Effect of rearing system intensiveness on biological features, culture performance and larval quality of meagre (Argyrosomus regius Asso, 1801) larvae

Effect of rearing system intensiveness on biological features, culture performance and larval quality of meagre (Argyrosomus regius Asso, 1801) larvae ROO, F. J., HERNÁNDEZ-CRUZ, C.M., FERNÁNDEZ-PALACIOS, H., SHUCHARDT AND IZQUIERDO, M.S Grupo de Investigación en Acuicultura (GIA).P.O. Box 56. 35200 Telde, Canary Islands. Spain. Abstract Results and discussion Acknowledgement Materials and methods Meagre, Argyrosomus regius A., is a new species for aquaculture in south Atlantic and Mediterranean regions, that can reach a mean fresh weight of 8.02±2.51g. at 95dah. However, hatchery techniques must be improved to optimize culture performance and larval quality. Eggs of meagre were cultured under intensive (75 indv.l-1 in 2m3 tanks) and semi-intensive system (7.5 indv.l-1 in 40m3 tanks) to evaluate the effect of the intensification on biological features, stress resistance and skeletal deformities. At 30dah, despite in semi-intensive system reared larvae a higher total length (19.08± 2.3mm vs 16.00±1.54mm), dry body weight (13.09± 2.43mg vs 6.46±0.52mg), and survival after the activity test (75.0± 13.8% vs 53.3±11.5%) was found, the use of intensive systems were also very suitable and cost-effective for larval rearing of this species. J.Roo, thanks the financial support provided by the Spanish Ministry of Science and Innovation and European Social Funds: “Programa Nacional de Contratación e Incorporación de Recursos Humanos de Investigación: MEC-PTA2008-1653-I”. - Intensive System (75 eggs.l-1) in 2m3 tanks. - Semi-intensive System (7.5 eggs.l-1) in 40m3 tanks. - Total length (n=25; 30dah). - Dry weight (n=25; 30dah). - Final survival (20, 30dah). - Activity test (120 seconds air exposure at 30dah). - Incidence of deformities (n= 500; 95dpe). Culture intensification reduce growth in TL and DW, (Table I). These results are in concordance with data reported for other species such as Diplodus sp. (Papandroulakis et al., 2004) or Pagrus pagrus (Roo et al., 2009b). Final survival (30dah) under intensive system (18.00±2.00%) were significantly improved with the used of semi-intensive conditions (25.67±2.51%) (Figure 1). Regardless, rearing system over 95 % of the fry produced showed no skeletal deformities. Fusions affecting vertebrae 10 to 15, were the most frequent anomaly (Figure 3). The use of intensive systems was also suitable and cost-effective for larval rearing of this specie (Table II). Thus, the feeding cost per fry produce at the end of the weaning period (35dah) were significantly lower under this type of system. The results of the activity test (Figure 2) suggest that larvae resist manipulation such as grading, that might reduce cannibalistic behaviour identified as the main cause of mortality from 20 to 30dah. Rearing techniques Determinations Table 1. Effect of culture intensiveness on growth at 30dah. Table II. Comparison of feed quantities (per fry produce) and feeding costs according to the rearing system at weaning (35dah). Figure 1. Effect of culture intensiveness on survival at 20 and 30 dah. Figure 3. Fry quality according to the rearing system. Figure 2. Survival after stress test at 30 dah. Growth Deformities characterization Survival Treatment Total Length (mm) Dry Weight (mg) Semi-Intensive 19.08±2.30a13.09±2.43a Intensive 16.00±1.54b6.46±0.52b Treatment Microalgae (ml) Rotifers(Mill) Artemia (Mill) Microdiet (g) Cost (€) Semi-Intensive 37.07 18.2 8.2 0.051 0.020a Intensive 26.28 21.4 5.1 0.025 0.015b Microdiet (150-300microms) o o o o o o o o o o o o Instar 11 (500 Indv.r 1) ~~~~~~~~~~~ Instar I (25-250 Indv.l-') "7OYOY ... - Rotifers (4-5 Indv.mr 1 in SMI;(5-10 Indv.mr 1 in IS) 00000000 Phytoplankton (250.000 cells.ml-') 00000000 10 20 Age (dah) 30 SO~------------------------------------------. a 40 b 30 20 10 0+----,--- 10 15 20 a 25 Age (dah) _ Semi-Intensive C:JI Intensive b 30 35 40 lOO~-----------------------. a 80 b 60 40 20 O -"--------- Semi-Intensive Intensive 40 · - .. ,. ' .... o· • 50 120,--------------------------------------------------, I I Normal _ Deformed 100 80 60 40 20 O~----------~--~----~----~----~--~----------~ Semi-Intensive Intensive