Fry Stage Research Articles

The Development of the Bacterial Community of Brown Trout (Salmo trutta) during Ontogeny.

Brown trout (Salmo trutta) is an important aquaculture species in Germany, but its production faces challenges due to global warming and a high embryo mortality. Climate factors might influence the fish's bacterial community (BC) and thus increase embryo mortality. Yet, knowledge of the physiological BC during ontogeny in general is scarce. In this project, the BC of brown trout has been investigated in a period from unfertilized egg to 95 days post fertilization (dpf) using 16S rRNA gene amplicon sequencing. Developmental changes differed between early and late ontogeny and major differences in BC occurred especially during early developmental stages. Thus, analysis was conducted separately for 0 to 67 dpf and from 67 to 95 dpf. All analyzed stages were sampled in toto to avoid bias due to different sampling methods in different developmental stages. The most abundant phylum in the BC of all developmental stages was Pseudomonadota, while only two families (Comamonadaceae and Moraxellaceae) occurred in all developmental stages. The early developmental stages until 67 dpf displayed greater shifts in their BC regarding bacterial richness, microbial diversity, and taxonomic composition. Thereafter, in the fry stages, the BC seemed to stabilize and changes were moderate. In future studies, a reduction in the sampling time frames during early development, an increase in sampling numbers, and an attempt for biological reproduction in order to characterize the causes of these variations is recommended.

Monitoring pond water quality to improve the production of Labeo rohita (Hamilton, 1822) in Bannu Fish Hatchery of Bannu district, Khyber Pakhtunkhwa province; An Implications for artificial fish culture.

The water quality parameters of a fish pond are essential to be managing properly under control for successful operations of fish culture. Improper management of pond water quality during the juvenile stages can create stressful conditions to produce various harmful diseases, which may decrease the fish quality and results in low profits. The present study was aimed to monitored important water quality parameters of nursery ponds of Labeo rohita culturing in Bannu fish hatchery. The study duration was 75 days extends from 10th June to 24th August 2019 for the successful culture of this specie which can play a significant role in breeding season. Furthermore, the concentration of some heavy metals like copper (Cu), nickel (Ni), manganese (Mn), iron (Fe), cadmium (Cd), and zinc (Zn) in pond water and fry stages of this species was also determined. The data obtained from all water quality parameters were analyzed expressed as range, mean and standard deviation using MS Excel 2013. The obtained results of 75 days study revealed that the water pH & temperature, electric conductivity, total dissolved solids (TDS), and total dissolved oxygen (DO) of pond water samples were found within a tolerable limit except salinity and dissolved ammonia concentration were not permissible for fish growth. The average concentration of heavy metals in pond water exhibited descending order Fe>Ni>Mn>Zn>Cd>Ni, which was found in acceptable ranges. Whereas, the average values of heavy metals in fry stages were in the order of Zn>Fe>Ni>Cu>Cd>Mn, and found within the recommended values of WHO/FAO. Thus, it was concluded from this study that good water quality is a precondition, maintaining balanced levels of water quality parameters is fundamental for both the health and growth of fish culture which is quite necessary for assuring increased fish productivity. It is recommended to monitor and assess water quality parameters on a routine basis for promoting healthy fish culture.

Assessments of some trace metals in water samples of nursery pond of Grass Carp (Ctenopharyngodon idella, Valenciennes, 1844) in Bannu Fish Hatchery of Khyber Pakhtunkhwa, Pakistan

Abstract The present investigation was aimed to examine the concentrations of trace metals including e.g copper (Cu), manganese (Mn), nickel (Ni), and zinc (Zn) in water samples collected from nursery pond of grass carp (Ctenopharyngodon idella) in Bannu Hatchery of Khyber Pakhtunkhwa during the period from April 2018 to January 2019. The temperature and pH of each water sample were measured for the whole study duration. The concentration of Copper (Cu), Manganese (Mn), Nickel (Ni), and Zinc (Zn) in collected water samples were measured in mg/liter by using Atomic Absorption Spectrophotometer. The blank and standard solutions for device calibration Standard solutions i.e., 2.0 mg, 4.0 mg, and 6.0 were used to measure the concentration of these metals in water samples to verify the measurements. The data was statistically analyzed on descriptive statistics (estimation of proportions and standard deviation) used to summarize mean concentration. The results obtained of both temperature and pH of water samples were found in ranged 10 to 36 0C and 7.0 to 8.44; whereas the size of fry stages was ranged from 4.0 to 56.0 mm in total length. The results of investigated metals found in pond water samples are in order of Zn>Mn>Ni>Cu, respectively. As optimum temperature and pH for grass carp were mostly between 15 0C and 30 0C and pH 6.5 to 8.0. It was concluded from obtained results that temperature, pH, and trace metals were found appropriate for the growth of Ctenopharyngodon idella from fry to fingerling stages, but the highest amount of zinc can cause its mortality. It is a preliminary study on grass carp culturing in Bannu fish hatchery so, it would provide useful information for model fish seed production unit in a hatchery.

Ontogenetic shifts in olfactory rosette morphology of the sockeye salmon, Oncorhynchus nerka.

Sockeye salmon, Oncorhynchus nerka, are anadromous, semelparous fish that breed in freshwater-typically in streams, and juveniles in most populations feed in lakes for 1 or 2years, then migrate to sea to feed for 2or 3 additional years, before returning to their natal sites to spawn and die. This species undergoes important changes in behavior, habitat, and morphology through these multiple life history stages. However, the sensory systems that mediate these migratory patterns are not fully understood, and few studies have explored changes in sensory function and specialization throughout ontogeny. This study investigates changes in the olfactory rosette of sockeye salmon across four different life stages (fry, parr, smolt, and adult). Development of the olfactory rosette was assessed by comparing total rosette size (RS), lamellae number, and lamellae complexity from scanning electron microscopyimages across life stages, as a proxy for olfactory capacity. Olfactory RS increased linearly with lamellae number and body size (p < .001).The complexity of the rosette, including the distribution of sensory and nonsensory epithelia and the appearance of secondary lamellar folding, varied between fry and adult life stages. These differences in epithelial structure may indicate variation in odor-processing capacity between juveniles imprinting on their natal stream and adults using those odor memories in the final stages of homing to natal breeding sites. These findings improve our understanding of the development of the olfactory system throughout life in this species, highlighting that ontogenetic shifts in behavior and habitat may coincide with shifts in nervous system development.

Fish seed and feed value chains analysis and their critical factors for aquaculture development in Tanzania

AbstractSeeds and feeds are among the most important inputs required for sustainable aquaculture industry development in any country worldwide. However, the value chain analysis of seeds and feeds in most developing countries including Tanzania has not been mapped, and the key actors are not identified and characterized. To address this knowledge gap, we mapped the fish seed and feed value chains in Morogoro, Dar es Salaam, Coast and Lindi regions in Tanzania, evaluated their performances, analyzed their contributions to aquaculture growth and finally assessed the critical factors impending aquaculture development before proposing appropriate strategies for upgrading. We found that the fish seed value chain comprised broodstock suppliers, seed producers, seed marketers, traders and fish farmers. Tilapia (Oreochromis sp.) and African sharptooth catfish (Clarias gariepinus) seeds produced were primarily sold to farmers at an advanced fry stage (1 to 5 g) at a price ranging from USD 0.09 to 0.13 and USD 0.22 to 0.27, respectively. The feed value chain consisted of suppliers, producers, importers, traders and fish farmers. The feeds produced were powdered, compressed and extruded pellets and granules sold at an average price of USD 2.50/kg. The seed and feed value chains in the four regions drive the aquaculture development and employ 137 and 109 people, respectively. The fish farming was mainly affected by insufficient seeds and feeds; inadequate extension services, inadequate technical skills in seed and feed production; limited farming equipment; insufficient capital and limited access to market. We propose increasing seed and feed production through collaborative research between researchers and the private sector, enhancing delivery of extension services to all fish farmers, providing fiscal incentives to hatchery and feed investors, organizing hatchery owners into associations, and undertaking marketing awareness campaign for aquaculture growth in the country for food, income and employment generation.

Modeling of Polyculture Fish Feed Using Mathematical Programming

This study incorporates the application of a linear programming technique for composition of fish feed mixture to minimize the cost without sacrificing the nutrients levels. Designing the best fish diet for fry, fingerling, and growth stages is the main goal of this study. Regarding nutrient composition and manufacturing costs, the study's results show that a variety of elements can be combined much more effectively than in commercially available feed. The combinations lead to significantly reduced costs while raising nutrient intake, which might be quite advantageous to neighboring fish farmers. . The suggested model was solved with Microsoft Excel to make it more user-friendly.

Timing of Postfertilization Pressure Shock Treatment for the Production of Mitotic Gynogens in Six Salmonid Species

AbstractDoubled haploid gynogens are individuals whose genetic material consists of two identical maternal chromosome sets and who lack paternal genetic contributions. These individuals can be useful in whole‐genome sequence assembly to eliminate allelic variation in an individual that otherwise complicates the discrimination of SNPs and paralogs in regular diploids. This is particularly important in salmonid species, which have extensive remnants of an ancestral whole‐genome duplication. Further, doubled haploid individuals are fully homozygous and can be used to generate clonal lines. Here, successful timing was determined for late pressure shocking for producing doubled haploid gynogens in five Oncorhynchus species (Chinook Salmon O. tshawytscha, Coho Salmon O. kisutch, Chum Salmon O. keta, Pink Salmon O. gorbuscha, and Sockeye Salmon O. nerka) and one Salvelinus species (domesticated Artic Char Salvelinus alpinus). For this study, sperm was treated with UV irradiation to inactivate the paternal nuclear DNA and used to fertilize eggs. The resulting zygotes were pressure shocked at various times following fertilization to form doubled haploid embryos via inhibition of the first cell division (mitotic gynogenesis). At an incubation temperature of 10.5°C, successful postfertilization pressure shock times for maximal survival of confirmed gynogens were 2.41–2.83 accumulated thermal units (ATUs) for Coho Salmon, 2.63–2.84 ATUs for Chum Salmon, 2.84–3.06 ATUs for Pink Salmon, 2.19 ATUs for Sockeye Salmon, and 2.63–3.06 ATUs for Chinook Salmon, whereas for Arctic Char a shock time of 2.29–2.54 ATUs at 4°C incubation was successful. Survival to fry stage ranged from less than 1% to 11.7%. Survivors were genotyped using microsatellite markers to assess nonpaternity and maternal homozygosity and were found to be 92.5% gynogens when averaged across all treatments and species. Mitotic gynogenetic individuals were produced in all six salmonid species and were used in subsequent studies to generate whole‐genome sequences for Chinook, Coho, Chum, and Sockeye salmons.

Insight into the aroma dynamics of Dongpo pork dish throughout the production process using electronic nose and GC×GC-MS

In this study, the aroma dynamic changes throughout the manufacturing process of Dongpo pork dish (DPD) model were investigated with electronic nose and two-dimensional gas chromatography coupled with mass spectrometry (GC × GC-MS). The results of both electronic nose and GC × GC-MS studies were consistent in that the frying and steaming stages had the greatest effect on the aroma composition of DPD. A total of 111 volatiles were detected, 59 of which were key volatiles. The odor activity analyses further revealed that pentanal, hexanal, 1-octen-3-ol, 2,3-pentanedione and (E)-2-octenal as key aroma contributors during the frying stage, while 3-methylbutyraldehyde were mainly formed during the steaming stage. These aromas were mainly generated through the thermal degradation of lipids and the Maillard reaction. Hence, this study, for the first time, provided some profound insights for the industrial production and flavor control of DPD products.

Selective breeding of saline-tolerant striped catfish (Pangasianodon hypophthalmus) for sustainable catfish farming in climate vulnerable Mekong Delta, Vietnam

Striped catfish (Pangasianodon hypophthalmus), a freshwater species cultured mainly in the Mekong Delta region in Southern Vietnam, is facing a significant challenge due to salinity intrusion as a result of climatic changes. Given these evolving environmental conditions, selecting new strains with a higher salinity tolerance could make production of striped catfish economically feasible in brackish environments. In this study, we carried out a selection program aimed at developing a striped catfish strain able to survive and grow fast in a saline environment. To implement the selection program, we first collected males and females from different provinces in the Mekong delta. We next performed a factorial cross of these breeders to produce half- and full-sib families. When fish reached fry stage (47 dph), we put them in a saline environment (10 ppt) and subsequently kept 50 % of the fastest-growing fish after 143 days post hatching (dph). We repeated this mass selection procedure after 237 dph and 340 dph. We maintained in parallel a randomly selected group in saline conditions and a group of fish reared in freshwater to serve as controls. After crossing the selected individuals, we performed several tests on the next generation of fish to evaluate the effectiveness of selection after one generation in saline conditions. Average direct responses to selection were 18.0 % for growth and 11.4 % for survival rate after one generation of selection. We estimated a moderate realized heritability (0.29) for body weight. The genetic gains obtained in our study for body weight and survival rate after one generation of selection under saline conditions suggest that selection can be effective to improve ability of striped catfish to cope with saline stress. We conclude that our selection program has succeeded in developing a productive strain of striped catfish with better tolerance to salinity.

Diluted Bitumen Affects Multiple Physiological Systems in Sockeye Salmon (Oncorhynchus nerka) Embryo to Juvenile Life Stages.

An understanding of the risks associated with diluted bitumen (dilbit) transport through Pacific salmon habitat necessitates the identification and quantification of hazards posed to early life stages. Sockeye from the embryo to juvenile stage (8 months old) were exposed to four concentrations of the water-soluble fraction of Cold Lake dilbit (summer blend; concentrations of 0, 13.7, 34.7, and 124.5 μg/L total polycyclic aromatic compounds). Significant mortality (up to 18% over controls) only occurred in the embryo to swim-up fry stage. Impaired growth was seen in the alevin, swim-up, and juvenile stages (maximum reduction 15% in mass but not fork length). Reductions in both critical (maximum 24% reductions) and burst (maximum 47% reductions) swimming speed in swim-up fry and juveniles were seen. Alterations in energy substrate reserves (reductions in soluble protein and glycogen content, elevations in whole-body lipid and triglyceride levels) at all stages may underlie the effects seen in swimming and growth. Dilbit exposure induced a preexercise physiological stress response that affected the recovery of postexercise biochemistry (cortisol, glycogen, lactate, triglyceride concentrations). The transcript abundance of the cytochrome P450 1A gene (cyp1a) was quantified in alevin head regions (containing the heart) and in the hearts of swim-up fry and juveniles and showed a concentration-dependent increase in the expression of cyp1a at all life stages. Environ Toxicol Chem 2022;41:1937-1949. © 2022 SETAC.

Molecular characterization of four innate immune genes in Tor putitora and their comparative transcriptional abundance during wild- and captive-bred ontogenetic developmental stages

The current study was designed to characterize immune genes and compare their expression during ontogenetic developmental stages in progenies of wild-collected and captive-matured T. putitora. The full-length cDNA sequences of Tptlr2, Tpmyd88, Tpcd36, and Tpil8 were 2814, 1545, 1807, and 653 bp in length, with ORFs of 2379 bp, 855 bp, 1410 bp, and 297 bp, encoding for putative peptides of 793, 284, 469 and 98 amino acids, respectively. The predicted peptide sequences of the genes had high sequence homology and structural conservation with other teleost fishes, especially cyprinids. The expression of Tptlr2 was relatively low in both wild- and captive-bred offsprings during the early embryonic stages, but significantly increased later in development. The mRNA abundance of the Tpmyd88 gene was significantly low until the blastula stage, then increased notably from the gastrula stage to the advanced fry stage. The Tpcd36 expression elevated during later developmental stages, peaking at advanced fry stage in both. On the other hand, expression of Tpil8 was relatively low until the blastula stage and showed a moderate increase from the organogenesis stage onwards in wild-bred offsprings, whereas a significant upregulation was seen in the captive-bred offsprings from the organogenesis stage until the advanced fry stage, with its maximum expression at the pre-metamorphosis stage. Overall, the findings suggest the crucial role of Tpmyd88, Tptlr2, Tpcd36, and Tpil8 in inducing innate immunity in embryonic and larval stages of T. putitora. Further, the considerably higher expression of the immune genes in the embryonic and larval stages of captive-bred offsprings may indicate a stronger immune system.

Development of a sensor-based fluorescent method for quality evaluation of used frying oils

The sensor-based fluorescent spectroscopy was developed for the rapid evaluation of oil quality at different frying stages. Manganese tetraphenylporphyrin was selected as the fluorescent sensor according to its sensitivity and selectivity to the oxidation products in frying oil. The performance of the selected fluorescent sensor was calculated based on density functional theory. The fluorescent sensor was then made to detect frying oil quality every 24 h within eighteen days. A fluorescence profile for each oil sample was obtained from the fluorescent sensor reacting with the oil sample. The feature data of fluorescence spectra were extracted using the parallel factor analysis algorithm. All oil samples were classified into three oxidation groups using principal component analysis and support vector machine algorithms. Finally, the classification algorithm of the support vector machine coupled with the genetic algorithm achieved the best classification accuracy of 96.67% and 93.33% in the training set and test set, respectively. The overall results demonstrated that this fluorescent sensor could successfully be applied in the discrimination of frying oil with different oxidation states.

Exploration of the consequences of a high carbohydrate and low protein diet in female broodstock trout

Adequate parental nutrition is essential to maintain high reproductive performances and to produce high quality gametes. Concerning teleost fish belonging to higher trophic level, broodstock have a high protein requirement but no specific requirement for dietary carbohydrates. Nevertheless, in farming practice, the protein‐rich fishmeal traditionally used in aquafeed formulation needs to be replaced, and plant‐derived carbohydrates appear as a possible substitute. In trout (Oncorhynchus mykiss), two previous studies have found some contradictory results. While a first study had demonstrated that the lowering of the protein‐to‐carbohydrate ratio in female broodstock ratio had surprisingly improved relative fecundity, hatchability and survival of their progeny at the eye‐up stage [1], a more recent study calls into question part of these results as they have not been confirmed [2]. Therefore, it is essential to deepen the exploration of the consequences of a maternal high carbohydrate and low protein nutrition on their reproductive performances, before increasing the fishmeal replacement by plant‐derived carbohydrates.To do so, two‐year old female trout were fed either a control diet formulated with no carbohydrate and a high protein content (65.7 %) or a diet containing 32.5 % carbohydrate but with a lower protein content (42.9 %) for an entire reproductive cycle. The reproductive performances, the quality of the unfertilized eggs and the development of the progeny (at the embryo and at the yolk‐sac fry stages) were carefully monitored.On the one hand, the spawn were of high quality (i.e. more than 90% of unfertilized eggs were viable) and, in average, the egg proximate composition was not affected. The relative fecundity (number of eggs produced per unit of weight) was also increased by the high carbohydrate – low protein nutrition, confirming the first results obtained in trout. On the other hand, the egg fatty acid profile was altered, and in particular, a decrease in EPA (20:5 n‐3) content was triggered by the maternal high carbohydrate/low protein nutrition in trout. Because this particular fatty acid is known to play an essential role during fish development, its diminution could be a cause for the lower survival observed at eyed stage. Moreover, females fed the high carbohydrate/low protein nutrition produced spawns whose eggs size were more variable.Altogether, even though the relative fecundity was significantly increased, the high carbohydrate and low protein nutrition in female broodstock could have deleterious consequences on their progeny development.[1] Washburn, B. S., Frye, D. J., Hung, S. S., Doroshov, S. I., &amp; Conte, F. S. (1990). Dietary effects on tissue composition, oogenesis and the reproductive performance of female rainbow trout (Oncorhynchus mykiss). Aquaculture, 90(2), 179‐195.[2] Callet, T., Hu, H., Larroquet, L., Surget, A., Liu, J., Plagnes‐Juan, E., … &amp; Marandel, L. (2020). Exploring the impact of a low‐protein high‐carbohydrate diet in mature broodstock of a glucose‐intolerant teleost, the rainbow trout. Frontiers in physiology, 11, 303.

Проведение адаптации и нереста донского рыбца (Vimba vimba (Linnaeus, 1758)) для индустриального рыбоводства

The intensive development of aquaculture in the Southern Federal District has made it possible to achieve high rates in manufacturing the aquaculture products about 80 thousand tons for 2019 year, the main commercial fish being carp and herbivorous fish. Introducing the new species (vimba) into aquaculture will enable to bring the high quality product to the market. In the south of Russia vimba is one of the most promising objects for introduction into aquaculture. Don vimba (Vimba vimba (Linnaeus, 1758)) is a valuable fish species, a regional delicacy on the Don. Decreasing the fish catches in the recent years (its catches amounted to 10.9 tons in the Azov Sea in 2015, but only 5.0 tons in 2019) requires to carry out the research on effective directions in conducting the spawning company and on the fish adaptation to the recirculating aquaculture systems. There was conducted an experiment on spawning the adapted to the recirculating aquaculture system vimba producers by two methods: on the substrate (in vivo) and in the Weiss apparatus (in vitro), the effectiveness of the methods used was proved. During the experiment, it was found out that the best indices of eggs incubation were obtained in the Weiss apparatus. The death of eggs on the substrate made about 80 %. The cause of death was the uneven distribution of the roe on the substrate. Growing vimba embryos and larvae with special equipment (in baths with running water) made it possible to obtain the viable larvae. It has been shown that in the special baths with running water, after the embryo has entered the larval stage, it is possible to transfer the larvae to active external feeding. The total development of the embryos and larvae to the fry stage took 55 days.

Asymmetric competition over space use and territory between native brown trout (Salmo trutta) and invasive brook trout (Salvelinus fontinalis).

Interference competition over food and territory can shape population structure and habitat use within and between species. The introduction of invasive species often leads to novel competitive interactions over shared resources and invaders can eventually exclude the native species from preferred habitats. Invasive brook trout (Salvelinus fontinalis) introduced to northern Europe have excluded native brown trout (Salmo trutta) from numerous headwater streams. The fact that invasive brook trout can displace the more aggressive brown trout is puzzling. However, the earlier spawning and hatching of brook trout, compared to brown trout, may lead to unequal competition due to size advantage and prior resident status of brook trout at the fry stage. In this study, we examine the effect of competition between brown trout and brook trout using the natural size distribution of the two species. In two consecutive experiments, we first measured space use and feeding of a fry (age 0+) in the presence of a juvenile (age 1+). In experiment 2, we assessed territorial interactions between the species at the fry stage (age 0+) and if smaller brown trout could compensate the disadvantage by manipulating residence duration. Fry of brook trout feed sooner and spend more time close to the larger individual than brown trout fry. We also found that brook trout fry won most territorial contests against brown trout, and that increased residence duration led to longer and more aggressive interactions. The results suggest that smaller brown trout are displaced to suboptimal habitats in the presence of a larger brook trout. Therefore, the later emergence from gravel beds resulting in the naturally occurring size disadvantage of brown trout at the fry stage may lead to unequal territorial interactions that could explain why brown trout are displaced from preferred habitats in sympatry with brook trout.

Capture of Spawning Brook Trout by Electrofishing Does Not Impair Embryo Survival

AbstractElectrofishing is widely used to capture fish in freshwater systems. Fisheries assessment and fish culture activities that occur during spawning do so in the absence of a meaningful base of evidence about the potential effects of electrofishing on fish reproduction. In this laboratory experiment, we assessed whether electrofishing adult Brook Trout Salvelinus fontinalis affected the survival of their embryos. We used two genetically distinct strains of Brook Trout (domestic and wild‐origin strains) to do so. Both strains and sexes of fish were exposed to pulsed‐DC electrofishing techniques in a fully factorial design (i.e., male shocked, female shocked, both parents shocked, or neither parent shocked [control]), after which their incubating offspring were monitored for survival to the eyed egg, alevin, and fry stages. We did not detect any effects of our electrofishing treatment or interactions with the sex or strain of the fish exposed to electrofishing, suggesting that electrofishing did not negatively impact gamete viability. Our results support the use of responsible electrofishing to collect spawning salmonids for the purpose of gamete collection for hatchery rearing.

Interactive effects of dietary protein and lipid on growth of Indian climbing perch, Anabas testudineus fry

Aim: To assess the optimum protein and lipid requirement of Anabas testudineus at its fry stage, based on the growth performance, feed efficiency and nutrient gain efficiency. Methodology: Eight experimental diets were prepared with four protein (35, 40, 45 and 50 %) and two lipid (9 and 13%) levels. The diets were designated as D1 (35 P/9L), D2 (35 P/13 L), D3 (40 P/9 L), D4 (40 P/13 L), D5 (45 P/9 L), D6 (45 P/13 L), D7 (50 P/9 L) and D8 (50 P/13 L). Each of the experimental diets was fed to triplicate groups of 10 fishes with an average individual body weight of 1.23 g in 24 glass aquaria. The diets were fed at about 4 % body weight per day in two equal rations for a period of 60 days. Results: Significantly (p&lt;0.05) higher weight gain (428 %), specific growth rate (2.77 % day-1), feed efficiency ratio (0.69) and protein efficiency ratio (2.34) and lower (p &gt; 0.05) food conversion ratio (1.45) was observed in fish fed with diet D5 (45% protein and 9% lipid). The nutrient retention parameters like protein retention, protein productive value, lipid productive value and apparent net protein utilization were also significantly (p &lt; 0.05) high in the treatment group D-5 fed with diet containing 45% protein and 9% lipid. Significantly (P&lt;0.05) higher whole body protein content was observed in the treatment group D5 (45% protein / 9% lipid) along with D4 and D6. Interpretation: The present findings on optimum protein and lipid requirement of 45% and 9%, respectively will help in formulating the cost-effective practical diets for Anabas testudineus fry, which is essentially required for quality seed production and grow out culture of this species in a commercial scale.

Larvae and fry culture of white cachama (Piaractus orinoquensis) in biofloc systems at different carbon/nitrogen (C/N) ratios

This work evaluated the effects of different carbon/nitrogen (C/N) ratios in the larvae and fry culture of Piaractus orinoquensis in biofloc system on the water quality, proximate analysis and growth performance. The experiment was conducted in two stages: (a) larval stage from 0 to 12 days post stocking (DPS) and (b) fry stage from 13 to 24 DPS, at a density of 10 larvae/L. Three groups of C/N ratios were evaluated as follows: T1: 10/1 ratio, T2: 15/1 ratio and T3: 20/1 ratio, each treatment with three replicates. Both in the larval and fry culture, total ammonia nitrogen (TAN) and nitrite were higher in the T2 and T3 treatments, while the nitrogen removal in T1 treatment was more efficient, resulting less TAN, nitrite and higher nitrate. However, the water quality parameters in all treatments were within the appropriate ranges for fish culture in biofloc. T2 treatment was nutritionally better, presenting higher levels of protein, lipids and energy. In both stages, P. orinoquensis survival and final weight were significantly higher in the T2 treatment. In conclusion, P. orinoquensis larvae and fry culture in biofloc is viable, improving the survival and growth at a C/N ratio of 15/1.

Feeding frequency on the growth and production of endemic near-threatened Ompok pabda (Hamilton 1822) in pond setup

Growth and production of near threatened Ompok pabda (Hamilton) were examined at different feeding frequencies in the present study. The experiment was conducted for four months in three earthen ponds from 1st April to 31st July 2018 at Tanore Upazila in Rajshahi district, Bangladesh. The experiment was performed using pabda, (Ompok pabda) fingerling (average) to study the effect of feeding frequency on growth performance. The study carried out considering three treatments, namely T1, T2, and T3; while the feeding frequency was two times per day in treatment T1, three times per day in treatment T2, and four times per day in treatment T3. Fish were fed considering three-stage of life span; these were fingerling stage, early growing stage, and growing stage. In the fry stage, the fishes were fed 20% feed, in the fingerlings stage the fish were fed 10% feed and in the growing stage, the fish were fed 8% feed of the body weight. The mean water temperature ranged between 27.13±2.10 and 27.29±2.16 °C among treatments, while water transparency ranged between 31.91±1.58 and 29.96±1.84 cm. pH ranged between 7.62±0.14 and 7.70±0.19; while the mean dissolved oxygen was ranged between 5.35±0.11 and 5.56±0.14 among treatments. The final weight gain was found to be highest (56.36±0.01) in the treatment T2 and lowest (38.23±0.01) in the treatment T3. The SGR value was higher (3.94±0.01) in the treatments T2 followed by treatments T1 and T3. Net weight gain was significantly (p&lt;0.05) higher in feeding frequency three (56.36±0.1), followed by feeding frequency four (38.23±0.1) and feeding frequency two (40.67±0.73). The FCR value ranged between 1.90 and 2.87 among treatments. The growth performance and specific growth rate were significantly (p&lt;0.05) higher in feeding frequency three. The highest (4049.1±0.1 kg/ha/120 days) production was observed in T2. Best cost benefit ratio was gained in treatment T2. Asian Australas. J. Biosci. Biotechnol. 2021, 6 (2), 89-102

Rating the Potential Suitability of Habitat in Michigan Stream Reaches for Arctic Grayling

Abstract Present-day environments and anticipated future conditions often pose a significant challenge to efforts to reintroduce extirpated species, highlighting the need for collaborative, thorough approaches to reintroductions. Such is the case in Michigan, where numerous partners are working to reintroduce Arctic Grayling Thymallus arcticus with hopes of reestablishing self-sustaining populations. With &amp;gt; 47,000 km of coldwater stream habitat in the state and limited numbers of eggs for reintroductions, a prioritization framework was needed to provide a standardized, fine-scale method for rating suitability of streams for reintroductions. Through facilitated discussions with stakeholders and experts, we developed an overall prioritization framework for rating Michigan streams with components evaluating a reach's thermal, instream habitat, biological, and connectivity characteristics. Within the context of this broader framework, we developed the habitat rating component for assessing suitability of instream conditions for egg, fry, juvenile, and adult life stages of Arctic Grayling. Life-stage-specific habitat metrics and scoring criteria from this effort were used to rate habitat conditions for 45 reaches in tributaries of Michigan's Manistee River, enabling identification of reaches likely having instream habitat most suitable for Arctic Grayling. Numbers of reaches meeting or exceeding 60%, 70%, and 80% of the maximum score for overall habitat suitability were 31, 8, and 1. Upon completion of the fish assemblage and connectivity components, the prioritization framework and habitat rating process described here will be used for comparing suitability among streams throughout the historical range of Arctic Grayling in Michigan and guiding reintroduction efforts. Though it will take considerable time before instream habitat suitability criteria can be evaluated for all life-stages of Arctic Grayling in Michigan, the collaborative stream prioritization framework developed for Arctic Grayling reintroduction can be readily adapted to reintroduction efforts for other species elsewhere.