Bacterial diversity of tilapia (Oreochromis niloticus) cultured in brackish water in Saudi Arabia

The bacterial flora occurring in brackish pond water, sediment, gills and intestine of healthy tilapia cultured in Saudi Arabia were estimated both quantitatively and qualitatively, and the isolates were identified to genus or species level. Total viable count of bacteria ranged from 1.4±1.5×10³ to 8.6±2.7×10³ cfu ml⁻¹; 1.2±3.1×10⁶ to 7.3±1.1×10⁷ cfu g⁻¹; 8.7±1.9×10⁵ to 2.1±0.9×10⁶ cfu g⁻¹; and 2.8±2.4×10⁷ to 1.0±1.6×10⁸ cfu g⁻¹ in the pond water, sediment, gills and intestine of brackish water tilapia, respectively. In total, 19 bacterial species were identified. The bacteria were predominantly Gram-negative rods (87%). Pond water and sediment bacteria influenced the bacterial composition of gills and intestine of tilapia. In contrast to gill bacteria, more diversification was observed in intestinal bacteria. The predominant (prevalence >10%) bacterial species were Vibrio parahaemolyticus, Vibrio carchariae, Vibrio alginolyticus, Chryseomonas sp., Vibrio vulnificus, and Streptococcus sp. in all the populations with the exception of the sediment population where Streptococcus sp. was replaced by Shewanella putrefaciens. Vibrio spp. (58% of the total isolates) dominated the total bacterial population.     

Effects of Stocking Density and Monosex Culture of Freshwater Prawn Macrobrachium rosenbergii on Growth and Production in Concrete Tanks in Saudi Arabia

Abstract This study was conducted to evaluate the effects of stocking density and monosex culture on growth, survival, yield and feed conversion ratio of freshwater prawn Macrobrachium rosenbergii in concrete tanks. Juvenile prawns with an average weight of 1.8 g were stocked into triplicate tanks at densities of 5, 10, 15 and 20 prawns/m², grown for 168 d and fed a 34% tilapia diet. Stocking density had significant effect on prawns. Final mean body weight decreased with the increasing density, being highest at 5 prawns/m² (29.6 9). and lowest at 20 prawns/m² (17.4 g). Total yield increased from 135 g/m² (1,350 kg/ha) at a density of 5 prawns/m² to 261 g/m² (2,610 kg/ha) at density 15/m^z to 245 g/m² (2,450 kg/ha) at 20/m^z. Feed conversion ratios were high and ranged from 3.7 (5 prawns/m²) to 5.6 (20 prawns/m²).
In monosex culture of freshwater prawns stocked in triplicate tanks at a density of 5 prawns/m² for 112 d, the all-male population had the best growth performance and feed conversion ratio, followed by the mixed-sex and all-female populations. The all-male population had 99% marketable prawns (>20 g) with an average yield of 159 g/m² (1,590 kg/ha); the mixed-sex population had 90% marketable prawns and the yield was 135 g/m^z (1,350 kg/ha); and the all-female population had 75% marketable prawns with an average yield of 108 g/m² (1,080 kgha).     

Effects of sex ratio, stocking density and age of hybrid tilapia on seed production in concrete tanks in Saudi Arabia

The influence of sex ratio, stocking density and age of hybrid tilapia (Oreochromis niloticus X O. aureus) brood fish on seed production in concrete tanks were evaluated in 1992 and 1993. A sex ratio of 1:2 and 1:3 (male: female) and a density of 2 fish m-2 gave the best result with respect to number of seed female-1 day-1 and number of seed kg-1-1 female day-1. Maximum seed production female-1 day-1 was recorded for 3-year-old females and the minimum for 1-year-olds, but in terms of seed kg-1 female day-1 and seed m-2 day-1, 1-year-olds produced the maximum number of seed followed by 2-, 3- and 4-year-old females. Seasonal pattern in seed production was apparently influenced by season and temperature. From the first harvest on 21 April 1993 the production increased gradually, reaching a peak during the third harvest and a second peak during the sixth harvest. Thereafter seed production gradually decreased, reaching a minimum during the tenth harvest on 27 October 1993. No seed were found during the last harvest of 18 November 1993. Maximum production coincided with the highest water temperature of around 28°C.     

Bacterial Populations of African Catfish,Clarias gariepinus (Burchell 1822) Cultured in Earthen Ponds

The aim of this study was to investigate the load and distribution patterns of the aerobic bacterial flora associated with pond water, sediments, gills, and intestines of healthy African catfish, Clarias gariepinus, cultured in Saudi Arabia. Counts of viable bacteria ranged from 7.9 ± 4.4 10³ to 4.3 ± 5.7 10⁴ colony forming units (cfu)/mL in water; 1.3 ± 2.7 10⁸ to 7.4 ± 4.6 10⁹ cfu/g in sediments; 8.7 ± 1.8 10⁶ to 6.6 ± 5.8 10⁷ cfu/g in gill filaments; and 8.8 ± 6.2 10⁸ to 4.3 ± 2.8 10¹⁰ cfu/g in intestines. The bacterial flora was predominantly comprised of gram-negative rods, accounting for 75% of the total isolated strains. Altogether, 11 bacterial species of 8 genera were identified: Aeromonas hydrophila, Shewanella putrefaciens, Vibrio cholerae, Staphylococcus sp., Corynebacterium urealyticum, and Vibrio vulnificus were the most common with the first three dominating (prevalence > 14%) in every population studied.     

Effect of different diets on growth of the sub-adult sea cucumber Holothuria scabra

Aquaculture International - In recent years, the demand for commercial sea cucumber diet increased due to the expansion of sea cucumber farming. In this study, we investigated alternative sources...     

Faecal coliforms in pond water, sediments and hybrid tilapia Oreochromis niloticus×Oreochromis aureus in Saudi Arabia

Total bacterial load, total coliforms faecal coliforms in pond water, sediment, intestine of hybrid tilapia Oreochromis niloticus×Oreochromis aureus and pigeon Columba livia faeces were investigated monthly over a period of 1 year from July 1999 to June 2000. Fish were collected randomly by a cast net. Samples were analysed for coliforms using the multiple‐tube fermentation technique. Results showed total viable bacterial counts in the pond water, sediment, intestine of tilapia and pigeon faeces ranging from 1.8±0.9×10² to 6.0±1.2×10⁴ cfu mL^?1, 3.2±1.2×10⁵ to 2.8±1.5×10⁷ cfu g^?1, 8.2±1.6×10⁵ to 9.9±1.5×10⁷ cfu g^?11.0±0.4×10⁷to9.7±0.2×10⁹ cfu g^?1respectively. The most probable number (MPN) of coliforms and faecal coliforms ranged from 287±12 to ≥1600±0 100 mL^?1 in pond water; the MPN ranges for sediment, tilapia intestine and pigeon faeces were 257±29 to ≥1100±0 g^?1, 237±46 to ≥1100±0 g^?1 and 403±98 to ≥1100±0 g^?1 respectively. The abundance of normal bacteria coliforms was greater in the warm months than in the cold months. Ground water was free from any sort of coliform organisms, and there were no sources of human faecal matter in the pond. So, it is clear that faecal coliforms from pigeon faeces significantly contaminated (P<0.05) the ponds and tilapia intestines. Escherichia coli was the only coliform organism found in pond water, sediment, intestine of tilapia and pigeon faeces.     

Quantitative and qualitative studies on bacterial flora of hybrid tilapia (Oreochromis niloticus × O. aureus) cultured in earthen ponds in Saudi Arabia

The bacterial flora of the rearing pond water and sediment as well as the gills and intestine of healthy hybrid tilapia cultured in Saudi Arabia was estimated quantitatively and qualitatively, the isolates being identified at genus or species level. Total viable counts of bacteria (measured as colony‐forming units, cfu) were in the range 5.6 ± 0.8 × 10³ to 2.4 ± 1.2 × 10⁴ cfu mL^?1 in pond water; 9.3 ± 1.1 × 10⁶ to 1.9 ± 1.5 × 10⁸ cfu g^?1 in sediment; 7.1 ± 0.7 × 10⁵ to 8.7 ± 1.1 × 10⁶ cfu g^?1 in the gills of tilapia; and 3.4 ± 1.8 × 10⁶ to 5.8 ± 0.4 × 10⁷ cfu g^?1 in the intestine of tilapia. In total, 15 bacterial genera and 18 species were identified. Pond water and sediment bacteria reflected the bacterial composition in the gills and intestine of tilapia. In contrast to gill bacteria, more diversification was observed in intestinal bacteria. Corynebacterium urealyticum, Shewanella putrefaciens and Aeromonas hydrophila predominated in all samples. In pond water, C. urealyticurn, S. putrefaciens, A. hydrophila, Flavobacterium sp. and Pseudomonas sp. were the most predominant bacterial species (prevalence > 10%), whereas A. hydrophila, C. urealyticum, S. putrefaciens and Escherichia coli were predominant in pond sediment, and C. urealyticum, S. putrefaciens and A. hydrophila were predominant in both the gills and intestine of tilapia.     

Bacterial Flora of Artemia Cultured in Earthen Saline Ponds

Aerobic bacteria in pond water, sediments, and Artemia in earthen saline ponds in Saudi Arabia were quantified. Total viable counts (TVC; mean ± SD) in pond water ranged between 7.9 ± 4.8 × 10³ and 1.6 ± 3.7 × 10⁴ colony forming units (cfu)/mL; in sediments between 7.1 ± 4.2 × 10⁶ and 6.5 ± 3.8 × 10⁷ cfu/g; on Artemia surfaces, 3.9 ± 0.9 × 10³ and 1.0 ± 2.9 × 10⁴ cfu/Artemia; and in Artemia homogenate, 4.6 ± 2.4 × 10⁷ and 3.2 ± 3.6 × 10⁸ cfu/g. The bacterial flora was predominantly Gram-negative rods, accounting for 89% of total isolates. Altogether, nine bacterial species of seven genera were identified. Bacteria in pond sediments were the most diverse compared to other populations. In all populations, Vibrio alginolyticus, Vibrio sp., and Staphylococcus sp. were dominant (P < 0.005). The bacterial flora of pond water and sediments were reflected in the bacterial composition on and in Artemia.     

Nutrient budgets in tanks with different stocking densities of hybrid tilapia

Nitrogen and phosphorus budgets were estimated in 12 indoor fiberglass tanks stocked with hybrid tilapia (Oreochromis niloticus×O. aureus) at densities of 1 kg, 5 kg, 10 kg and 15 kg/m³ and reared for 14 days. Each density was replicated three times, and the experiment was repeated five times. The water in each tank was changed daily. Fish were fed a 34% protein tilapia feed to satiation twice daily. Feed consumption rate significantly decreased (P<0.05) with increasing density, but the FCR did not vary significantly (P>0.05) among the treatments. The production of one kilogram of fish required 2.0–2.2 kg of feed in different stocking density treatments, while 87.1–95.6 g nitrogen and 12.6–13.8 g phosphorus were released into the water, as metabolic waste. Of the feed input, 21.4% of the nitrogen and 18.8% of the phosphorus were incorporated in the fish harvested.