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MEPS prepress abstract   -  DOI: https://doi.org/10.3354/meps14110

Using molecular and stable isotope markers to identify the main predators of Nephrops norvegicus in Mediterranean deep-water ecosystems

Maria Vigo*, Joan Navarro, Joan Giménez, Núria Andón, Andrés Martínez-Lage, Joan B. Company, Guiomar Rotllant

*Corresponding author:

ABSTRACT: To obtain a better understanding of the functioning of ecosystems and how they respond to disturbance, it is necessary to identify the involved biotic interactions and specific trophic roles. Predation is one of the most important biotic interaction that can also define other species' spatial patterns. Many predators are considered key species for the functioning and maintenance of ecosystems, as they play an important ecological role that can influence the dynamics at lower trophic levels. The Norway lobster (Nephrops norvegicus) is one of the most valued European fishing stocks. However, its value and captures have declined over the last decade. In the Atlantic Ocean, Atlantic cod (Gadus morhua) is the main predator of N. norvegicus. Nevertheless, this species is not present in the Mediterranean Sea, where only a few studies suggest which species might prey on N. norvegicus. Here, we combine two methodologies — genetic identification on stomach contents and stable isotope analyses — to identify, for the first time, the main predators of N. norvegicus in the Mediterranean Sea. Moreover, we created the Predation Index, which determines the most influential predator affecting N. norvegicus population dynamics. Our results revealed that the major predators were the cephalopods Sepietta sp. and Abralia veranyi, probably affecting the early stages of N. norvegicus and followed by the elasmobranch Scyliorhinus canicula and the bony fishes Merluccius merluccius, Trigla lyra and Conger. To evaluate possible fluctuations of N. norvegicus population, we consider that is crucial to include the assessment of the population of these predators.