In situ determination on food consumption and ecological conversion efficiency of a marine fish species, Hyporhamphus sajori

The food consumption and ecological conversion efficiency of a species marine pelagic and small size fish, Hyporhamphus sajori, were determined by using in situ stomach content method presented by Eggers. The results showed that:(1) the fish was taken in food all day, so empty-stomach rate was very low, taking up about 4.5% of the total determined fish number. However, the fish still has significant daily feeding rhythm. A feeding peak was found 0:00 o'clock at night, but feeding level was always high in the daytime; (2) relationship between instantaneous food content in stomach and corresponding time could be described as S_t=a·e^-b·t. There was not significant difference of instantaneous gastric evacuation rate between two determinations, with average value being 0.13×10^-2g/(g·h) (wet weight); (3) the daily food consumption tended to change in irregular waving form, with average value being (10.16×10^-2±1.19×10^-2) g/(g·d) (wet weight) or (55.56×10^-2±6.51×10^-2) kJ/(g·d). The wave distance is constant and about 14 d, but the wave height changed largely;(4) actual determining value of daily growth rate was 3.24×10^-2g/(g·d) (wet weight) or 12.91×10^-2kJ/(g·d), from which 31.89% (wet weight) or 23.24% kJ of ecological conversion efficiency could be obtained.