EFFECTS OF DIFFERENT FEEDING RATES ON GROWTH OF JUVENILE MEAGRE, ARGYROSOMUS REGIUS (ASSO, 1801)

The meagre is a very interesting species for aquaculture because of its fast growing and the excellent sensorial qualities (white flesh with desirable flavour and texture) (García-García et al., 2008). Besides it can be cultured in tanks and cages. Argyrosomus regius is a carnivorous species and very voracious so it’s interesting to determine the feeding rate to achieve the highest growing with the lowest consumption of food. In this way the production is optimum. In the present study different feeding rates have been tested and a comparison of the growing have been done in order to determine which one gives better results.

 

Material and Methods
540 juveniles meagre, Argyrosomus regius, averaging a total length 81±5mm and a weight of 7±1g were stocked in 9 tanks of 300L. Feeding rate of 2.5%, 5.0% and 10.0% of body weight per day (% bw day-1), have been tested by triplicate during 30 days (88-118DAH). Food was given using automatic feeders, 4 times a day. Every week a sampling was done by measuring total length and weight of 10 fingerlings of each tank, previously anesthetized with clove oil. Several parameters of the water were measured daily (temperature (ºC), oxygen (ppm) and salinity (g.L-1)) or weekly (pH, nitrite (ppm), ammonia (ppm) and flow (L.min-1)). The average temperature and salinity was mantained at 22ºC and 40g.L-1, respectively. The differences in growing have been measured by using rates such as WG (weight gain), SGR (specific growth rate)and TGC (thermal growth coefficient) (Cho, 1992) and feeding was measured with FCR (food conversion rate) and PER (protein efficiency ratio) (Zoccarato et al., 1994; Eroldogan et al., 2004). Growth data were treated using one-way analysis of variance (ANOVA) and the Tuckey’s test to compare mean values among the different groups.

 

Results and Discussion
No statistically significant differences (P>0.05) were observed in growing, neither in length nor in weight. WG, SGR and TGC were similar at feeding rates 2.5% and 5.0%.bw.day-1 and lower at 10.0%.bw.day-1 (Table I). With regard to feeding parameters, in fish fed at 10.0%.bw.day-1 FCR has been significantly higher. Besides the results obtained with the 2.5%.bw.day-1 for PER have been higher (P<0.05) than the others feeding rates (Table I). This results agrees with the observations of Eroldogan et al., (2004) in Dicentrarchus labrax, who obtained the highest feed efficiency at a feeding rate of 2.0%.bw.day –1, while fish fed to satiation had a lower feed efficiency. Under a condition of low feeding rate, fish tend to optimize their digestion to extract more nutrients more efficiently (Zoccarato et al., 1994; Van Ham et al., 2003).

 

Conclusions
According to the results obtained, fingerlings of meagre feeding at 2.5 and 5%.bw.day-1 at 22ºC in seawater showed the lowest FCR than at 10.0%.bw.day-1 and at 2.5%.bw.day-1 showed the highest protein efficiency ratio (PER) than at 5.0 or 10.0%.bw.day-1. Overfeeding fish may cause water quality problems and increase the costs.