Co-occurring bighead and silver carps show similar food preference but different isotopic niche overlap in different lakes

Abstract

Silver carp (Hypophthalmichthys molitrix) and bighead carp (Hypophthalmichthys nobilis) are among the most important fish species in aquaculture and have been introduced to many countries. The feeding ecology of these filter-feeding cyprinids is not well understood and has been mostly based on gut content analyses. We analyzed δ 13 C and δ 15 N stable isotope ratios of food resources and fish muscle tissues in four Chinese lakes, where these two species co-occur. Data analysis through Bayesian mixing models revealed that both fish species had similar diets within lakes, and where dietary shifts occurred, both species displayed dietary shifts simultaneously. Diet was generally based on plankton, however, detritus was the main food in eutrophic lake subjected to urban pollution, likely due to resource availability. Niche overlap and width were also variable but in general clear size-based resource partitioning was observed, with bighead carp preying more on zooplankton and occupying a higher trophic position and silver carp feeding more on phytoplankton. Food particles smaller than 64 μm, had little importance in their diets.

Resources utilization and trophic niche between silver carp and bighead carp in two mesotrophic deep reservoirs

“…Hence, for fish >40 cm, muscle tissue SI values can better represent their long dietary periods. Jayasinghe et al (2015) indicated that SC is more likely a phytoplankton feeder, while BC is more likely a zooplankton feeder. However, the categories that we used to classify food types would not result in either a phytoplankton-only feeder or zooplankton-only feeder, because both plankton types consisted of species with a wider range in body sizes.…”

“…Although both species utilize the suspending particle resources, they can coexist by regulating their proportions of these particles and the trophic level. Jayasinghe et al (2015) pointed out that co-occurring SC and BC showed similar food preference but a different isotopic niche overlap in different lakes with variation of resource availability. In our study, we found that in order to coexist, BC occupied a larger isotopic niche overlap in the Nianyushan Reservoir in our study, possibly because they had to live when differences in relative survival ability were small.…”

“…They also share a similar diet, but a different food composition because of different meshes of their gill rakers (Li et al 2013). Jayasinghe et al (2015) indicated that SC is more considered as a phytoplankton feeder, while BC is more likely a zooplankton feeder.…”

“…Stable isotopes of carbon (d 13 C) and nitrogen (d 15 N) can be used in measuring trophic niche since the stable isotope values in consumer tissues are closely related to their food resources (Gu et al 1996a;1996b;Jayasinghe et al 2015). Hence, the SI technique has been used to analyze the trophic dynamics of SC and BC (Gu et al 1996b, Li et al 2013, as well as the dietary overlap between both species (Gu et al 1996a;Li et al 2013;Jayasinghe et al 2015;Yao et al 2016). Most researches indicated that food resources were responsible to the trophic niche and overlap.…”

“…Most researches indicated that food resources were responsible to the trophic niche and overlap. For example, Jayasinghe et al (2015) pointed out that niche overlap was variable with food resources but in general clear sizebased resource partitioning was observed, with bighead carp preying more on zooplankton and occupying a higher trophic position. However, except food resources, their trophic niche and overlap may be affected by fish stocking ratio either.…”