1. Introduction
Marine fish culture in Mexico is still at an experimental level. Spotted sand bass Paralabrax maculatofasciatus has been identified, among other fish, as a potential
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candidate for aquaculture Matus-Nivon et al., 1990 . The distribution of this species
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ranges from Monterey Bay, USA to Mazatlan, Sinaloa, Mexico Miller and Lea, 1972 . Ž
It inhabits shallow waters up to 60 m in northwest Mexico Thomson et al., 1987; .
Lluch-Cota, 1995 , and is eurythermal because it tolerates temperatures from 7.58C to Ž
. 328C Thomson et al., 1987 . Spotted sand bass is carnivorous, preying mainly during
daytime on small crustaceans, bivalves, gastropods, cephalopods, ophiuroids, and fish Ž
. Ferry et al., 1997 . This Serranid species shows adaptability to culture conditions and
low territoriality. Sexual maturation and artificial propagation have been successfully Ž
. done Rosales-Velazquez, 1997 . The spotted sand bass can reach about 45-cm total
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length Van der Heiden, 1985 , and its white meat is of excellent quality; however, very little information is available on its nutritional requirements. Protein is the most
expensive component in fish feeds; hence, optimizing dietary concentrations is essential to minimize feed cost and to formulate feeds, which allow good growth and protein
utilization. The dietary protein level needed for maximum growth of carnivorous species
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under culture conditions has been reported to vary from 40 to 55 Tucker, 1998 . The only information available on the nutritional requirements of spotted sand bass
juveniles indicate those at 2.5-g mean weight need at least 55 dietary protein for best growth when casein is the sole protein source. However, in terms of feed conversion
Ž ratio apparently the requirement could be lower Anguas-Velez, personal communica-
´
. tion . We need to determine the requirements for each species and for each stage of
development to produce appropriate practical diets. In the present study, the effect of the dietary protein level on growth and body composition of spotted sand bass juveniles fed
practical diets was evaluated.
2. Materials and methods
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Three-month-old juveniles 9.5 1.5 g were selected from fish produced at the Unidad Piloto de Maricultivo CICIMAR-IPN, La Paz, Mexico. Fish were randomly
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distributed 42rtank in nine 600-l tanks. These tanks were connected to an enclosed water recirculating system of 22 cylindrical fiberglass tanks. Photoperiod was set to
13:11 light:dark cycle and temperature ranged from 238C to 258C. Salinity varied Ž
. Ž
between 30‰ and 35‰. Total ammonia 0.02 and 0.49 mgrl and nitrite 0.02 and 0.71 .
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mgrl were measured using spectrophotometric methods Strickland and Parsons, 1972 . Dissolved oxygen during the experiment ranged between 6.2 and 8.0 mgrl, and was
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measured using a YSI oximeter model 58 Ohio, USA . Three experimental diets were formulated to contain 40, 45, or 50 crude protein
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dry matter basis . The protein level was adjusted by replacing sardine meal with wheat Ž
meal. The diets were isocaloric and the total lipid level was maintained constant Table .
1 . All dry ingredients were sieved through a 500-mm mesh.
Table 1 Ingredient content, proximate analysis, and gross energy content of the experimental diets
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Ingredients gr100 g diet Diet 40
Diet 45 Diet 50
a
Sardine meal 31.33
41.59 51.96
a
Soybean protein meal 10.00
10.00 10.00
a
Squid meal 10.00
10.00 10.00
a
Wheat meal 33.81
24.31 14.65
b
Bakery yeast 6.00
6.00 6.00
a
Sardine oil 1.98
1.21 1.00
a
Soybean lecithin 1.50
1.50 1.00
c
Vitamin premix 0.70
0.70 0.70
d
Mineral premix 2.00
2.00 2.00
e
Sodium alginate 2.40
2.40 2.40
Choline chloride 0.20
0.20 0.20
f
Ascorbic acid 0.08
0.08 0.08
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Proximate composition dry matter, except moisture. MeanSD Crude protein
41.920.26 46.370.09
52.520.09 Ether extract
8.900.03 8.530.26
8.110.01 Ash
9.560.07 11.010.12
11.520.02 Fiber
1.350.07 1.190.32
0.740.11
g
NFE 38.27
32.94 27.17
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Gross energy calrg 482127
484215 493412
Moisture 22.270.09
18.560.30 23.920.17
a
PIASA, La Paz, Baja California Sur, Mexico.
b
Los Volcanes, Queretaro, Mexico.
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c
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Vitamin supplement except where units are given, values are in mgrkg diet : Vit. A retinol, 2500 IU; Vit. D , 2400 IU;
DL
-alpha-tocopheryl acetate, 50 IU; menadione 10; thiamin, 1; riboflavin, 4; pyridoxine, 3;
3
pantothenic acid, 20; niacin, 10; d-biotin, 0.15; folic acid, 1; cyanocobalamin, 0.01; inositol, 300. Filler sorghum meal.
d
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Mineral premix grkg diet : CaCl 2H O, 5.14; Na HPO , 11.4; MgSO 7H O, 2.98; FeSO 7H O,
2 2
2 4
4 2
4 2
0.043; ZnSO 7H O, 0.055; MnCl 4H O, 0.019; CuSO 5H O, 0.005; KI, 0.006 mg; SeS , 0.083 mg.
4 2
2 2
4 2
2 e
ALGIMAR, CICIMAR-IPN, La Paz, Baja California Sur, Mexico.
´
f
Stay-C. Roche.
g
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NFE s Nitrogen-free extract, calculated as 100- ProteinqEther extractqAshqFiber .
Each diet was prepared by first mixing the macroingredients; sardine meal, squid meal, wheat meal, soybean protein meal, and baker’s yeast, in a blender for 10 min. The
microingredients; ascorbic acid, mineral premix, vitamin premix, sodium alginate, and choline chloride were mixed in a coffee grinder before being added to the microingredi-
ents in the blender. Dry ingredients were mixed for 10 min before the fish oil and soybean lecithin was added. The oil and lecithin had also been manually blended for 10
min to obtain an emulsion. Finally, all the ingredients were mixed together for another
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10 min, then water was added 400 ml to the mixture to form a dough. The dough was passed through a meat grinder to form 4-mm pellets, which were dried in an air flux
oven at a temperature of 308C for 12 h. Pellets were manually crumbled to different sizes as needed. Diets were stored in a freezer at y108C until used. The growth trial
lasted 93 days and each dietary protein level was tested in triplicate. Fish were fed to
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apparent satiation twice per day 0900 and 1700 during a 30-min period, and the Ž
. amount of diet consumed was recorded daily. Every 2 weeks, the standard length SL
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and wet weight W of the total population were recorded. At the end of the experiment, Ž
. 90 fish were killed 10 per replicate to assay for crude protein, ether extract, and ash
content of liver and muscle. For each replicate, two or three whole fish were used to Ž
. determine proximate composition according to AOAC 1995 methods, and gross energy
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in an adiabatic bomb calorimeter Parr model 1261 Moline, IL, USA . All samples were stored at y508C, then lyophilized before the analytical procedures. The biochemical
analysis of diets, fish, and tissue samples were conducted in triplicate. Growth rate was determined after a logarithmic transformation of the wet weight, by
b X
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a covariance analysis using the model Y s ae Everhart et al., 1953 . The comparison
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. between slopes b was made using a Tukey test Zar, 1996 . Survival was evaluated at
the end of the experiment, using the test of hypothesis of the difference among the Ž
. proportions of two populations Daniel, 1997 . Normality of distribution and homogene-
ity of variance were tested. Data were analyzed by a one-way ANOVA with level of protein as factor. When the data were not normally distributed, a Kruskal–Wallis
Ž analysis was used SL, proximate composition of whole fish, muscle, and liver, growth
. variables . Means were compared by a Duncan’s multiple range test or Tukey nonpara-
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metric multiple test. Statistical analyses were made using STATISTICA v. 5.1
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StatSoft, Tulsa, OK, USA . All analysis were made at 0.05 significance level.
3. Results
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