No abstract

No abstract

No abstract

No abstract

No abstract

No abstract

Rrc tivrd April fi, i gyo; accrptcd .Jiinc i !), I 990.

An automatic dispenser of dry fish food is described that effectively disperses small quantities of very fine granules of food. It is well adapted for supplying food to small groups of fish that must be fed at frequent intervals.A major problem encountered in the rearing of young fish larvae with dry food instead of live zooplankton is ensuring an adequate supply of food particles in the water. Live prey remain available for a long time after their introduction into rearing tanks, but dry food particles tend to sink to the bottom of the tank where they lose their availability. Attempts to keep these particles in suspension with water currents have some inherent drawbacks, such as loss of nutritive value due to leaching. Better larval feeding can be accomplished by continually dispensing food particles at carefully adjusted delivery rates. Insufficient food supply leads to starvation of larvae, and excess feeding leads to deteriorated water quality from accumulation of uneaten food. Automatic feeders have been reviewed in detail by Berka (1973); these utilize apertures closed by electromagnetic devices, endless screws, disks, or moving paths. However, these feeders appear to be more adapted to mass rearing than to small-scale larval rearing. A food dispenser was designed for small-scale operations (CharIon and Bergot 1984) based on the rotating system introduced by MacFarlane (1976). Improvements in their design are described in the present work. The feeder includes two removable units--a food dispenser and a holder. The food dispensing unit is a 33-mm-diameter, transparent polystyrene tube, 70 mm in length (Figure 1). The top of the tube is fitted with a small plate and a cap, each with a 12-ram-diameter hole. A slit of varying size can be obtained by adjusting the relative position of the holes in the cap and plate, allowing different rates of food delivery. The bottom of the tube is removed and the threaded female part of a 32ram-diameter polyvinyl-chloride (PVC) plug is glued inside.