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

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.

Morphological abnormalities in seven American round ray specimens: A review of America's batomorph anomalies

“…However, this free‐living report should be considered doubtful. Recent biological information available for this species off the northwestern coast of Mexico confirms a birth size range between 381 to 420 mm DW (Burgos‐Vázquez et al., 2019; Ehemann et al., 2019) compared with the ≈200 mm DW abnormal specimen, meaning that the latter corresponded to a fully developed embryo. Although capture‐induced parturition has not yet been confirmed for this species (Adams et al., 2018), this scenario is also plausible to be considered for the abnormal Mexican cownose ray.…”

Richness and relative abundance of batoids from the artisanal fishery in the Espiritu Santo archipelago, BCS, Mexico

“…Investigaciones relacionadas con batoideos en la IES han aumentado en años recientes (Burgos-Vázquez et al, 2017, 2019a2019b;Ehemann et al, 2017a;2017b;2019;) La riqueza específica de batoideos reportada para la IES así como para Isla Cerralvo, puede estar relacionada con la presencia de "bajos" o montañas submarinas y de arrecifes rocosos en las Islas. Esto se asocia con hábitats que favorecen una alta diversidad y abundancia de alimento, así como procesos de enriquecimiento, producto del corte y transporte vertical de las corrientes, remolinos del Golfo de California, entre otros, que incrementan los recursos tróficos potenciales para la comunidad de batoideos (Del Moral-Flores, 2010;Restrepo-Gómez, 2017;Cabrera-Meléndez, 2018;González-Rodríguez et al, 2018;Ehemann et al, 2019).…”

Untitled

“…Investigaciones relacionadas con batoideos en la IES han aumentado en años recientes (Burgos-Vázquez et al, 2017, 2019a2019b;Ehemann et al, 2017a;2017b;2019;) La riqueza específica de batoideos reportada para la IES así como para Isla Cerralvo, puede estar relacionada con la presencia de "bajos" o montañas submarinas y de arrecifes rocosos en las Islas. Esto se asocia con hábitats que favorecen una alta diversidad y abundancia de alimento, así como procesos de enriquecimiento, producto del corte y transporte vertical de las corrientes, remolinos del Golfo de California, entre otros, que incrementan los recursos tróficos potenciales para la comunidad de batoideos (Del Moral-Flores, 2010;Restrepo-Gómez, 2017;Cabrera-Meléndez, 2018;González-Rodríguez et al, 2018;Ehemann et al, 2019).…”