Diel changes in resource use and diet overlap in temperate stream fishes

Abstract

Interspecific variation in diel‐scale temporal niches is common in natural communities. Such variation changes population dynamics via effects on the growth and reproduction of individuals. Also at the community level, theory predicts that animals can reduce competition for shared resources by changing diel activity in certain situations. However, the role of diel activity at the community‐level has not been examined sufficiently. In this study, to examine whether the diel‐scale temporal niche act as a competition‐mitigating mechanism for stream fishes at the community level, we surveyed diel changes in microhabitat use and foraging, and the pattern of interspecific diet overlap in the middle reaches of a temperate stream where various fish species that seemed to be either nocturnal or diurnal coexisted. Our results suggest that the fishes forage during both daytime and night, but change their foraging mode at different times of the day, so that the foraging habits of these fish species cannot be divided simply into nocturnal and diurnal. Furthermore, fishes appeared to aggregate in the vicinity of common food resources during time zones with high availability of the resources, and therefore, inter‐guild diet overlap was high during certain time zones. On the other hand, when inter‐guild diet overlap was low, each fish species used foods or microhabitats that did not any have the potential to be used by species of another guild. Therefore, we conclude that variation in diel niche use is influenced by variation in the fundamental niche and food supply or availability rather than by competitive interaction between fishes in the stream fish community.

Contribution of environmental and spatial factors to the structure of stream fish assemblages at different spatial scales

“…However, the fraction explained by environmental variables was not large in the lower reaches, but it was large at two sites in the upper reaches (Table 3). In addition, a previous study reported the interspecific variation in habitat use of the dominant fish species in the upper-middle reaches of the research area (Nakagawa et al 2012). Therefore, the effect of an environmental factor probably does not explain the small contribution of environmental factors in the assemblage structuring of stream fishes at the fine scale.…”

“…For example, in general, water temperature gradually increases from upper to lower reaches at the kilometre scale, and therefore, the distribution of a fish species determined by temperature tolerance would be responsive at this scale (Fausch et al 1994). Pinpoint habitat patches such as cover and boulders are used as short-term habitats for refuge or foraging sites (Sechnick et al 1986;Fuselier & Edds 1995;Nakagawa et al 2012); thus, these were considered fine-scale factors. Pinpoint habitat patches such as cover and boulders are used as short-term habitats for refuge or foraging sites (Sechnick et al 1986;Fuselier & Edds 1995;Nakagawa et al 2012); thus, these were considered fine-scale factors.…”

“…Water temperature was therefore categorised as a medium-scale factor. Pinpoint habitat patches such as cover and boulders are used as short-term habitats for refuge or foraging sites (Sechnick et al 1986;Fuselier & Edds 1995;Nakagawa et al 2012); thus, these were considered fine-scale factors.…”

“…); cobbles for Rhinogobius spp., Tridentiger kuroiwae and Chaenogobius urotaenia(Kawanabe and Mizuno 1989, Tamada 2010); boulders for Pseudobagrus nudiceps, Liobagrus reinii and Cottus pollux(Yamane et al 2004;Watanabe 1994;Natsumeda 2001;Nakagawa et al 2012)] Medium scale Mean cover frequency of a research site A determinant factor of the density of feeding sites, shelter and reproductive substrate (e.g., Shirvell 1990; Inoue et al 1997) Reproductive substrate for some Japanese Cyprinids; Squalidus gracilis, Carassius auratus (Nakamura 1969) Medium scale Water depth at a plot Refuge of predators (e.g., Power 1984) Fine scale Current velocity at a plot A factor affecting foraging efficiency (e.g., Hill & Grossman 1993; Nakano 1995) Fine scale Frequency of each substrate type at a plot Feeding site for some benthic feeders (review in Lammens & Hoogenboezem 1991) Shelter from predator or high current speed (e.g., Fuselier & Edds 1995; review in Matthews 1998) Feeding site or shelter for some Japanese fishes [e.g., sand for Pseudogobio esocinus, Squalidus gracilis and Hemibarbus longirostris (Nakamura 1969); Boulders for Pungtungia herzi, Niwaella delicata, Pseudobagrus nudiceps, Liobagrus reinii and Cottus pollux(Nakamura 1969;Kawanabe and Mizuno 1989, Nakagawa et al 2012)] …”

Feeding habits of the Chinese minnowRhynchocypris oxycephalus(Sauvage & Dabry de Thiersant, 1874) from the upper Yangtze River, China

“…In China, R. oxycephalus is one of the dominant species in fish communities in headwaters of streams with high elevations (Luo, ). Previous studies on R. oxycephalus focused on the geographical distribution (Han, Fukushima, Kameyama, Fukushima, & Matsushita, ; Kano et al., ; Nakagawa et al., ; Yamazaki, Haramoto, & Fukasawa, ), molecular biology (Takai et al., ), faunistic and ecological aspects (Dai & Li, ; Yi, Wu, Liu, Wang, & Xu, ; Yu, Luo, & Zhou, ; Zhang et al., ; Zhu et al., ) and reproductive biology (Xiong, ). However, information on the feeding habits of this species is scarce, particularly for the upper Yangtze River.…”