fmars.2019.08.00182
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Received:
19 May 2019;
Published Online:
27 Sep 2019.
*
Correspondence:
Dr. Julio Valeiras, Oceanographic Center of Vigo, Spanish Institute of Oceanography, Vigo, Spain, julio.valeiras@ieo.csic.es