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Zeros as a result in diet studies, is this really bad? Rhinoptera steindachneri as a case study

Published online by Cambridge University Press:  20 June 2019

N. R. Ehemann
Affiliation:
Instituto Politécnico Nacional, Centro Interdisciplinario de Ciencias Marinas (CICIMAR-IPN), Avenida Instituto Politécnico Nacional, s/n, Apartado Postal 592, La Paz, Baja California Sur, 23096, México
L. A. Abitia-Cardenas*
Affiliation:
Instituto Politécnico Nacional, Centro Interdisciplinario de Ciencias Marinas (CICIMAR-IPN), Avenida Instituto Politécnico Nacional, s/n, Apartado Postal 592, La Paz, Baja California Sur, 23096, México
A. F. Navia
Affiliation:
Fundación colombiana para la investigación y conservación de tiburones y rayas, SQUALUS, Cali, Colombia
P. A. Mejía-Falla
Affiliation:
Fundación colombiana para la investigación y conservación de tiburones y rayas, SQUALUS, Cali, Colombia
V. H. Cruz-Escalona
Affiliation:
Instituto Politécnico Nacional, Centro Interdisciplinario de Ciencias Marinas (CICIMAR-IPN), Avenida Instituto Politécnico Nacional, s/n, Apartado Postal 592, La Paz, Baja California Sur, 23096, México
*
Author for correspondence: L. A. Abitia-Cardenas, E-mail: laabitia@gmail.com

Abstract

Rhinoptera steindachneri is a commercially important, medium-sized, pelagic migratory batoid fish with benthic feeding habits. It has been considered a specialized predator that feeds on molluscs as well as benthic ophiurids and arthropods off the Mexican Pacific coast. Most biological aspects of this species in La Paz Bay are unknown, despite its being a commercially important species of conservation interest. Therefore, the aim of this study was to characterize the feeding habits of R. steindachneri based on specimens caught in artisanal fisheries. The stomach contents of 310 specimens (146 females and 164 males) were analysed, all captured from 2013 to 2015. The vacuity index was 97.1%, and the most important prey species were Mysidium spp. and Cylichna spp. Because of the high frequency of empty stomachs recorded, it was not possible to describe with precision the general diet of the species. Three hypotheses were developed to try to explain why this characteristic occurred in this species, ranging from eating habits to physiology and prey digestion and geographic location of the study. However, considering the mechanical process of prey handling of R. steindachneri, several hypotheses were formulated, with the hour of capture, chemical processes and physiology and prey digestion being the most probable to explain this high vacuity index reported in this study.

Information

Type
Research Article
Copyright
Copyright © Marine Biological Association of the United Kingdom 2019 

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