Thermal Tolerance and Survival of Nile Tilapia and Blue Tilapia under Rapid and Natural Temperature Declination Rates

Abstract

Blue Tilapia Oreochromis aureus and Nile Tilapia O. niloticus are indigenous to Africa and the Middle East but now are globally popular in aquaculture and for private and public stocking as forage fish for sport species and biological control for nuisance vegetation. The invasive nature of these species at a global scale and the lack of recent and applicably tested thermal tolerance methodology require research to assess the current potential for invasion risk in North Carolina and elsewhere. In this thermal tolerance experiment we focused on a moderate declination rate (1°C per 3 d) and a slow declination rate (1°C per week) in water temperature to assess the thermal minima of Blue Tilapia, common Nile Tilapia, and a “white” strain of Nile Tilapia. The moderate rate was used to compare results to previous literature, and the slow rate was used to mimic natural seasonal water temperature decline in North Carolina. As lineage and breeding history may vary by supplier, fish from multiple suppliers within each species group were tested. Our results indicate that in general, these tilapias cannot survive below 8°C. We did not observe differences in temperature at death or survival curves between species in the moderate rate treatment. Under the slow declination rate, we found significant differences in the mean temperatures at death of Blue Tilapia (9.5°C) and white Nile Tilapia (9.3°C) relative to the less‐cold‐tolerant common Nile Tilapia (10.8°C); this result was reflected in statistically different survival curves. In addition, although there was some variation in temperature at death among different supplier groups (0.0–0.6°C) within a species, all fish died at 8°C or above. Our results suggest that selective breeding of white Nile Tilapia may have resulted in increased thermal tolerance during the process of developing this color variant. Furthermore, the minimum lethal temperature of 8°C may explain why these tilapia species have been restricted to reservoirs with heated effluent in North Carolina.

The Impact of Sampling Season and Catching Site (Wild and Aquaculture) on Gut Microbiota Composition and Diversity of Nile Tilapia (Oreochromis niloticus)

“…The optimum water temperature for rearing Nile tilapia is between 27 and 32 °C [ 8 ]. The fish begins to die when the water temperature drops to 11 °C, and it cannot survive below 8 °C [ 9 ].…”

Cold tolerance and performance of selected Nile tilapia for suboptimal temperatures

“…In another study, the cold tolerance of Nile tilapia and blue tilapia commercialized in the USA was evaluated, and the authors concluded that when the temperature decreased moderately (1°C every three days), there was no difference in temperature average mortality between the two species, but when the temperature slowly decreased (1°C per week), the blue tilapia was more tolerant (Henson et al., 2018). This study shows that the results obtained from cold tolerance in tilapia can change according to the methodology used during the assay.…”

Application of second-generation sequencing (SGS) and third generation sequencing (TGS) in aquaculture breeding program

“…To cope with mass mortalities of farmed species and huge profit loss, selective breeding programs have been established to improve robustness of farmed species with significant heritability and genetic gain in disease resistance and increased tolerance towards changing aquatic environmental conditions such as in Pacific oyster (Degremont et al, 2007;de Melo et al, 2016), rainbow trout (Sae-Lim et al, 2015, tilapias, Oreochromis spp. (Henson et al, 2018), common carp (Zhao et al, 2021 and chinook salmon, Oncorhynchus tshawytscha (Lulijwa et al, 2021). While reducing environmental loads, selective breeding may also enhance efficiency of resource utilization for aquaculture production through shorter production period and improved feed efficiency in robust animals (Sae-Lim et al, 2017).…”