Feces Production and Ammonia Excretion of Pacific Abalone, Haliotis discus hannai , Fed Kelp, Laminaria japonica , in Relation to Water Temperature and Shell Length

Nitrogen excreted by aquatic animals mainly takes the form of metabolic wastes such as feces and ammonia, which is accumulated in the intensive aquaculture system and causes serious environmental contamination. So it is very important to determine the waste excretion characteristics of aquatic animals for the development of practical and nonpolluting land‐based aquaculture. Abalone has a unique feeding habit and feeding regime, different from those of finfish; abalone gnaw feed seaweed to produce feces and ammonia continuously. In this study, the rates of feces production and ammonia excretion of pacific abalone, Haliotis discus hannai , of three shell lengths (3, 5, and 7 cm) were investigated under three different temperature conditions (12, 16, and 20 C). All experiments were performed in triplicate in a semirecirculating aquaculture system. Feces were collected for 5 d, and ammonia concentrations (total ammonia nitrogen [TAN]) in the tank inlet and outlet were monitored every 4‐h interval for 24 h at the fourth day of the feces collection. The regressions for the weight‐specific feces production rate (g feces/kg abalone/d) and the weight‐specific TAN excretion rate (mg TAN/kg abalone/d) in relation to water temperature ( T , C) and shell length ( L , cm) were weight‐specific feces production rate = exp(1.575 − 281.2/ T 2  – 0.142 L ), r 2  = 0.9550, and weight‐specific TAN excretion rate = exp(5.052 − 277.1/ T 2  − 0.136 L ), r 2  = 0.9598. Pacific abalone produced 108.3–111.7 g feces and excreted 3.83 g TAN/kg seaweed ingested (dry weight).