Effect of climate change on hematotoxicity/hepatoxicity oxidative stress, Oncorhynchus mykiss, under controlled conditions

practices. In this context, it is important to emphasize that as a result of the growing demand for water, it has become necessary to investigate biotic and abiotic factors that may pose a threat to the industry [4–6]. Temperature is one of the key factors for the growth and survival of aquatic organisms. It is well known that temperature changes can directly affect some physiological processes, from metabolic rate, immunity and oxygen demand to contact uptake. Temperatures above the thermal threshold not only increase oxygen demand but also suppress immunity by reducing feed intake. This mechanism of action is explained by the negative impact of tem- perature change on aerobic metabolism. Temperature limits the solubility and availability of oxygen [7–9]. According to the Intergovernmental Panel on Climate Change, severe global warming is expected in many parts of the world by 2100 2100 [10]. In these climate change models, an increase of up to 3 ˚C is predicted for the next century, especially in tropical water tempera- tures. In addition, in aquaculture, temperature fluctuations can affect production in various dimensions, such as metabolic rate, oxygen solubility, thermal stress tolerance, tolerance to environmental pollutants, immune response, reproductive/ growth and development perfor- mance, feed intake. Overall, these negative impacts suggest that even small temperature changes can cause significant suppression of individual or population performance [8, 11–13]. However, it is known that fish actively seek their preferred temperature, which is not always

possible depending on habitat characteristics and species biogeography. Consequently, experi- menting with acute thermal shocks under laboratory controlled conditions is crucial to iden- tify the basic mechanism by which fish cope with this stress. While it is known that many stress-related physiological parameters of fish are generally altered by chronic high tempera- ture exposures, the mechanisms of these alterations are not yet fully understood [7, 12, 14, 15]. Rainbow trout (Oncorhynchus mykiss, Walbaum, 1792) is the most widely cultivated trout species in Turkey with a high commercial value [16]. Due to its fast growth and high nutri- tional value, it is widely cultivated in many countries. Rainbow trout live in cold, clear and well-oxygenated rivers and lakes with a water temperature of 20–21 ˚C [7]. When aquaculture in Turkey is analyzed, trout is the most widely cultivated species in terms of inland fish pro- duction. Trout farming covers 35.47% of our total aquaculture production in inland waters and in the sea in recent years, together with the so-called Turkish salmon, which is produced in the sea. In recent years, aquaculture in Turkey has gained momentum in parallel with the develop- ing technology and economic growth. As a result of overfishing and population decline, the importance of aquaculture is increasing day by day. Aquaculture studies were first started in inland waters, then they were replaced by marine environments, and with the determination and application of economic cultivation methods, the studies in the dimension of initiative

have gained a sectoral structure [17]. Global warming affects water quality as well as water flow. Waters that are already heavily exposed to pollution factors will also have to absorb more pollution concentrations with the decrease in water, and with increasing water temperatures, it will negatively affect the amount of dissolved oxygen, which is very important for aquatic life, as well as many quality criteria in waters. Due to climate change and the resulting global warming, the earth’s temperature has increased by around 0.7–0.8 ˚C 96 over a period of approximately one hundred years in the 20th and 21st centuries. If necessary measures are not taken, temperatures will gradually increase. As a result, glaciers will gradually decrease, sea levels will rise, forest cover will decrease and natural disasters such as desertification, forest fires and extreme floods will increase. Agricultural production will be significantly affected due to drought, and many plant and animal species may face the danger of extinction due to deterioration of living conditions PLOS ONE Effect of temperature on fish physiology and biochemistry PLOS ONE | https://doi.org/10.1371/journal.pone.0294656 November 30, 2023 2 / 13