Feeding Design for Intensively Reared Larval and Juvenile Ayu Plecoglossus altivelis

Abstract

To determine the efficacy of daily rations for ayu Plecoglossus altivelis, we applied multiple regression analysis allocating the increment in ayu biomass as the response variable and such food items as rotifer Brachionusplicatilis, brine shrimp Artemiasalina nauplii and artificial edible compound (AEC), and ambient water temperature as the regressors. We examined the correlation between the parameters and the production rate of ayu cohort. In addition, we estimated the efficiency of the total food supply utilizing the “index of exhausted consumption” φ which measures the ratio of the discarded food against the utilized food.
The regression analysis was effective in 72 instances out of 91. The estimates of the regression coefficient which satisfies the non-zero test were counted to 2, 31, 34 and 56, respectively for water temperature, rotifer, brine shrimp and AEC. About a half the parameters for rotifer were negative. The production rate changed correlatively to AEC, but was not significantly affected by rotifer or brine shrimp. The influence of temperature was not clarified. The estimates of φ value for rotifer, brine shrimp and AEC were 167±15.2%, 49.0±3.42% and 39.3±3.06% (mean±S. E.), respectively. The indices correlated positively to the daily decreasing rate of individuals.