Olive barb, Puntius sarana (Hamilton) is a potential candidate species for introduction into the grow-out carp polyculture system

The compatibility of olive barb, Puntius sarana (Hamilton) with major carps was studied in grow-out carp polyculture system for one year in a set of nine earthen ponds of 0.08 ha each. Three different species combinations evaluated were Control: catla (Catla catla Ham.), silver carp (Hypophthalmichthys molitrix Valenciennes), rohu (Labeo rohita Hamilton) and mrigal (Cirrhinus mrigala Hamilton) at 0.5:0.5:1:1; T1: catla, silver carp, rohu and olive barb at 0.5:0.5:1:1 and T2: catla, silver carp, mrigal and olive barb at 0.5:0.5:1:1 at combined density of 7500 fingerlings/ha. While survival levels of the carps did not differ significantly in treatments (P > 0.05), silver carp recorded highest survival levels (94–96%) followed by olive barb (87–90%), mrigal (72–74%), rohu (72–73%) and catla (67–69%). The specific growth rate (SGR) and average harvested body weight (ABW) of catla and silver carp did not differ significantly among the treatments revealing their competition with mrigal or olive barb to be minimum. In absence of rohu in T2, both mrigal and olive barb showed higher SGR and ABW revealing minimal competition between these two species, while their lower performance in presence of rohu in Control and T1 indicated inter-specific competition with the latter. Such olive barb–rohu inter-specific competition, however, failed to yield significant effect on growth of rohu as revealed from its non-significant SGR difference in presence and absence of olive barb. The lower FCR (2.54 ± 0.06) and higher treatment biomass production (3418.4 ± 95.0 kg ha^− 1 year^− 1) in T1 with rohu–olive barb combination compared to T2 with mrigal–olive barb (2.84 ± 0.11; 3155.1 ± 104.7 kg ha^− 1 year^− 1) indicated feasibility and advantage of culturing rohu with olive barb rather than mrigal in carp polyculture. Further, similar biomass production in Control and T1 also indicated feasibility of replacing mrigal with olive barb in the grow-out carp polyculture system.     

Compatibility of silver barb Puntius gonionotus (Bleeker) with Indian major carps in a grow-out polyculture

The compatibility and growth performance of silver barb Puntius gonionotus (Barbonymous gonionotus) with the three Indian major carps, i.e., Catla catla, Labeo rohita and Cirrhinus mrigala, were assessed in a 10‐month carp polyculture trial. Treatments T‐1, T‐2, T‐3 and T‐4 were stocked with three of the above four carp species, with an absence of silver barb, mrigal, rohu and catla, respectively, while all four species were stocked in treatment T‐5. The treatments were stocked at 6000 fingerlings ha⁻¹, with an equal species ratio maintained in each treatment. Incorporation of silver barb into the polyculture system neither affected the survival of any carp irrespective of species combination nor yielded significant changes in biomass production among treatments, except for the one without catla, where it was significantly low. The study revealed a higher extent of competition between silver barb and rohu, perceptible from the lower growth of one in the presence of the other. Although a certain level of competition of silver barb with mrigal was evident, competition with catla was not perceptible. Irrespective of species combination with silver barb as a component species, similar total biomass production in treatments revealed the feasibility of its incorporation into the Indian major carp‐based polyculture practice without affecting the total yield.     

Appropriate Timing of Supplemental Feeding for Production of Nile Tilapia, Silver Carp, and Common Carp in Fertilized Polyculture Ponds

In an attempt to identify appropriate times for initial application of supplemental feed in polyculture fertilized fish production earthen ponds, a study was conducted for 19 wk to establish the growth performance, yield, survival, and body composition of Nile tilapia, common carp, and silver carp as influenced by four different feeding regimens (treatments). The four treatments were: 1) supplemental feeding beginning at onset of the experiment (T-I) (control treatment); 2) 6-wk delay of feeding after fish stocking (T-II); 3) 13-wk delay of feeding after fish stocking (T-III), and 4) no supplemental feed application (T-IV). Two ponds were assigned to each treatment and each pond was stocked with a similar number and weight of each fish species. A commercial pelleted fish feed (25% protein) was used to feed fish in T-I, T-II, and T-III at 3% of their body weight, twice a day. At the end of the experiment, fish species (except for silver carp) in T-II showed weight gain, growth rates, and yields significantly higher than fish in T-III or T-IV. Also, the total fish production and net profit in T-II were significantly higher than in T-III or T-IV. Fish species in T-II showed weight gain, growth rates, survival rates, and yields similar to those of T-I (control treatment) with no significant differences. The amount of feed consumed by fish in T-II was reduced by approximately 7.3% compared to that consumed by fish at T-I. Moreover, there was increase in th net profit in T-II by 4.8% over that achieved in T-I. Therefore, T-II appears to be the most appropriate among the tested feeding treatments and recommended for use in order to achieve the best growth, production, and net profit.     

Polyculture of a Critically Endangered Olive Barb,Puntius sarana (Ham.), with Indigenous Major Carps in Earthen Ponds

Polyculture of olive barb with indigenous major carps was carried out for 8 mo at different densities in earthen ponds. All the experimental ponds were stocked with fingerlings of major carps viz., catla, Catla catla, and rohu, Labeo rohita, at the rate of 3750/ha each. In addition, olive barb, Puntius sarana, was stocked at the rate of 10,000, 12,500, and 15,000 fingerlings/ha in treatment‐1 (T₁), treatment‐2 (T₂), and treatment‐3 (T₃), respectively. Fish in all the ponds were fed with supplementary feed comprising of rice bran (70%), mustard oil cake (25%), and fish meal (5%) at the rate of 3–6% of the estimated body weight. Physicochemical parameters and plankton populations of pond water were within the acceptable range for fish culture. The mean final weight, weight gain, and specific growth rate of catla were very similar in all the treatments while those for rohu and olive barb were significantly higher in T₁ than in T₂ and T₃. The gross and net productions in T₁ were significantly higher than in T₂ and T₃. The net benefit was also highest in T₁ followed by T₂ and lowest in T₃. Under the conditions of this experiment, growth, production, and benefits were greatest at a stocking density of olive barb at 10,000/ha in polyculture with other major carps.     

Genetic variations in survival of rohu carp (Labeo rohita, Hamilton) after Aeromonas hydrophila infection in challenge tests

A challenge test against Aeromonas hydrophila was conducted using 2062 rohu carp (Labeo rohita) fingerlings obtained from 52 dams and 87 sires (87 full-sib families) of two year-classes (2003 and 2004). Attempts to establish a cohabitant challenge model were not successful. Therefore, fish were challenged by intraperitoneal injection with A. hydrophila in two replicate tanks per year-class, and dead fish were collected hourly. The mortality reached its peak at 16–22 h after challenge and had almost completely stopped after 58 h. The test was terminated after 382 h at which the average survival was 43.9 and 48.9% in the two 2003 year-class tanks, and 77.1 and 35.8% in the two 2004 year-class tanks. Heritability estimates for survival were obtained from sire and dam threshold models (THR) and sire and dam linear repeatability models (LINR). For both types of models the heritability estimates based on data from single tanks were not consistent. For both year-classes, data from one of the two challenged tanks demonstrated significant additive genetic variation in survival during the A. hydrophila infection, whereas the heritability estimates were not significantly different from zero for the other tank. Further, genetic correlation between survivals in the two replicate tanks in each year-class was not significantly different from zero. The differential results from the replicate tanks demonstrate that additional challenge test experiments are needed before firm conclusions can be drawn about the magnitude of additive genetic variation for survival to aeromonasis in rohu carp. A cohabitant challenge model that allows the testing of important defence mechanisms in the skin and mucous membranes of the fish might have been more appropriate. To establish a valid cohabitant challenge model for rohu carp should be given high priority.     

Grow‐out performance of Kuria labeo,Labeo gonius (Hamilton), with major carps in carp polyculture system

A year‐long grow‐out carp polyculture trial was conducted in nine earthen ponds to study the growth performance of Kuria labeo (Labeo gonius) with the different major carps such as catla (Catla catla), silver carp (Hypophthalmichthys molitrix), rohu (Labeo rohita) and mrigal (Cirrhinus mrigala). Suitable water quality parameters were maintained in ponds through intermittent liming, manuring and fertilization. Three different species combinations of carps were evaluated using silver carp and catla as the common species and varying other carp components as rohu–Kuria labeo, mrigal–Kuria labeo and rohu–mrigal in the three treatments. The ponds were stocked at a combined density of 7500 fingerlings ha^?1. Silver carp and catla showed similar growth performances in all the three combinations, suggesting that other carps in the combination do not have any differential influence on their growth. Kuria labeo was compatible with rohu, while competition was observed with mrigal. Although growth performance of Kuria labeo was inferior to that of mrigal, better compatibility of Kuria labeo with rohu helped this combination to yield a biomass equivalent to the mrigal–rohu combination, suggesting feasibility to use Kuria labeo as an alternative species to mrigal in the major carp polyculture system without compromising the total biomass yield.     

Improved survival of rohu, Labeo rohita (Hamilton-Buchanan) and silver carp, Hypophthalmichthys molitrix (Valenciennes) fingerlings using low-dose quinaldine and benzocaine during transport

The effects of fingerlings immersion in low‐dose benzocaine (15 and 30 mg L⁻¹, silver carp and rohu) and quinaldine (100 μL L⁻¹ silver crap and 250 μL L⁻¹ rohu) for 1, 3 and 6 h on stress responses and survival of rohu, Labeo rohita and silver carp, Hypophthalmichthys molitrix fingerlings were evaluated in a transport simulation experiment. Both quinaldine and benzocaine showed low mortalities (0–2%). The total mortality in control (with no anaesthesia) was 30% for rohu and 14% for silver carp. Quinaldine and benzocaine‐treated fingerlings had significantly higher plasma chloride levels than the control in both species. Benzocaine, quinaldine, as well as the control, had an initial elevation of plasma cortisol levels. Benzocaine lost its effectiveness after 3 h exposure while quinaldine persisted throughout the 6 h experimental period. Both sedatives reduced bacterial build‐up compared with the control. No post‐exposure mortality was observed for any of the transport methods assessed 48 h after the treatment. This study suggests that the use of low‐dose benzocaine or quinaldine during transport has positive effect on the survival and health of rohu and silver carp fingerlings.     

Existence of APGWamide in the testis and its induction of spermiation in Haliotis asinina Linnaeus

Immunolocalization by using rabbit polyclonal antibody against APGWamide demonstrated that there was APGWamide immunoreactivity (APGW-ir) in the varicosed nerve fibers in the capsule, connective tissue and trabeculae of the testis whereas there was no APGW-ir in the ovary of sexually mature broodstocks of Haliotis asinina. In vivo bioassay, by injecting APGWamide into foot muscle of mature males and females (age over 24 months), showed that most males (87.50%) injected with 200 μl of 10^− 3 M APGWamide (170 μg APGWamide/animal) could be induced to spermiate whereas fewer males (43.75%) injected with 200 μl of 10^− 6 M APGWamide (0.17 μg APGWamide/animal) could spermiate. Following injection with 10^− 3 M, 53% of males spawned within 3 to 4 h, while the remaining males spawned within 2 to 3 h. The former tended to release more sperm at the range of 1.04 to 2 × 10⁹, and the latter at the range 3.62 × 10⁷ to 2.07 × 10⁸ cells, respectively, and that the sperm of the former group appeared to be more motile. Following the injection of 10^− 6 M, all inducible males spawned within 2–3 h, and 43% of spawned males have sperm around 2 × 10⁹, while 57% have fewer sperm number ranging from 2.75 × 10⁷ to 9.94 × 10⁸ cells. In contrast to males, none of the mature females with ripen ovary could be induced to ovulate. These data suggest that APGWamide is an important signaling molecule that plays a role in the male reproductive process that could be used to induce spermiation.     

Variation in spawning responses, egg and larvae productions from induced rohu (Labeo rohita) during pre-monsoon and monsoon seasons: Relationship with hormonal changes and oocyte responsiveness during final maturation

Early induced spawning in captive rohu (Labeo rohita) often encounters with reduced spawning performances and devaluation of final product. The present study attempted to gain insight into the problems associated with poor performance of rohu during pre-monsoon spawning. A combination of sGnRHa and domperidone was used to induce final oocyte maturation (FOM) and ovulation in rohu during early (pre-monsoon, PM) and normal (monsoon, MN) spawning. The spawning performance parameters such as, spawning response, production and quality of egg and larvae showed significantly lower values (p < 0.05) in PM, when compared with MN spawning. The egg and spawn productions were recorded as 2.6 ± 0.05 and 2.41 ± 0.05 during the MN season, which were reduced by almost 50% in the PM season. Moreover the quality of egg and hatchling was devaluated significantly (p < 0.05) and exhibited higher percentage of mortality and abnormality in PM than those recorded in the MN season. The plasma concentration of carp gonadotropin (cGtH), 17β-estradiol (E) and 17α20β-dihydroxy-4-pregnen-3-one (DP) in relation to progress of FOM and ovulation at different seasons exhibited marked variation in hormonal profiles particularly in E and DP of PM fish. Higher initial plasma E (3.8 ± 0.3) and a distinct E peak clearly indicated the lack of transition from vitellogenic to post-vitellogenic stages that prevailed in PM rohu. Delayed DP and cGtH surge during FOM and ovulation resulted in longer latency period in spite of higher water temperature (31.5 °C) that prevailed during the PM period. In-vitro study on oocyte maturational competence (OMC) clearly depicted the lack of maturational competence in ovarian follicles during PM than MN in rohu. However priming the fish with purified carp gonadotropin (PCG) enhanced the acquisition of OMC in PM rohu in such an extent, that no marked seasonal differences (p > 0.05) in OMC were remained further, when compared with MN follicles. The PCG mediated acquisition of maturational competence was found to be dependent fully on new mRNA and protein synthesis in PM fish. The present study clearly demonstrated that the oocytes' unresponsiveness to hormonal induction was mainly responsible for reduced spawning performance in PM rohu, which could be ameliorated through PCG priming to achieve better spawning response in rohu during the pre-monsoon period. Thereby, the rohu fry production could be initiated successfully as early as May, allowing public and private hatcheries to produce larger age-0 rohu fingerlings ensuring reliable steady source of stocking materials for grow-out system earlier in the season.     

Evaluation of minor carps intercropping in carp polyculture vis‐à‐vis other grow‐out cropping patterns of carp farming

One year grow‐out evaluation of four cropping patterns of carps, viz. control: single stock single harvest (SSSH); T‐1:intercrop of minor carps and Indian major carps (IMC); T‐2:single stock multiple harvests (SSMH); and T‐3:multiple stock multiple harvests (MSMH) was conducted in eight earthen ponds (0.09 ha each). Ponds were stocked with three IMCs (catla, rohu and mrigal) at 1:1:1 ratio at 10,000 fingerlings/ha combined density. T‐1 was additionally stocked with 10,000 fingerlings/ha of minor carps (Puntius gonionotus, Labeo fimbriatus and Puntius sarana), while T‐2 with additional 10,000 fingerlings/ha of the IMC. Periodic removal of partial biomass ensured prevalence of better water quality in treatments (higher water pH, higher dissolved oxygen and reduced inorganic nutrients). It helped to improve fish growth as average harvested weight of rohu and mrigal remained similar in treatments despite the presence of greater inter‐ and intraspecific competitions in intercrop and SSMH, respectively, and periodic stocking of younger juveniles in MSMH. Catla showed significantly higher growth in MSMH. The biomass yield in intercrop, SSMH and MSMH were 21%, 17% and 24% higher than SSSH, but the respective net incomes were 32.9, 21.3 and 56.5% higher. Partial harvest also helped reducing FCR in the order T‐3<T‐2<T‐1<control. While the study showed MSMH as the most productive cropping pattern for biomass yield, the intercrop of minor carps and IMCs proved to be the most water productive (gross and consumptive water use) cropping method to produce varied fish protein with higher biomass yield.     

Tagging: on the use of passive integrated transponder (PIT) tags for the identification of fish

To determine the efficacy of passive integrated transponder (PIT) tags for marking rohu Labeo rohita (Ham.) in the selective breeding programme, a series of experiments has been carried out at the Central Institute of Freshwater Aquaculture (CIFA) under the Indo–Norwegian project of ‘Selective breeding of rohu’. Six groups of rohu fingerlings with weight ranging from 2 g to 20 g were tagged with PIT tags to determine a suitable size range for tagging. Fingerlings weighing 8–15 g were found to be quite suitable for tagging with a PIT tag. Recovery of the PIT tag depends upon the survival of tagged fish under field conditions. Rejection of the PIT tag by rohu was observed to be only 0.05%. Through effective management practice, the survival of tagged fish increased up to 95%, and thus tag loss was minimized.     

Dietary Tryptophan Requirement for the Growth of Rohu,Labeo rohita

ABSTRACT

The dietary tryptophan requirement for rohu, Labeo rohita (an Indian major carp) was determined by conducting a growth study. Diets (40% protein) contained casein and gelatin supplemented with crystalline amino acids to provide an amino acid profile similar to rohu muscle, except for tryptophan. The experimental diets contained graded levels of tryptophan (0.15, 0.38, 0.63, 0.88, 1.13, 1.38% dietary protein). Each test diet was fed to triplicate groups of rohu fingerlings twice daily to satiation for 8 weeks. The dietary tryptophan requirement estimated by employing broken-line regression analysis was 1.13% of dietary protein. Maximum survival, food efficiency, and specific growth rate were obtained by fish fed the diet containing above level of tryptophan.     

Effects of increasing the stocking density of large carps by 20% on 'cash' carp–small fish polyculture of Bangladesh

This experiment was carried out in the framework of a project to develop a viable fish polyculture technology under Bangladeshi conditions that allows simultaneous fish production of small indigenous species for the farmers' family consumption and of large carp species as a cash crop. The objectives of this experiment were to assess the effects on fish performance and on the environment of adding 20% large fish to the basic ‘cash crop’ carp–small fish polyculture consisting of 10 000 fish ha^?1 of the large carp rohu Labeo rohita (Hamilton), catla Catla catla (Hamilton) and common carp Cyprinus carpio (L.) at a species ratio 1:1:1, and 15 000 fish ha^?1 of each small indigenous fish punti Puntius sophore (Hamilton) and mola Amblypharyngodon mola (Hamilton) (control). The treatment ponds were stocked with additional 2000 large fish ha^?1, either all rohu, or all catla, or all common carp, or half rohu and half common carp, or half catla and half common carp. The results obtained and the analysis of interactions through the food web that affect food resource availability of the different fish species and account for the trends and differences observed among treatments confirm the positive effect of common carp on rohu reported in previous experiments and show that a 20% increase in large carps stocking neither affect the survival of the large carps nor reduce harvesting biomass of the small fish for the farmer's family consumption. Increased stocking densities of each large carp species did not significantly reduce its own harvesting weight and mean growth rate, while significantly increased rohu and catla (but not common carp) harvesting biomass and yield. The complex relations between species led to inter‐ and intraspecific competition, which in some treatments increased growth or yield of one species and in other treatments of other species, so that the gains on one species and the losses on the other led to no significant total harvested biomass differences between treatments. Yet, the results herein reported may help farmers to select their species stocking ratios. Thus, if the main target of the farmer is rohu, then a stocking density increase of 10% common carp and 10% rohu would improve rohu growth rate (due to common carp) and result in 50% higher rohu harvesting biomass and yield. If the main target of the farmer is catla, then a 20% increase in catla stocking density would lead to 20% higher catla harvesting biomass.     

Digestive proteases of three carps Catla catla, Labeo rohita and Hypophthalmichthys molitrix: partial characterization and protein hydrolysis efficiency

Characteristics and functional efficacy of digestive proteases of Catla catla, catla, Labeo rohita, rohu and Hypophthalmichthys molitrix, silver carp were studied. Total protease activity was significantly (P < 0.05) higher in rohu (1.219 ± 0.059 U mg protein⁻¹ min⁻¹) followed by silver carp (1.084 ± 0.061 U mg  protein⁻¹ min⁻¹), and catla (0.193 ± 0.006 U mg  protein⁻¹ min⁻¹). Trypsin activity of silver carp and rohu was 89–91% higher than catla. Chymotrypsin activity was significantly (P < 0.05) higher in silver carp compared with rohu and catla. The protease activity of rohu and silver carp displayed bell‐shaped curves with maximum activity at pH 9; whereas in catla, maximum activity was found between pH 8 and 11. Inhibition of protease activity with soybean trypsin inhibitor (SBTI), phenylmethylsulfonyl fluoride (PMSF) revealed the presence of serine proteases and inhibition of activity with N‐α‐p‐tosyl‐L‐lysine‐chloromethyl ketone (TLCK) and N‐tosyl‐L‐phenylalanychloromethane (TPCK) indicated the presence of trypsin‐like and chymotrypsin‐like enzymes in all these three carps. SDS‐PAGE showed the presence of several protein bands ranging from 15.3 to 121.9 kDa in enzyme extracts of catla, rohu and silver carp. The substrate SDS‐PAGE evidenced the presence of various protease activity bands ranging from 21.6–93.7, 21.6–63.8 and 26.7–98.5 kDa for catla, rohu and silver carp respectively. In pH‐stat hydrolysis of Chilean fishmeal showed significantly (P < 0.05) higher degree of hydrolysis compared with soybean meal, silver cup (a commercial fish feed of Mexico) and wheat flour, with enzyme preparations of three fishes. The rate of hydrolysis was significantly (P < 0.05) higher in silver carp compared with others.     

Food selection, electivity and dietary overlap among planktivorous Chinese and Indian major carp fry and fingerlings grown in extensively managed, rain-fed ponds in Bangladesh

Abstract. The fry of four species of planktivorous carp, silver carp, Hypophthalmichthys molitrix (Valenciennes), bighead carp, Aristichthys nobilis (Richardson), rohu, Labeo rohita (Hamilton), and catla, Catla catla (Hamilton), were grown in monoculture in ponds in Mymensingh, Bangladesh in order to determine electivity and the extent of dietary overlap. Other than an avoidance for Cyanobacteria, electivity was found to be low in most instances, although the low productivity of the ponds may have had some influence. Dietary overlap was greatest between catla and silver carp (0–52) and between catla and bighead carp (0–48).     

Effects of varied levels of incorporation of Labeo gonius in carp polyculture system in India

Growth performance of kuria labeo, Labeo gonius as a component species in the major carp polyculture system was evaluated at two incorporation levels against a control without the species through a year‐round grow‐out study in nine earthen ponds (0.08 ha). Three species ratio of catla, silver carp, rohu, mrigal and kuria labeo at 15:15:40:30:0 (T‐1: control), 15:15:40:20:10 (T‐2) and 15:15:40:10:20 (T‐3) were evaluated as three treatments. The carps were stocked at a combined density of 7500 fingerlings ha^?1. Silver carp demonstrated the highest survival (75–81%) followed by rohu (70–76%), catla (69–76%), kuria labeo (69–71%) and mrigal (67–69%). Species‐wise yield attributes such as survival, harvest weight, SGR and biomass yield of silver carp, catla and rohu were similar in their respective treatments. Kuria labeo at 10% inclusion demonstrated 12% higher harvest weight than its 20% inclusion. However, such higher weight gain could not affect the total biomass yields of carps which remained similar among the treatments. Furthermore, harvest weight of kuria labeo at 10% inclusion was comparable to that of mrigal when the latter incorporated at 20–30% level. Therefore, the study suggested 10% to be a suitable incorporation level for kuria labeo in the commercial grow‐out carp polyculture system.     

Effect of Ocimum sanctum Linn. (Tulsi) extract on the immunity and survival of Labeo rohita (Hamilton) infected with Aeromonas hydrophila

A 60 days study was conducted to evaluate the efficacy of water extract of Ocimum sanctum Linn. leaf on the immune response and disease resistance of Labeo rohita fingerlings against the Aeromonas hydrophila infection. Ocimum sanctum extract was incorporated in the diets (at 0.0%, 0.05%, 0.1%, 0.2%, 0.5% and 1%) of Labeo rohita, rohu fingerlings (6.6 ± 0.013 g). After 42 days blood, plasma and serum were sampled to determine super oxide anion production, lysozyme activity, total immunoglobulin in plasma, blood glucose, serum total protein, albumin, globulin, albumin:globulin ratio, WBC, RBC, haemoglobin content. Fish were challenged with A. hydrophila after 42 days and mortalities were recorded over 18 days post infection. The results demonstrate enhanced super oxide anion production, lysozyme activity, total immunoglobulin in plasma, serum total protein, globulin, total RBC counts, total WBC counts and haemoglobin content (P < 0.05) in treatments group compared with control group. Dietary O. sanctum extracts of 0.2% showed significantly (P < 0.05) higher protection relative percentage survival (RPS 40.00 ± 5.773%) against A. hydrophila infection than control. These results indicate that O. sanctum leaf extract stimulates the immunity and makes L. rohita more resistant to bacterial infection (A. hydrophila).     

Cryopreservation of dead fish spermatozoa several hours after death of Indian major carp, Labeo rohita and its successful utilization in fish production

Cryopreservation of semen collected from dead fishes showed that it is possible to use it for fish production. We humanely killed individuals of the Indian major carp rohu, Labeo rohita and stored at different temperature regimes of 31 °C, 0 °C, − 10 °C and − 30 °C till 8 h. At every one hour interval semen from these fishes were collected by Pasteur pipette and evaluated for sperm yield/kg body weight, motility, pH, spermatocrit (%) and sperm count. The semen having suitable characteristics such as; 70% spermatocrit or above and motility index of 4 or above was cryopreserved by following a specific protocol. The cryopreserved semen of the dead fishes was stored for 7 days and then thawed in a water bath at 37 °C for 50 s. It was found that up to 8 h, spermatozoa of rohu were viable when stored at 0 °C or − 10 °C. Sperm collected after 8 h of fish death and maintained at 0 °C was the best stored condition that showed 30% larval survival. The spermatozoa collected 8 h after fish death was mostly normal as observed under scanning electron microscope and the total length of rohu spermatozoa was 25-30 μm. The hatchlings produced with this cryopreserved semen grew normally and juvenile fishes of rohu could be produced. This study suggests that germ cells such as spermatozoa of dead fishes can be cryopreserved and utilized for restoration of a species. It has the potential use in cryo-conservation of endangered fishes, restoration of animals through fertilization and genetic manipulation studies.     

Effect of light on oxygen consumption and ammonia excretion in Haliotis discus discus, H. gigantea, H. madaka and their hybrids

Oxygen consumption and ammonia excretion rates of three abalone species, Haliotis discus discus, H. gigantea, H. madaka and their hybrids were measured at 20 °C by incubating for 3 h under dark and light (N = 9–13 for each species and hybrid). Animals were fasted before and during the experiment and measurements were made first under dark followed by light on the next day. The rates increased with the increase in body weight and were higher under light than dark. On average, H. discus discus had higher oxygen consumption (DD; dark = 0.039, light = 0.04 ml/g/h) than H. gigantea (G; D = 0.033, L = 0.036) and H. madaka (M; D = 0.034, L = 0.035); the hybrids had varied patterns with respect to their parental species [DD × M (D = 0.032, L = 0.038); M × DD (D = 0.03, L = 0.038); G × DD (D = 0.035, L = 0.04) and DD × G (D = 0.03, L = 0.034), mother first]. M (0.261, 0.298 μmol/g/h) had the highest ammonia excretion rate while G (0.162; 0.264) and DD (0.229; 0.232) had the lowest under dark and light, respectively. The hybrids had varied patterns in comparison with their parents (DD × M = 0.247, 0.32;M × DD= 0.177, 0.28; DD × G = 0.249, 0.364 and G × DD = 0.116, 0.155). The O/N ratios under both conditions in all species and hybrids indicated that they had carbohydrate dominated metabolism. Results demonstrated physiological variability among the species and hybrids indicating necessity of different strategies for their management and aquaculture.     

Over-wintering growth of Macrobrachium rosenbergii (de Man) with carp polyculture in Bangladesh fed formulated diets

An experiment was conducted from December 2003 to April 2004 to observe the over‐wintering growth of freshwater prawn, Macrobrachium rosenbergii, with catla, Catla catla and rohu, Labeo rohita in polyculture using formulated diets. The study was conducted in eight experimental ponds, each 80 m². Three experimental diets containing 30% protein were prepared using fish meal, meat and bone meal, mustard oilcake, rice bran, wheat bran and molasses (binder), and assigned to treatments T₁, T₂ and T₃ respectively. A commercial diet from Saudi‐Bangla Fish Feed was assigned to T₄ (reference diet). Each treatment had two replicate ponds. Juvenile prawns and catla and rohu fingerlings (initial weight 1.60±0.10, 30.0±1.2 and 25.0±1.1 g respectively) were stocked at a ratio of 2:1:1 (prawn:catla:rohu). A total of 160 prawn and fish (20 000 ha^?1) were stocked in each pond. Fish were fed twice daily at 3% body weight (b.w.) for the first 3 months and 5% b.w. for the last 2 months. Prawns in T₁ fed diet 1 had significantly higher (P<0.05) weight gain compared with that of T₃. The reference group and T₂ had intermediate values not significantly different from either. Weight gains of catla and rohu were significantly higher in T₁. The feed conversion ratio values of different diets ranged between 1.89 and 2.13. Survival (%) ranged from 90.0% to 95.0% for catla, 87.5% to 92.5% for rohu and 70.0% to 76.3% for M. rosenbergii, and there were no significant differences (P>0.05) among different treatments. Total production ranged between 2196 and 2679 kg ha^?1, with T₁ showing significantly higher production and net profit (taka 56 531.9 ha^?1). The results of the study demonstrated that it is possible to culture M. rosenbergii with carp in polyculture during the winter utilizing the late‐produced PLs. Further study is needed to determine the optimum stocking density of M. rosenbergii in carp polyculture.