The effects of acclimation temperature, salinity, and behavior on the thermal tolerance of Mozambique tilapia (Oreochromis mossambicus)

Abstract

Mozambique tilapia have been shown to be incredibly stress tolerant with respect to environmental salinity, hypoxia, and ammonia concentrations. Temperature challenges to this species have shown that they have difficulty with cold acclimation. The purpose of this study was to measure the effects of acclimation temperature and salinity on the thermal tolerance of Mozambique tilapia as assessed by critical thermal maxima (CT) and critical thermal minima (CT). We also monitored fish behavior and quantified ventilation rate. To our knowledge, this study was the first to investigate upper and lower thermal tolerances, and the effect of environmental salinity in this physiologically impressive species. Using predictive regression analyses of the thermal limits, thermal tolerance polygons were constructed and total areas were calculated 678.9°C for freshwater (FW)-acclimated tilapia, and 739.4°C seawater (SW)-acclimated tilapia. During the thermal challenges, we observed two novel behaviors in response to thermal challenge, ventilation cessation behavior (VCB) and aquatic surface respiration (ASR), and we conclude that the use of these behaviors extended the thermal limits of these fish in both FW and two-thirds SW by limiting the exposure of the gill epithelium to the changing environment.

Take time to look at the fish: Behavioral response to acute thermal challenge in two Amazonian cichlids

“…Our results suggest that fish were experiencing physiological hypoxia at water temperatures approaching CT max that led to the initiation ASR to increase oxygen delivery to the tissues. King and Sardella (2017) observed ASR during CT max trials in the Mozambique tilapia ( Oreochromis mossambicus ), and they also reported ventilation cessation behavior, which we did not observe in M. insignis or A. agassizii . King & Sardella attributed the use of ASR in the Mozambique tilapia to increased metabolic demands on the fish during acute thermal increase and hypoxemia that would occur with ventilation cessation behavior.…”

Infection of Tilapia tilapinevirus in Mozambique Tilapia (Oreochromis mossambicus), a Globally Vulnerable Fish Species

“…Therefore, Mozambique tilapia has been used in breeding to improve the saltwater and cold tolerance of other tilapias [21,26,27]. The species has also been used as a model to study environmental factors [28,29] and response to pathogens [30]. Mozambique tilapia is native to the river of South Africa [31], but its numbers have decreased due to introduction of invasive fish species, including Nile tilapia.…”

Identification of Genes Related to Cold Tolerance and Novel Genetic Markers for Molecular Breeding in Taiwan Tilapia (Oreochromis spp.) via Transcriptome Analysis

“…Research comparing the cold-tolerance characteristics among the different Nile tilapia species located in different geographic locations such as Egypt, Ghana, and the Ivory Coast revealed that Nile tilapia have survived through natural selection for many years, and the physiologies and lethal temperature ranges reflect different cold-tolerant phenotypic characteristics acquired from their ancestral populations [ 42 , 43 ]. Although it is well known that there are intraspecies phenotypic differences in temperature tolerance [ 44 , 45 , 46 , 47 ], there is still a lack of information regarding this genetic variation. The physiological basis of this study was the long-term collection of populations possessing different cold-tolerant phenotypes.…”