Physiology of Finfish and Shellfish (2+1)

Description

This apparatus (Fig.1) is a smaller version of Blazka’s fish activity apparatus. Because of the limitation of size only smallfish can be used in this apparatus. It consists mainly of two concentric glass cylinders, one fitted inside the other. The two ends of the outer cylinder (OC) are closed with rubber stoppers (RS) (size No. B1/8). Through the stopper at one end passes a shaft(RS) for a propeller (PR) which is fixed to rotate just inside the inner cylinder (IC). The rotation of the propeller induces a water current inside the inner cylinder. The water circulates back to the propeller end through the clearance between the outer and inner cylinders. Water currents of required velocities could be obtained with the help of a voltage regulator (‘Dimmerstat’) connected to the motor (M). The apparatus is so designed that water can flow in and out of the respirometer (open system) or can be left to stagnate (closed system) when the fish is being excercised depending on the experimental needs. Fish can be inserted into the inner cylinder by removing the rubber cork, away from the propeller end. Through this stopper is introduced two wires (EW) which end in a shocker grid (SG) closing the inner cylinder. A3 volt A. C. current is supplied to these wires through a step-down transformer from the mains. The shocker grid serves two purposes, one of closing the inner cylinder without letting the fish escape and the other of preventing the fish from resting on it. When a fish rests on the grid the exposed wires become connected and a circuit is established resulting in a shock to the fish. Unless a fish is unable to swim due to low oxygen or is really fatigued it will not rest on the gird. The shocker is put on during the initial training period only or to test if the fish is really fatigued.