Depth equilibration of a shallow-water cichlid fish |
| |
Authors: | B. J. Hill, A. J. Ribbink,&dagger |
| |
Affiliation: | Zoology Department, Rhodes University, Grahamstown;6140 South Africa |
| |
Abstract: | The cichlid Melanochromis exasperatus has a natural distribution which is restricted to a single island in Lake Malawi, Africa. Diving observations indicated that it does not occur below 4.5 m depth. Measurements of depth equilibration in a pressure tank showed that males can equilibrate to a depth of 25 m and females to 18 m. Mean maximum sustained rate of depth equilibration was 2 m day−1. M. exasperatus survived a pressure decrease of 40% every 12 h from the maximum equilibration depth to the surface. The fish swim actively during the day but rest on the bottom at night when they are equilibrated to a depth 1 m deeper than ambient. Reduced activity at night is reflected in a drop in oxygen consumption to nearly half of the daytime active value. |
| |
Keywords: | |
|
|