Aerobic Bacterial Flora of Common Carp (Cyprinus carpio L.) Cultured in Earthen Ponds in Saudi Arabia

ABSTRACT

Quantitative and qualitative estimation of bacterial flora present in pond water, sediments, gills, and intestine of healthy common carp Cyprinus carpio cultured in Saudi Arabia were performed and identified to species level where possible. Mean total viable bacterial counts in pond water ranged from 1.2?±?2.9?×?10⁴ to 2.5?±?3.5?×?10⁵ cfu/mL; in sediments, 9.3?±?2.1?×?10⁷ to 2.7?±?3.5?×?10⁹ cfu/g; in gills filaments, 4.3?±?2.9?×?10⁶ to 1.6?±?3.9?×?10⁷ cfu/g; and in intestine, 8.7?±?4.1?×?10⁹ to 5.4?±?3.2?×?10¹⁰ cfu/g. Gram-negative rod-shaped bacteria dominated (76%) the populations. In total, 12 bacterial genera and 15 species were identified. Pond water and sediment bacteria had the reflection on bacterial composition of gills and intestine of carp. Intestinal bacteria showed more diversification in contrast to gill bacteria. Aeromonas hydrophila, Shewanella putrefaciens, Vibrio cholerae, Corynebacterium urealyticum, Vibrio vulnificus, Vibrio sp., and Staphylococcus sp. were the common bacteria in all the populations. In pond water and carp intestine, A. hydrophila, S. putrefaciens, V. cholerae, and C. urealyticum were the most dominant bacteria (prevalence ≥ 10%) where pond sediments and the carp gills experienced with more one dominant bacterium V. vulnificus. Only the A. hydrophila covered one fourth (25%) of the total bacterial populations.     

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.     

Inherent variation in growth efficiency of African catfish Clarias gariepinus (Burchell, 1822) juveniles

Understanding the major causes of growth variation is crucial for the success of fish farming since its reduction contributes to maximize production efficiency, reduce food waste and improve water quality. The growth variation observed in aquaculture has been associated with the establishment of social hierarchies. However, some studies suggest that this variation may not be mainly a consequence of social hierarchies but mainly a result of inherent (genetic) differences. This study investigates the magnitude of individual responses, independently of group effects (fish housed individually), in growth efficiency and feeding behaviour of African catfish Clarias gariepinus (Burchell 1822). Despite the low variation in initial body weight (6.5%) and cumulative feed consumption (7.5%) over the experimental period, catfish exhibited high variation in final body weight (18.1%), specific growth rate (17.2%) and feed conversion ratio (27.9%), suggesting that individual variation in growth efficiency is important in determining growth rate. This individual variation may be related with individual differences in protein/fat deposition since faster growing fish deposited more protein and less fat than slower growing fish. Pronounced individual differences in feeding behaviour (reaction towards feed and time spent eating) were also observed and correlated with individual differences in growth efficiency. Fast eaters were the fast growers. We suggest that the growth variation observed in African catfish may be inherent and that the use of grading to increase uniformity should be further investigated.     

Optimal dietary carbohydrate to lipid ratio in African catfish Clarias gariepinus (Burchell 1822)

An 8-week feeding trial was conducted in a recycling water system at 28±1°C to investigate carbohydrate to lipid ratio (CHO:L ratio) in African catfish Clarias gariepinus (12.32±0.04g). Five isonitrogenous (40% crude protein) and isoenergetic (20kJg^–1 gross energy (GE)) fishmeal based diets with varying carbohydrate to lipid (CHO:L g/g) ratios of 0.74, 1.13, 1.66, 2.47 and 3.42 for diets 1–5, were tested, respectively. The diets containing a fixed protein to energy ratio (P:E ratio) of 20-mg proteinkJ^–1 GE were fed to triplicate groups of 20 fish (per 30-L tank). Fish were fed 5% of their body weight per day adjusted fortnightly. Diet 1, containing 14% carbohydrate and 21% lipids with a CHO:L ratio of 0.74 produced the poorest (P<0.05) growth rates, feed and protein efficiency. Increasing carbohydrate content in the diets to 27% concomitant with a reduction in lipid content to 16% with a CHO:L ration of 1.66 of diet 3 significantly improved (P<0.05) growth rates, feed and protein efficiency. A further increase in dietary carbohydrate up to 38% and a decrease in lipids levels to 11% with a CHO:L ratio ranging from 1.66 to 3.42 (diet 3 – 5) did not significantly improve the fish performance. Apparent net protein utilisation (ANPU) of fish fed diet 4 was higher (P<0.05) than for diets 1–3 but did not differ from diet 5. Higher lipid deposition (P<0.05) in whole body and liver were observed with decreasing dietary CHO:L ratios as increasing lipid levels. Whole body protein and liver glycogen content, digestive enzyme activities (protease and lipase) and histological examination of intestine and liver of fish fed varying CHO:L diets did not show any discernible changes among the dietary treatments. However intestinal -amylase activity increased (P<0.05) with increasing dietary carbohydrate levels. This study revealed that African catfish can perform equally well on diets containing carbohydrate ranging from 27 to 38% of the diet, with lipid content ranging from 16 to 11% or at CHO:Lg/g ratio of 1.7–3.4.     

The Development of a Functional Digestive System in the African Catfish Clarias gariepinus (Burchell)

The morphological and physiological development of the intestine, stomach, liver and pancreas of the African catfish, Clarius guriepinus (Burchell 1822), was investigated from hatching until 9 days after the start of exogenous feeding by histological, histochemical and immunohistochemical procedures. During the yolk sac period, lasting 48 hours at 30 C, the digestive system develops from a rather undifferentiated system into a distinct liver and pancreas and a segmented intestine (parts I to III). Insulin and glucagon producing cells were clearly found in the endocrine pancreatic islets from 14 hours after hatching onwards, while at the start of exogenous feeding, the exocrine pancreas showed an intense zymogen colouration. Exogenous feeding started three days after fertilization, i.e., 48 hours after hatching. At that moment, the rearing temperature was lowered to 27.5 C. The first day of feeding was referred to as day zero, changing into day 1 when the first 24 hours of feeding were completed. From the start of exogenous feeding onwards, aminopeptidase, non-specific esterase and ATP-ase were detected in the digestive system. Morphologically, the stomach was completed at day 4 of exogenous feeding. Gastric acid secretion started on day 4 and lead to a pH below 3.3 in the stomach on day 5. During the first four days of exogenous feeding, C-t-gastrin immunopositive cells were found throughout the gut, including the gastric epithelium. After day 4, the C-t-gastrin cells were only detected in the anterior intestine. The completeness of the stomach development was also marked by the appearance of non-specific esterase activity in the stomach epithelial cells on day 5. All data together clearly indicate that in Clarius gariepinus , the ontogeny of a functional digestive system has been completed on day 5 after the start of exogenous feeding, marking thereby the end of the larval period.     

Approaches to optimizing dietary protein to energy ratio for African catfish Clarias gariepinus (Burchell, 1822)

An 8‐week feeding trial was conducted in a recycling water system at 28 ± 1 °C to investigate protein to energy ratio (P/E ratio) in African catfish Clarias gariepinus (10.9 ± 0.04 g). Six fishmeal‐based diets of two protein levels (330 and 430 g kg^?1), each with three lipid levels (40, 80 and 120 g kg^?1) resulted in P/E ratios ranging from 15.5 to 21.3 mg protein kJ^?1 gross energy (GE) were fed to 20 fish (per 30‐L tank) in triplicate. Fish were fed 50 g kg^?1 of their body weight per day adjusted fortnightly. Significantly higher (P < 0.05) growth rates and feed conversion efficiency were evident in fish fed with higher protein diet. The highest growth rate was found by fish fed 430 g kg^?1 protein, 21.2 kJ^?1 GE with a P/E ratio of 20.5 mg protein kJ^?1 GE. Significantly indifferent (P > 0.05) values of protein utilization were found in‐between the both (higher and lower) protein diets. Higher lipid deposition (P < 0.05) in whole body and liver was observed with increasing dietary lipid level at each protein diet and as higher (P < 0.05) for the lower protein diets. Liver glycogen tended to decrease with increasing gross energy at each protein diet and higher protein diet showed comparatively lower values (P > 0.05). Digestive enzyme activities (protease and lipase) and histological examination of intestine and liver of fish fed varying P/E diets found no significant differences in response to experimental diets. The study reveals that African catfish C. gariepinus performed best the diet containing 430 g kg^?1, 21.2 kJ g^?1 and 20.5 mg protein kJ g^?1 GE protein, gross energy and P/E ratio, respectively.     

池塘主养白须公试验

在0.27 hm2土池进行了主养红白须公秋片鱼种试验,放养红白须公夏花33855尾,白鲢夏花6000尾,花鲢夏花2000尾。经97 d饲养,出塘红白须公秋片17360尾,1675.24 kg,平均体重96.5 g,成活率51.2%,花、白鲢秋片580 kg,平均产鱼8457.15 kg/hm2,其中红白须公占77.3%,产值达108 750元/hm2。     

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.     

Urea and ammonia excretion by embryos and larvae of the African catfish Clarias gariepinus (Burchell 1822)

Yolk-sac larvae and starved larvae of Clarias gariepinus (Burchell 1822), reared at 28°C, were predominantly ammonotelic, but urea excretion contributed about 19±7% to the total nitrogen excretion. Exogenously feeding larvae of C. gariepinus were mainly ammonotelic until 180-205 h post fertilization, but from then on the relative urea excretion stabilized at 44±13%. The contents of total free amino acids (FAA) and ammonia in C. gariepinus peaked around complete yolk absorption. During the first period after hatching 64% of the FAA and 60% of the total ammonia were located in the yolk compartment. The body compartment contained the highest amount of FAA and total ammonia at the end of the yolk-sac period (65 and 77%, respectively). The amount of nitrogen originating from catabolism of amino acids was balanced within 6% by the excreted sum of ammonia and urea. The high degree of ureotelism in C. gariepinus larvae may constitute an adaptive mechanism to a habitat of temporal water shortage.     

Artificial Spawning of African Catfish,Clarias gariepinus

Abstract

The effects of controlled reproduction of African catfish, Clarias gariepinuswere investigated in an experiment with carp pituitary (at the dose 4 mg/kg body weight) or Ovopel (1 pellet/kg body weight) used as ovulation stimulators. The application of the synthetic stimulator led to the significantly (P≤0.01) greater weight of eggs (expressed in grams and as percentage of female body weight) and to the significantly (P≤0.05) higher quality of eggs after 24-hour incubation as compared with the hypophysation effects. Two categories of females were used in the experiment, i.e., light (mean body weight of 3.75 kg) and heavy (mean body weight of 8.86 kg) fish. The results show that a significantly (P≤0.01) greater weight of eggs (expressed in grams) was obtained from heavier females. The quality of eggs expressed as the percentage of live embryos after 12- and 24-hour incubation was significantly (P≤0.01 and P≤0.05, respectively) higher for lighter females. The higher weight of obtained eggs and their better quality after Ovopel stimulation compared to the weight and quality of eggs obtained after hypophysation allow for the recommendation of this ovulation stimulator for the fish species investigated.     

The urogenital papillae as an indicator of sexual maturity in male African catfish,Clarias gariepinus, (Burchell, 1822)

The present study investigated a non‐invasive method based on macroscopic morphological features of male Clarias gariepinus for the assessment of sexual maturity stage. As African catfish cannot be stripped for semen as in most other fish species; they have to be killed to obtain semen from the testes. This method could be used to ensure that males used to obtain sperm are sexually mature to increase the concentration and quality of mature sperm for egg fertilization in the production of C. gariepinus. Morphological features including the length and width of the urogenital papillae (UGP), an external secondary sexual characteristic of C. gariepinus (n = 89) were measured and calculated as a percentage of total body length. The urogenital papillae length (L_UGP) and width (W_UGP) index of each fish were used and compared with the macroscopic and microscopic maturity stage of the testes. The results revealed that although positive, a significant correlation does not exist between the L_UGP or W_UGP and maturity stage of the testes. Therefore, although this procedure would be valuable as an initial non‐invasive assessment of maturity, it does not provide an accurate or reliable indication of the maturity stage of the fish.     

Response of African Catfish, Clarias gariepinus (Burchell, 1822), to Diets of Pigeon Pea, Cajanus cajan, Subjected to Different Processing Methods

Raw undehulled pigeon pea, Cajanus cajan, seeds were processed by toasting, boiling, and soaking before milling to produce pigeon pea meals (PPMs). African catfish, Clarias gariepinus, were fed eight diets formulated with these meals at two dietary inclusion levels of 600 and 650 g/kg in combination with fish waste meal levels of 350 and 330 g/kg, respectively, to yield a protein and energy contents of 35.96 ± 2.1% dry matter and 18.04 ± 0.2 kJ/g. Fish (mean weight 0.46 g) were weighed and distributed to 24 experimental tanks (seven fish per tank). Triplicate fish groups were fed restricted ration (5% of biomass) per day in two portions for 56 d in static water. Results showed that fish groups fed raw PPM diets had low body weight gain (BWG), inferior specific growth rate (SGR), and high feed conversion ratio (FCR) when compared to other feeding groups. The hematocrit, hemoglobin concentration, and red blood cell and white blood cell counts decreased significantly (P < 0.05) with raw PPM diets. Slight decrease also was recorded among groups fed diets of other processing methods when compared with initial fish. However, soaking for 16 h enhanced best fish BWG, SGR, FCR, and hematological values and can be recommended as a good processing method of PPM for African catfish diets.     

Optimum histidine requirement of fry African catfish, Clarias gariepinus (Burchell)

Dietary histidine requirement of fry African catfish, Clarias gariepinus (2.57 ± 0.02 cm; 0.22 ± 0.03 g) was quantified by feeding casein–gelatin-based isonitrogenous (40% crude protein) and isocaloric (17.90 kJ g⁻¹ gross energy) amino acid test diets with graded levels of histidine (0.25%, 0.30%, 0.35%, 0.40%, 0.45% and 0.50% dry diet) in eighteen 80 L indoor circular aqua-coloured troughs provided with the flow-through system for 12 weeks. Maximum absolute weight gain (2.66), best feed conversion ratio (1.29), highest protein efficiency ratio (1.94), protein retention efficiency (34%) and energy retention efficiency (70.4%) were achieved at 0.40% dietary histidine. Broken-line and non-linear regression models were adopted to assess dietary histidine requirement for C. gariepinus . When analysed using broken-line regression model these parameters were also best at 0.40% dietary histidine corresponding to 1.0% protein, respectively, whereas using second-degree polynomial regression analysis, histidine requirement was obtained at 0.42%, 0.41%, 0.40%, 0.41% and 0.41% of dry diet, corresponding to 1.05%, 1.02%, 1.0%, 1.02% and 1.02% protein respectively. Based on the broken-line and second-degree polynomial regression analyses of the growth and nutrient retention data, optimum histidine requirement of fry C. gariepinus was found to be in the range of 0.40–0.42% dry diet, corresponding to 1.0–1.05% of dietary protein.     

Soybean meal replacement by roquette (Eruca sativa Miller) seed meal as protein feedstuff in diets for African Catfish, Clarias gariepinus (Burchell 1822), fingerlings

Apparent digestibility coefficient (ADC) values for mechanically extracted meal derived from roquette (Eruca sativa) seeds were obtained. The digestibility of dry matter (DM), protein and energy was measured using an inert marker in the diets and by faeces collection using the dissection method. Soybean meal and roquette meal had similar ADC values for protein and energy. Roquette seed meal was thereafter evaluated as a protein source in diets (400‐g crude protein, 120‐g crude lipid and 18.00 MJ gross energy kg^?1 DM) fed to African catfish, Clarias gariepinus, fingerlings (10.4±0.4 g) to apparent satiation twice daily for 70 days. The test diets contained roquette seed meal as replacement for soybean meal protein in a control diet, providing 20%, 40% or 60% of the total protein. Catfish mortality was low (<10%) and not diet related. Substituting soybean meal protein with roquette seed meal protein providing 20% of total protein did not affect weight gain, growth response, feed conversion ratio, protein utilization or carcass composition of catfish. Catfish growth was, however, retarded and feed was poorly utilized only when roquette seed meal provided above 20% of total protein, caused by reduced energy digestibility, deficiencies in some essential amino acids and presence of antinutritional factors. Livers of catfish fed high dietary levels of roquette seed meal showed severe histological abnormalities.     

Effects of the probiotic, Lactobacillus acidophilus, on the growth performance, haematology parameters and immunoglobulin concentration in African Catfish (Clarias gariepinus, Burchell 1822) fingerling

This experiment was carried out to evaluate the effects of the probiotic, Lactobacillus acidophilus , on the growth performance, haematology parameters and immunoglobulin concentration in African catfish Clarias gariepinus fingerling. Two experimental diets were formulated to contain 35 g kg⁻¹ crude protein and 10 g kg⁻¹ lipids accordingly and fed three times daily for 12 weeks to 25 C. gariepinus fingerlings per fibreglass tank in 12 replicates each. The control diet was prepared with no probiotic supplementation whereas the second diet was prepared supplemented with a probiotic, L. acidophilus , containing about 3.01 × 10⁷ colonies/g of diet. The results show that growth performance [specific growth rate (SGR) and relative growth rate (RGR)], nutrient utilization [protein efficiency ratio (PER) and feed conversion ratio (FCR)] and survival were significantly ( P <0.05) higher in fish maintained on the probiotic-supplemented diet compared with those on the control diet. Haematology parameters (packed cell volume, haemoglobin, erythrocyte sedimentation rate, red blood cell and white blood cell, total serum protein, Ca²⁺, Mg²⁺, Cl⁻, glucose and cholesterol) and total immunoglobulin concentrations were also significantly better in fish fed the probiotic-supplemented diet than in the control. Although the water quality parameters monitored were better in the fish fed the probiotic-supplemented diet than in the control, the parameters were not significantly different ( P >0.05). From the results of this experiment, we conclude that L. acidophilus can be used as a probiotic agent in African catfish culture, to enhance fish health, survival and better feed efficiency and growth performance.     

The effect of diet and photoperiod on ammonia efflux rates of the African catfish, Clarias gariepinus (Burchell, 1822)

Total ammonia efflux rates of the African catfish, Clarias gariepinus (Burchell), were measured under different combinations of photoperiod (LD 24:0. LD 0:24, LD 12:12) and feeding regime (50% protein diet, 41% protein diet and zero food). A time-dependent variation of ammonia efflux following feeding was observed, with postprandial excretion rates in the first 12 h being greater than those in the following 12 h. Ammonia efflux rates were directly related to the level of protein in the diet under all photoperiod conditions. Photoperiod had no effect on ammonia efflux rate, except in the LD 24:0-high protein diet group, which may indicate a stress response.     

Swim-up fry production in the African Catfish Clarias gariepinus (Burchell) broodstocks fed with differently heated soybean-based diets

Four hundred and eighty matured yearlings of Clarias gariepinus (Burchell) (female=182±10 g; males=208±5 g) distributed into groups of 30 specimens (sex ratio 1:1) were fed differently heated soybean‐based diets. Seven approximately iso‐nitrogenous (31% crude protein) and iso‐caloric (13.97 kJ g^?1) diets were prepared from either raw soybean (SAMSOY 2, TGX 636–02D) or soybean seeds autoclaved for 5, 10, 15, 20, 25 and 30 min. The untreated and the variously heat‐treated soybean meals were mixed with other ingredients to prepare diets designated as DSoy0, DSoy5, DSoy10, DSoy15, and DSoy20, DSoy25 and DSoy30 according to the treatment time of the soybean portion of the diets, and were fed to the fish broodstocks for 84 days. The fishmeal‐based diet (DFM) served as the reference diet. The duration of heating soybean component of the experimental diet significantly (P<0.05) affected the growth performance and the number of eggs produced by the broodstocks, the percentage number of eggs fertilized and hatched as well as the survival of the progenies. The progenies of the brood fish fed diets DFM and DSoy25 with a yolk sac size of 2.78±0.6 and 2.42±0.5 mm, respectively, had significantly (P<0.05) larger yolk sacs, which were also absorbed at a significantly faster rate of 0.61±0.02 and 0.51±0.03 mm day^?1, respectively, than progenies of broodstocks fed other experimental diets. Swim‐up fry survival rates were also better in hatchlings from broodstocks fed DFM (89.5%), DSoy25 (83.8%) and Dsoy 20 (80.5%) diets than progenies from other experimental diets. This study showed that soybean meal portion processed at 116°C and 1.2 kg cm^?2 pressure for 25 min in the diet, which ensures normal reproductive function and production of healthy progenies in C. gariepinus, could serve as a substitute for fishmeal in the broodstock diets.     

Progression of African Catfish Clarias gariepinus (Burchell) early stages challenged with two common pond fertilizers in incubation media

Early‐stage indicators of the African catfish Clarias gariepinus (Burchell) (egg fertilization and hatching rates, larval survival rate and time to hatch) were assessed in aqueous solutions of NPK 15‐15‐15 and layer manure. Recommended use rates (RUR) of NPK 15‐15‐15 and layer manure have volume‐equivalent of 15 mg/L and 28 mg/L respectively. Solutions containing *0.7RUR, *1.0RUR and *1.5RUR dilutions were used as treatments within‐fertilizer. There were significant differences in pH, dissolved oxygen (DO), total hardness and total metal levels in treatments of NPK (p < 0.0001) and layer manure (p < 0.0001). Fertilization, hatching rate and larval survival were significantly lower while incubation was significantly longer in treatments of NPK (p < 0.001) and layer manure (p < 0.0001) in comparison with control. In NPK treatments, the indicators correlated with pH (r ?0.96 to ?0.98, p < 0.0001), with 99.1%–99.6% (p < 0.0001) of changes of indicators explained by pH. In manure treatments, the indicators correlated with DO and pH (r = 0.92 to 0.998) (p < 0.0001), with 98.1%–99.7% (p < 0.0001) of changes explained by DO and pH. NPK and layer manure have deleterious effect on C. gariepinus early stages. The toxicity and explanatory physico‐chemical parameters should be considered when the fertilizers target aquatic productivity.