Analyses of the Sex Ratio for Bullet Tuna, Atlantic Bonito and Little Tunny from Portuguese and Spanish Waters

Event Abstract Back to Event Analyses of the sex ratio for bullet tuna, Atlantic bonito and little tunny from Portuguese and Spanish waters Samar Saber1*, Josetxu Ortiz De Urbina1, Pedro G. Lino2, María José Gómez-Vives1, Lola Godoy1, Rui Coelho2, Cristina Ciércoles1, Rubén Muñoz-Lechuga2 and David Macías1 1 Oceanographic Center of Málaga, Spanish Institute of Oceanography (IEO), Spain 2 Estação Piloto de Piscicultura de Olhão, Instituto Português do Mar e Atmosfera, Portugal INTRODUCTION The small tuna species Auxis rochei (bullet tuna), Sarda sarda (Atlantic bonito) and Euthynnus alletteratus (little tunny) are widely distributed in Atlantic and Mediterranean waters. Although these species have a high socio-economic relevance for a considerable number of local communities at the regional level, the status of these fish stocks is unknown. Information on life history traits should be considered to develop realistic models to assess fish stocks; these models could then be used as the basis for the sustainable exploitation, management, and conservation of fish species. Sex ratio can be male- or female-biased with increasing length or age. In general males of marine fish species predominate in small length classes while females predominate in the large ones. However in species of the genus Thunnus, which are large tunas, males are more numerous in the larger length classes. Bullet tuna and Atlantic bonito from the Iberian Peninsula are belong to the same populations (Ollé et al., 2017., Viñas et al., in press), whereas no genetic studies have been addressed for little tunny. The aim of this study is to analyse the sex ratio for the three mentioned small tuna in the western Mediterranean Sea and Atlantic margin of south Iberian Peninsula. MATERIAL AND METHODS Individuals of bullet tuna, Atlantic bonito and little tunny were collected from 32 localities throughout the Mediterranean Sea (Spanish coast) and Atlantic Ocean (south of the Iberian Peninsula) between 2003 and 2017 (Figure 1). The individuals of the three species were caught by both commercial and recreational fisheries. Fork length (FL) was measured either to the nearest 0.1 cm (when fish was measured in the lab or at landings) or to the nearest 0.5 cm (fish measured on board). A total of 3929 fish (bullet tuna, 1280; Atlantic bonito, 1388; little tunny, 1261) were sampled. The sex was identified and classified as male, female and undetermined (individuals with small gonads, which sex cannot be identified visually) (Table 1). Sex ratio was calculated as the proportion of females by 2 cm FL class. The observed female proportions by length class were modelled by means of a binomial generalised linear model (GLM). Statistical differences between length classes were assessed by means of the chi-square test. RESULTS A total of 186 bullet tuna were classified as undetermined. The size of males ranged between 26.0 and 48.7 cm FL (n = 540) and females ranged between 24.0 and 47.5 cm FL (n = 554). Significant differences in the proportion of females were found between length classes (χ2 = 23.54, df = 12, p = 0.02). The sex ratio was 1:1 in the length class group between 34 and 36 cm FL. Females predominated in length class less than 26 cm FL. The analysis of the predicted sex-ratio by length showed a trend of abundance of males in the larger length classes (Figure 2a). A total of 197 Atlantic bonito were classified as undetermined. The size of males ranged between 25.6 and 79.3 cm FL (n = 520) and females ranged between 23.9 and 71.0 cm FL (n = 671). Significant differences in the proportion of females were found between length classes (χ2 = 39.87, df = 23, p = 0.02). The analysis showed that females predominated in almost all of the length class groups. The sex ratio was 1:1 in the length class group between 40 and 42 cm FL. Predicted sex-ratio by length is shown in (Figure 2b). A total of 384 little tunny were classified as undetermined. Two intersex fish were sampled in the trap located in Mazarrón (for details, see Macías et al., 2014). The size of males ranged between 30.6 and 101.0 cm FL (n = 414) and females ranged between 28.5 and 99.0 cm FL (n = 461). Significant differences in the proportion of females were found between length classes (χ2 = 73.49, df = 36, p = 0.0002). The analysis showed that males were more abundant in the larger length classes (> 96 cm FL). Predicted sex-ratio by length is shown in (Figure 2c). CONCLUSIONS Females predominated in small length classes; however, this result should be considered with caution because for the smallest fish (i.e. fish with tiny gonads), the ovaries are easier identified than testes. The analysis of sex ratio by length for both bullet tuna and little tunny indicated that females predominated in the smaller length classes and males in the larger length classes. Specifically, for the Atlantic bonito the trend showed that were consistently more females than males across all sizes classes. Figure 1 Figure 2 Figure 3 Figure 4 Acknowledgements We are grateful to all fishermen for their collaboration during the samplings. We also thank the effort of the scientific observers. This work has been carried out within the framework of the ICCAT small tunas year research program. This work has been co-funded by the IEO and the EU through the European Maritime and Fisheries Fund within the National Program of collection, management and use of data in the fisheries sector and support for scientific advice regarding the Common Fisheries Policy. References Macías D., Saber S., Osuna A., Cruz-Castán R., Gómez-Vives M. J., Báez J.C., 2014. First record of intersexuality in Euthynnus alletteratus (Rafinesque 1810) in the Mediterranean Sea: histological description. Marine Biodiversity Records 7, 1–3. Ollé J., Pérez-Bielsa N., Allaya H., Saber S., Macías D., Viñas J. 2017. Implications for fishery management in small tunas the case of genetic population structure of bullet tuna in the west Mediterranean. Collective Volume of Scientifics Papers ICCAT, 74(1): 121–127. Viñas et al., 2019 in press. Report for the short-term contract for ICCAT SMTYP for the biological samples collection for growth, maturity and genetics studies. ICCAT, SCRS/2019/105. Keywords: Sex ratio, Auxis rochei, Sarda sarda, Euthynnus alletteratus, Western Mediterranean, Atlantic Ocean Conference: XX Iberian Symposium on Marine Biology Studies (SIEBM XX) , Braga, Portugal, 9 Sep - 12 Sep, 2019. Presentation Type: Oral Presentation Topic: Fisheries, Aquaculture and Biotechnology Citation: Saber S, Ortiz De Urbina J, Lino P, Gómez-Vives M, Godoy L, Coelho R, Ciércoles C, Muñoz-Lechuga R and Macías D (2019). Analyses of the sex ratio for bullet tuna, Atlantic bonito and little tunny from Portuguese and Spanish waters. Front. Mar. Sci. Conference Abstract: XX Iberian Symposium on Marine Biology Studies (SIEBM XX) . doi: 10.3389/conf.fmars.2019.08.00195 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 20 Sep 2019; Published Online: 27 Sep 2019. * Correspondence: Mx. Samar Saber, Oceanographic Center of Málaga, Spanish Institute of Oceanography (IEO), Málaga, Spain, samar.saber@ieo.es Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract Supplemental Data The Authors in Frontiers Samar Saber Josetxu Ortiz De Urbina Pedro G. Lino María José Gómez-Vives Lola Godoy Rui Coelho Cristina Ciércoles Rubén Muñoz-Lechuga David Macías Google Samar Saber Josetxu Ortiz De Urbina Pedro G. Lino María José Gómez-Vives Lola Godoy Rui Coelho Cristina Ciércoles Rubén Muñoz-Lechuga David Macías Google Scholar Samar Saber Josetxu Ortiz De Urbina Pedro G. Lino María José Gómez-Vives Lola Godoy Rui Coelho Cristina Ciércoles Rubén Muñoz-Lechuga David Macías PubMed Samar Saber Josetxu Ortiz De Urbina Pedro G. Lino María José Gómez-Vives Lola Godoy Rui Coelho Cristina Ciércoles Rubén Muñoz-Lechuga David Macías Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.