The underwater photic environment of Cape Maclear, Lake Malawi: Comparison between rock- and sand-bottom habitats and implications for cichlid fish vision

Shai Sabbah, Suzanne M. Gray, Emmanuel S. Boss, James M. Fraser, Richard Zatha, Craig W. Hawryshyn

Research output: Contribution to journalArticlepeer-review

Abstract

Lake Malawi boasts the highest diversity of freshwater fishes in the world. Nearshore sites are categorized according to their bottom substrate, rock or sand, and these habitats host divergent assemblages of cichlid fishes. Sexual selection driven by mate choice in cichlids led to spectacular diversification in male nuptial coloration. This suggests that the spectral radiance contrast of fish, the main determinant of visibility under water, plays a crucial role in cichlid visual communication. This study provides the first detailed description of underwater irradiance, radiance and beam attenuation at selected sites representing two major habitats in Lake Malawi. These quantities are essential for estimating radiance contrast and, thus, the constraints imposed on fish body coloration. Irradiance spectra in the sand habitat were shifted to longer wavelengths compared with those in the rock habitat. Beam attenuation in the sand habitat was higher than in the rock habitat. The effects of water depth, bottom depth and proximity to the lake bottom on radiometric quantities are discussed. The radiance contrast of targets exhibiting diffused and spectrally uniform reflectance depended on habitat type in deep water but not in shallow water. In deep water, radiance contrast of such targets was maximal at long wavelengths in the sand habitat and at short wavelengths in the rock habitat. Thus, to achieve conspicuousness, color patterns of rock- and sand-dwelling cichlids would be restricted to short and long wavelengths, respectively. This study provides a useful platform for the examination of cichlid visual communication.

Original languageAmerican English
Pages (from-to)487-500
Number of pages14
JournalJournal of Experimental Biology
Volume214
Issue number3
DOIs
StatePublished - Feb 2011
Externally publishedYes

Keywords

  • Beam attenuation
  • Body coloration
  • Radiance contrast
  • Spectral irradiance
  • Visibility
  • Visual communication

All Science Journal Classification (ASJC) codes

  • Insect Science
  • Ecology, Evolution, Behavior and Systematics
  • Aquatic Science
  • Animal Science and Zoology
  • Molecular Biology
  • Physiology

Fingerprint

Dive into the research topics of 'The underwater photic environment of Cape Maclear, Lake Malawi: Comparison between rock- and sand-bottom habitats and implications for cichlid fish vision'. Together they form a unique fingerprint.

Cite this