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Depth equilibration by two predatory cichlid fish from Lake Malawi
Author(s) -
Ribbink A. J.,
Hill B. J.
Publication year - 1979
Publication title -
journal of fish biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.672
H-Index - 115
eISSN - 1095-8649
pISSN - 0022-1112
DOI - 10.1111/j.1095-8649.1979.tb03548.x
Subject(s) - cichlid , biology , predation , fish <actinopterygii> , ecology , zoology , fishery
The cichlid fish, Haplochromis polystigma and Haplochromis livingstonii are piscivorous ambush predators endemic to Lake Malawi, Africa. Experimentally it was found that large adult H. livingstonii could equilibrate to 38 m, but that juveniles were restricted to shallower depths. Mean depth attained by 8 H. polystigma was 45 m but two individuals exceeded the maximum simulated depth (59 m). H. livingstonii had a mean equilibration rate of 4–7 m day −1 for the first 10 m declining to 2·4 m day −1 thereafter. The mean rate of descent for H. polystigma was 3·8 m day −1 for the first 10 m and 2·8 m day −1 thereafter. The fish were decompressed at a rate of a 20% decrease every 12 h. Although cichlid fishes occur down to 200 m depth in Lake Malawi, experimental and field data indicate that the depth distribution of individual species is restricted and that the restriction is largely related to swimbladder physiology. All cichlid species so far tested equilibrate slowly to depth (2 to 5 m a day) and are not capable of rapid decompression.