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Institution: Centre expérimental du Syndicat Mixte de l'Equipement du Littoral Title: Growth rate of the European abalone, Haliotis tuberculata
Growth rate of the European abalone, Haliotis tuberculata, fed an artificial diet (Adam & Amos) and macroalgae Olivier Basuyaux*, 2000
*Centre expérimental du Syndicat Mixte de l'Equipement du Littoral, 50560 Blainville sur mer, France. MATERIAL AND METHODS Feeding experiments The abalone, Haliotis tuberculata, used in these experiments originated from a semi-closed rearing system (hatchery, nursery and on-growing). Twelve lots of 50 abalone were randomly selected from urchins of 1.13(± 0.10) g fresh weight (length of 18.6(± 0.5) mm) for a total weight per lot of 60.5(± 1.3) g . The experiment was carried out for three successive periods of 4 weeks with a measurement made at the end of each period (May-August 2000). Each measurement consisted of a count of total numbers and global weight (0.1g) after drainage. The mean individual weight was calculated for each lot. Daily growth rate (GR in %/day) was calculated as follows: GR = [(Wf/Wi)1/t - 1] x 100 (1) where Wi and Wf are the mean initial and final weights and t the number of days of the experiment. Four feeding diets were tested: P. palmata and artificial diet A, B, C (Adam and Amos). The algae were harvested twice a month and were held in aerated tanks. The dry weights of the algae and the artificial diet were obtained after drying in a ventilated oven at 90°C until constant weight. The ratio fresh weight/ dry weight was calculated: DM = FW/DW (2) where FW and DW are the fresh weight and teh dry weight. During this period, DM for dartificial diet was 0.90, 0.87 and 0.86 (for A, b and C, constant all year), DM for P. palmata was 0.15. The urchins were fed ad libitum. The quantity of feed was weighed (g). The conversion ratio (CR) was calculated as: CR = A / (Wf x Nf - Wi x Ni) (3) Where : A is the quantity of ingested food converted to dry weight (g) Wi and Wf are the initial and final weights of the abalone (g) Ni and Nf are the initial and final numbers of urchins The abalones were placed in 3 mm polyethylene mesh baskets. The baskets were rectangular (0.16 x 0.19 m), had a surface area of 0.03 m² and were placed in the toboggan-type rearing structure with circulating water (8 m3/h) as described in Le Gall (1989). Water depth was of 5 cm and the water renewal rate of 6%/day enabled a good water quality in the rearing system to be maintened. Water temperature was held constant at 18.5(± 1)°C by a heat exchange pump. Water characteristics were: temperature: pH: 8.3(± 0.1), alkalinity: 4± 0.5 meq/l, NH3-4: <0.5 mgN/l, NO2: <0.5 mgN/l, NO3:<2 mgN/l, salinity: 32(± 1)‰. RESULTS Any mortality is not observed during the experiment. Variance analysis shows that feed has a strong influence on growth (Test PLSD of Fisher, P<0.02, a =0.05). Abalones fed the Palmaria palmata and artificial diet A grew faster than those fed artificial diet B and C (Fig. 1). 
Click on graph to enlargeFigure 1: Growth in weight for each feed tested on abalone rearing in a semi-closed system. Growth rates were similar for abalones fed on P. palmata and artificial diet A (1.37(0.02) and 1.36(0.03)%/day, respectively). Artificial diet B and C gave a significantly lower growth rate than with algae (P<0.05, a =0.05). Data concerning growth and conversion ratio are in Table 1. Table 1: Growth rate (GR), conversion ratio to fresh weight and dry weight.
Conversion ratios were quite significantly different (P<0.001, a =0.05) between the diets. The lowest conversion ratio (fresh weight) is obtained for artificial diet A (1.30(± 0.15)). Few degradation of artificial diet could be visually observed after 2 days in the rearing water. The colour of the shell is different according to the type of food: red when abalones are fed with P. palmata and green when abalones are fed with artificial diet. Conclusion Costs evaluating The price for the palmaria palmata is from 0.82 to 1.05 Aus$ So food cost to make a kilogram of abalones is of 4.04 in 5.19 Aus$. The price for the artificial food is of 2.95 Aus$ (+450 Aus$ / ton), So food cost to make a kilogram of abalones is of 4.42 Aus$.The artificial food A is a good food. The price is the same that that of P. palmata. So, this food could be to use in complement or as a replacement to the P. palmata. The easy stocking of the food allows to have it permanently an available stock in the breeding.Adam & Amos PO Box 1029 Mount Barker, South Australia 5251
  
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