ISSN: 2577-4050
Authors: Ceron Fatima JM*
Nile tilapia is a widely farmed species globally, due to its resistance to environmental challenges. Additionally, it is a generalist consumer and a prolific breeder. In Brazil, this fish is recognized as an invasive species because of its high dispersion and establishment rates, which compromise native biota. Estuarine waters (0.06 - 32‰) are being used in tilapia aquaculture, which is a promisor fish farming for euryahalinity species. The tilapia’s euryhalinity is well-know, but most protocols are based on gradual exposure. This research showed the tolerance of Nile tilapia on abrupt exposure to 0‰ (FW), and 10, 20, 30, 35 or 40‰, over in 6, 12 and 24 hours. An abrupt exposure resistance demonstrate that this fish can use estuaries to disperse for other watersheds. After experimental design the blood sample was taken after anesthesia was administered. Subsequently, fish was euthanized by spinal section, for muscle and gills samples collections. All samples were keep freezing until ionic, dehydration and enzyme measurement. Nile tilapia survived 24h until 30‰, 12h at 35‰ and 9h at 40‰. Osmolality increase and muscle dehydration decrease both above 20‰. While sodium levels keep regulated in all salinities, chloride, potassium and magnesium levels also increased above 20‰. These results prove that tilapia can easily tolerate abrupt exposure until 20‰ without an osmotic stressor. Gill carbonic anhydrase (C.A.) activity decreased at 30‰, and NKA did not change along salinities and times. These results complements plasma and dehydration averages, showing the large tolerance of this specie to salinity challenges, even in abrupt exposure. Then, these results can be used for discuss about the estuary fish farming system for tilapia, as this species may use estuarine waters to nearby rivers and also can harm the native ecosystem.
Keywords: Nile Tilapia; Invader Species; Osmoregulatory Plasticity
