Sodium alginate supplementation modulates gut microbiota,health parameters,growth performance and growth‐related gene expression in Malaysian Mahseer Tor tambroides

This study investigated the effects of sodium alginate supplementation on gut microbiota composition, health parameters, growth performances and growth‐related gene expression of Malaysian mahseer. Five test diets were formulated by supplementing 0%, 0.1%, 0.2%, 0.4% and 0.8% sodium alginate. Triplicate groups of juvenile Tor tambroides (2.19 ± 0.05 g) were stocked in 15 aquaria (20 individuals per aquarium) and fed at 3.0% body weight per day for 60 days. PCoA and UPGMA analysis showed that gut bacterial community were more convergence in higher sodium alginate‐supplemented diets. The percentage of Porphyromonadaceae, Bacteroides, Plesiomonas and Shewanella were substantially higher and Aeromonas, Entomoplasmatales and Prevotellaceae were drastically lower in higher sodium alginate (0.2%–0.8%) diets. Sodium alginate supplementation (≥0.2%) significantly improved the haematocrit value and respiratory burst activity of T. tambroides. Growth performances and feed utilization were significantly higher in 0.2%–0.4% sodium alginate‐supplemented diets. The increased growth rate of T. tambroides was governed by both hyperplastic and hypertrophic muscle growth. Real‐time PCR data demonstrated that most of the growth‐related genes were significantly upregulated in 0.2%–0.4% sodium alginate‐supplemented diet. Finally, it can be concluded that sodium alginate should be supplemented at 2 g/kg in practical fish feed formulation.     

Effect of cryoprotectants, equilibration periods and freezing rates on cryopreservation of spermatozoa of mahseer, Tor khudree (Sykes) and T. putitora (Hamilton)

A study was conducted to standardize a protocol for cryopreservation of spermatozoa of the endangered mahseer, Tor khudree (Sykes) and T. putitora (Hamilton). The suitability of the cryoprotectants, dimethyl sulphoxide (DMSO) and glycerol, and the combination of the two were tested. Four equilibration periods and four freezing rates were also tested for their standardization. A combination of 9% DMSO and 11% glycerol gave significantly higher mean percentage of hatching in both T. khudree (45.59±1.86%) (control 71.08±0.59%) and T. putitora (45.00±1.25%) (control 73.48±1.19%) among the eight different treatments. Among the four different equilibration periods tested, the equilibration period of 30 min^?1 yielded the highest mean hatching percentage in T. khudree (39.46±1.94%) (control 71.70±0.61%) and T. putitora (38.28±1.06%) (control 73.11±0.82%). Freezing straws at a height of 8 cm above LN₂ surface for 10 min^?1 gave higher hatching percentages for both T. khudree (41.75±1.72%) (control 73.99±1.17%) and T. putitora (41.34±2.04%) (control 72.48±1.51%). The study reports the superior performance of the combination of DMSO and glycerol for the first time.     

Recreational angling markets to advance the conservation of a reach of the Western Ramganga River,India

• 1. Mahseer fishes of the genus Tor are ‘iconic species’ in Indian rivers, representing ‘flagship’ species for conservation purposes but with additional exploitable, cultural and economic values. Conservation action is required to address their vulnerability to numerous pressures on multiple habitats, and connections between them, across the extended aquatic ecosystems supporting different life stages.
• 2. Recreational angling for mahseer, along with associated wildlife and cultural tourism, is a growth industry dependent upon healthy river ecosystems.
• 3. A cyclic, ecosystem‐based model in which local people can benefit economically from sustainable mahseer exploitation through catch‐and‐release fisheries can form a basis for conservation of both mahseer and the wider river ecosystem.
• 4. Experience on the Western Ramganga River in the vicinity of the town of Bikhyasen, Uttarakhand State (in the Himalayas in northern India), demonstrates the importance of involving local people in the benefits associated with angling, wildlife and cultural tourism. This creates local incentives for river protection, and may be the most effective means for preventing destructive over‐exploitation in poor rural communities.
• 5. Recognition of this value and its recirculation to local people can form the basis for a ‘paying for ecosystems services’ (PES) market. This will benefit river ecosystems, local people, tour operators and visiting anglers, provided that local people benefit to a greater extent than through the killing of fish for non‐renewable consumption or sale.
• 6. This is the basis for a potentially transferable model which may support regional development through involving local people in markets for iconic species. Copyright © 2010 John Wiley & Sons, Ltd.

     

Effects of dietary fish oil replacement by various vegetable oils on growth performance,body composition and fatty acid profile of juvenile Malaysian mahseer,Tor tambroides

The current study was carried out to investigate the effects of replacing dietary fish oil with different vegetable oil sources and ratios on the growth performance and tissue fatty acid profiles of juvenile Tor tambroides. Three different vegetable oils (sunflower oil, linseed oil and palm oil) were used in two different substitution ratios (50% and 100%). A diet without replacement (100% fish oil) was used as a control. Triplicate groups of T. tambroides juveniles (5.0 ± 0.4 g) were fed the test diets for 9 weeks. The highest weight gain was observed in fish fed palm oil diets that, of course, were reared in aquaria. There was a significant effect (P < 0.05) of the percentage of fish oil replacement on the liver weight after controlling for the effect of fish weight (P < 0.05). The viscera weight significantly increased (P < 0.05) in fish on vegetable oil diets, and its highest amount observed among fish fed palm oil diets. Vegetable oil inclusion significantly reduced eicosapentaenoic acid and docosahexaenoic acid (DHA) concentrations in both muscle and liver of fish except for fish on 50% palm oil diet that had similar liver DHA content with those on control diet.     

Antioxidant Properties and the Preservative Effect of Whole Radish Extract on Quality of Deccan Mahseer (Tor khudree) Steaks during Chilled Storage

ABSTRACT

The effect of dip treatment with solvent-free whole radish extract (WRE) on quality characteristics of Deccan mahseer steaks was evaluated during the chilled storage. In-vitro antioxidant activities of the extract were evaluated based on total phenolic and flavonoid contents, DPPH radical scavenging activity, and metal chelating ability prior to the dip treatment. The quality parameters, including total volatile base nitrogen (TVB-N), trimethylamine nitrogen (TMA-N), and free fatty acid (FFA), were significantly (p < .05) reduced in WRE treated steaks compared to the control (CT) steaks. WRE treatment of fish steaks significantly controlled the lipid oxidation parameters of thiobarbituric acid reactive substances (TBARS) and peroxide value (PV). Total plate count (TPC) of CT sample was higher than the treated sample and remained within the limit of 7 log₁₀ cfu/g at the end of storage. As per the sensory analysis, shelf life of Deccan mahseer was determined to be 15 days for WRE treated steaks and 9 days for control steaks during chill storage. Based on the results, it can be concluded that WRE treatment can limit the progress of fish spoilage bacteria in fish steaks and can be used as a substitute for synthetic additives.     

Breeding performance of Malaysian mahseer, Tor tambroides and T. douronensis broodfish in captivity

Tor tambroides and T. douronensis are highly valued freshwater cyprinids. Owing to their cultural and economic importance, and concerns over their conservation status, a captive artificial propagation programme was established in Sarawak, Malaysia, to produce seedstock for conservation and aquaculture purposes. This paper describes work that followed the initial breakthrough in artificial propagation of captive, pond‐reared broodfish of the two Tor species, primarily on the overall breeding performance of broodfish over a 3‐year period. Breeding performance generally increased through the study period, indicating an overall improvement in husbandry and breeding techniques since commencing breeding trials. Spawning was induced in most months of the year. Seasonal patterns in spawning performance were not clear, but nevertheless the influence of monsoonal climate patterns was evident as higher breeding performance indicators were observed during the northeast monsoon. Some individual broodfish were injected and stripped up to 11 times during the study, and there were as little as 30 days between successful strippings. Considerable variability was observed in each of the breeding performance indicators with successive hypophysation, although in T. tambroides, there were signs of an increase in some of these indicators with successive hypophysation attempts. Multiple injection of Ovaprim, and repeated stripping of eggs, does not appear to reduce breeding performance, at least for T. tambroides.     

Optimization of dietary protein requirement for pond-reared mahseer Tor putitora Hamilton (Cypriniformes: Cyprinidae)

A feeding trial was conducted to study the effect of six iso‐energetic diets containing 25, 30, 35, 40, 45 and 50% crude protein (CP) on growth, survival and feed conversion ratio (FCR) as well as the protein requirement of an endangered cyprinid, Tor putitora. Triplicate groups of fingerlings with initial total length of 10.0–11.0 cm and weight of 12.0–12.5 g were reared in earthen ponds and fed diets at 5% of body weight for 120 days. Performance was evaluated on the basis of total length gain, body weight gain, survival rate, feed efficiency, FCR, protein efficiency ratio, specific growth rate, energy retention, gross and net yield in kg ha^?1. Whole‐body carcass composition of fish was analysed at the start and the end of the experiment. Growth and FCR were influenced significantly (P<0.05) by dietary CP contents; higher growth and lower FCRs were obtained with increasing dietary protein. Dietary protein also influenced the whole‐body carcass composition of the fish. Higher protein and ash, and lower moisture and lipid in the whole body were observed with increasing dietary protein. Broken‐line regression analysis indicated that the optimum dietary protein level for maximal growth of mahseer lies between 45% and 50% (45.3%). Overall feed utilization and growth performance of the fish is comparable to that of other aquaculture species and the fish offers high potential for commercial aquaculture.     

Some characteristics and short-term preservation of spermatozoa of Deccan mahseer, Tor khudree (Sykes)

Over the years, the natural stocks of Tor khudree (Cyprinidae) have depleted due to anthropogenic activities and hence it is considered a threatened species in India. Several in situ and ex situ conservation strategies have been suggested for the revival of T. khudree stocks. The total volume of milt obtained from hormone‐injected (gonadotropin‐releasing hormone analogue+domperidone) T. khudree were significantly higher (six to seven times) than that of uninjected fish. The total number of spermatozoa per fish was also higher in injected fish (6.5 × 10⁸–7.6 × 10⁸) than that obtained from uninjected counterparts (1.3 × 10⁸–1.8 × 10⁸). On the contrary, the spermatozoa density and spermatocrit were found to be lower in injected fish than that of the controls. Spermatozoa density and spermatocrit ranged between 4.1 × 10⁸–4.4 × 10⁸ spermatozoa mL^?1 and 38.1–39.4%, respectively, in injected fish, whereas the figures fluctuated between 6.0 × 10⁸–7.8 × 10⁸ spermatozoa mL^?1 and 61.5–63.1%, respectively, in uninjected fish. However, there was no significant difference in the spermatozoa motility rates between experimental and control fish. Different spermatozoa‐activating media revealed no significant difference in spermatozoa motility between hormone‐injected and uninjected mahseers. But motility duration was the longest with NaCl+urea (190–193 s) and the shortest with tap water (50–55 s) in the experimental and control groups. Short‐term preservation of the spermatozoa of T. khudree indicated that spermatozoa stored at 4°C had higher motility rates than those preserved at room temperature either in the presence or absence of oxygen.     

Induced spawning, larval development and rearing of two indigenous Malaysian mahseer, Tor tambroides and T. douronensis

The Mahseers (Tor spp.) are highly valued freshwater fishes across the Himalayan and South‐east Asian regions. Over exploitation of natural stocks because of high demand and the deteriorating environmental conditions have resulted in marked decline of mahseers in the wild. Malaysian mahseers, T. tambroides (Bleeker) and T. douronensis (Valenciennes), locally known as empurau, kelah or belian and semah, respectively, have significant cultural and economic importance but both species are now threatened in the wild because of environmental degradation and over fishing. A captive breeding programme was instigated to attempt to propagate these two species artificially for conservation and aquaculture purposes. Both pond‐reared and tank‐held T. tambroides and T. douronensis reached sexual maturity in captivity and were successfully induced to spawn using hormone treatments. Ovaprim (0.5 mL kg^?1) was the most successful hormone treatment for both species. Pre‐treatment of fish with Ovaplant (28–68 μg kg^?1, 2–7 weeks before spawning induction) greatly improved the success rate of spawning induction. Repeat spawning (within 4 months of initial spawning) was induced in some captive fish. Use of formalin baths improved hatching by preventing fungal infections. Embryonic development and hatching are described. Juveniles were reared in static greenwater ponds. Tor tambroides reached 142–179 g (max 270 g) in 60 weeks. These results represent the first successful captive spawning and rearing of both species. Options for future research to improve production are discussed.