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LENGTH-WEIGHT RELATIONSHIP, NATURAL FOOD AND FEEDING SELECTIVITY OF NILE TILAPIA, Oreochromis niloticus L. IN FERTILIZED EARTHEN PONDS
Abstract
Nile tilapia, Oreochromis niloticus (L.) was stocked in fertilized earthen ponds and received both organic and inorganic fertilizers. Fish samples were collected for growth determination and were categorized into different sizes, i.e. detritus>zooplankton at all fish sizes. Detritus consisted mainly of scraps of macrophytes and mud, and its contribution to gut content decreased by increasing fish size, while phytoplankton contribution increased. Zooplankton did not exceed 1% of total stomach's contents. The main algal species found in fish stomach belonged to Cyanobacteria, Chlorophyceae, Bacillariophyceae and Euglenophyceae. Bacillariophyceae represented the main phytoplanktonic division at small fish size (75 g/fish). Results revealed that Nile tilapia could select Cyanobacteria and Euglenophyceae at all sizes. Chlorophyceae and Bacillariophyceae were eaten with slight selectivity at large sizes.
... Such studies were conducted concerning natural food of Tilapia fish such as Fattah et al. (2008) which showed that natural food of tilapia included phytoplankton (blue-green algae, green algae, Bacillariophyceae, Cyanophyte) and zooplankton (Copepod, Cladocera, Rotifera, Ostracoda). While Abdel-Tawwab and El-Marakby (2004) added that Tilapia fish also consumed Euglenophyceae, while Cyanobacteria and Euglenophyceae were the most food found in the stomach of Tilapia. ...
... The analysis on the stomach content showed that not all plankton species were consumed by Tilapia fish. Abdel-Tawwab and El-Marakby (2004) showed that Tilapia fish consumed Cyanobacteria and Euglenophyceae as the main food. Figueredo and Giani (2005) mentioned that the selection in fish feeding was determined by the capability of feed capture. ...
Silvofishery application in Semarang was expected to provide several advantages for aquaculture activity, such as its support to the availability of natural food for Tilapia. This research aimed to analyze the suitability of Tilapia fish stomach content and the composition of plankton in the silvofishery pond in Semarang. Data collection included plankton abundance in A. marina and R. mucronata silvofishery plot and stomach content of Tilapia fish. Data were collected through field sampling occupying 6 silvofishery plot (3 for each vegetation type) and 6 fish samples (3 from each vegetation types). Water sampling was conducted by filtering 10 litres of water to 100 ml. Plankton identification was conducted in the laboratory. The result showed there were 7 plankton species found in the stomach content of Tilapia fish. Six similar species were found in the A. marina pond and only 5 similar species were found in R. mucronata pond. There was no similarity on the community structure of plankton found in the A. marina pond, R. mucronata pond and stomach content of Tilapia fish. The plankton abundance of A. marina plot was higher than the plankton abundance of R. mucronata plot.
... Given the declining status of wild fish stocks, aquaculture may one day surpass capture fisheries in terms of food-fish production. In addition to the economic contributions, aquaculture has the potential for mitigating environmental impacts, because it does not emit greenhouse gases in to the atmosphere and that makes fish species desirable for production [1][2][3]. Tilapia fish species are among the most important warm water fishes used for aquaculture production in the tropics and sub-tropics [4]. ...
... Egypt is the second largest producer of farmed Nile tilapia, which considered the most common fish currently being, cultured commercially [21]. However, Nile tilapia is an omnivorous fish which eats detritus, phytoplankton and zooplankton [23,24] and, consequently, can accumulate copper compounds. To measure the effects of single or complex mixture of contaminants on the organisms, toxicity tests are conducted. ...
This study was carried out to evaluate the response of Nile tilapia, Oreochromis niloticus to acute copper toxicity. Nile tilapia fingerlings (2.97 g/f ± 0.37) were acclimated and randomly distributed at a rate of 10 fish per 60-L aquarium. In a series of static renewal-toxicity tests, fish were exposed to concentrations of 0, 5, 10, 15, 20, 25, 30, 35 and 40 mg L-1 copper sulfate (CuSO4·5H2O). Fish not exposed to any chemical served as negative controls. Histological sections were done in fish gills and liver in all treatments. Estimates of mean 96-h LC50 values (median lethal concentration) value of copper sulfate was 31.2 mg L-1 (7.94 mg copper L-1). In all exposure groups, some of the typical gill lesions are presented. The main alternations observed after the exposure to the cupper were epithelial hyperplasia, lifting of the lamellar epithelium, edema in the filamental epithelium, Curling, clubbed tips of secondary lamella and finally a complete fusion of several secondary lamellae at the 35 mg CuSO4 concentration. The severity of the lesions detected increased with the increase of copper sulfate concentration. Exposure to concentrations of copper sulfate more than 10 mg L-1 increased the arithmetic thickness of secondary lamella epithelium in O. niloticus which was significantly higher (P<0.001) than the corresponding control. However, the liver of the Cu-treated fish showed histological alternations such as cytoplasmic rarefaction, an increase of cytoplasmic vacuolation, decreasing the number of hepatocytes nucleus in hepatic tissue and nuclear pyknosis.
... As in other ponds in this region, Chlorophyceae (Sipaúba-Tavares et al., 2006;Lachi & Sipaúba-Tavares, 2008) were dominant in the fish ponds (FP1, FP2 and FP3). Chlorophyceae can be an important food for fish, especially tilapia (Abdel-Tawwab & El-Marakby, 2004). The relative abundance of Chrysophyceae was significantly higher in FP3 than in the other ponds during the study period and was accompanied by lower abundances of Zygnemaphyceae and Cyanobacteria. ...
This study was conducted to evaluate the plankton communities and water quality at a fee-fishing farm over a 1-year period. Samples for the determination of biotic and abiotic variables were collected monthly during the study year. Water samples were collected at 7 sampling sites: inlet water, wetland, fishponds (3 sites), soil filter system and outlet water. The temperature, dissolved oxygen, pH and nutrients were measured. A similarity analysis for plankton densities and nutrients detected 4 groups of sites. The outlet water site differed markedly from the other sites. Higher nitrate and nitrite concentrations were observed at the inlet water and wetland sites in association with species belonging to the Bacillariophyceae, Cyanobacteria and Zygnemaphyceae. Fishpond sites 2 and 3 were associated with species belonging to the Chlorophyceae and with variables such as temperature, dissolved oxygen and pH. Zooplankton communities were most distinctive in the soil filter system. Rotifers were the most representative group among the zooplankton communities. The results demonstrated that plankton communities and abiotic variables were affected by water flow and by animals in the neighbouring areas. The soil filter system at the effluent of the fee-fishing farm was found to be an important tool, suitable for adoption in aquaculture systems to improve outlet water quality.
... The main plankton genera found in tilapia stomach belongs to Cyanobacteria, Chlorophyceae, Bacillariophyceae and Euglenophyceae, Copepoda and Rotifers. The composition percentage of food items in stomach contents of tilapia was ranked as phytoplankton>detritus>zooplankton at all fish sizes (Abdel-Tawwab and El-Marakby, 2004). This was corroborated by Moriarty and Moriarty (1973) who reported that phytoplankton feeder Nile tilapia's total length was 6 cm whereas zooplankton feeder tilapia growth was 5 cm. ...
This study was conducted to assess the growth performances of cage reared GIFT strain of tilapia (Oreochromis niloticus) fingerling using length-weight (LW) relationship technique. Along with this, condition factor (K) of fish and pond water quality parameters were also brought under this study to have broader understanding. For LW relationship and K, a sample size of 120 fingerlings was made from randomly selected three different cages in a pond at Tarala village in Kaharole Upazila of Dinajpur District, Bangladesh. The length-weight relationship of tilapia fingerlings reared in cages managed by Adivasi people was significant. The value of correlation coefficient (r) and the coefficient of determination (r2 ) were 0.97 and 0.94 respectively. This suggests that growth of tilapia from fry to fingerling was normal in cages. The condition factor of different size group of fish was almost closed to 2, indicating fish health as satisfactory. All the water quality parameters including temperature, transparency, dissolved oxygen, ammonia-nitrogen, phosphate-phosphorus, nitrate-nitrogen and pH were within suitable range both in cages and outside the cage in pond. About 5 phyla and 25 genera of phytoplankton from Bacillariophyceae, Cyanophyceae, Chlorophyceae, Euglenophyceae and Rhodophyceae groups and one phylum and 5 genera of zooplankton from Rotifera group were found in cage installed in ponds. These all indicate the growth of tilapia fingerling in cages was satisfactory which was technically sound for landless adivasi households.
... Nile tilapia Oreochromis niloticus is one of the most important species for tilapias (El-Sayed 2006) and it is an omnivorous ¢sh that can utilize a wide range of food items including blue-green algae (Getabu 1994;Abdel-Tawwab & El-Marakby 2004). Therefore, the present study was conducted to determine the e¡ects of graded levels of Spirulina (A. plantensis) on the growth performance, feed utilization, non-speci¢c immune responses and resistance of Nile tilapia to Aeromonas hydrophila infection. ...
The use of antibiotics to control fish disease is one of the constraints in tilapia farming. Hence, the use of probiotic and live organisms as alternative strategies has received much more attention. This study was undertaken to evaluate the use of Spirulina (Arthrospir platensis) as a growth and immunity promoter for Nile tilapia, Oreochromis niloticus (L.). Fish (1.88 g) were randomly distributed at 20 fish per 100 L aquarium and fed a diet containing either 0.0, 1.25, 2.5, 5.0, 7.5 or 10.0 g Spirulina kg−1 diet for 12 weeks. After the feeding trial, fish of each treatment were challenged by pathogenic Aeromonas hydrophila, which was given by an interperitoneal injection, and they were kept under observation for 10 days to record any abnormal clinical signs and the daily mortality rate. The growth-promoting influence of Spirulina was observed with fish, and the optimum growth and feed utilization were obtained at 5.0 g Spirulina kg−1 diet. No significant changes were observed in fish survival among the different treatments. Spirulina supplementation improved the protein and lipid contents in fish bodies without significant differences among them, especially when fed 2.5–10.0 g kg−1 diet, but no significant differences in the moisture and ash contents were observed among different treatments. The physiological parameters were improved when fish were fed a Spirulina-enriched diet. However, the highest red blood cells, white blood cells and nitro blue tetrazolium values were obtained at 5.0–10.0 g Spirulina kg−1 diet; meanwhile, the lowest value was obtained in the control. Total fish mortality due to A. hydrophila infection decreased with an increase in the Spirulina level in fish diets. These results indicate that Spirulina supplement is promising as an alternative method to antibiotics for disease prevention in tilapia aquaculture, and the optimum level of Spirulina in the fish diet should be 5.0–10.0 g kg−1 diet.
... Nile tilapia is a native fish species of Egypt that has become popular species worldwide mainly as a valuable fish, easy to breed and grow in a variety of aquaculture systems (El-Sayed, 2006). However, Nile tilapia is an omnivorous fish consuming detritus, phytoplankton and zooplankton (Abdelghany, 1993;Abdel-Tawwab, 2000;Abdel-Tawwab and El-Marakby, 2004). Thus, treating plankton with copper compounds may lead to copper bioaccumulation reaching a toxic level in fish. ...
This study was carried out to evaluate the response of Nile tilapia, Oreochromis niloticus (L.), pre-exposed to calcium oxide for 4 days, and exposed to copper for 6 weeks. Fish (8.3 ± 0.1 g) were stocked in 1.5 m3 fiberglass tank and exposed to calcium oxide at a rate of 100 mg Ca2+ L− 1 for 4 days. After that, fish were transferred and randomly distributed at a rate of 15 fish per 100-L aquarium. Then, fish were post-exposed to concentrations of 0, 0.503, or 1.25 mg Cu2+ L− 1 (T1, T2 and T3, respectively). Three other groups were not pre-exposed to Ca and exposed to the same Cu concentrations (T4, T5 and T6, respectively). A fish diet containing 30% crude protein was offered to fish at a daily rate of 3% of live body weight twice daily; 5 days a week for 6 weeks. The final weight, weight gain and SGR were affected significantly by both Cu concentrations and Ca pre-exposure (P < 0.05). Fish pre-exposed to Ca (T2 and T3) exhibited better growth compared to non-exposed groups (T5 and T6). Fish mortality increased significantly with increasing the Cu concentration (P < 0.05). Feed intake reduced, while FCR increased significantly with increasing the Cu concentration (P < 0.05). The feed intake and FCR in T2 and T3 were better than those of T5 and T6 groups. Moisture content was not significantly differed at different treatments (P > 0.05). Crude protein decreased significantly at T6 (P < 0.05). Total lipids in T2 and T3 were higher than those of T5 and T6 (P < 0.05). Ash content and Cu residues in T2 and T3 were significantly lower than those of T5 and T6 (P < 0.05). Fulton condition factor, liver somatic index, and viscera somatic index were affected significantly by Cu toxicity (T5 and T6; P > 0.05), while they exhibited non-significant differences in T1–T4 groups. RBCs counts, Hct and Hb values were significantly affected by Cu toxicity (P < 0.05), while they were similar to control group in Ca pre-exposed groups (P > 0.05). Uric acid, creatinine, and AST were significantly affected by both Ca pre-exposure and Cu toxicity (P < 0.05). There was no significant changes in uric acid among T2, T3 and T5 (P > 0.05). The highest value of uric acid was obtained at T6 (P < 0.05). Creatinine, AST and ALT in T2 and T3 were lower than those of T5 and T6 (P < 0.05). Lipids in plasma and liver were high, while protein in plasma and liver were low in T5 and T6 (P < 0.05). Histological sections were done in fish's gills, liver and kidney in all treatments (T1–T6). The pathologic lesions were observed due to Cu toxicity. These damages became severe with increasing Cu concentration. Tissue alterations in T2 and T3 were less than that in T5 and T6. The present study displayed that Ca pre-exposure may play a factor then it reduced Cu toxicity resulting in a better fish growth.
Aim
This study was carried out to determine which phytoplankton species, as a natural food, can be ingested and digested by Nile tilapia (Oreochromis niloticus L.).
Methods
During this study, phytoplankton in the gut contents of Nile tilapia collected from three fishponds in southern Egypt were investigated during the period Oct. 2012-Sep. 2013. Samples of tilapia fish were grown in aquarium containing filtered pond water to detect undigested phytoplankton species in the feces.
Results
The majority of the phytoplankton found in the gut of Nile tilapia was Cyanobacteria (36-50%) and Chlorophyta (27-38%). Other groups such Diatoms, Euglenophyta and Dinophyta were also found but with lower percentages (<19%). The most important and dominant phytoplankton species found in Tilapia gut were the potentially toxic cyanobacteria, Anabaena, Anabaenopsis, Cylindrospermopsis, Microcystis and Planktothrix. Only diatoms were recorded in the feces, indicating the ability of Tilapia to digest all phytoplankton except diatoms.
Conclusions
The data of this study could be useful for biomanipulation of nuisance phytoplankton blooms in eutrophic aquacultures.
Growth parameters and feeding indices, such as condition factor (CF), of the Iranian cichlid, Iranocichla hormuzensis, the only native cichlid of Iran, were investigated during the period between August 2008 and August 2009. The estimated b value (the slope in length–weight equation) for males and females was 2.94, which is not significantly different from 3 that is indicative of isometric growth (p > 0.05). There was a significant difference (p < 0.05) between mean CFs of males and females. Males in the length group of 56–85 mm showed a higher CF than those in smallest (46–55 mm) and largest (86–100 mm) length groups. A total of 432 guts (217 of males and 195 of females) were investigated during the thirteen-month study period. The mean gut length, gut weight, relative gut length (RGL) and relative gut mass were significantly higher for males than females (p < 0.05). The RGL of males ranged between 1.12 and 8.24 (5.31 ± 1.26) and that of females between 0.58 and 10.43 (4.55 ± 1.53). Although I. hormuzensis is an omnivorous fish, our findings suggest that by their feeding habits, males tend to be herbivores and females carnivores.
The study aimed to check morphometric relationships and feeding habits of the Nile tilapia Oreochromis niloticus (L.). A total 573 fish samples from 4.7 cm to 35.2 cm Total Length (TL) and from 1.67 g to 780.0 g Total Weights (TW) were collected from Lake Koka during dry (May) and wet (August) months of 2011. The relationship between TL and Standard Length (SL) was linear (SL = 0.8482TL-0.8674) and the relationship between TL and TW was curvilinear (TW = 0.0153TL3.0541). From the total number of fishes 488 (85.2%) stomach was observed with food and remaining 85(14.8%) was empty. The major food items found in the stomach content was phytoplankton, macrophytes and detritus. Phytoplankton occurred in 80.1% of the stomach contents examined and contributed 47.45% of the total volume of food items. Macrophytes and detritus was found in 61.1 and 75.2% of the stomach contents and contributed 26.2 and 15.5% of the total volume of the diet, respectively. Zooplankton and insects was recorded in 54.1 and 19.9% of the stomach and volumetrically accounted for 7.06 and 2.43% of the bulk, respectively. During the dry month phytoplankton was observed in 96.4% of the stomach and constituting 66.1% of the total volume of the diet. During wet month macrophytes was the most important food items found in 98.1% of the stomach contents and constituting 79.1% of the total volume of the food items. Ontogenetic dietary shift was observed during the present study. Small sized fish (<10 cm) fed mainly on insects and zooplankton. When the fish size increased phytoplankton, macrophytes was increased in their food contents and zooplankton, insects and ostracods declined.
A comparison of feeding selectivity of wild and pond-cultured Nile tilapia Oreochromis niloticus was conducted in 2008. Water and fish samples were collected in Shirati Bay, Lake Victoria, and from fish ponds in Tarime district using a La Motte water sampler and seine nets, respectively. Cyanophytes were abundant and were the major diet component of fish in both habitats. Chlorophytes were selected by pond fish. Bacillariophytes were selected by fish in both habitats, despite their low abundance in pond water. Astrionella sp. and Rhopalodia vermicularis (bacillariophytes) and Peridinium sp. (dinophyte) were selected by fish in both habitats. Astrionella sp., Aulacoseira nyassensis, Navicula sp. and Rhopalodia vermicularis (bacillariophytes) were the species most selected by lake fish, whereas Ankistrodesmus falcatus (chlorophyte), Lyngbya circumcreta (cyanophyte) and Nitzschia acicularis (bacillariophyte) were the species most selected by pond fish. These results suggest that Nile tilapia is a selective feeder. It is therefore recommended that nutrient enrichment should be controlled to prevent excessive growth of cyanophytes, which form excessive blooms and thereby prevent growth of other algae such as diatoms, which were selected by fish in both habitats.
In this study we present estimates of phenotypic and genetic parameters for body size measurements, reproductive traits, and gut length for Nile tilapia (Oreochromis niloticus) selected for growth in fertilized earthen ponds for two generations. Throughout the experiment, ponds were fertilized daily with 50 kg dry matter, (dm)/ha chicken manure. No supplementary feeds were added. For the analysis, 6429 fully pedigreed experimental fish from G0, G1 and G2 were used. Generations were discrete and therefore parameters were estimated separately for each year. Heritability estimates for body measurements ranged from 0.4–0.6 for standard length to 0.69–0.79 for head length. Phenotypic correlations between body weight and body measurements ranged from 0.64 to 0.89. Genetic correlations were close to unity. The heritability estimate for maturity at harvest (corrected for sex) was 0.13. Heritabilities for carcass traits were estimated from G1 only and were 0.16 for gutted weight and 0.06 for dressing percentage. Phenotypic correlation between body weight and gutted weight was 0.84 and the genetic correlation was 0.20. Heritability estimate for gut length was 0.22. We also estimated a high genetic correlation between gut length index and standard length (0.78) but a low genetic correlation between gut length index and body weight (0.22 ± 0.28). These results suggest that selection for growth on an herbivorous diet could result in a correlated response in gut length.
In semi-intensive aquaculture systems, cultured fish can rely on natural food, produced through fertilization, up to certain size. Beyond this size, supplemental diet becomes imperative to sustain optimum fish growth. The application of supplemental diet to fish ponds should be optimized. In this regard, the present study was carried out to examine the relative importance of top-down (fish predation) and bottom-up (nutrient addition) control to phytoplankton dynamics in earthen fish ponds receiving different rates of supplemental feed for 19 weeks, and polycultured with Nile tilapia, Oreochromis niloticus (L.); common carp, Cyprinus carpio (L.); and silver carp, Hypophthalmichthys molitrix (V.). Ten earthen ponds (0.1 ha each) were used in this study. Each pond was stocked with 1,000 Nile tilapia (13.7±1.2 g), 200 common carp (10.7±1.7 g) and 1,000 silver carp (1.8±0.3 g). The supplemental diet was provided to the ponds at a daily rate of 0.0% (control), 0.5%, 1%, 3%, and 5% of fish biomass. Water quality analyses revealed that water temperature, pH, free ammonia, and water conductivity were not significantly affected by feeding rate, while dissolved oxygen, orthophosphate, and nitrate levels were significantly (P < 0.05) increased with increasing feeding levels. Average Secchi disk reading was significantly (P < 0.05) lower at higher feeding rates. Chlorophyll a content and phytoplankton and zooplankton densities were also directly correlated to feeding rate up to 5%. The maximum growth of Nile tilapia and common carp was obtained at feeding rate of 3% and 5%, respectively, while the maximum growth of silver carp was obtained at 0.5% feeding rate. The best total fish production was obtained at 3% feeding rate. This study suggested that the optimum feeding rate for Nile tilapia, common carp, and silver carp reared in a polyculture system, in earthen ponds is 3% of fish biomass.
The filter-feeding activity of Nile tilapia, Oreochromis niloticus L., was observed during a 24-h feeding cycle for five consecutive days. The feeding activity was high from afternoon to midnight, with a peak after dusk, and lowest from midnight to morning. The clearance rate of cyanobacteria dominated water was estimated during the low morning and high evening feeding periods. The tilapia cleared 34 mg C/l suspended particulate organic carbon in 4.5 h during the reduced morning period (beginning 07:00) and 45 mg C/l in 1 h during the peak evening period (beginning 20:30). Clearance rates of the cyanobacterial water were 13.4±1.2 l/kg fish/h in the morning and 66±3.6 l/kg fish/h in the evening.
A comparative study of the stomach length and food contents of Tilapia mariae (Boulenger), T. zillii (Garvais) and Oreochromis niloticus (Linneus) was carried out over a 24 month period in Agulu Lake basin, southeastern Nigeria. Results showed that T . zillii was herbivorous while T . mariae and O. niloticus subsisted mainly on a wide variety of plankton. Generally, considerable quantities of zoo – and phyto-plankton were present in the food of the three species. Variations were observed in the gut lengths and dental anatomy of the tilapias which related to their food preferences. Nutritive value of food showed no significant difference (P < 0.05) in all species and crude protein evaluation showed that stomach contents were adequate. Journal of Aquatic Sciences Volume 16, April 2001, pp. 57-60
KEY WORDS: Stomach length, Tooth structure, Food habits, Tilapia.
Four different-sized (390±3, 140±2, 40±2, 16±1 g) Nile tilapia, Oreochromis niloticus (L.), stocked at the same biomass in timed pulse feeding chambers were provided 27–29°C water dominated by Microcystis (82%) and Scenedesmus (18%) to determine the effect of fish size on filtration rates. The number of Microcystis and Scenedesmus units filtered from the water decreased significantly with increasing tilapia size. The shaping constants and maximum filtration rates for Ivlev's feeding model used to describe the relation between filtration rates and the suspended particulate organic carbon (POC) concentrations were significantly different among the four sizes. Filtration rates of 763, 671, 512 and 300 mg C kg−1 h−1, which correspond to 70%, 82%, 86% and 90% saturation levels, were achieved at POC levels of 30, 32, 32 and 33 mg C L−1 for 16, 40, 140 and 390 g Nile tilapia respectively. Smaller tilapia achieved these rates at lower POC concentrations than larger tilapia.
The food of Oreochromis niloticus in Lake Chamo, Ethiopia was studied from the stomach contents of 449 adult (290B570 mm total length, tl) and 145 juvenile (61B115 mm tl) fish. O. niloticus was found to be essentially phytoplanktivores in Lake Chamo, and the composition of the phytoplankton diet varied seasonally. The diet of both adult and juvenile fish consisted of 10 genera of blue greens whereas green algae and diatoms each contributed 8 genera. Blue greens as a group contributed the bulk of the diet of adult fish. The most frequently encountered genera from the blue greens were Anabaena (96B100), Lyngbya (85B100), Microcystis (81B100) and Oscillatoria (41B100). Cosmarium (79B100) from the green algae and Navicula (82B100) from the diatoms were also frequently observed. In terms of percentage composition by number, the blue greens contributed over 60% of the total food ingested. Of these, more than 50% was due to Anabaena, Lyngbya and Microcystis. Zooplankters occurred on rare occasions in the stomach contents of both adult and juvenile fish. The feeding pattern of adult O. niloticus was observed to have a diel rhythm. O. niloticus in Lake Chamo is a continuous feeder during the day and peaked at 16 hr. Daily ingestion of phytoplankton was estimated to be about 3.7% of its wet body weight at an average water temperature of 26E C. SINET: Ethiopian Journal of Science Vol. 23, No. 1 (June 2000), pp. 1-12Key words/phrases: Ethiopia, Food, Lake Chamo, Oreochromis niloticus
The feeding habits of the cichlid Cichlasoma urophthalmus were studied in a brackish-water lagoon in Yucatan Peninsula, Mexico, from spring 1985 to spring 1986. The strong mandibular, maxillary and pharyngeal teeth, and the short intestine strongly suggest that C. urophthalmus is primarily a carnivore. Subsequent gut contents analysis revealed that this species feeds principally on invertebrates throughout the year and that there were few differences between the five seasons studied. The algal material found in some stomachs may be consumed as a consequence of predation on small invertebrates, but the feeding structures and short intestine makes this species unable to digest vegetable materials efficiently. Differences with other cichlids used in aquaculture are discussed.
The study was carried out to quantify the periphyton biomass developed on glass substrates over time, to investigate the effects of periphyton quantity and fish size on the ingestion rate by fish, and to determine the feed conversion ratio (FCR) of periphyton by tilapia Oreochromis niloticus. Periphyton was grown in two fertilised 1000-l tanks on glass slides and monitored as dry matter (g), ash-free dry matter (g) and chlorophyll a concentrations (mg) per unit surface area (m2) over a six week period. Ingestion rate was determined for two sizes of tilapia (7 and 24 g) which were provided with four different periphyton densities. Determination of FCR was made after feeding three individual fish ad libitum with periphyton for two weeks.
Periphyton ash-free dry matter increased sharply during the first half of the trial with a peak being recorded at week 3 (75.5 g m−2). Productivity was 2.4 g ash-free dry matter m−2 d−1 during the first three weeks. Mean chlorophyll a concentration showed a cyclic pattern throughout the study with the lowest value being measured during the last week. Ingestion rates were 0.90 and 0.18 mg dry matter g fish body weight−1 h−1 for small and medium fish respectively. Ingestion rate among small fish increased significantly (P < 0.05) with periphyton density, but not for medium size fish. Although periphyton ash content was high (55% dry matter), fish growth was sustained. Fish harvested 70% of total periphyton dry matter that was offered to them. The FCR for periphyton was 2.81 on a dry matter basis and 1.34 on an ash-free dry matter basis.
The alimentary tract of the pike is described, relating its feeding habits to its intestinal gut histology. It is a carnivorous species having a short oesophagus, pouch-like stomach and a short intestine with two convolutions. Stratified epithelium with columnar cells and many goblet cells are present in the oesophagus, columnar epithelial cells only in the stomach, and both cell types in the intestine.
Eosinophils in the mucosa of the oesophagus originate from connective tissue cells and lymphocytes and neutrophils are present. The lamina propria is composed of a stratum granulosum, stratum compactum, blood vessels and loose areolar tissue. The stratum compactum is a strengthening substance, composed of collagen, characteristic of carnivorous teleosts. The circular and longitudinal muscle layers and serosa are similar to those of other carnivorous teleosts.
The pancreas and liver are briefly described, the pancreas being the unusual compact type not often found in teleosts. The B cells are seen in the periphery and a cells in the centre of the islets. The liver is a unilobular organ, having oil storage as a major function.
The distribution of goblet cell mucin is given, differentiating it into neutral and acid mucosubstances. Nine levels of alimentary tract were examined in the mucin distribution study. The functions of mucin in the pike are digestion, absorption, protection and lubrication.
The patterns of coiling of the gut were compared in 22 species of Eurasian Cyprinidae. In selected species, also the length of gut and mucosal surface structure were compared. Piscivorous (Aspius aspius), planktivorous (Abramis ballerus) fishes as well as species feeding mainly on plankton and wind-borne‘ drift’(Alburnus alhurnus, Pelecus cultratus) have the relatively shortest guts, with only a single loop. The same simple arrangement of a short gut is present in many euryphagous species with more or less carnivorous tendencies (Abramis sapa, Alburnoides bipunctalus, Abramis brama, Blicca bjoerkna, Chalcalburnus chalcoides memo, Gobio gobio, Leuciscus cephalus, Leuciscus leuciscus, Rutilus rutilus, Scardinius erythrophthalmus. Tinea tinea, Vimba vimba). Some benthivorous winnowers (oropharyngeal sorters) and species with herbivorous feeding tendencies have relatively long guts showing a more complex pattern of loops and coils (Barbus barbus, Carassius carassius, Chondrostoma nasus, Ctenopharyngodon idella, Cyprinus carpio). The goldfish, Carassius auratus, has the most complex coils. Scanning electron microscopy of the mucosal surface revealed five types of folding in the intestinal bulb which were only loosely related to feeding: 1, smooth surface (Aspius aspius, Leuciscus cephalus, Vimba vimba); 2, irregularly branching folds (Alhurnus alburnus, Barbus barbus, Blicca bjoerkna, Chalcalburnus chalcoides memo, Leuciscus leuciscus, Rutilus rutilus, Scardinius erythrophthalmus); 3, curl-like folds (Tinea tinea); 4, net-like folding pattern (Abramis brama); 5, honeycomb-like mucosal structure (Cyprinus carpio).
Daily food consumption and feeding rhythm of silver carp (Hypophthalmichthys molitrix) from fry to fingerling (6.6–195 mm in total length) were measured from June 1985 to August 1986 using a method of intestine filling index. Absolute food consumption (expressed as wet weight of food consumed per fish each day) was positively related with the body weight of silver carp, and relative food consumption (expressed as wet food consumed as percentage of fish body weight) decreased with increases in body length of the fish. The relative food consumption of silver carp averaging 6.6–8.6 mm in total length was 139.2±6.6%; as the fish grew, relative food consumption reduced to 30.7±3.3%. However, when total length reached 21.7–26.0 mm, relative food consumption increased to 63.2±5.0% (P<0.05), but decreased again to 16.5±1.2% for fish 132–195 mm in total length. The variation in food consumption was due to a change in feeding habits from zoo-plankton to phytoplankton and the difference in nutritive contents of the plankton consumed by silver carp. An obvious daily feeding rhythm was observed. The fish did not feed from 22.00 h to 04.00 h, but from 09.00 h to 11.00 h and 17.00 h to 21.00 h the fish fed actively. The difference in intestinal filling indices between the feeding peak and low feeding level became less and less as the fish grew. The reason for this might be improvement in digestion.
Eight cyprinids with four different feeding habits fall into two distinct groups according to morphological adaptations of the intestine: (i) carnivorous and omnivorous cyprinids with large gut diameter and large mucosal surface which decreases from the foregut to the hindgut; (ii) benthivorous and phytoplanktivorous cyprinids with small gut diameter and small mucosal surface which is more or less uniformly built along the intestine, although relative gut length may vary considerably (1.45–6.10). Although the intestine of phytoplanktivorous cyprinids is extremely elongated, it appears less adapted for processing a refractory diet than that of cichlids with similar feeding habits.
Quantitative aspects of the filter-feeding of the tilapia,Oreochromis niloticus, on two species of the blue-green algae —Anabaena cylindrica andMicrocystis aeruginosa — were investigated in the laboratory. The ingestion rate of 85 mm SLO. niloticus was best fitted using a linear regression over the range of biovolume concentrations studied (3 106 – 3 108 m3 ml–1). The ingestion rate of 40 mm SL fish gave a curvilinear relationship and was best fitted using a logarithmic regression. For each size class of fish, ingestion rates were higher when fed the largerAnabaena thanMicrocystis. The results of ingestion and filtration rates are comparable to work on other aquatic suspension feeders and tend to substantiate a universality in the fundamental regulatory mechanism of filter feeding.
A graphical method is discussed which allows a specification of the optimal diet of a predator in terms of the net amount of energy gained from a capture of prey as compared to the energy expended in searching for the prey. The method allows several predictions about changes in the degree of specialization of the diet as the numbers of different prey organisms change. For example, a more productive environment should lead to more restricted diet in numbers of different species eaten. In a patchy environment, however, this will not apply to predators that spend most of their time searching. Moreover, larger patches are used in a more specialized way than smaller patches.
Standard Methods for the Examination of Water and Wastewater, 16th edition
- Health American
- Apha Association
American Public Health Association, APHA. 1985. Standard Methods for the Examination of Water and Wastewater, 16th edition. American Public Health Association, Washington, D.C., USA
Contribution of natural food and compound feed to the gut content of hybrid tilapia (Oreochromis niloticus x Oreochromis aureus) in pond culture
- Hydrobiologia
- U Rfocken
- C Schlechtriem
- K Becker
Hydrobiologia, 272: 105-123. rFocken, U., C. Schlechtriem and K. Becker. 2000. Contribution of natural food and compound feed to the gut content of hybrid tilapia (Oreochromis niloticus x Oreochromis aureus) in pond culture. pp. 157-162. In: K. Fitzsimmons and J.C. Filho (eds.), Tilapia Aquaculture in the 21st Century. Proceedings from the 5th International Symposium on Tilapia Aquaculture, 3-7 Sept. 2000, Rio de Janeiro, Brazil
Occurrence of phytoplankton in stomach content and its selectivity by Nile tilapia (Oreochromis niloticus L.) cultured in fertilized earthen ponds
- M Abdel-Tawwab
Abdel-Tawwab, M. 2003. Occurrence of phytoplankton in stomach content and its
selectivity by Nile tilapia (Oreochromis niloticus L.) cultured in fertilized earthen
ponds. Qatar Univ. Sci. J. 23:153-166.
The assimilation of carbon from phytoplankton by two herbivorous fishes: Tilapia nilotica and Haplochromis nigripinnis
- D J W Moriarty
- C M Moriarty
Moriarty, D.J.W., and C.M. Moriarty. 1973. The assimilation of carbon from phytoplankton by two herbivorous fishes: Tilapia nilotica and Haplochromis
nigripinnis. J. Zool. London 171: 41-55.
Food and feeding habits of Oreochromis niloticus. I. Types and amount of food taken by the fish and its size and patterns of feeding
- S N Saha
- S Dewan
Saha, S.N., and S. Dewan. 1979. Food and feeding habits of Oreochromis niloticus.
I. Types and amount of food taken by the fish and its size and patterns of
feeding. Bang. J. Zool. 7:53-60.
Study on food habit of Tilapia nilotica. 1-Changes of food habits of T. nilotica with growth in fed and unfed ponds
- T Yada
Yada, T. 1982. Study on food habit of Tilapia nilotica. 1-Changes of food habits of
T. nilotica with growth in fed and unfed ponds. Aquacult. 29:1-10.