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Trophic ecology of young of the year Alboran Sea bluefin tuna (Thunnus thynnus) and Atlantic bonito (Sarda sarda) by stable isotope analyses

Ignacio Baro1, Amaya Uriarte2, Salvador García-Barcelona3, Maria Jose Gomez-Vives3, Samar Saber1, Jose M. Quintanilla2, Raul Laiz-Carrion2*, David Macias3 and Alberto García García2
  • 1 Universidad de Málaga, Departamento de Biología Animal, Spain
  • 2 Instituto Español de Oceanografía. C.O. Málaga, Spain
  • 3 Instituto Español de Oceanografía. C.O. Málaga, Spain

Bluefin tuna (Thunnus thynnus) and Atlantic bonito (Sarda sarda) spawn during summer in the oligotrophic waters of the Balearic Sea (NW Mediterranean). As they grow from larvae to juveniles, they migrate southwards reaching the more productive waters of the Alborán Sea. During August 2015, young-of-the-year (YOY) of both species was caught as forming part of the bycatch of the sardine purse seine fishery. The size range of YOY was from 16-21cm for bluefin and 19-25cm for bonito. Nowadays, knowledge on the trophic ecology of these YOY specimens is very scarce. This study has the objective of analyzing the trophic ecology and estimating trophic position (TP) of both species by bulk stable isotope analysis (SIA) and by compound specific isotope analysis of amino acids (AA-CSIA). Bluefin specimens were caught in two environmentally differentiated sites from the hydro-biological viewpoint, the Bay of Málaga and Gulf of Vera (Almería). Atlantic bonito specimens used for this study come from the Bay of Málaga only. SIA showed differences between bluefin and Atlantic bonito, the latter showing significantly higher values of the nitrogen stable isotope. No differences between species were observed with respect to the stable isotope of carbon. Although no baseline levels were available to determine trophic position by SIA, it can be assumed that both species have similar baselines. Therefore, we can infer that bonito show a greater trophic specialization in comparison to bluefin. On the other hand, AA-CSIA determines TP without needing trophic baselines. The models proposed by Chikaraishi et al. (2009) for aquatic food-webs and modified by Bradley et al. (2015) for marine teleosts, using glutamic acid as trophic AA and phenylalanine as source AA were used for this study. The estimated TP showed similar results to SIA where bonito YOY recorded higher TP in comparison to bluefin YOY. Nonetheless, the difference was not significant probably due to small sample size for AA-CSIA. SIA showed differences by site sampled in bluefin YOY where Malaga Bay specimens showed significantly higher □□15N values. No differences between sites were observed with respect to □□13C values. TP by site did not show significant differences. However, TP showed a positive linear relationship with fork length (FL) suggesting a greater trophic specialization with growth. SIA and CSIA are tools widely used for early life food web dynamics and this study shows the complementary uses of both approaches. Significant differences of stable isotopes values for some trophic amino acids possibly indicate dietary differences of prey consumption. Further complementary studies contemplating stomach content analysis will contribute to a better understanding of the trophic ecology at early life stages in tunas like species.

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Acknowledgements

This study was partly funded by ATAME project (CTM2011-29525-C04-02). A.Uriarte was recipient of a predoctoral fellowship FPI-IEO 2011/03 (Spanish Institute of Oceanography).

This work was supported by grant ECOLATUN CTM2015-68473-R (MINECO/FEDER). Amaya Uriarte was recipient of a predoctoral fellowship FPI-IEO 2011/03 (Spanish Institute of Oceanography).

References

Chikaraishi Y., Ogawa N.O., Kashiyama Y., Takano Y., Suga H., Tomitani A., Miyashita H., Kitazato H. and Ohkouchi, N. 2009. Determination of aquatic food-web structure based on compound-specific nitrogen isotopic composition of amino acids. Limnology Oceanography: Methods 7: 740–750.
Bradley C.J., Wallsgrove N.J., Choy C.A. Drazen J.C., Hetherington E.D., Hoen D.K. and Popp B.N. 2015. Trophic position estimates of marine teleosts using amino acid compound specific isotopic analysis Limnol. Oceanogr.: Methods 13(9): 473-493.

Keywords: Bluefin tuna, Atlantic bonito, young of the year, trophic ecology, stable isotope

Conference: XIX Iberian Symposium on Marine Biology Studies, Porto, Portugal, 5 Sep - 9 Sep, 2016.

Presentation Type: Poster Presentation

Topic: 4. FISHERIES, AQUACULTURE AND BIOTECHNOLOGY

Citation: Baro I, Uriarte A, García-Barcelona S, Gomez-Vives M, Saber S, Quintanilla JM, Laiz-Carrion R, Macias D and García García A (2016). Trophic ecology of young of the year Alboran Sea bluefin tuna (Thunnus thynnus) and Atlantic bonito (Sarda sarda) by stable isotope analyses. Front. Mar. Sci. Conference Abstract: XIX Iberian Symposium on Marine Biology Studies. doi: 10.3389/conf.FMARS.2016.05.00191

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Received: 29 Apr 2016; Published Online: 03 Sep 2016.

* Correspondence: PhD. Raul Laiz-Carrion, Instituto Español de Oceanografía. C.O. Málaga, Fuengirola, Málaga, 29640, Spain, raul.laiz@ieo.csic.es