Study on the feeding habits and trophic levels of the gillnet catches of Qiandao Lake in autumn by stable isotope technology

Abstract:

By using stable isotope techniques, the food sources and trophic levels of catches from gillnets were analyzed from September to November, 2011 in Qiandao Lake. Results showed that δ¹³C values of each food sources varied between -29.7 ‰——23.9 ‰, among which, the highest δ¹³C values was seen in phytoplankton, with the lowest in particulate organic matter (POM). The food sources of δ¹⁵N value range is small, with the highest phytoplankton (8.5 ‰), the lowest particulate organic matter the lowest (5.1 ‰). In contrast to isotope value distribution trend of food sources,consumers of δ¹³C values range was relatively small (-29.7‰——21.6‰), and then δ¹⁵N range was relatively large (5.1 ‰-14.8 ‰). Consumers of trophic level from 1.9 to 3.6, belong to the three nutrition levels, the trophic level of fishes all distributed between the third to the fourth trophic level having good consistency with the feeding characteristics. But as an invasive species, herbivores fish Megalobrama amblycephala and omnivorous fish Ietalurus punetaus trophic level as high as 3.4 and 3.0, which inicated that feeding habits changed greatly in Qiandao Lake. Isotope tracer method research results also showed that the carbon source primarily is phytoplankton in Qiandao Lake water ecosystem.