Feeding ecology and prey resource partitioning of lenok (Brachymystax lenok) and Baikal grayling (Thymallus arcticus baicalensis) in the Eg and Uur rivers, Mongolia

Abstract

Baikal grayling (Thymallus arcticus baicalensis) and lenok (Brachymystax lenok) are two salmonids which co‐occur in lakes and rivers of the Selenga River and Lake Baikal drainage in northern Mongolia and Siberia. Populations of both species have declined due to habitat loss and overfishing. Previous studies have established that diets of both species are comprised of aquatic and terrestrial invertebrates, but none have examined how prey resources are partitioned between the species. We explored resource partitioning between these species using information from stomach content analysis and stable isotope analysis of carbon and nitrogen. Stomach content data were also compared to invertebrate prey availability estimated from drift and benthic samples. Stomach content analysis indicated that lenok were benthic specialists, while Baikal grayling exhibited a more generalised and surface‐oriented diet, preying upon both terrestrial and aquatic invertebrates. In addition, drifting invertebrate prey availability was positively related to diet overlap based on stomach content analysis, suggesting that competition was involved in the prey resource partitioning we observed. Our analysis of assimilated diet using stable isotopes was generally consistent with stomach contents, indicating that prey partitioning was sustained over a period of several months, but also revealed a greater importance of fish prey to lenok diets. This study provides a baseline description of prey utilisation and prey resource partitioning between lenok and Baikal grayling, which may be used to guide management and future research of these threatened species.

Preliminary assessment of the trophic structure of demersal fish community in the Sea of Oman

“…Similar conclusions have been presented by recent studies (Carassou et al, 2016 andKeller et al, 2016;Olson et al, 2016). Stomach contents indeed only provide very short-term information on consumer's diet, while isotopic ratios in the tissues reflect dietary habits over longer time scales (Cortés, 1997;Hobson, 1999;Post, 2002;Olson et al, 2016). In our study in particular, the low number of specimens collected for each species, together with the occurrence of fish with empty stomachs, further limited the efficiency of stomach content analysis for capturing the full range and variability in prey diversity characterizing demersal fish feeding regimen.…”

“…Our results therefore highlight how essential insights from stable isotope analysis had proven to complement stomach content data, in order to fully apprehend the variability in feeding habits of consumers. Similar conclusions have been presented by recent studies (Carassou et al, 2016 andKeller et al, 2016;Olson et al, 2016). Stomach contents indeed only provide very short-term information on consumer's diet, while isotopic ratios in the tissues reflect dietary habits over longer time scales (Cortés, 1997;Hobson, 1999;Post, 2002;Olson et al, 2016).…”

“…In this context, stable isotopes of carbon ( 13 C/ 12 C, or δ 13 C) and nitrogen ( 15 N/ 14 N, or δ 15 N) are the most often measured in food web studies (Hobson, 1999;Post, 2002). The combination of stomach content with δ 13 C and δ 15 N analyses is now recognized as a pertinent methodology in order to quantify fish diet and address its spatial and temporal variability in a given ecosystem (Hamidan et al, 2016;Keller et al, 2016;Malek et al, 2016;Olson et al, 2016;Weidner et al, 2017). In addition to carbon and nitrogen isotopic ratios, sulfur isotopes are also useful to trace the origin of the prey consumed by consumers in aquatic ecosystems (Peterson, 1999;Post, 2002;Fry and Chumchal, 2011).…”

Trophic relationships in fish assemblages of Neotropical floodplain lakes: selectivity and feeding overlap mediated by food availability

“…Interspecific food overlap is a common occurrence in fish communities (Ross, 1986;Correa & Winemiller, 2014), even for those species which resource partitioning is important (Gerking, 1994;Olson et al, 2015). The absence of correlation between interspecific diet overlap and resource availability suggests that resource partitioning rather than resource segregation may be occurring in the diet of the fish assemblages of these floodplain lakes.…”

“…Also, the species that coexist in nature can segregate their use of resources along many dimensions, such as time and various aspects of the habitat (Hutchinson, 1957;McPeek, 2014). This condition allows ecologically similar species to coexist, and can reduces competition among them (Schoener, 1974;Correa & Winemiller, 2014;Olson et al, 2015). Habitat structure and the daily activities of the species as important factors in determining interspecific interactions may also be considered (Gelós et al, 2010;Carniatto et al, 2012;Almeida-Silva et al, 2015); these aspects were not evaluated in this study.…”