1Tohoku National Fisheries Research Institute, Fisheries Research Agency, Shiogama, Miyagi 985-0001, 2National Research Institute of Aquaculture, Minami-Ise, Mie 516-0193, Japan
A laboratory study of the decomposition of fish food and feces in seawater showed that first-order decay constants of the highly reactive particulate organic carbon (k1) of fish food were 0.28 and 0.16 day−1 under oxic and anoxic conditions, respectively. Those of the less reactive one (k2) were 0.008 and 0.005 day−1, respectively. The decay constants of fish feces were similar to those of fish food except the k1 under the oxic condition. Relative contents of the highly reactive particulate organic carbon fraction in fish food were 88 and 80% under oxic and anoxic conditions, respectively. On the other hand, it was 67 and 39% in fish feces, suggesting that the influence of feces might continue longer in the bottom environment.