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Abstract. Establishing thermal limits for species of conservation concern is important for husbandry outside the native range. The pitch-black fulu, Astatotilapia piceata is a pseudocrenilabrine Lake Victoria cichlid which is possibly extinct in the wild. To establish whether A. piceata can be cultured extensively in outdoor settings in the U.S. state of Florida and in other suitable habitats, the study experimentally determined the critical thermal limits (minimum and maximum) for A. piceata. The critical thermal minimum was 11.6°C, while the maximum was 37.1°C, resulting in a thermal tolerance range of 25.5°C. These results indicate culture would be possible in subtropical regions worldwide. In Florida, specifically, year-round outdoor culture would be restricted to the southern peninsula.
Key Words: critical thermal maximum, critical thermal minimum, pitch-black fulu, thermal tolerance.
Introduction. In this technical note we identify the critical thermal limits for the pitchblack fulu, Astatotilapia piceata (Haplochromis piceatus; Yssicchromis piceatus), a species first described in 1969 (Greenwood & Gee 1969), which is possibly extinct in the wild (Hemdal & McMullin 2013) (Figure 1). A. piceata is just one member of the Lake Victoria pseudocrenilabrine (Tribe Haplochromini) cichlid species flock, an evolutionary radiation that may have numbered ca. 500 endemic species prior to a mass extinction event that peaked during the mid-1980's (Ogutu-Ohwayo 1990; Kaufman 1992; Witte et al 2007). Ecologically, this species was an epibenthic to midwater zooplanktivore, feeding largely on the aquatic larvae of dipteran flies. Its associates in the water column prior to limnological and community reorganization included about one dozen species of the more morphologically specialized zooplanktivores in the genus Yssichromis plus a variety of other zooplanktivorous and insectivorous taxa. A. piceata underwent a diel vertical migration in Mwanza Gulf, where it has been most thoroughly studied in the wild (Goldschmidt et al 1990). A captive stock of A. piceata was established in Leiden, Netherlands by the Haplochromine Ecology Study Team (HEST) during the 1980's and 1990's. Descendants of this population were incorporated along with several other haplochromines into a conservation captive breeding program for the Lake Victoria haplochromines, the Lake Victoria Fishes Species Survival Program (LVSSP). Surplus 1stock from the LVSSP was the source of the animals used in this study.
Critical thermal methods utilize rapid temperature changes (increases or decreases) and...