Back-Calculation of Fish Size in Diet Analysis of Piscivorous Predators: A New Index for the Alien Silurus glanis

Renato Bacchetta, Andrea Marotta, Alessandro Nessi and Paolo Tremolada
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Renato Bacchetta: Department of Environmental Science and Policy, Università degli Studi di Milano, 26, via G. Celoria, I-20133 Milan, Italy
Andrea Marotta: Department of Environmental Science and Policy, Università degli Studi di Milano, 26, via G. Celoria, I-20133 Milan, Italy
Alessandro Nessi: Department of Environmental Science and Policy, Università degli Studi di Milano, 26, via G. Celoria, I-20133 Milan, Italy
Paolo Tremolada: Department of Environmental Science and Policy, Università degli Studi di Milano, 26, via G. Celoria, I-20133 Milan, Italy

Sustainability, 2021, vol. 13, issue 8, 1-14

Abstract: The wels catfish Silurus glanis has been constantly spreading in many European basins, outside its native range. Being a voracious predator, it is considered to have a severe impact on local fish communities. In the Ticino River (Northern Italy), bones of S. glanis were found in feces from the top predator Lutra lutra . To estimate the control capability of L. lutra for this species and to back-calculate S. glanis ’ size from its bone remains, whole skeletons from 27 differently sized S. glanis specimens were analyzed. A double pharyngeal element and all caudal vertebrae emerged as significant items for species identification. The mean length of the pharyngeal element was directly related to fish mass, while for vertebrae, a K-index was proposed to identify the position of each vertebra along the spine and, from this, to calculate the original fish mass. This methodology allowed us to establish that the length of the preyed S. glanis was 85–435 mm, and the ages were between 0+ and 2+ years. The proposed methodology opens new perspectives for more detailed studies on the efficiency of predation by piscivorous species on allochthonous ones.

Keywords: invasive species; Lutra lutra; diet analysis; bone remains; fish mass quantification; spraint analysis (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2021
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