Environmental variations are having a significant impact on the growth and other physiological processes of aquatic organisms. The mullet Mugil incilis is a native species of the Colombian Caribbean, euryhaline and eurythermal, capable of tolerating a wide range of temperatures and salinities without affecting its physiology and metabolism, which provides it with an adaptive advantage in the face of variable or abrupt environmental conditions. Our aim was to determine the effect of water temperature and salinity on the physiological responses of the mullet cultivated in captivity. A total of 150 wild adult mullets (67.92 ± 1.10 g) were transported from the Ciénaga Grande de Santa Marta to the Aquaculture Laboratory of the University of Magdalena. They were acclimated for one month in circular PVC tanks (250L) at 0 ppt and ambient temperature (28 °C). They were fed an experimental diet (3.2% of biomass), distributed in three feedings per day. Over a period of 28 days, four experimental treatments (250L) were established in closed systems with constant aeration: T1: 28°C/0ppt; T2: 34°C/0ppt; T3: 28°C/10ppt; T4: 34°C/10ppt, with 3 replicates per treatment and 13 fish per replicate. The fish cultivated at 10 ppt were gradually adapted (5 ppt/day). Biometric measurements (growth and yield of the culture) were conducted, and every 7 days, blood samples were taken from 5 fish per treatment to evaluate glucose and cortisol levels. A simple and two-way ANOVA was applied to assess the effects among the factors and their interactions.
The growth and performance indicators did not exhibit significant differences across treatments (p > 0.05), nor were there any notable interactions between temperature (ºT) and salinity (S‰). However, the condition index (K) revealed significant differences between treatments T2 and T3, as well as between T3 and T4 (p = 0.0161), with superior values observed at higher temperatures (T2 = 0.73 and T4 = 0.71) at 34°C (p = 0.0110). Final survival rates showed significant differences between T1 and T2, and between T2 and T3 (p = 0.0110), indicating a significant temperature effect, with higher survival rates at 28°C (p = 0.0024). Regarding glucose levels at the start of the experiment, no significant differences were found among treatments. However, after 28 days of cultivation, differences emerged between treatments (p = 0.0231), alongside a significant effect of salinity at 10 ppt (p = 0.0121), with higher values compared to 0 ppt. Initial cortisol levels were elevated in the treatment at 28°C/10 ppt, although this response did not persist over time.
Mugil incilis demonstrated a significant physiological tolerance to variations in temperature and salinity, sustaining stable growth and high survival rates. Temperature emerged as the most influential factor, with superior survival rates observed at 28 °C and an improved condition index at 34 °C. These findings underscore the potential of this species for cultivation in variable environments, representing a sustainable and resilient alternative in response to the challenges posed by climate change.
This research was funded by Project BPIN 2021000100084 titled: "Fortalecimiento de las capacidades institucionales para la investigación del cultivo y reproducción inducida de la lisa (Mugil incilis) como una alternativa para su conservación en el Caribe Colombiano, Magdalena" supported by the Ministry of Science, Technology, and Innovation of Colombia (MINCIENCIAS- Regalías).