Biological interactions between fish and jellyfish in the northwester mediterranean

• Autores: Uxue Tilves Matheu
• Directores de la Tesis: Ana Sabatés (dir. tes.), Verónica Fuentes (codir. tes.), Manuel Espino Infantes (tut. tes.)
• Lectura: En la Universitat Politècnica de Catalunya (UPC) ( España ) en 2019
• Idioma: español
• Tribunal Calificador de la Tesis: Stefano Piraino (presid.), Cruz Palacín Cabañas (secret.), Laura Prieto Galvez (voc.)
• Programa de doctorado: Programa de Doctorado en Ciencias del Mar por la Universidad de Barcelona y la Universidad Politécnica de Catalunya
• Materias:
  • Ciencias de la vida
    • Biología animal (zoología)
      • Ecología animal
      • Zoología marina
    • Biología vegetal (botánica)
      • Botánica marina
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• Resumen

  • Jellyfish are important components of marine ecosystems, being a key link between lower and higher trophic levels. Jellyfish blooms occur sporadically and unpredictably in coastal areas and often have important socio-economic consequences for fisheries and tourism. This PhD thesis addresses some questions regarding the potential impact, positive and/or negative, that jellyfish have on fish populations in the Catalan coast (NW Mediterranean). Firstly, the natural diet of one of the most abundant jellyfish in the area, the scyphomedusa Pelagia noctiluca, was studied analyzing its gut contents and conducting biomarker analyses (stable isotopes and fatty acids). These results were complemented with laboratory experiments to calculate their digestion times and also with the records of fish larvae and jellyfish abundances in the field. All together, these results were used to estimate the potential feeding impact of P. noctiluca on fish eggs and larvae and competition between both groups of organisms. Results suggest that the potential consumption of ichthyoplankton by the jellyfish and competition between them may be high. Secondly, the association between the jellyfish Rhizostoma pulmo and Cotylorhiza tuberculata and the carangid fishes Trachurus mediterraneus, Trachurus trachurus and Caranx rhonchus was studied in detail. For this purpuse, field observations of jellyfish and their hosted fish were carried out during summer to describe fish behavior. Moreover, laboratory experiments were performed to determine the survival capability of the jellyfishassociated fish to the venom of their hosts. Finally, biomarker analyses were conducted to understand the significance of the association. All this information demonstrated the benefit of the association for the fish.