GLOBAL CHANGE: Resilience, climate, pollution, habitat restoration - 1.2.4 - Nonhle Mlotshwa

Title: 4 Phenotypic variability in the aerobic scope of an exploited population of bronze bream, an important target of the recreational marine shored-based fishery Speaker: Nonhle Mlotshwa Abstract: The impacts of climate-mediated stressors such as temperature and dissolved oxygen (DO) have been known to influence the physiology and performance of marine fish. When fish are subjected to these stressors at levels outside their tolerance thresholds, this often leads to reduced growth, performance, biomass and diversity fluctuations. Exposure to prolonged periods of these stressors may, in the worst-case scenario, result in fish kills and accelerated ecosystem destabilization. This puts a strain in our marine resources, ultimately impacting the sustainability and persistence of fisheries due to the lack of goods and services provided by the marine environment. Fortunately, it is thought that in some fish populations there exist individuals with diverse physiological phenotypes that enhance the performance of fish populations, making them resilient to environmental perturbation. This study therefore seeks to assess the physiological capacities and phenotypic variation of an important coastal fishery species, the bronze bream (Pachymetopon grande) when subjected to thermal variability. This was achieved through the use of intermittent flow respirometry to measure the aerobic scope, hypoxia tolerance and performance phenotype of P. grande at three different test temperatures (10, 18 and 22 °C). It was found that within the sample P. grande population existed diverse performance phenotypes and that temperature had a significant effect on their aerobic scope of (p less than 0.05). This species also displayed a decrease in its hypoxia tolerance, with increasing temperatures, highlighting the mismatch between oxygen supply and demand as temperatures increase. These results provide insight into some of the important physiological aspects required within fish populations to combat climate mediated perturbations and the role played by diverse physiological phenotypes in the persistence and survival of transgenerational populations in the Anthropocene