Low-temperature tolerance of Nile tilapia,Oreochromis niloticus: effects of environmental and dietary factors

Abstract

This study was conducted (1) to evaluate the effects of photoperiod (fixed vs. decreasing light), fish size (136 vs. 220 mm), dissolved ions (hardness and salinity) and diet (menhaden oil vs. coconut oilbased) on the tolerance (survival) of Nile tilapia, Oreochromis niloticus, to low temperatures (decreased by approximately 0.5 8C per day) and (2) to evaluate the effect of dietary fatty acid composition on selected physiological characteristics of Nile tilapia exposed to decreasing temperatures. Size significantly affected mortality, with smaller fish being less tolerant to low temperatures than larger fish. Results were equivocal in the photoperiod, dissolved ion and dietary lipid experiments, and were dependent on the method of data analysis employed. Diet significantly affected plasma osmolarity, with higher values in fish fed the menhaden-based diet. Haematocrit, serum glucose, sodium and cortisol concentrations, serum and splenic lysozyme activities, lymphocyte count and hepatosomatic index were not affected by diet. Haematocrit, white cell count and serum glucose and sodium concentrations were significantly affected by temperature, but serum and splenic lysozyme content, hepatosomatic index, and serum cortisol concentrations were not. The results of this series of experiments indicate that altering the environment or diet has little effect on the ability of Nile tilapia to survive low temperatures.

Vegetable oil sources in diets for freshwater angelfish (Pterophyllum scalare, Cichlidae): growth and thermal tolerance

“…This result suggests that the high levels of polyunsaturated fatty acids of the n-3 series, and higher n-3/n-6 ratio increases the cold tolerance for red drum. However, a similar study with Nile tilapia (Atwood et al, 2003) did not show significant differences for cold tolerance, in spite of the profile changes in the body fatty acids observed.…”

Modulation of the immune system of fish by their environment

“…One study looked at lysozyme values for fixed photoperiod (light/dark 12:12, 24:0, and 14:10) in rainbow trout and noticed that LD 24:0 increased lysozyme after 7 days and for LD 14:10 after 30 days [11]. Another study showed no change in lysozyme of N1ile tilapia to reduced light periods [12]. The photoperiod was initially set to 12 L:12 D. Fish were allowed to acclimate for 6 days.…”

Bayesian genetic parameters for body weight and survival of Nile tilapia farmed in Brazil

“…Mortality rate is also an important trait, and it can have direct implications on farm productivity. The survival of tilapia is affected by a great variety of factors, such as age (Wagner et al, 2004), cultivation density and water quality (Yi & Lin, 2001), and temperature and diet (Atwood et al, 2003). Few experiments have been carried out to study the genetic control of survival in tilapia (Chiayvareesajja et al, 1999;Charo-Karisa et al, 2006;Rezk et al, 2009).…”