Effect of darting phenomenon of African catfish Heterobranchus longifilis (Burchell 1822) on growth performance of Nile tilapia: Oreochromis niloticus (Linnaeus, 1758)

Replicate Ponds of 0.02ha stocked at 500 catfishes with 20,000 tilapia/ha were used to assess growth performance of O.niloticus, average weight 50.4g with (i) darted catfish; H.longifilis (shooters) average weight 60.3g (ii) non-shooters of H.longifilis, average weight 35.4g. Final mean weight, mean growth rate, specific growth rate and food conversion ratio were 499.5g 26g/day, 1.36% and 5.58% respectively for O.niloticus stocked with longifilis (shooters) and 440.4g 2.3g/day 1.23% and 5.58% respectively for O.niloticus stocked with H.longifilis (non- shooters) and 246.9g, 1.2g/day, 0.93, 6.30% respectively for tilapia in monoculture. The least growth was noted for O. niloticus in monoculture while the best growth was recorded O. niloticus in polyculture with darted catfish

Effects of substituting fish meal with grasshopper meal on growth and food utilization of the Nile Tilapia, Oreochromis niloticus fingerlings

The effects of substituting fish meal with grasshopper meal in fish diets on the growth, food utilization and survival of the Nile tilapia, Oreochromis niloticus (mean weight = 40.1g) were investigated. The results show that the best growth and food utilization were recorded in the fingerlings fed in the 10% grasshopper meal and 30% fish meal while the poorest growth and food utilization indexes were recorded with the 25% grasshopper meal and 15% fish meal. In general, at 10% inclusion, the fingerlings performed even better than the control (40% fishmeal and no grasshopper meal)

Estimation of growth and financial analysis through the application of Ipil ipil (Leucaena leucocephala) leaf meal as supplements to soybean and fish meal in the diet of juvenile monosex tilapia (Oreochromis niloticus)

Among plant protein ingredients,ipil ipil (Leucaena leucocephala) leafmeal (ILLM) is considered the most nutritive plant protein source after soybean meal in aquatic feeds. That was proven in a 21-day experiment conducted to assess the response of juvenile Monosex Nile tilapia Oreochromis niloticus with four iso-nitrogenous formulated diets: One control diet was formulated based on fishmeal, one on soybean meal and one on rice bran, ipil ipil leafmeal was also included in experimental diets.

Application of ipil- ipil leaf meal (IILM) as feed Ingredient for Monosex tilapia fry (oreochronis niioticus) : In terms of growth and economics

The Ipil-ipil (Leucaena leucocephal) leaf analyzed for crude protein (CP), fat, crude fibre (CF), ash content, moisture content and nitrogen free extract (NFE). The CP 23± 0.12 % , fat 8 ± 0.11 %, CF 18 ± 0.15 % , ash 10 ± 0.13 %, moisture 14. ± .16% and NFE 29.± 1.10 % were recorded. A twenty one days experiment was conduced to assess the response of juvenile monosex tilapia with different iso-nitrogenous formulated diets for find out the feasibility study of using ipil-ipil leaf meals as feed ingredient for juvenile tilapia. Three experimental diets were formulated by using fish meal, soybean meal, rice bran and ipil ipil leaf meal. One control diet was formulated by using fish meal, soybean meal and rice bran. Considering the high demand, limited availability of fish meal and soybean meal, ipil ipil leaf meal was incorporated in juvenile tilapia feed. Among plant protein ingredients ipil ipil leaf meal was considered as the most nutritive plant protein source after soybean meal. However, high concentration of toxic element limited the incorporation level of ipil ipil leaf meal in fish feed. Use of 15 % ipil ipil leaf meal in fish feed was more significant from the view of growth performance and economics. The higher Absolute Growth was 1119.26 gm, higher Specific Growth Rate was 6.52% /day higher Feed Conversion Efficiency was 41.23% , higher Protein Efficiency Ratio was 1.178 and higher Average Daily Growth rate was 14.00% recorded in diet-4 ( which contained 15% IILM). The lower Feed Conversion Ratio 2.42 and lower cost for per unit production 34.65 taka/kg were recorded in diet-4. The higher cost for per unit fish production 45.6 tk./kg was recorded for diet-1 where no ipil ipil leaf meal.. The results suggest that tree legumes Ipil-ipil (Leucaena leucocephal) leaf has potential and excellent source of feed ingredients as protein supplements for juvenile monosex

Changes in feeding biology of Nile tilapia, Oreochromis niloticus (L.), after invasion of water hyacinth, Eichhornia crassipes (Mart.) Solms, in Lake Victoria, Kenya

Oreochrimis niloticus (L.) was introduced to Lake victoria in the 1950s. It remained relatively uncommon in catches until 1965, when the numbers began to increase dramatically. It is now the third most important commercial fish species after the Nile perch, Lates niloticus (L.) and Rastrineobola argentea (Pellegrin). Oreochromis niloticus is considered a herbivore, feeding mostly on algae and plant material. The diet now appears to be more diversified , with insects, fish, algae and plant materials all being important food items. Fish smaller than 5 cm TL have a diverse diet but there is a decline in the importance of zooplankton, the preferred food item of small fish, as fish get larger. The shift in diet could be due to changes which have occurred in the lake. Water hyacinth, Eichhornia crassipes (Mart.) Solms, which harbours numerous insects in its root balls, now has extensively coverage over the lake. The native fish species which preyed on these insects (e.g. haplochromines) have largely been eliminated and O. niloticus could be filling niches previously occupied by these cichlids and non cichlid fishes. The change in diet could also be related to food availability and abundance where the fish is feeding on the most readily available food items.

A comparative study of consumption rates and preference for some species of aquatic plants by Tilapia rendalli

The daily consumption rates and preference of juvenile Tilapia rendalli for some macrophytes, Ceratophyllum demersum, Lagarosiphon major, Najas pectinatas and Valisneria aethiopica were determined. Fish were offered single macrophyte diets to determine daily consumption and a mixture of the 4 macrophytes in equal quantities to determine selection. Consumption rates were 821.50 mg, 829.05 mg, 940.00 mg and 2293.53 mg per fish per day, respectively. The differences in consumption rates were significant. Preference was shown for V.aethiopica, whilst C.demersum was least selected. Fish fed on single species lost weight whereas those fed on a variety of macrophytes gained in weight.

Age validation, growth, mortality, and demographic modeling of spotted gully shark (Triakis megalopterus) from the southeast coast of South Africa

This study documents validation of vertebral band-pair formation in spotted gully shark (Triakis megalopterus) with the use of fluorochrome injection and tagging of captive and wild sharks over a 21-year period. Growth and mortality rates of T. megalopterus were also estimated and a demographic analysis of the species was conducted. Of the 23 OTC (oxytetracycline) -marked vertebrae examined (12 from captive and 11 from wild sharks), seven vertebrae (three from captive and four from wild sharks) exhibited chelation of the OTC and fluoresced under ultraviolet light. It was concluded that a single opaque and translucent band pair was deposited annually up to at least 25 years of age, the maximum age recorded. Reader precision was assessed by using an index of average percent error calculated at 5%. No significant differences were found between male and female growth patterns (P>0.05), and von Bertalanffy growth model parameters for combined sexes were estimated to be L∞=1711.07 mm TL, k=0.11/yr and t0=–2.43 yr (n=86). Natural mortality was estimated at 0.17/yr. Age at maturity was estimated at 11 years for males and 15 years for females. Results of the demographic analysis showed that the population, in the absence of fishing mortality, was stable and not significantly different from zero and particularly sensitive to overfishing. At the current age at first capture and natural mortality rate, the fishing mortality rate required to result in negative population growth was low at F>0.004/ yr. Elasticity analysis revealed that juvenile survival was the principal factor in explaining variability in population growth rate.

Genetic variability in spotted seatrout (Cynoscion nebulosus), determined with microsatellite DNA markers

Variation in the allele frequencies of five microsatellite loci was surveyed in 1256 individual spotted seatrout (Cynoscion nebulosus) obtained from 12 bays and estuaries from Laguna Madre, Texas, to Charlotte Harbor, Florida, to St. John’s River on the Florida Atlantic Coast. Texas and Louisiana collection sites were resampled each year for two to four years (1998−2001). Genetic differentiation was observed. Spotted seatrout from Florida waters were strongly differentiated from spotted seatrout collected in Louisiana and Texas. The greatest genetic discontinuity was observed between Tampa Bay and Charlotte Harbor, and Charlotte Harbor seatrout were most similar to Atlantic Coast spotted seatrout. Texas and Louisiana samples were not strongly structured within the northwestern Gulf of Mexico and there was little evidence of temporal differentiation within bays. These findings are contrary to those of earlier analyses with allozymes and mitochondrial DNA (mtDNA) where evidence of spatial differentiation was found for spotted seatrout resident on the Texas coast. The differences in genetic structure observed among these markers may reflect differences in response to selective pressure, or may be due to differences in underlying genetic processes.

Exploitation and reproduction of the spotted eagle ray (Aetobatus narinari) in the Los Frailes Archipelago, Venezuela

We studied a small artisanal fishery for the spotted eagle ray (Aetobatus narinari) off Margarita Island in northeastern Venezuela. We analyzed data from 413 fishing trips directed at A. narinari over a 29-month sampling period (August 2005–December 2007). These trips yielded 55.9 metric tons and 1352 individuals from which a subsample of 846 females and 321 males was used for biological data. Maximum fishing effort and landings occurred between February and May, and catch per unit of effort was highest between December and February and between July and October with an overall average of 3 individuals and 133 kg per trip. The overall sex ratio was significantly different from 1:1 with a predominance of females. Females ranged in size with disc widths (DW) from 64 to 226 cm. Males ranged in size between 97 and 190 cm DW. There was no statistically significant difference between male and female length-weight relationships. Mean fecundity was estimated at 3.09 embryos per female, and the largest embryo measured 44.5 cm DW. Females in different maturity stages were found in all months, except November 2007, the month when all females were immature. Postgravid females occurred mainly during the periods of January–May and July–October. Mean length (L50) at maturity was estimated at 129.2 cm DW for males and 134.9 cm DW for females. This study provides much needed information on the biology and life history of A. narinari for the management of an intensive, directed, small-scale fishery for this little known species in northeastern Venezuela.

Morphometric differentiation in small juveniles of the pink spotted shrimp (Farfantepenaeus brasiliensis) and the southern pink shrimp (F. notialis) in the Yucatan Peninsula, Mexico

The morphometric and morphological characters of the rostrum have been widely used to identify penaeid shrimp species (Heales et al., 1985; Dall et al., 1990; Pendrey et al., 1999). In this setting, one of the constraints in studies of penaeid shrimp populations has been the uncertainty in the identification of early life history stages, especially in coastal nursery habitats, where recruits and juveniles dominate the population (Dall et al., 1990; Pérez-Castañeda and Defeo, 2001). In the western Atlantic Ocean, Pérez-Farfante (1969, 1970, 1971a) described diagnostic characters of the genus Farfantepenaeus that allowed identification of individuals in the range of 8−20 mm CL (carapace length) on the basis of the following morphological features: 1) changes in the structure of the petasma and thelycum; 2) absence or presence of distomarginal spines in the ventral costa of the petasma; 3) the ratio between the keel height and the sulcus width of the sixth abdominal somite; 4) the shape and position of the rostrum with respect to the segments and flagellum of the antennule; and 5) the ratio between rostrum length (RL) and carapace length (RL/CL). In addition, she classified Farfantepenaeus into two groups according to the shape and position of the rostrum with respect to the segments and flagellum of the antennule and the ratio RL/CL: 1) F. duorarum and F. notialis: short rostrum, straight distally, and the proximodorsal margin convex, usually extending anteriorly to the end of distal antennular segment, sometimes reaching to proximal one-fourth of broadened portion of lateral antennular flagellum, with RL/CL <0.75; and 2) F. aztecus, F. brasiliensis, F. paulensis, and F. subtilis: long rostrum, usually almost straight along the entire length, extending anteriorly beyond the distal antennular segment, sometimes reaching to the distal one-third of broadened portion of lateral antennular flagellum, with RL/CL >0.80. Pérez-Farfante stressed that, for the recognition to species level of juveniles <10 mm CL, all the characters listed above should be considered because occasionally one alone may not prove to be diagnostic. However, the only characters that could be distinguished for small juveniles in the range 4−8 mm CL are those defined on the rostrum. Therefore, it has been almost impossible to identify and separate small specimens of Farfantepenaeus (Pérez-Farfante, 1970, 1971a; Pérez-Farfante and Kensley, 1997).

Duration of unassisted swimming activity for spotted dolphin (Stenella attenuata) calves: implications for mother-calf separation during tuna purse-seine sets

Size-related differences in power production and swim speed duration may contribute to the observed deficit of nursing calves in relation to lactating females killed in sets by tuna purse-seiners in the eastern tropical Pacific Ocean (ETP). Power production and swim-speed duration were estimated for northeastern spotted dolphins (Stenella attenuata), the species (neonate through adult) most often captured by the fishery. Power required by neonates to swim unassisted was 3.6 times that required of an adult to swim the same speed. Estimated unassisted burst speed for neonates is only about 3 m/s compared to about 6 m/s for adults. Estimated long-term sustainable speed is about 1 m/s for neonates compared to about 2.5 m/s for adults. Weight-specific power requirements decrease as dolphin calves increase in size, but power estimates for 2-year-old spotted dolphin calves are still about 40% higher than power estimates for adults, to maintain the same speed. These estimated differences between calves and adults are conservative because the calculations do not include accommodation for reduced aerobic capacity in dolphin calves compared to adults. Discrepancies in power production are probably ameliorated under normal circumstances by calves drafting next to their mothers, and by employing burst-coast or leap-burst-coast swimming, but the relatively high speeds associated with evasion behaviors during and after tuna sets likely diminish use of these energy-saving strategies by calves.

Weed control by adult and juvenile tilapia Tilapia rendalli in rainfed ponds

Two studies were conducted in consecutive years over the time period 14 January to 1 July to determine whether labor-savings and fish growth enhancement could be achieved by stocking Tilapia rendalli directly into ponds containing weeds left from a dry period. Six replicates 200 sq. m ponds located at the Malawi National Aquaculture Centre, Domasi were drained, left dry for 63 days and natural growth of weeds was allowed. All ponds were stocked with 200 T. rendalli fingerlings (study 1) or adults (study 2) averaging 4.6 g (40 mm TL) and 47.7 (130 mm TL), respectively. For T. rendalli juveniles, final standing stock, growth and offspring production were significantly (P<0.05) better in fed than in weedy ponds. Average weight of fingerlings were significantly (P<0.05) different between the two treatments. For T. rendalli adults, final standing stock, growth and offspring production were not affected by the presence of weeds.

Genetic analysis of immunological traits in tilapia

The immunological response to handling stress of four tilapia species is evaluated.Polymorphism is examined in genes known to influence immune response in fish.

The introduction of exotic fish in Sri Lanka with special reference to tilapia

Introductions of exotic finfish between 1948 and 1953 are reported in this paper, with a brief reference to earlier and later introductions. Exotic fish were introduced principally to develop the potential for aquaculture in fresh and brackish waters in order to increase the availability of fish for rural communities through the biological control of aquatic vegetation. The algal feeding tilapia (Sarotherodon mossambicus) has created a new food industry in inland and brackishwaters. It has supplemented marine fishery production in a community where animal protein intake consists mainly of fish. It is also being cultured in flooded rice fields and used in the control of malaria. This excellent table fish has not had any adverse environmental impact.

Pawpaw seed as fertility control agent on male Nile tilapia

To find out if pawpaw (Carica papaya) seeds can induce sterility in male Nile tilapia (Oreochromis niloticus) and to determine if sterility so induced is reversible or otherwise, mature male tilapia of mean weight 40 g were treated for 30 days with a low dose (4.9 g/kg/day) and a high dose (9.8 g/kg/day) of ground pawpaw seeds incorporated into their feed. Fish of similar sizes in the control experiment were fed with feed that did not contain pawpaw seed. The pawpaw seeds induced permanent sterility in the fish that received the high dose, while sterility in the low dose treatment was reversible. Fish in the control experiment spawned two weeks into the experiment and again in the fifth week. Fish in the low dose treatment spawned three weeks after the treatment had been discontinued. Histological sections of the testes showed that pawpaw seeds produced swollen nuclei in the low dose treatment and disintegrated cells in the high dose treatment. The study showed that pawpaw seeds, which are easy to obtain, can be incorporated into fish feeds and used by farmers to control prolific breeding of Nile tilapia.