Thermal dynamics and physiological implications in pacu Piaractus mesopotamicus anaesthetised with Ocimum basilicum essential oil

Abstract

The aim of this study was to evaluate the haematological, biochemical and body temperature parameters of pacu Piaractus mesopotamicus juveniles after capture stress followed by anaesthetic induction. Fish (30.4±1.4 g) were divided into five groups (12 fish each group): control (water only handling), ethanol handling (600 µL L-1), handling with 100, 350 and 600 mg L-1 of essential Ocimum basilicum oil. Fish were caught and anaesthetised, followed by biometric handling, blood collection and thermographic images. Increased anaesthetic concentrations had a linear positive effect on haemoglobin content, erythrocytes, mean corpuscular haemoglobin concentration (MCHC), monocytes and granular leukocyte PAS positive (LG-PAS) (P<0.05). A quadratic effect (P<0.05) was observed for lymphocytes, with a maximum peak at the 350 mg L-1 concentration. The fish surface temperature ranged was 25.9-29.9 oC, with the highest values in the non-anaesthetised fish’s cephalic regions. The fish anaesthetised with the O. basilicum essential oil 100 mg L-1 concentration showed a lower surface temperature. Using O. basilicum essential oil in biometric handling procedures was unable to prevent stress-related haematological alterations in juvenile pacu. Employing infrared thermography to assess surface temperature provides useful data to understand the effects of anaesthesia on fish, but more studies are needed to better understand this technique as a measure of well-being in fish farming.