Fry Length Research Articles

Multiple climate change stressors reduce the emergence success of gravel-spawning fish species and alter temporal emergence patterns

Climate change, with its profound effects on stream sediment, hydrological, and temperature dynamics, will exacerbate impacts on habitat conditions for many species, particularly those with vulnerable early life stages relying on the hyporheic zone, such as gravel-spawning fishes. Due to the complex and interactive nature of multiple stressor effects, we employed large-scale outdoor mesocosms to systemically test how the reproductive success of three gravel-spawning fish species brown trout (Salmo trutta), nase, (Chrondrostoma nasus) and Danube salmon (Hucho hucho) was affected by individual and combined effects of warming (+3–4 °C), fine sediment (increase in <0.85 mm by 22 %) and low-flow (eightfold discharge-reduction). Fine sediment had the most detrimental effect on emergence rate and fry length in all three species, reducing the emergence rate to zero in brown trout, 9 % in nase, and 4 % in Danube salmon. The emergence mortality caused by fine sediment surpassed that of hatching distinctly, suggesting that negative effects due to hypoxia were considerably exacerbated by entombment. Warming had only minor effects as a single stressor, but low flow reduced emergence rates of the spring spawning species nase and Danube salmon by 8 and 50 %, respectively. In combined treatments including fine sediment, however, the emergence success of all three species responded strongly negatively, even in the cyprinid species nase, which showed little interactive effects between stressors regarding hatching success. Warming and fine sediment also led to the earlier emergence of fry, implying a risk of asynchrony with available food resources. This study dramatically shows that climate change can have deleterious impacts on the reproductive success of gravel-spawning fish species, irrespective of taxonomic or ecological traits.

Growth patterns of saffron cod &lt;i&gt;Eleginus gracilis&lt;/i&gt; Tilesius (Gadidae) in the first year of life

Patterns of linear and weight growth of saffron cod in the first year of life are considered on the data of measurements and cited materials for different habitats of this species. The growth curve is approximated by logistic function. Monthly increments for the body length of larvae and fry are about 50–60 % in the first four months of life with the highest growth rate. Then the relative growth decreases significantly in fall-winter and does not exceed 1–4 % to the end of the first year of life. The absolute length increments increase during the first half of the year up to the maximum value of 25–30 mm/month in late summer – early autumn. Saffron cod grow faster in the southern areas of their habitat. The weight growth patterns are different from the linear growth. The weight growth is higher in the first five months of life, with gradual decreasing of the monthly weight increments form 156 % to 105 %. The relative weight increments exceed significantly the length increments in this period. When the body weight reaches app. 5 g, the relative weight increments decrease abruptly, though the absolute increments continue to increase until the 6–8th months of life when they reach 5–6 g per month for fish with body length &gt; 86 mm. The body weight increases by 60 % in this short period of the highest weight growth. Time lag between the peaks of absolute linear growth (in July-September) and weight growth (in September-November) is about 2 months.

Nursing and management of early produced larvae of Thai pangas (Pangasianodon hypophthalmus) using greenhouse concept

This experiment was conducted for the development of nursing techniques of early produced larvae of Thai pangus (Pangasianodon hypophthalmus) using Greenhouse concept for a period of 40 days from 10th February to 20th March 2020. The experiment was designed into two treatments (i) Greenhouse pond (GP) and (ii) Control or open ponds (CP) having three replicates each. Greenhouse concept was used for increasing the temperature during the winter month for proper growth and survival of the spawn. For this purpose, three ponds were covered with transparent polyethylene sheet fastened into bamboo frame and three ponds with no such covering. All the nursery ponds were stocked at a density of 20 g hatchling/decimal with 3 days old P. hypophthalmus. After 40 days of nursing period, the highest mean final length, weight gain and survival rate of fry were found to be 9.75 cm, 12.44g and 73.19% in greenhouse pond where in Control ponds it was 6.39 cm, 7.22g and 58.08%, respectively. A significantly higher (p&lt;0.05) mean gross production of 6.07 kg/ decimal was found in greenhouse pond where in Control ponds it was 2.80 kg/ decimal in 40 days of nursing period. Water quality parameters were found to be better with good primary production in the green house ponds due to retaining day light temperature by polyethylene sheet. Results from the present experiment indicated that greenhouse technique can be suitable for the nursing and management of early produced larvae of Thai pangas with proper growth and good survival rate.

Development and verification of the signal to noise ratio for a layer of turbulence in a multi-layer atmosphere.

Wide-field image correction in systems that look through the atmosphere generally requires a tomographic reconstruction of the turbulence volume to compensate for anisoplanatism. The reconstruction is conditioned by estimating the turbulence volume as a profile of thin homogeneous layers. We present the signal to noise ratio (SNR) of a layer, which quantifies how difficult a single layer of homogeneous turbulence is to detect with wavefront slope measurements. The signal is the sum of wavefront tip and tilt variances at the signal layer, and the noise is the sum of wavefront tip and tilt auto-correlations given the aperture shape and projected aperture separations at all non-signal layers. An analytic expression for layer SNR is found for Kolmogorov and von Kármán turbulence models, then verified with a Monte Carlo simulation. We show that the Kolmogorov layer SNR is a function of only layer Fried length, the spatio-angular sampling of the system, and normalized aperture separation at the layer. In addition to these parameters, the von Kármán layer SNR also depends on aperture size, and layer inner and outer scales. Due to the infinite outer scale, layers of Kolmogorov turbulence tend to have lower SNR than von Kármán layers. We conclude that the layer SNR is a statistically valid performance metric to be used when designing, simulating, operating, and quantifying the performance of any system that measures properties of layers of turbulence in the atmosphere from slope data.

Pemanfaatan Kubis sebagai Bahan Pakan Buatan untuk Pertumbuhan Benih Ikan Lele Mutiara (Clarias gariepinus)

Pearl catfish has the main advantage of fast growth. To maximize this growth, one of the things that must be considered is the feed given. The use of factory feed for catfish seeds is common, so it is necessary to use feed raw materials that are around to be used as raw materials for homemade feed. Vegetable waste such as cabbage and tofu dregs can be used as fish feed which is processed into pellets. Cabbage vegetable waste, tofu dregs, bamboo shoots and bran have protein and carbohydrates that can be used for fish growth. This study consisted of 2 stages, namely stage 1 analyzing the comparison between factory feed and homemade feed and stage 2 analyzing the difference in dosage of homemade feed on the growth and efficiency of pearl catfish (C. gariepinus) seed feed. Data were analyzed using 2 independent samples (unpaired) t-test and ANOVA test. The results showed that the provision of factory feed and homemade feed did not have a significant effect on the growth of length, weight, and feed efficiency of catfish fry. Catfish seeds can be fed homemade feed with ingredients from fermented cabbage waste, tofu dregs flour, rebon flour, bran flour, plus vitamins and minerals. The results of the analysis of variance in the treatment of different feed doses (4%, 5%, 6%, 7%, and 10% per fish body weight), had a significant effect on the growth of catfish length and weight, and had no significant effect on feed efficiency. The higher the dose given for the maintenance period of 30 days of catfish fry gave a good effect with the best dose of 10% per fish body weight

Survival of Embryos and Fry of Sea Trout (Salmo trutta m. trutta) Growing from Eggs Exposed to Different Concentrations of Selenium during Egg Swelling.

Simple SummarySelenium-poor areas are defined in the Earth. Adequate selenium (Se) consumption enhances the health and growth of organisms, but overdose of it can be harmful and pathogenic. The objective of the study was to investigate Se supplementation effects in the non-feeding stages of fish. Fertilised eggs of sea trout were immersed in water enriched with Se during the egg-swelling period. Se at a concentration from 0.5 to 8 mg Se L−1 slightly impacted the hatching rate. A higher concentration of Se resulted in declined survival of embryos. Accumulation of Se in the body of hatch increased with the increase of element concentration in the aqueous environment during egg swelling. The survival of fry was similar in all groups, while the fry length and weight correlated positively with Se concentration in its body. In Se-poor areas, immersion of fertilised eggs in water enriched with Se during egg swelling can be used to supplement the deficient element to fish in order to improve breeding outcomes in aquaculture.Adequate selenium (Se) availability enhances the health and growth of organisms, but overdose of it can be harmful and pathogenic. The study’s objective was to analyse the impact of short-term exposure of sea trout fertilised eggs to inorganic selenium (SeO2) at concentrations from 0 to 32 mg Se L−1 to find the optimal and toxic dose of Se on early fish development. Se accumulated in the body, embryos’ survival rate, and growth in the first four months of life was examined. Swelling of fertilised eggs in water supplemented with Se at a concentration from 0.5 to 8 mg Se L−1 was associated with a slightly positive impact on the hatching rate. At higher Se concentration, a harmful effect on the survival of the embryo was observed. The survival of fry was similar in all groups, while the fry length and weight correlated positively with Se concentration in its body. Immersion of fertilised eggs in water enriched with Se during egg swelling can constitute a method to supplement the element to non-feeding stages of fish. In selenium-poor areas, this innovative method can be implemented in aquaculture to improve breeding outcomes. Se concentration should be adjusted to the chemical compound, fish species, and Se’s content in the yolk.

PENGARUH JENIS BAKTERI PROBIOTIK TERHADAP PERTUMBUHAN IKAN LELE MUTIARA YANG DIPELIHARA MENGGUNAKAN SISTEM BIOFLOK

The main problems faced by fish farmers are waste, uneaten feed and feces. Which can reduce water quality and have a significant impact on fish growth and survival. This study aims to determine the effect of giving various types of probiotics on the growth rate and viability of Mutiara catfish raised using the biofloc system. We used Lactobacillus sp., Bacillus subtilis, and Nitrobacter as probiotic bacteria. This study used a completely randomized design experimental method with 4 treatments and 3 replications, namely K = probiotic less/control, P1= Lactobacillus probiotic, P2= Bacillus subtilis probiotic, P3= Nitrobacter probiotic. Catfish are reared for 30 days, feeding 3 times a day with FR 5% of body biomass. The parameters observed were absolute length growth, survival, Feed Conversion Ratio (FCR) and Specific Growth Rate (SGR) which were analyzed using ANOVA (P &lt;0.05) and Duncan's test to see the differences between treatments. The results showed that the bacteria probiotic treatment had no significant effect on FCR and fish survival, but had a Lactobacillus sp significant effect on growth in absolute length (3.96 ± 0.06 cm) and the growth rate of daily specific weight (5,45±0,18 %/day). To increase the length and weight growth of catfish fry, probiotic bacteria of the type Lactobacillus sp. on cultivation media.Key words :biofloc, growth rate, lactobacillus, mutiara catfish, probiotics

Small biased body size of salmon fry preyed upon by piscivorous fish in riverine and marine habitats

Predator–prey interactions must be considered when aiming to enhance populations by releasing artificially reared individuals into natural environments. Released individuals create an abundance of prey for predators, and a basic hypothesis of predator–prey interactions suggests that predators select large prey due to the high caloric content. An alternative hypothesis is that small individuals are vulnerable to predation due to their poor predator avoidance. This study tested these hypotheses using stocked chum (Oncorhynchus keta) and masu (Oncorhynchus masou) salmon fry and piscivorous salmonids in marine and riverine habitats in Hokkaido, Japan. Stomach contents were sampled from predators, and fork length of prey fry was measured. Then, their fork length was compared with whole stocked fry (range of mean fork length (±SD): 45.8 ± 2.55 to 49.2 ± 2.76 mm) for each habitat. As a result, prey fry were ∼3%–6% smaller than whole stocked fry, even under a prey-abundant condition (i.e., just after hatchery reared salmon fry were stocked). Piscivorous salmonids pursue schooling fry, and small fry may be easily caught due to their slow speed in avoiding predators.

Influence of Ovaprim And Pituitary Gland on The Reproductive Indices and Growth of &lt;i&gt;Clarias garipienus&lt;/i&gt; (Burchell, 1822) Broodstock Reared in An Indoor and Outdoor Pond

Ovaprim and pituitary gland from C. gariepinus was used to ascertain the reproductive indices and growth value of the hatchlings (F1) of C. gariepinus at the Fisheries and Research Institute Baga. Broodstocks mean body weight males (1200 g) and females (800 g) was collected from Lake Chad and transported to the institute hatchery complex. It was injected with ovaprim and pituitary gland. The fecundity, sperm volume and weight of the testes were estimated after the latency period. While the hatchlings were reared for eight weeks in a complete randomized design setup in an indoor and outdoor facility to evaluate the weight and length increase. The result revealed significant difference ( P >0.05) in the fecundity of the females, ovaprim had 10,500 while pituitary gland had 7,000. There was significant difference ( P >0.05) in % fertility and hatchability of the eggs. However, the male injected with ovaprim had higher milt volume (2.2 mL). Subsequently, there was no significant difference ( P >0.05) in weight and length parameters across the treatments for the period of the research, the mean weight gains of fry reared indoor induced with ovaprim was 8.77 g while pituitary gland extract was 8.13 g. Meanwhile, the fingerlings reared four weeks in an outdoor pond had a significant growth, the fingerlings induced with ovaprim had 14.35 g in weight gain while pituitary gland was 14.42 g. There was no significant ( P >0.05) difference between the two hormones on fingerling production. There was no significant difference ( P >0.05) between increase in length of fry reared indoors and outdoors for four weeks. This study proved that pituitary can effectively be used to induce Catfish breeding, when considering its availability and high cost of purchasing ovaprim.

Features of rainbow trout farming technology in PE “Zakhidna Rybna Kompania”, for feeding with Aguafeed Fischfutteer

The production of trout products in ponds and aquaculture farms is based on modern and long-term plans for technology and intensification of production, through the introduction of the latest approaches, by borrowing the experience of leading foreign producers, expanding production areas and sectoral investments. The main indicator that characterizes the efficiency of fisheries and reflects the state of production and the level of its economic indicators. is fish productivity Growing trout in aquaculture in a closed water supply is associated with high planting densities per unit area, the use of high-protein granular feed, which must fully meet the needs of fish in all necessary nutrients to ensure a balanced diet. In modern farms for feeding trout use high-protein feed mixtures in the form of grits and pellets. The dynamics of the intensity of growth and development of rainbow trout mainly depends on the location of the farm, the quality of the water supply source, the feeding regime of fish and the quality of feed. Therefore, the aim of the work was based on a review of literature sources and analysis of economic activity of the studied farm to give a general description of trout feed, Aquafeed Fischfutter, used for fish feeding, and determine their effectiveness, taking into account geographical location and abiotic and biotic factors . In addition, the study fish performance when feeding these feeds. Conduct research on the growth rate of rainbow trout, changes in weight and length of larvae, fry, yearlings and commercial fish, in tray, pool and pond cultivation. Develop a scheme for growing all age groups of trout on these feeds. Establish indicators of quality, nutritional value, feed ratio of starting, growth and production feeds. To give an objective assessment of their impact on the growth of larvae, fry, yearlings and commercial rainbow trout in the conditions of trout farming PE “Zakhidna Rybna Kompania”, Perimyshlyany district, Lviv region. The conducted research gives the basis to claim that this compound feed guarantees high daily gain. Being a high-energy feed, its use does not lead to obesity of fish. With intensive feeding, a good ratio of price and productivity of farmed fish is realized. The risk of contamination of water bodies and fish is very low, due to the low phosphorus content and good digestibility of feed – 1.1 kg of feed/kg of fish growth. The feed corresponds to the best world indicators in accordance with buoyancy and stability in water.

Optimising water requirement for nursery rearing of rohu Labeo rohita (Hamilton, 1822) in large outdoor concrete tanks: influence of water depth on seed performance

A study was conducted to find the optimum water depth requirement for nursery rearing of rohu Labeo rohita (Hamilton, 1822). Nine concrete tanks of 50 m2 each (10 x 5 x 1.2 m) were grouped into three treatments T1, T2 and T3 and were filled upto 1.0, 0.75 and 0.5 m water depths, respectively. Each tank was stocked with 0.5 lakh hatchery produced spawn and reared for 20 days. The study revealed significant influence of water depth on growth and survival of fry (p&lt;0.05). Though the final length of fry did not differ among the treatments (p&gt;0.05), T3 with 0.5 m water depth showed significantly lower survival, final body weight and specific growth rate than the other two treatments (p&lt;0.05), whereas tanks with 1.0 and 0.75 m water depths showed almost similar survival, final weight and SGR (p&gt;0.05). Assessment of water use for production of every 1000 fry revealed significant reduction in total water use (TWU) with decreased water depth (p&lt;0.05), while the consumptive water use (CWU) in terms of water exchange and replenishment did not differ between water depth treatments of 1.0 and 0.75 m. The results of the study indicate 0.75 m to be the ideal water depth with better water use efficiency for fry production of the species.

Evaluation of Addition Chromium Feed to the Efficiency of Gouramy (Osphronemus goramy) Nursery Time

This research aims to determine the efficiency of gouramy nursery time by providing chromium feed. Chromium feed is carried out by adding lemna meals containing chromium to commercial feed with Cr concentration of each treatment at 0 ppm; 1.3 ppm; 1.5 ppm; and 1.7 ppm. Based on preliminary test Lemna sp. which was cultured in tannery wastewater for five days could accumulate Cr in the tannery wastewater in its tissue in an organic form of 2,319 mg kg-1. This research was conducted using a completely randomized experimental design (CRD) method with four treatments. Treatment A (Control commercial feed without Lemna), B (Commercial feed + Lemna 56.06 g kg-1), C (Commercial feed + Lemna 64.68 g kg-1), D (Commercial feed + Lemna 73.31 g kg-1) and each treatment was repeated four times. The addition of Cr in commercial feed can give significantly different results on increasing the absolute length of gouramy fry, while in survival it does not give a real difference. Giving Lemna sp. with Cr 2,319 mg kg-1 content as much as 73.31 g kg-1 in commercial feed or equivalent to 1.7 ppm Cr produces survival rate, absolute length increase and the best maintenance time efficiency in gouramy fry successively at 87.5 ± 5%; 1.89 ± 0.04 cm and with a maintenance time of 42 days to achieve an increase 2 cm length, 1.6 times faster than the control treatment.

Evaluation of Two Formalin Concentrations During Yellow Perch Egg Incubation

Daily 15-minute treatments of formalin at 1667 mg/L are typically used to prevent water mold infestations in coolwater fish eggs. This study evaluated the use of a reduced concentration of 834 mg/L during yellow perch Perca flavescens egg incubation until the eyed stage of egg development. No water mold was observed on the perch eggs using either formalin treatment regime. Median survival to the eyed stage of egg development was not significantly different between the treatments and approached 90%. There was also no significant difference in egg survival to hatch. In addition, fry length at hatching, although relatively short overall, was not significantly different between the formalin treatment concentrations. The results of this study indicate that reducing daily 15-minute formalin concentration from 1667 to 834 mg/L during yellow perch egg incubation will not affect survival through hatch or larval length at hatching.

Use of Fermented Azolla in Diet of Tilapia Fry (Oreochromis niloticus)

The present study was undertaken to evaluate the effect of fermented azolla as fish meal substitute in the tilapia fry diet (Oreochromis niloticus) on growth performance, survival and feed utilization. In the experiment, the fry length initially ranging between (2.160±0.090 cm and 2.540±0.060 cm) and weight initially ranging between (0.190±0.010 g and 0.210±0.010 g) were fed on practical basal diet (30% crude protein) in the form of pellet during rearing period of 60 days. The fermented azolla were incorporated in the experimental diet at various levels such as 0% azolla, 10% fermented azolla, 20% fermented azolla and 30% fermented azolla to formulate four different test diets along with control diet. (Basal diet, without incorporation of fermented azolla, was used as control diet). The experimental fishes were fed with the experimental diet at of 7% of the body weight twice a day. Among the experimental treatments, the treatment 20% fermented azolla showed significantly higher growth parameters such as length gain (178.586±11.313%), weight gain (1346.770±70.251%), specific growth rate (4.449±0.083%), average daily growth (2.840±0.057%) and survival (95.556±2.222%). The feed utilization in terms of feed conversion ratio (1.236±0.030%) was significantly lower in 20% fermented azolla than control group, whereas protein efficiency ratio (4.145±0.169) in 20% fermented azolla showed significantly higher than that of other treatments.

Sex-specific effects of outbreeding on offspring quality in pike (Esox lucius).

Intraspecific genetic admixture occurs when previously separated populations within a species start interbreeding, and it can have either positive, negative, or neutral effects on reproductive performance. As there currently is no reliable predictor for the outcome of admixture, an increased knowledge about admixture effects in different species and populations is important to increase the understanding about what determines the response to admixture. We tested for effects of admixture on F1 offspring quality in three subpopulations of pike (Esox lucius). Gametes were collected in the field, and eggs from each female were experimentally fertilized with milt from a male from each population (one “pure” and two “admixed” treatments). Three offspring quality measures (hatching success, fry survival, and fry length) were determined and compared between (a) pure and admixed population combinations and (b) the sex‐specific treatments within each admixed population combination (based on the origin of the male and female, respectively). The results suggested that although there were no overall effects of admixture on offspring quality, the consequences for a given population combination could be sex‐specific and thus differ depending on which of the parents originated from one or the other population. All offspring quality traits were influenced by both maternal ID and paternal ID. Sex‐ and individual‐specific effects can have implications for dispersal behavior and gene flow between natural populations, and are important to consider in conservation efforts.

Development of Components for Adaptive Optics Systems for Solar Telescopes

Wavefront aberrations at the entrance aperture of the Large Solar Vacuum Telescope were measured with a wavefront sensor of the adaptive optics system by a sunspot. To calculate the image shifts, a correlation algorithm with quadratic interpolation of the correlation function maximum position is used. The quality of astronomical vision, characterized by the Fried length, was estimated from the same experimental data as the statistical characteristics of the fluctuations of the coefficients of expansion of wavefront aberrations in Zernicke polynomials. The results were obtained at a Fried length of 51.6 mm in a sample 43 s long with a sampling frequency of 70 Hz. The means and standard deviations of the expansion coefficients are calculated. The analysis of the given spectra shows that the wavefront aberrations should be compensated in the frequency band 0–20 Hz for the effective correction of the images formed.

Factors Influencing Brook Trout (Salvelinus frontinalis) Egg Survival and Development in Streams Influenced by Agriculture

Increased sedimentation in surface waters due to anthropogenic activities can lead to the deterioration of salmonid spawning habitat through infiltration of excessive fine sediment into redds. This study assessed the effects of sediment on salmonid reproductive habitat on Prince Edward Island, Canada by evaluating egg survival and fry length using brook trout egg in situ incubations. In-stream egg incubators were buried in the substrate of streams in three watersheds with between 10 and 69% agricultural land-use during 2012-2013 and 2013-2014. Accumulated incubator sediment load and associated particle size, incubator organic matter and stream parameters temperature, velocity, bed sediment and particle size were measured over the period of study. There was no significant difference in embryo survival among watersheds. Survival was not related to fine sediment; instead, it increased with higher average temperature that was in turn associated with the presence of groundwater upwelling in the stream. The size of the fry was also not significantly different between watersheds with varying agricultural activity. Fry length was most strongly related to sediment organic matter content. Brook trout are widespread in PEI rivers, including in many rivers that have high sediment loads due to intensive agricultural land use. This species may avoid the adverse effect of fine sediment through their natural adaptation of using groundwater upwelling for spawning.

Retrospective analysis of growth of pink salmon Oncorhynchus gorbuscha from scales: Interannual variability

Results of study of scale structure of 17 generations of pink salmon Oncorhynchus gorbuscha from the southeastern coast of Sakhalin (return in 1994–2001, 2005–2013) are presented. The absence of statistically significant correlation between the number of sclerites on scale and duration of staying of fish of separate generations in seawaters and body length was established. Values of intersclerite distances on scales positively correlate with fish length, which allows the use of this index for characteristic of pink salmon growth. At calculation of the rate of growth of fish, fry length at the moment of formation of central scale plate was introduced into the formula. It was found that interannual variation of scleritograms of the first annual zone of the growth of scales by its magnitude is comparable to regional. Specific features of growth of pink salmon to a greater extent are apparently determined by temperature conditions rather than the level of development of its food resources. Survival of generations of pink salmon during marine period of life positively correlates with the rate of growth of fingerlings, which can be used in prognostic purposes.

Scintillation characterization for multiple incoherent uplink Gaussian beams

By means of numerical simulations, we analyze the scintillation characterization for multiple incoherent uplink Gaussian beams under weak fluctuations cases. Because truly independent beams are difficult to create, we present a more general but approximate model for the multiple of beams traveling through partially correlated paths. This model compares with wave-optics simulations and highlights the reduced correlation coefficient as the beam separation is increased. The scintillation index of three and six incoherent uplink Gaussian beams is also induced. The result shows that the scintillation index decreases with the increase of beams amount and beam separation. When the beams amount and strength of atmospheric turbulence are fixed, the reduction of scintillation index is affected by the ratio of beams separation and the Fried length. The corresponding physical mechanisms for the results are discussed.

Aspects of the Reproductive Biology ofTilapia Guineensis (Bleeker, 1862) Under Laboratory Conditions

Aspects of the reproductive biology of Tilapia guineensis was carried out in the laboratory. Twelve ripe male and female brooders of T. guineensis (body length, 12.2 - 12.9cm and weight, 100 - 130g) paired 1 ≅: in triplicate were made to spawn naturally in glass aquaria (60 x 30 x 30cm 3 ). Results show mean fecundity to be 1,269 eggs per female spawner with mean egg size of 1.48mm. Hatching of eggs started 47-48hours after fertilization at a mean temperature of 27.4 0 C. Percent hatch was 74.8% and length of hatchling as 3.8mm. Time of yolk sac absorption was observed to be 4 days with swim-up fry length, 5.7mm and weight, 1.67mg. Parental care was prominently displayed by both parents.