The effects of handling time, ambient light, and anaesthetic method, on the standardized measurement of fish colouration

• Published in: Canadian journal of fisheries and aquatic sciences Vol. 68; no. 2; pp. 330 - 342
• Main Authors: Gray, Suzanne M, Hart, Francine L, Tremblay, Maude E.M, Lisney, Thomas J, Hawryshyn, Craig W
• Format: Journal Article
• Language: English
• Published: Ottawa, ON National Research Council of Canada 01.02.2011; NRC Research Press; Canadian Science Publishing NRC Research Press
• Subjects: Agnatha. Pisces; Animal, plant and microbial ecology; Applied ecology; Aquatic sciences; Biologi; Biological and medical sciences; Biology; Cichlidae; Color; Comparative analysis; Effects; Essential oils; Exploitation and management of natural biological resources (hunting, fishing and exploited populations survey, etc.); Fish; Freshwater; Fundamental and applied biological sciences. Psychology; Light intensity; Maylandia zebra; Measurement; Melanochromis auratus; Methods; NATURAL SCIENCES; NATURVETENSKAP; Optical properties; Physiological aspects; Reflectance; Spectra (Spectroscopy); Spectrometry; Spectrum analysis; Ultraviolet radiation; Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution; Malawi; Africa; Canada; Sweden; Africa, Nyasa L; Stain; Color; Ice; Method; Bath; Capture; Luminous intensity; Vertebrata; Spectrometry; Light; Manipulation; Pisces; Anesthesia; Coloration; Reflectance
• ISSN: 0706-652X; 1205-7533; 1205-7533
• DOI: 10.1139/F10-151

The effects of handling time, ambient light intensity, and anaesthetic method, on the collection of spectral reflectance data were assessed in two species of Malawi cichlids ( Melanochromis auratus and Metriaclima zebra ). Using spectrometry, colour patches were measured over 10 min, under increasing ambient light levels, and using three anaesthetic methods. As time elapsed, maximum percent reflectance (R max ) decreased across all anaesthetic methods and species, suggesting that measurements should be taken immediately after capture and anaesthetization. With increasing light intensity, R max increased significantly, suggesting that measurements should be taken under natural ambient conditions when possible. Finally, we found that anaesthetizing fish using an ice bath produced significantly higher R max than using either MS-222 (tricaine methanesulphonate) or clove oil (eugenol). However, the highest proportion of ultraviolet (UV) colouration was recorded while fish were anaesthetized with clove oil. Our results highlight the variation involved in measuring fish colour patterns using two related species, and thus indicate the need for a standardized approach to collecting spectral reflectance data in fish.