Effects of dietary n‐3HUFA on different growth stages of the white shrimp,Litopenaeus vannamei: Growth,haematological characteristics,enzyme activities and fatty acid profiles

This study investigated the effects of n‐3 high unsaturated fatty acid (n‐3HUFA) levels on the growth performance, antioxidant enzyme activities and fatty acid profiles of both subadult and adult Litopenaeus vannamei (L. vannamei). Seven iso‐nitrogenous and iso‐lipidic diets were used, containing n‐3HUFA concentrations of 1.6 (control), 4.8, 7.4, 13.9, 23.9, 29.2 and 34.4 g/kg, respectively. Two 8‐week feeding trials were conducted to determine the dietary n‐3HUFA requirements of L. vannamei with an initial body weight of 4.25 ± 0.00 g (subadults) and 8.50 ± 0.01 g (adults). The results showed that the dietary n‐3HUFA level significantly affected the weight gain rate (WGR), specific growth rate, the feed conversion ratio and the hepatosomatic index (HSI) (p < 0.05), but did not significantly affect the survival rate (p > 0.05). At appropriate level, dietary n‐3HUFA improved growth performance and HSI of both subadult and adult L. vannamei. Both subadults and adults showed significant differences in body composition (p < 0.05), except for moisture and crude ash (p > 0.05). Cholesterol and low‐density lipoprotein significantly decreased with increasing dietary n‐3HUFA both in subadults and adults (p < 0.05); however, triglyceride showed no significant change (p > 0.05). High‐density lipoprotein (HDL) in subadults was significantly affected by dietary n‐3HUFA (p < 0.05), but followed no apparent regularity; HDL significantly changed in adults and showed an upward trend followed by a downward trend (p < 0.05). There was no significant effect on aspartate transaminase (AST) activity in subadults, but AST in adults and alanine transaminase (ALT) in subadults and adults were significantly affected (p < 0.05). Dietary n‐3HUFA significantly affected serum polyphend oxidase, malic dehydrogenase, alkaline phosphatase, superoxide dismutase and sodium‐potassium adenosine triphosphatase enzyme activities in gills (p < 0.05). The fatty acid composition of the shrimp tissue was associated with the fatty acid composition of the diet. Dietary n‐3HUFA supplementation significantly improved the contents of tissue ∑HUFA and n‐3HUFA, increased the n‐3/n‐6 ratio in the tail muscle and decreased the contents of tissue polyunsaturated fatty acid and saturated fatty acid (p < 0.05). Based on the WGR, the broken‐line equations indicated that the optimum requirements of dietary n‐3HUFA were determined to be 9.0 and 5.1 g/kg for subadult and adult L. vannamei, respectively.     

Growth and gut morphology of diploid and triploid juvenile Atlantic cod (Gadus morhua)

The objective of this paper was to compare the growth and gut morphology of juvenile diploid and triploid Atlantic cod (Gadus morhua) reared under similar conditions. Individually tagged 36‐week‐old diploid (mean weight 49.3 ± 13.8 g) and triploid (mean weight 43.6 ± 11.2) juvenile cod were measured at intervals during a 29‐week growth trial. Data for weight, length, condition factor (K), hepato‐somatic index (HSI), gonado‐somatic index (GSI), Relative Gut Length (RGL) and pyloric caeca number were collected and results were analysed in relation to ploidy status, gender and family contribution. At the end of the experiment, only one family (M2xF3) had many representatives with a relatively even distribution of sexes and ploidies. Diploid females were significantly heavier and had higher K than triploid females in the M2xF3 family (body weight 371.2 ± 120.2 vs. 298.4 ± 100.7 g; K 1.1 ± 0.1 vs. 0.93 ± 0.1), but no differences were found between diploid and triploid males. In the other families (pooled data), no differences in body weight were found between the ploidy groups. In general, triploids had a shorter intestine (RGL) and fewer pyloric caeca than their diploid siblings regardless of gender suggesting possible impairments in nutrient utilization and growth.     

Phenotypic and genetic parameters for body traits in the giant freshwater prawn (Macrobrachium rosenbergii) in India

Phenotypic and genetic parameters were estimated for three body traits (harvest weight, carapace length and standard length) and for adult male morphotypes of the giant freshwater prawn Macrobrachium rosenbergii in a fully pedigreed synthetic population in India. The data set included 9,173 progeny produced over four generations from 162 sires and 234 dams. Variance components and genetic parameters were estimated fitting an animal model using the residual maximum‐likelihood methodology. The heritabilities for harvest body weight (HW), carapace length (CL) and standard length (SL) were moderate (0.22 ± 0.056, 0.22 ± 0.055 and 0.25 ± 0.059 respectively). The common environmental effects for HW, CL and SL were 0.10 ± 0.020, 0.08 ± 0.018 and 0.10 ± 0.021 respectively. As M. rosenbergii is sexually dimorphic, we estimated heritabilities within each sex. Heritability of HW in females (0.27 ± 0.068) was greater than that in males (0.15 ± 0.057). CL and SL followed the same pattern. The occurrence of male morphotypes is a unique characteristic of adult populations of M. rosenbergii. Populations from culture ponds exhibit a wide range of sizes. To examine whether there was a heritable component in male morphotype frequencies, we treated male morphotypes as traits. The additive genetic variance (and hence the heritability) was zero for male morphotype, indicating that selective breeding to increase the proportion of desirable male morphotypes would not be effective. The genetic correlations among body traits were all positive, high and approaching unity. The results are discussed in relation to selection plans for the giant freshwater prawn.     

Effect of the dietary phosphatidylcholine at different growth stages of Pacific white shrimps,Litopenaeus vannamei

This study investigated the effects of dietary phosphatidylcholine (PC) at different growth stages of Litopenaeus vannamei (L. vannamei) with an initial weight of 0.70 ± 0.00 g (juvenile) and 4.25 ± 0.00 g (subadult) for 8 weeks. Six isonitrogenous and isoenergetic diets containing PC (0, 1.7, 5.1, 6.8, 10.2 and 13.6 g/kg) were confected using formulated with redfish meal, dehulled soybean meal and peanut meal as protein source, fish oil and corn oil as fat source. The juveniles were reared in 0.3 m³ aquarium at the density of 40 in triplicates, as well as the subadults in 0.5 m³ at the density of 40 in triplicates. Results showed PC level had significant effects on weight gain rate (WGR), specific growth rate, feed conversion ratio in juvenile and subadult shrimps and hepatosomatic index in juvenile shrimps (p < 0.05). No significant differences were found in moisture, whole body protein and crude ash (p > 0.05). Crude fat of juveniles had no significant change (p > 0.05), but subadults increased significantly (p < 0.05). Both juveniles and subadults showed that triglyceride and low‐density lipoprotein presented a downward trend with PC elevating, but high‐density lipoprotein increased gradually. Cholesterol in juveniles presented upward, but downward in subadults (p < 0.05). Dietary PC also significantly reduced the aspartate transaminase in juveniles and alanine transaminase in subadults (p < 0.05). PC supplementation significantly improved the glutathione S‐transferase activity and reduced the content of malondialdehyde in the hepatopancreas (p < 0.05). PC supplementation significantly improved gill filament sodium‐potassium adenosine triphosphatase enzyme of juvenile shrimps (p < 0.05), but subadult shrimps were not influenced (p > 0.05). PC supplementation significantly elevated the content of hepatopancreas eicosapentaenoic acid, highly unsaturated fatty acid (HUFA) and n‐3HUFA (p < 0.05), but the content of linoleic acid significantly reduced (p < 0.05). The broken‐line and quadratic regression model based on WGR showed the optimum dietary PC requirement was 10.3 g/kg and 6.5 g/kg for juveniles and subadults, respectively.     

Biological performance of Octopus vulgaris in ‘integrated aquaculture’ models: effect of two potential fresh diets,sex and sexual maturation during the grow‐out phase

Two fresh diets were tested on the biological performance of males and females of Octopus vulgaris under industrial rearing conditions in floating cages. The presence of females could potentially release paralarvae to the natural environment (‘integrated aquaculture’). Octopuses were fed on a single diet of bogue (aquaculture by‐product), and on a mixed diet (60–40% crab‐bogue), in two trials. In Trial 1 (918 ± 125 g), growth was higher in octopuses fed on the mixed diet (1.9–2.0%d^?1) than in those fed on the bogue diet (1.8–1.9%d^?1) irrespective of sex, and mortality was 3% regardless of sex and diet. In Trial 2 (1483 ± 269 g), growth was higher in males fed on the mixed diet (1.8%d^?1) than in males fed on the bogue diet (1.4%d^?1), both higher than females (1.1–1.3%d^?1), and mortality was 22–28% regardless of sex and diet. Best biological performance in trial 1 was related to the lack of functional maturation in females, evidence by the low average gonadosomatic index (2.0–3.6%) in comparison with trial 2 (8.8–11.4%), regardless of diet. No correlations between final weight and sexual maturity indices were found, so the length of the rearing period to maximize biomass increment or to release paralarvae depends on functional maturation in females.     

Induction of meiotic gynogenesis in bagrid catfish (Pseudobagrus ussuriensis) with homologous sperm and its confirmation for female homogamety

The bagrid catfish, Pseudobagrus ussuriensis, exhibits significant sexual dimorphism in growth rate and body size with males growing faster than females. Therefore, an all‐male culture can dramatically increase the output and profitability of fishery products. According to the monosex breeding route, super‐male individuals’ acquirement by XY male sex reversal and artificial gynogenesis is the key step. An effective protocol to induce meiotic gynogenesis using homologous sperms has been developed in this study. The most effective UV irradiation for sperm genetic inactivation was found to be at a distance of 20 cm with 66 μW/cm² light intensity for 25 min. Optimal treatment for cold shock was 5 min post‐fertilization at 0‐4°C for 30 min, which gave the best survival rate of 13.65 ± 2.87%. The sex ratio in the meiotic gynogens showed a significant female‐biased deviation (p < .05); thirty meiogynogens and their parents were further analysed using a male‐specific AFLP marker, of which only the male parent produced a male‐specific DNA band of 412 bp. These results indicated the female homogametic XX/XY sex determination system in P. ussuriensis. The optimization of a protocol for the successful induction of meiogynogenesis in the bagrid catfish lays the basis for all‐male production and is useful in ascertaining the genetic sex determination system in this promising aquaculture species.     

Heritability for growth traits in giant freshwater prawn,Macrobrachium rosenbergii (de Mann 1879) based on best linear unbiased prediction methodology

In this study, heritability was estimated for growth‐related traits of giant freshwater prawn (Macrobrachium rosenbergii) before and after morphological sexual differentiation. Estimation was made on data from 16 full‐sib and eight half‐sib families. The variance estimation was performed using a univariate mixed linear animal model and variance components were analysed following an animal model using restricted maximum likelihood procedure using average information algorithm. Heritability estimates (h²) varied considerably with ages. At 2 months old, h²for carapace length (CL; 0.35±0.15) and body weight (BW; 0.26±0.13) were higher than those estimated at 5 months old, based on mixed sex data. However, when data were sorted by sex, h² calculated from data of females were higher than those of males for CL (0.26±0.16 vs. 0.10±0.06), BW (0.28±0.17 vs. 0.12±0.08), body length (0.40±0.17 vs. 0.11±0.07), total length (0.47±0.18 vs. 0.11±0.07) and claw length (0.29±0.16 vs. 0.03±0.04). The same trend was observed for traits at 6 months old in both bulk and individual rearing.     

Conditioning,maturation and year‐round natural spawning of orange‐spotted grouper,Epinephelus coioides (Hamilton, 1822), in recirculating aquaculture system

The present experiment was aimed at studying the conditioning, maturation and natural spawning of orange‐spotted grouper, Epinephelus coioides, in a recirculatory aquaculture system (RAS). Thirty fish (n = 30; 3.35 ± 0.05 kg) were stocked in a circular tank of 125 m³ capacity fitted with an RAS for conditioning and broodstock development. After 15 days, 15 fish were implanted with 17 α methyl testosterone and letrozole at the rate of 5 mg and 0.2 mg/kg body weight, respectively, for conversion from female to male. The gonadal development started after 1 month, and by 90th day, 63.53 ± 3.78% and 2.07 ± 0.84% of the oocytes attained a size of 400–500 μm and 500–600 μm respectively. Natural spawning commenced in the RAS from 4th month onward after stocking and spawning continued round the year. The spawning pair showed courtship behaviour with a typical vertical burst of swimming just before release of gametes. The total number of eggs spawned during 1 year was 47.23 million with spawning frequency varying form 5 to 13 times per month. The association of spawning events with new moon day (lunar cycle) weakened as time progressed. The mean monthly fertilization and hatching rates varied from 77.80 ± 3.34% to 83.70 ± 1.76% and 82.80 ± 4.21% to 88.33 ± 1.39% respectively. The study proved that RAS is an efficient system that provides a stable, controllable and conducive environment for year‐round natural breeding of orange‐spotted grouper.     

Dietary fatty acid enrichment during the spawning season increases egg viability and quality in Hippocampus hippocampus

Control of the reproductive cycle is essential to achieve a successful aquaculture industry. Seahorse reared in captivity often shows eggs of poor quality and low offspring survival due to unsuitable rearing and nutritional protocols. This study aimed to evaluate the effect of dietary enrichment, added exclusively during the spawning season, on the egg quality of Hippocampus hippocampus. The effect of enriching mysis throughout the spawning season was analysed in terms of female fecundity, egg viability, egg size and fatty acid profile. The results showed that fecundity was not affected by the enrichment of the diet, but egg viability was increased when females were fed the enriched mysis (84.9 ± 4.1% compared to 62.2 ± 9.4%). Moreover, the content of several PUFA (20:4n‐6, 18:2n‐6, 22:5n‐3, 22:5n‐6, sum of n‐6) decreased throughout the spawning season, especially in the last clutch, in eggs originated from females fed non‐enriched mysis. Eggs from females fed the enriched diet maintained the fatty acid profile throughout the spawning season. In conclusion, enrichment of the diet of H. hippocampus improved egg viability and avoided a decrease in the quality of eggs by maintaining PUFA content in the last clutches of the spawning season.     

Pharmacokinetics and physio‐metabolic response of single and multiple dose of fenbendazole in Labeo rohita (Hamilton, 1822) fingerlings

An experiment was carried to determine the plasma fenbendazole (FBZ) concentration and physio‐metabolic responses in juveniles of Labeo rohita (90 ± 4 g) after oral administration of single doses at 10, 20 and 50 mg, 20 mg FBZ/kg b.wt. in multiple times on 1st, 3rd and 7th day. The blood samples were collected at 0.5, 1, 2, 4, 8, 12, 24, 30, 48, 72, 96 and 120 hr, after single‐dose administration, and regularly (upto 15 day) in multiple dose. Plasma FBZ concentration was determined up to the limit of detection (LoD) of 0.09 µg/ml by HPLC. There was no parent drug detected in plasma for administration of 10 mg FBZ/kg b.wt. The drug attained the peak concentration (C_max) 1.85 and 3.09 µg/ml in plasma at 4 hr (T_max) after administration of 20 and 50mg FBZ/kg b.wt. respectively. Plasma FBZ was detectable up to 96 and 120 hr with concentration 0.09 ± 0.007 and 0.098 ± 0.006 µg/ml, respectively, after single‐dose administration of 20 and 50mg/kg b.wt. In case of multiple‐dose administration, the maximum concentration of FBZ was 1.01 ± 0.03 µg/ml on 7th day that was less than to the single dose at 50 mg/kg b.wt. However, FBZ was detected up to 11 day after multiple doses. The study revealed that the hepatic antioxidant enzymes activities like superoxide dismutase, catalase and glutathione‐S‐transferase were significantly affected by increasing FBZ in single and multiple doses. The results of the present study could reveal that single‐ or multiple‐oral administration of FBZ at 20 mg/kg b.wt. in feed as antihelminthic drug in L. rohita could be considered as the safe dose.     

Genetic parameters for resistance against Flavobacterium columnare in Nile tilapia Oreochromis niloticus (Linnaeus, 1758)

Columnaris disease is a major cause of mortality in tilapia hatcheries and commonly occurs during the summer season in Thailand. One way of reducing the problem is by selective breeding for increased disease resistance. The objective of this study was to estimate quantitative genetic parameters for resistance against columnaris in the Chitralada 4 strain of Nile tilapia. Data from 43 full‐sib families (2,580 records) of fry (age = 32 ± 4 days post‐hatch) were used in the analyses. Initially, fry were subjected to bath challenge with Flavobacterium columnare (LD₅₀ concentration = 1.2 × 10⁶ CFU/ml) for 14 days. Disease resistance was defined as the number of days from challenge until death (DD) or as a binary trait (dead/alive) on day 14. Linear animal and sire‐dam models were used for DD, while threshold animal, threshold sire‐dam, binary linear animal and binary linear sire‐dam models were used for binary outcomes. Covariate effect of age, fixed effect of challenge day and random effects of the individual animals or sires and dams were included in the models. Mean survival was 32.4 ± 11.6%, and survival rates of the best and poorest families were 70% and 8%, respectively. The highest estimate of heritability (0.30 ± 0.025) was obtained under the threshold sire‐dam model. Heritability estimates for DD (0.16 ± 0.034 and 0.17 ± 0.046) were comparable to those obtained from the threshold animal (0.15 ± 0.031) and the binary linear (0.14 ± 0.045 and 0.15 ± 0.044) models. The linear animal and sire‐dam models for DD and the threshold sire‐dam models performed equally with similar values of r_EBV (0.629, 0.628 and 0.627) and accuracy of selection (0.793, 0.793 and 0.791). This study reveals the potential of selective breeding to increase disease resistance to F. columnare in the studied population of Nile tilapia.     

Fertilization rate,motility, lipid peroxidation and pH changes after chilled storage of rainbow trout (Oncorhynchus mykiss) eggs and spermatozoa by a RMPI medium

The aim of this study was to evaluate the effects of Roswell Park Memorial Institute (RPMI) 1,640 medium on chilled storage of eggs and spermatozoa of rainbow trout (Oncorhynchus mykiss). After 3 days of storage, eggs in RPMI 1,640 media (pH 8.2, 9 and 10), Cortland medium and coelomic fluid were inseminated with fresh spermatozoa (Experiment 1). Eggs in RPMI 1,640 medium at pH 8.2 shown the lowest thiobarbituric acid‐reactive substances (TBARS, 0.053 ± 0.003 nmol/ml) and pH changes (from 8.20 ± 0.01 to 8.18 ± 0.01), the highest fertilization rate (82 ± 3%). Undiluted and diluted spermatozoa at ratios of 1:2 and 1:9 with RPMI 1,640 media (pH 8.2, 9 and 10) and Cortland medium were inseminated with fresh eggs (Experiment 2). Spermatozoa in RPMI 1,640 medium at pH 9 (1:9) caused the lowest TBARS content (0.037 ± 0.002 nmol/ml) and pH changes (from 9.00 ± 0.01 to 8.98 ± 0.01), the highest fertilization rate (77 ± 2%) and motility parameters. Based on Experiments 1 and 2, eggs and spermatozoa were stored for another 3 days in RPMI 1,640 medium at pH 8.2 and 9 (1:9) respectively (Experiment 3). Fertilization rate of storage eggs and spermatozoa in Experiment 3 was 79 ± 5%, showing successfully storage of rainbow trout gametes with the same medium.     

Enzyme-linked immunosorbent assay (ELISA) measurement of vitellogenin in plasma and liver histopathology in barfin plaice <Emphasis Type="Italic">Liopsetta pinnifasciata</Emphasis> from Amursky Bay,Sea of Japan

Vitellogenin (Vg) of the barfin plaice Liopsetta pinnifasciata was isolated and purified. In native polyacrylamide gel electrophoresis, Vg appeared as one band. After being subjected to sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS–PAGE), Vg fraction produced several polypeptides with molecular masses of 180, 98, 70, 52, 41 and 37 kDa. MALDI–TOF mass spectrometry (MS) of the 180- and 98-kDa Vg polypeptides from the SDS–PAGE gel and de novo sequencing of their four peptide fragments based on MS/MS analysis confirmed that the purified proteins were vitellogenins, which shared high similarity with the Vgs of the barfin flounder Verasper moseri and Atlantic halibut Hippoglossus hippoglossus. The most part of the predicted sequences obtained from the L. pinnifasciata 180-kDa polypeptide has previously been found in the V. moseri vitellogenin type B, the sequences obtained from the 98-kDa polypeptide were found in V. moseri vitellogenin type A, so these findings allow us to propose that L. pinnifasciata has at least two different forms of Vg. Rabbit polyclonal antibodies against Vg were produced, and a quantitative enzyme-linked immunosorbent assay was developed. The concentration of Vg in barfin plaice from the moderately contaminated area of Amursky Bay in the Sea of Japan was detected based on the maturity stage of their gonads. In November 2008, the Vg concentration in the plasma of females with advanced oogenesis varied from 5.295 to 28.367 mg/ml (mean 16.38 ± 6.73 mg/ml, CV = 41.1%); in the plasma of males, the concentration ranged from non-detectable to 0.957 mg/ml (0.29 ± 0.42 mg/ml, CV = 127.9%). In October 2009, the Vg concentration in female plasma was lower than in November 2008 (2.21–13.87 mg/ml). High individual variability of plasma Vg was characteristic for maturing males (CV = 200.3%) and immature females (CV = 255.5%), and there was no significant difference between plasma Vg concentrations in males captured in November 2008 and October 2009 or in maturing males and immature females. Vacuolisation of hepatocytes was more typical for males with low plasma Vg concentrations and females with high plasma Vg concentrations. Necrosis and pyknosis of hepatocyte nuclei were more frequent in males with high Vg concentrations and in females with low plasma Vg concentrations.     

Reproductive biology of blue marlin <Emphasis Type="Italic">Makaira nigricans</Emphasis> around Yonaguni Island,southwestern Japan

We studied the spawning seasonality and gonadal development of blue marlin Makaira nigricans using specimens captured around Yonaguni Island in southwestern Japan between February 2003 and February 2006. The mean (±SD) lower jaw–fork length of females (234 ± 24 cm) was greater than that of males (191 ± 12 cm). The smallest mature female and male were 183 and 160 cm, respectively. Most of the 717 females had immature ovaries. However, in March and from May to September, the ovaries of 26 females contained oocytes with yolk globules, hydrated oocytes, or postovulatory follicles. Most males had testes with a large amount of spermatozoa throughout the year. The occurrence of mature blue marlin at Yonaguni Island suggests that spawning occurs here. The mean condition factors (fatness of the fish) of both sexes decreased from March to June or July, presumably as they expended energy to reproduce. We discuss our results in the context of migration theory for blue marlin in the western North Pacific Ocean.     

In vitro oocyte maturation and blood‐circulating steroid hormones in Sterlet (Acipenser ruthenus) and Siberian sturgeon (Acipenser baeri)

The oocyte of Sterlet (Acipenser ruthenus) and Siberian sturgeon (Acipenser baeri) was evaluated after incubation with 17α, 20β‐Dihydroxyprogesterone (DHP) in artificial media. Concentration of testosterone (T), progesterone (P4) and 17‐β estradiol (E2) in blood and their relation to fertilization rate were measured during experimental period. The oocytes at the same developmental stages were incubated in SIS (based on sturgeon blood ionic composition), RM2 (Ringer solution modified for sturgeons) and L‐15 (Leibovitz medium) artificial mediums in the presence of 1 μg/ml of 17α, 20β‐Dihydroxyprogesterone for 12, 18 and 24 hr. The result of this study demonstrated that fertilization rate decreased with the increasing duration of incubation in all mediums. In the Siberian and Sterlet sturgeon, the highest fertilization rate was observed in the oocytes incubated in RM2 (0.81 ± 0.4) and SIS (0.44 ± 0.8) mediums for 12 hr respectively. In the Siberian sturgeon, fertilization rate decreased significantly (p < .05) with incubation time in all three mediums. In Starlet, fertilization rate decreased significantly (p < .05) with time and reached a minimum after 24 hr (0.16 ± 0.1) in L‐15 medium. No significant (p > .05) differences were observed between blood plasma hormones and fertilization rate. The results of this study indicated that 17α, 20β‐Dihydroxyprogesterone is essential for induction of in vitro oocyte maturation in these species.     

Distribution patterns of saprolegniosis cutaneous lesions in wild and farmed brown trout (Salmo trutta L.) obtained using a geographic information system (GIS)

A retrospective study was conducted using 250 clinical records of brown trout (Salmo trutta L.) with saprolegniosis by Saprolegnia parasitica, which had been collected from 8 rivers and 1 fish farm in the province of León (Spain). A geographic information system (GIS) was used to obtain skin lesion distribution patterns in males and females. Lesions in wild brown trout affected 15.31 ± 13.33% of the body surface, with a mean of 12.76 ± 6.56 lesions per fish. In addition, 51.23% of wild trout presented lesions with necrosis of the skin or fins. The pattern obtained when not distinguishing between sexes indicated that saprolegniosis lesions are mainly located above the lateral line and most frequently affect the dorsal cephalic region, the adipose fin, the peduncle and the caudal fin. However, differences were observed between males and females. Farmed trout presented a lower percentage of affected body surface (2.06 ± 4.36) and a lower number of lesions with and without necrosis because they received preventive treatment for saprolegniosis.     

Prawn (Macrobrachium rosenbergii)–plant (Hydrilla verticillata) co‐culture system improves water quality,prawn production and economic benefit through stocking density and feeding regime manage

The effects and commercial implications of aquatic plant addition, and variable prawn stocking density and supply of commercial aquafeed on water quality, prawn production and economic benefit, are investigated in a prawn (Macrobrachium rosenbergii) + plant (Hydrilla verticillata) co‐culture system. Our experimental design includes a control (PM, prawn monoculture without H. verticillata, with 30 prawns/m²) and four treatments with 15% plant cover of total pond area in each replicate. Dissolved oxygen, pH, N, P, total ammoniacal nitrogen, nitrite and nitrate in this co‐culture system were significantly lower than those of PM. Prawn survival (96.2 ± 14.9%), average final weight (68.5 ± 4.9 g) and yield (879.1 ± 102.4 kg/ha) in treatment 20W80%A (20 prawns/m², 80% of control aquafeed) were obviously greater than in PM and other treatments. Despite small males (SM) and immature females (IF) being predominant in prawn + plant cultures, more than 77.2% of prawns reached or exceeded 40 g on completion of trials, and by six months were of appropriate size for market. We report culture of M. rosenbergii with H. verticillata to be both feasible and profitable. The optimal treatment, a stocking density of 20 prawns/m² with these plants, enabled reduction of commercial aquafeed to 20% conventional culture levels. For this optimal treatment, we estimate total gross revenue, profit and internal rate of return to be US$ 6,593.3 ± 103.3 ha^?1, US$ 3,095.5 ± 42.6 ha^?1 and 127.5 ± 20.7% for 20W80%A respectively; we estimate U.S. Dollar (US$) invested generates 3.87 times conventional culture revenue. Co‐culture of M. rosenbergii and plants renders prawn production ecologically and economically feasible on larger farms.     

Survival,male morphotypes,female and male proportion,female reproductive status and tag loss in crosses among three populations of freshwater prawn Macrobrachium rosenbergii (de Man) in India

The present study examined the variation in survival, proportion of male morphotypes, female and male proportion, female reproductive status and tag losses in nine crosses from a complete (3 × 3) diallel mating of three populations of Macrobrachium rosenbergii in India. The populations originated from Gujarat (north‐west), Kerala (south‐west) and Odisha (east), representing different agro‐ecological regions in India. Progeny from 60 families (4773 juveniles) were individually tagged and reared for 16–17 weeks in earthen ponds. Binary logistic regression was used to analyse the data. Survival rate was greatest (0.88) for Kerala × Odisha (KO; the first letter represents the sire), whereas it was lowest (0.75) for both Kerala × Kerala (KK) and Gujarat × Kerala (GK). Significantly greater proportions of large male morphotypes were observed in KK cross and in combinations involving Kerala population. The highest proportion of immature females, as well as of non‐berried females, was observed in the Odisha × Odisha (OO) cross. Tag loss was greatest for KK (0.35) and lowest for GG (0.19). We found significant variations among crosses for all studied traits suggesting the possibility of including them in genetic improvement programmes of this species.