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Auteur (up) BROSSET, P.; FROMENTIN, J.-M.; MENARD, F.; PERNET, F.; BOURDEIX, J.-H.; BIGOT, J.-L.; VAN BEVEREN, E.; PEREZ RODIA, M.A.; CHOY, S.; SARAUX, C.
Titre Measurement and analysis of small pelagic fish condition: A suitable method for rapid evaluation in the field Type Article scientifique
Année 2015 Publication Journal Of Experimental Marine Biology And Ecology Revue Abrégée
Volume 462 Numéro Pages 90-97
Mots-Clés Anchovy; Fatmeter; Lipids; Mediterranean Sea; Sardine; Sprat
Résumé As condition is a key variable in population dynamics (especially for survival, growth and reproduction), the use of well-defined and accurate fish condition indices is capital. In particular, condition indices (morphometric, bioenergetic and biochemical) have never been compared and validated for the European anchovy Engraulis encrasicolus, the European pilchard Sardina pilchardus and the European sprat Sprattus sprattus. The accuracy of two indirect methods, the morphometric relative condition index Kn and the bioenergetics index determined with the Distell Fish Fatmeter was investigated by comparing with a direct measure of relative lipid content carried out with a thin layer chromatography-flame ionization detector. Estimations from the fatmeter correlated quite well with the relative lipid contents of all species, regardless of the reproductive period (R2 = 0.69 for anchovy, R2 = 0.75 for sprat and R2 = 0.48 for sardine). Kn correlated more poorly with relative lipid content (R2 = 0.22 for anchovy and R2 = 0.41 for sardine, ns for sprat), especially during the reproductive period, pointing out the difficulty for such an index to precisely reflect changes in fat allocation. During the reproductive period, changes in Kn could reflect other processes, such as changes in protein content. Therefore, these different types of commonly used indices do not reflect exactly the same type of energy stores. The high repeatability of the fatmeter was brought to light, so that only one measurement on each fish side may be necessary to evaluate the relative lipid content of a small pelagic fish. Finally, fatmeter measurements were not affected by freezing storage up to one month for anchovy (R2 = 0.66) and sardine (R2 = 0.90), making it possible to use frozen samples of both commercial and scientific survey. In contrast, the freezing storage for sprat should be avoided. Based on this study, the Fatmeter appears to be a suitable indirect method to assess condition and fat content of sardine and anchovy on a large number of individuals.
Adresse IFREMER, Laboratoire des sciences de l'Environnement Marin, LEMAR, Technopole Brest Iroise, BP 70, 29280 Plouzané, France
Auteur institutionnel Thèse
Editeur Lieu de Publication Éditeur
Langue Langue du Résumé Titre Original
Éditeur de collection Titre de collection Titre de collection Abrégé
Volume de collection Numéro de collection Edition
ISSN 0022-0981 ISBN Médium
Région Expédition Conférence
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ 33741 collection 984
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Auteur (up) Letessier, T.B.; Juhel, J.-B.; Vigliola, L.; Meeuwig, J.J.
Titre Low-cost small action cameras in stereo generates accurate underwater measurements of fish Type Article scientifique
Année 2015 Publication Journal of Experimental Marine Biology and Ecology Revue Abrégée
Volume 466 Numéro Pages 120-126
Mots-Clés Body size; Length; Monitoring; Stereo-photogrammetry; Videography
Résumé Abstract

Small action cameras have received interest for use in underwater videography because of their low-cost, standardised housing, widespread availability and small size. Here, we assess the capacity of GoPro action cameras to provide accurate stereo-measurements of fish in comparison to the Sony handheld cameras that have traditionally been used for this purpose. Standardised stereo-GoPro and Sony systems were employed to capture measurements of known-length targets in a pool to explore the influence of the type of camera, distance to camera rig, angle to the optical axis and target speed on measurement accuracy. The capacity to estimate fish length in situ was also compared by measuring the same fish on a coral reef with two baited remote underwater video systems, each fitted with both a GoPro and a Sony camera system. Pool trials indicated that the GoPros were generally less accurate than the Sonys. Accuracy decreased with increased angles and distance for both systems but remained reasonably low (< 7.5%) at 5 m distance and 25° angle for GoPros. Speed of target movement did not result in any consistent decrease in accuracy. In situ measurements revealed a strong correlation (R2 = 0.94) between Sony and GoPro length measurements of the same individual fish, with a slope not different from 1 and an intercept not different from 0, suggesting that GoPro measurement errors do not result in a consistent bias at the level of individual fish. Moreover, the investigation of kernel density functions of the length distribution of the entire fish assemblage indicated that difference in measurement accuracy becomes negligible for purposes of comparing population size structure. We suggest a measurement protocol for the use of GoPro stereo-camera systems that improves accuracy, where distance to target is limited to 5 m and angle to optical axis is restricted to 25°. For distances up to 7 m, angles should be restricted to 15°. This protocol supports the use of small action cameras such as the GoPro system, providing reductions in cost and increases in effective sampling efforts, compared with traditional rigs based on relatively expensive handheld cameras.
Adresse
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Editeur Lieu de Publication Éditeur
Langue Langue du Résumé Titre Original
Éditeur de collection Titre de collection Titre de collection Abrégé
Volume de collection Numéro de collection Edition
ISSN 0022-0981 ISBN Médium
Région Expédition Conférence
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Numéro d'Appel MARBEC @ alain.herve @ collection 1315
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Auteur (up) VAN BEVEREN, E.; BONHOMMEAU, S.; FROMENTIN, J.-M.; BIGOT, J.-L.; BOURDEIX, J.-H.; BROSSET, P.; ROOS, D.; SARAUX, C.
Titre Rapid changes in growth, condition, size and age of small pelagic fish in the Mediterranean Type Article scientifique
Année 2014 Publication Marine Biology Revue Abrégée
Volume 161 Numéro 8 Pages 1809-1822
Mots-Clés
Résumé Since 2007, the ecosystem of the Gulf of Lions has shifted to a different regime, characterised by a low anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) biomass and a remarkably high sprat (Sprattus sprattus) biomass. Surprisingly, the abundance and recruitment of anchovy and sardine remained high. To understand which processes (bottom-up or top-down control, etc.) could have caused this shift, we studied the changes in body condition, growth and size and age of anchovy, sardine and sprat over 1984–1985 and 1992–2012, using data from scientific surveys. The annual age structure of anchovy and sardine was estimated using Bayesian mixture models based on size frequency data with priors on the age–length relationship derived from independent otolith readings. The results indicated periods during which anchovy and sardine were in an average (1992–2004), good (2005–2007) or poor (2008–2012) overall state of condition. For sardine, the shift towards smaller fish observed during these past 4 years was explained by a combination of slower growth and the disappearance of older individuals (ages 2+). Despite the increase in biomass of sprat since 2008, indications were found that sprat was also smaller than in the past. As growth and condition decreased and overexploitation has not been documented or suspected for those three species in this area, we propose that the current decline in sardine and anchovy biomass could be due to qualitative and/or quantitative modifications in the planktonic production (i.e. a bottom-up control) or mass mortalities of adults due to an epidemic disease.
Adresse Univ Montpellier 2, Res Unit EME UMR 212, F-34203 Sete, France.
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Editeur Springer Lieu de Publication Éditeur
Langue Langue du Résumé Titre Original
Éditeur de collection Titre de collection Titre de collection Abrégé
Volume de collection Numéro de collection Edition
ISSN 0025-3162 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ 30335 collection 986
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