Effects of water flow on ventilation rate and plasma cortisol in Nile tilapia introduced into novel environment

Author(s)

Roza e Silva, Maria Luiza ^[1] ; Pereira, Rafaela Torres ^[1] ; Arvigo, Alexandre Luiz ^[1] ; Zanuzzo, Fabio Sabbadin ^[2] ; Barreto, Rodrigo Egydio ^[1]

Affiliation

^[1] UNESP, Dept Struct & Funct Biol, Inst Biosci Botucatu, CAUNESP, Rua Prof Dr Antonio Celso Wagner Zanin 250, BR-18618689 Botucatu, SP - Brazil

^[2] Mem Univ Newfoundland, Dept Ocean Sci, St John, NF A1C 5S7 - Canada

• Document type: Journal article
• Source: AQUACULTURE REPORTS; v. 18, NOV 2020.
• Web of Science Citations: 0

Abstract

Water flow is a typical hydrodynamic variable of natural occurrence in fish's lifetime and understanding its impact on biological processes (e.g. stress) can contribute to improve welfare in captive/farmed fish. For that, we tested whether water flow is a stressor by itself in a non-rheophilic (i.e. theoretically sensitive to water flow) fish species: Nile tilapia (Oreochromis niloticus). Additionally, this species was chosen due to its importance for world aquaculture and because is cultivated in a number of systems which the water flow could potentially be a stressor such as indoor tanks, recirculating aquaculture systems, biofloc system and cages. Here, we exposed fish to a novel environment with (520 L h(-1)) or without a deliberated water flow, and we measured plasma cortisol and ventilation rate (VR) as indicators of stress. In a first experiment, the VR was reduced by flow immediately after tilapia transference to a novel environment (16 min of evaluation), but cortisol was not affected. The plasma cortisol levels were also measured in a second experiment, 30 min, 1, 2 and 4 h after transference to a novel environment, but was also not affected by the presence of flow. In a theoretical perspective, flow is not a stressor by itself in a non-rheophilic species. It acted as a hydrodynamic factor that decrease the magnitude of ventilation response in a fish introduced into a novel environment, without effects on plasma cortisol levels. Therefore, the water flow eventually can be used to assist fish oxygenation after a disturbance event, such as introduction into a novel environment. (AU)

• FAPESP's process: 17/21594-7 - Mild swimming activity and stress in Nile tilapia
• Grantee: Maria Luiza Roza e Silva
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• FAPESP's process: 16/19518-8 - Predator control in Fisheries: Assessment of predator-induced biological changes in cultured Nile Tilapia
• Grantee: Rodrigo Egydio Barreto
• Support Opportunities: Regular Research Grants