Physiology of Finfish and Shellfish (2+1)

Description

A respirometer is a device used to measure the rate of respiration or respiratory quotient (RQ) of a living organism by observing its movement or activity in the medium. Many gadgets or devices can be attached to it measure different parameters like amount of dissolved O₂, CO₂, NH₃ etc. Hence, this instrument can be helpful in study of effect of age, activity, disease, light, chemicals and other factors on the respiration of fish.

‘Fry’s modified respirometer’ is a modified from of ‘Fry’s modified respirometer’ originally developed by fry. The modifications were brought by kutty et al. (1971). In contrast to fry’s respirometer which was bulky and had moving sensors, this modified respirometer is not so bulky, but with enough space for movement of fish and has fixed sensors. These sensors count the activity or movement of fish inside the respirometer chamber.

The ‘Fry’s modified respirometer’ has two circular chambers made up of transparent material (glass or plastic). The inner-shorter chamber has light arrangements, which is sensed by the sensors and also used to view the movement of organism. The larger outer circular chamber is meant for the observation of movement of fish or organism. It can be filled with water and fish can be kept for observation. The light falling from the inner chamber falls on the sensors attached outside the outer chamber. When the light is obstructed due to movement of fish, it is registered on the activity counter, attached to the sensors. The transparent chambers may be encased with a black box like cover with 4 small windows at the 4 lateral sides for observation. The display (LCD) shows the activity sensed by the sensors. A thermometer can also be in-built to record the temperature.

Number of sensors = 8

Height of each sensor = 18cm

Distance between adjacent sensors = 25cm

Radius of inner chamber = 17cm (r₁)

Radius of outer chamber alongwith inner chamber = 30cm (r₂)

Height of chambers (depth) = 19cm (h)

From above measurements we can calculate the volume or capacity of the outer chamber as

V = π (r₂²-r₁²) x h

Hence volume of outer chamber = π (30²-17²) x 19 cm³

= 22/7 x (30+17) (30-17) x 19 cm³

= 22/7 x 47 x 13 x 9 cm³

= 36485.429 cm³

= 36.485 l