Responses of Nile tilapia to different levels of water salinity

Abstract

A 45 day experiment was carried out to evaluate the effect of water salinity on the performance, haematological parameters and histological characteristics of the gills of the Nile tilapia, Oreochromis niloticus. The water salinity levels evaluated were: 0, 7, 14 and 21 g L-1. Nile tilapia specimens (1.62 ± 0.01 g), distributed into 20 fibreglass tanks (100 L) at a density of 15 fish per tank. There were no significant differences of the water salinity levels on daily feed intake; however, there were differences (P < 0.05) on the daily weight gain, feeding conversion rate and survival. The best results were observed for the water salinity levels of 0 and 7 g L-1. There were no differences (P > 0.05) between these levels. Regarding the haematological parameters, it was observed that the percentage of the haematocrits and the erythrocyte count were influenced (P < 0.05) by the water salinity level, which was not observed for the leukocyte count. The observed histopathological alterations were chloride cell hypertrophy, epithelial lifting, structure alteration, telangiectasia, primary lamellae cells aggregation, fusion and occurrence of aneurisms of different sizes in some secondary lamellae. Regarding the frequency of gills infection intensity, there were slight changes between the salinities of 0, 7 and 14 g L-1 and moderate changes at 21 g L-1. It is concluded that Nile tilapia can be reared in water salinities of up to 7 g L-1 without damage to the parameters evaluated in this work.

A systematic review and meta‐analysis of the relationship between farm management, water quality and pathogen outbreaks in tilapia culture

“…Salinity outside of its optimal ranges have demonstrated effects on fish survival, hatching rate, endocrinology, histopathology and consequently in the immune responses (Choi et al, 2013; De Azevedo et al, 2017; Güner et al, 2006; Yada et al, 2012). A causal relationship was found with pathogens, such as V. alginolyticus and Vibrio vulnificus to salinity at <10 g/L (Chen et al, 2006; Younes et al, 2016), as well as in Branchiomyces sp., S. agalactiae , V. alginolyticus , V .…”

“…Salinity outside of its optimal ranges have demonstrated effects on fish survival, hatching rate, endocrinology, histopathology and consequently in the immune responses (Choi et al, 2013;De Azevedo et al, 2017;Güner et al, 2006;Yada et al, 2012) (Chang & Plumb, 1996).…”

Tilapia Farming in Bangladesh: Adaptation to Climate Change

“…Besides growth parameters, salinity concentration also influences hematological parameters of Nile tilapia. According to de Azevedo et al [127], hematocrit and the erythrocyte count significantly decrease at high water salinity (14 ppt). The authors also observed histological and histopathological alterations with the increased intensity of salinity.…”

“…However, changes in water salinities can decrease growth performance and can alter the physiology of tilapia. For example, Nile tilapia can grow better when reared in water with a salinity of up to 7 ppt (salinity is usually measured in parts per thousand (ppt), which is equivalent to grams of salt per liter water (g/L)) [126,127], while T. rendalli can tolerate 10 ppt salinity with no significant effect on their growth [128]. The salinity tolerance of another strain Rufiji tilapia (Oreochromis urolepis urolepis) is higher than other tilapia strains; it is 25 ppt in which concentration SGR, daily growth rate, and total body weight showed higher rates even than in 5 ppt salinity [129].…”

Combined Effects of Temperature and Salinity on the Pharmacokinetics of Florfenicol in Nile Tilapia (Oreochromis niloticus) Reared in Brackish Water

“…As a tropical freshwater fish, the optimal water temperature and salinity of Nile tilapia for the growth performance are between 28-32 • C and 0-8 ppt, respectively (2,(4)(5)(6)(7). Nevertheless, it has been suggested that Nile tilapia is also suitable for brackish water aquaculture for the salinity level up to 15 ppt (3,8).…”