Bycatch of the European purse-seine tuna fishery in the Atlantic Ocean for the period 2010-2016

This paper presents an update for the period 2010-2016 of the bycatch estimations for the European tuna purse seine fishery operating in the Atlantic Ocean. Bycatch data were collected by observers onboard. Observer coverage increased progressively from 15 trips in 2010, to 114 and 107 trips in 2015 and 2016 respectively. Bycatch data, as collected by the observers, were stratified by quarter and fishing mode (free school and floating object sets). The ratio of total to observed catches of the target species (skipjack, bigeye and yellowfin tunas) in each stratum was then used as raising factor. The average of the annual total bycatch estimated for the studied period was 9,515 t. Tunas (neritic tunas and small size tunas) represent the major part of the bycatch, followed by fin fish, sharks, billfishes, rays and turtles.En prens

In support of the IOTC ecosystem report card: Advances in monitoring the impacts on and the state of the “foodweb and trophic relationships” ecosystem component

In support of the development of the ICCAT Ecosystem Report Card, this paper addresses the “foodweb/trophic relationships” ecosystem component. Specifically, it contributes towards developing the following elements: (1) we describe what this component means in the context of ICCAT species and fisheries and the importance of monitoring it; (2) we describe the role of ecological indicators and ecosystem models in monitoring this ecosystem component; (3) we present a list of candidate ecological indicators that could be estimated to monitor this component; (4) we discuss the main challenges in monitoring this ecosystem component and indicator development; and finally (5), we draft a work plan to guide our future work. We invite the ICCAT community and others to contribute towards the development of ecological indicators and ecosystem models to monitor this ecosystem component. If interested, contact the corresponding authors to find out how you can contribute to this initiative

In support of the ICCAT ecosystem report card: advances in monitoring the impacts on and the state of the “foodweb and trophic relationships” ecosystem component.

In support of the development of the ICCAT Ecosystem Report Card, this paper addresses the “foodweb/trophic relationships” ecosystem component. Specifically, it contributes towards developing the following elements: (1) we describe what this component means in the context of ICCAT species and fisheries and the importance of monitoring it; (2) we describe the role of ecological indicators and ecosystem models in monitoring this ecosystem component; (3) we present a list of candidate ecological indicators that could be estimated to monitor this component; (4) we discuss the main challenges in monitoring this ecosystem component and indicator development; and finally (5), we draft a work plan to guide our future work. We invite the ICCAT community and others to contribute towards the development of ecological indicators and ecosystem models to monitor this ecosystem component. If interested, contact the corresponding authors to find out how you can contribute to this initiative.Versión del editor

Toothed whale and shark depredation indicators : a case study from the Reunion Island and Seychelles pelagic longline fisheries

Depredation in marine ecosystems is defined as the damage or removal of fish or bait from fishing gear by predators. Depredation raises concerns about the conservation of species involved, fisheries yield and profitability, and reference points based on stock assessment of depredated species. Therefore, the development of accurate indicators to assess the impact of depredation is needed. Both the Reunion Island and the Seychelles archipelago pelagic longline fisheries targeting swordfish (Xiphias gladius) and tuna (Thunnus spp.) are affected by depredation from toothed whales and pelagic sharks. In this study, we used fishery data collected between 2004 and 2015 to propose depredation indicators and to assess depredation levels in both fisheries. For both fisheries, the interaction rate (depredation occurrence) was significantly higher for shark compared to toothed whale depredation. However, when depredation occurred, toothed whale depredation impact was significantly higher than shark depredation impact, with higher depredation per unit effort (number of fish depredated per 1000 hooks) and damage rate (proportion of fish depredated per depredated set). The gross depredation rate in the Seychelles was 18.3%. A slight increase of the gross depredation rate was observed for the Reunion Island longline fleet from 2011 (4.1% in 2007-2010 and 4.4% in 2011-2015). Economic losses due to depredation were estimated by using these indicators and published official statistics. A loss of 0.09 EUR/hook due to depredation was estimated for the Reunion Island longline fleet, and 0.86 EUR/hook for the Seychelles. These results suggest a southward decreasing toothed whale and shark depredation gradient in the southwest Indian Ocean. Seychelles depredation levels are among the highest observed in the world revealing this area as a "hotspot" of interaction between pelagic longline fisheries and toothed whales. This study also highlights the need for a set of depredation indicators to allow for a global comparison of depredation rates among various fishing grounds worldwide

UE - France. Rapport national destiné au Comité scientifique de la Commission des thons de l’océan Indien, 2011-2012 Commission des thons de l’océan Indien, 2015

Pour ce qui concerne la France en incluant dorénavant le département de Mayotte, rattaché à la flotte de l’UE depuis le 1er janvier 2014, cinq flottilles ont des activités de pêche thonière dans l'océan Indien : - les senneurs opérant pour l’essentiel à partir des Seychelles et de l’Ile Maurice, - les palangriers basés à La Réunion, les palangriers basés à Mayotte, et à un moindre degré les pêches artisanales réunionnaise - La flottille thonière française à la senne exerçant dans l’océan Indien atteint 13 navires en 2014 et ses capture se sont élevées à 58 421 tonnes, soit un niveau largement supérieur à celui de 2013 (39958 t) en lien avec une augmentation de l’effort de pêche de 2 291 jours de pêche en 2013 à 3756 jours en 2014. Le programme observateur mis en place depuis 2005, qui a permis de fournir les premières évaluations des rejets et des prises accessoires en 2008, a du être stoppé mi 2009 pour raison de sécurité, face au développement de la piraterie, puis faute de place disponible à bord car des forces de sécurité ont du être embarquées. Ce programme a repris en 2011 a été complété en 2014 par le programme OCUP (Observateur Commun Unique et Permanent) mis en place par Orthongel ce qui a permis d’atteindre un taux de couverture de l’observation des activités de la pêcherie française à la senne de 33%. - La flottille palangrière basée à La Réunion se compose en 2014 de 35 navires actifs, 22 entre 10 et 24 mètres et 13 de moins de 10 mètres. Les captures totales de la partie hauturière de cette flottille (plus de 10m) ont augmenté entre 2013 et 2014, en passant de 1834 tonnes à 2027 tonnes. Si l’espadon (Xiphias gladius) reste l’espèce cible, la part des autres espèces de thons (Thunnus albacares, l’albacore, Thunnus obesus, le thon obèse, et Thunnus alalunga, le germon) est loin d’être négligeable (pourcentage situé entre 41 et 53% selon les années). Le programme « observateur » des activités de cette flottille a démarré en 2007, avec un taux de couverture global d’environ 4% en 2009 et 2010 et de l’ordre de 10 % pour ces mêmes années pour le segment des unités de plus de 20 m suivi par les observateurs embarqués. A partir de 2011, un programme d’auto échantillonnage a été mis en place principalement sur les 2 segments des unités de tailles comprises entre 10 m et 16 m d’une part et 16 m et 20 m d’autre part. En cumulant l’effort de pêche exprimé en nombre d’hameçons suivi par ces 2 programmes, le taux de couverture de l’activité de pêche a été estimé à 13,66 % en 2014 soit proche du niveau de 14,18% atteint en 2013. - La petite pêche côtière réunionnaise exploitant les métiers de la ligne à main représente plus de 80 % du nombre de bateaux de pêche réunionnais actifs. Avec 152 bateaux actifs en 2014, elle a peu évolué ces dernières années et est composée de deux types d’embarcations : les barques faiblement motorisées (inférieur à 6 m, 80 navires actifs en 20143) et les vedettes, plus puissantes (6 – 12 m, 72 navires actifs en 2014). La plupart de ces navires pratiquent les métiers de la ligne (lignes de traîne, de fond, calées ou dérivantes). Les captures de grands pélagiques représentent une part importante des captures de cette flottille et sont estimées à 610 tonnes en 2014. - La flottille palangrière mahoraise est composée en 2014 de 6 navires actifs ciblant l’espadon et le thon à la palangre horizontale dérivante. Ces navires ont débarqué 94t en 2014, ce qui constitue une progression régulière depuis 2006, liée à l’augmentation du nombre de navires actifs. Les rendements par filage sont cependant en nette diminution pour atteindre 260 kg/filage, - La petite pêche côtière mahoraise représente 140 barques de pêche professionnelle qui côtoient près de 300 navires non-homologués en pêche professionnelle mais exerçant une activité de pêche vivrière à stratégie très similaire, ainsi que 750 pirogues à balanciers. 120 navires, dont une majorité de professionnels, pratiquent la pêche à la traîne ou la palangrotte sur DCP afin de capturer des espèces pélagiques, parfois en alternance avec d’autres types de pêche ciblant les poissons de récifs. Les principales espèces de poissons pélagiques ciblés sont la bonite à ventre rayé (Katsuwonus pelamis), le thon albacore (Thunnus albacares), le thon obèse (Thunnus obesus) et le thon blanc (Thunnus alalunga). Bien que les données précises pour cette flottille ne soient pas encore produites, on estime grossièrement la production totale de la petite pêche mahorais à environ 2000t/an, dont une la moitié de poissons pélagiques. Le dispositif de recherche sur les grands pélagiques actuel de la France (IRD & Ifremer principalement) couvre des activités de type observatoire, l’étude des comportements migratoires des grands pélagiques, des études génétiques pour la délimitation des stocks, des études sur la biologie de la reproduction, la mise au point de mesures d’atténuations des prises accessoires et l’étude de la dynamique de l’écosystème tropical. La plupart des projets sont financés sur appels d’offre internationaux, européens ou nationaux. On trouvera dans le rapport la liste des différents projets qui se sont poursuivis ou ont débuté en 2014-2015. Dans l’ensemble, la France a participé activement à tous les groupes de travail organisés par la CTOI, et a présenté 21 contributions scientifiques en 2014. Une dernière, la 22ème sera présentée lors du 18ème Comité Scientifique qui se tiendra à Bali du 23 au 27 Novembre 2015. Noter que J. Bourjea et E. Chassot ont présidé les groupes de travail « Poissons porte épée » et « Collecte des données et Statistiques », respectivement

Lacunae rostralis A new structure on the rostrum of sailfish Istiophorus platypterus

Recent comparative studies of billfishes Istiophoridae and Xiphiidae have provided evidence of differences in the form and function of the rostra bill among species. Here, we report the discovery of a new structure, lacuna rostralis, on the rostra of sailfish Istiophorus platypterus, which is absent on the rostra of swordfish Xiphias gladius, striped marlin Kajikia audax and blue marlin Makaira nigricans. The lacunae rostralis are small cavities that contain teeth. They were found on the ventral rostrum surface of all I. platypterus specimens examined and dorsally in half of them. Ventrally, the lacunae rostralis were most prominent in the mid section of the rostrum. Dorsally, they occurred closer to the tip. The density of lacunae rostralis increased towards the rostrum tip but, because they are smaller in size, the percentage of rostrum coverage decreased. The teeth located within the lacunae rostralis were found to be different in size, location and orientation from the previously identified micro teeth of billfish. We propose two potential functions of the lacunae rostralis that both relate to the use of the bill in feeding mechanoreception of prey before tapping it with the bill and more efficient prey handling via the creation of suction, or physical gri

Injury-mediated decrease in locomotor performance increases predation risk in schooling fish.

The costs and benefits of group living often depend on the spatial position of individuals within groups and the ability of individuals to occupy preferred positions. For example, models of predation events for moving prey groups predict higher mortality risk for individuals at the periphery and front of groups. We investigated these predictions in sardine (Sardinella aurita) schools under attack from group hunting sailfish (Istiophorus platypterus) in the open ocean. Sailfish approached sardine schools about equally often from the front and rear, but prior to attack there was a chasing period in which sardines attempted to swim away from the predator. Consequently, all sailfish attacks were directed at the rear and peripheral positions of the school, resulting in higher predation risk for individuals at these positions. During attacks, sailfish slash at sardines with their bill causing prey injury including scale removal and tissue damage. Sardines injured in previous attacks were more often found in the rear half of the school than in the front half. Moreover, injured fish had lower tail-beat frequencies and lagged behind uninjured fish. Injuries inflicted by sailfish bills may, therefore, hinder prey swimming speed and drive spatial sorting in prey schools through passive self-assortment. We found only partial support for the theoretical predictions from current predator-prey models, highlighting the importance of incorporating more realistic predator-prey dynamics into these models.This article is part of the themed issue 'Physiological determinants of social behaviour in animals'

Linking hunting weaponry to attack strategies in sailfish and striped marlin

Linking morphological differences in foraging adaptations to prey choice and feeding strategies has provided major evolutionary insights across taxa. Here, we combine behavioural and morphological approaches to explore and compare the role of the rostrum (bill) and micro-teeth in the feeding behaviour of sailfish (Istiophorus platypterus) and striped marlin (Kajikia audax) when attacking schooling sardine prey. Behavioural results from high-speed videos showed that sailfish and striped marlin both regularly made rostrum contact with prey but displayed distinct strategies. Marlin used high-speed dashes, breaking schools apart, often contacting prey incidentally or tapping at isolated prey with their rostra; while sailfish used their rostra more frequently and tended to use a slower, less disruptive approach with more horizontal rostral slashes on cohesive prey schools. Capture success per attack was similar between species, but striped marlin had higher capture rates per minute. The rostra of both species are covered with micro-teeth, and micro-CT imaging showed that species did not differ in average micro-tooth length, but sailfish had a higher density of micro-teeth on the dorsal and ventral sides of their rostra and a higher amount of micro-teeth regrowth, suggesting a greater amount of rostrum use is associated with more investment in micro-teeth. Our analysis shows that the rostra of billfish are used in distinct ways and we discuss our results in the broader context of relationships between morphological and behavioural feeding adaptations across species

Oil gland and oil pores in billfishes: in search of a function

Billfishes are well known for their distinctive elongated rostra, i.e. bills. The functional significance of billfish rostra has been frequently discussed and the recent discovery of an oil gland (glandula oleofera) at the base of the rostrum in swordfish, Xiphias gladius, has added an interesting facet to this discussion regarding the potential co-evolution of gland and rostra. Here, we investigated the oil gland and oil pores (through which the oil is brought to the skin surface) of four billfish species – swordfish, Atlantic blue marlin (Makaira nigricans), Indo-Pacific sailfish (Istiophorus platypterus) and striped marlin (Kajikia audax) – and provide detailed evidence for the presence of an oil gland in the last three. All four species had a high density of oil pores on the forehead which is consistent with the hypothesis of hydrodynamic benefits of the oil. The extension of the pores onto the front half of the rostrum in sailfish and striped marlin, but not in swordfish or blue marlin, suggests that the oil may have additional functions. One such function could be linked to the antibacterial and anti-inflammatory properties of the oil. However, the available evidence on predatory rostrum use (and hence the likelihood of tissue damage) is only partly consistent with the extension of pores on rostra across species. We conclude that the oil gland probably serves multiple, non-mutually exclusive functions. More detailed information on rostrum use in blue marlin and swordfish is needed to better link behavioural and morphological data with the aim of accomplishing a full comparative analysis