S. S. Giri

Larval survival and growth in Wallago attu (Bloch and Schneider): effects of light, photoperiod and feeding regimes

Abstract An in-door rearing study was conducted for 11 days with Wallago attu larvae fed on live zooplankton alone (control) or combinations of zooplankton and dry feed containing either fish meal (F1), meat meal (F2) or shrimp meal (F3) under 24 h continuous light (24L), 12 h light–12 h dark (12L:12D), 24 h red light (24RL) or complete darkness (0L). The percent survival of larvae was significantly different (P

Nutrient digestibility and intestinal enzyme activity of Clarias batrachus (Linn.) juveniles fed on dried fish and chicken viscera incorporated diets

A feeding trial was conducted for 56 days to study the effect of replacement of fish meal by dried fish and chicken viscera, and a combination of oil cakes, in the diet of Clarias batrachus juveniles. The nutritional values of these by-products were studied through a digestibility experiment. No significant difference in nutrient digestibility was observed in different diets. Even 19.59% lipid in the diet of catfish did not affect the nutrient digestibility. Both amylolytic and proteolytic enzymes in the intestine of juveniles were studied. A decreased protease activity due to replacement of animal protein by plant protein and a decreased (P < 0.01) aspartate aminotransferase (ASAT) activity could be observed after inclusion of 22% of dried fish viscera in the diet of the catfish. Though body lipid content increased in fish fed a high level of lipid, fat-free body composition did not vary among the fish fed on different diets.

Utilization of fermented silkworm pupae silage in feed for carps.

Fermented silkworm pupae (SWP) silage or untreated fresh SWP pastes were incorporated in carp feed formulations replacing fishmeal. The feed formulations were isonitrogenous (30.2-30.9% protein) and isocaloric (ME = 2905-2935 kcal/kg). Feeding under a polyculture system consisting of 30% each of catla (Catla catla), mrigal (Cirrhinus mrigala) and rohu (Labeo rohita) with 10% silver carps (Hypophthalmychthys molitrix) was carried out in ponds to evaluate the nutritive quality of SWP silage. Survival rate, feed conversion ratio and specific growth rate, respectively, were 84.2%, 2.10 and 2.39 for fermented SWP silage, 65.8%, 2.98 and 2.26 for untreated SWP and 67.5%, 3.16 and 2.20 for fishmeal indicating clearly that the fermented SWP silage was nutritionally superior to untreated SWP or fishmeal. The dietary influence on the proximate composition of whole fish was marginal.

Molecular characterization of two kiss genes and their expression in rohu (Labeo rohita) during annual reproductive cycle.

Kisspeptin is an important regulator of reproduction in mammals and presumably non-mammalian species. In the Indian subcontinent, rohu (Labeo rohita) is a commercially important seasonal breeder freshwater fish species, but till date, the expression of kisspeptin gene during different phases of annual reproductive cycle has not been investigated. To address this, we cloned and characterized kiss1 and kiss2 full-length cDNA by RACE (rapid amplification of cDNA ends), and analyzed their expressions in brain-pituitary-gonad (BPG) axis by quantitative real time PCR (qRT-PCR) assay at various gonadal developmental stages of the annual reproductive cycle. Full-length rohu kiss1 and kiss2 cDNA encodes 116 and 125 amino acids respectively, and in the adult fish, they were widely expressed in brain, pituitary, gonad, liver, muscle, kidney, intestine and eye. In male, kiss1 mRNA in brain and testis showed the highest level of expression during meiosis division of the gonad. The kiss2 mRNA revealed the highest expression during recrudescence stages in the brain, spermiation stages in pituitary and post-spawning stages in testes. In females, significantly (p<0.05) a higher level of kiss1 transcript was expressed in brain and ovary, in the full grown oocyte stages, whereas during pre-vitellogenic and vitellogenic stages in pituitary. The kiss2 gene expression was almost similar at various gonadal developmental stages in the brain and ovary, but, highest expression was detected in full grown oocyte stages in the pituitary. These results together may suggest the involvement of two kiss genes in the control of seasonal gonadal development in rohu.

Dietary fish oil replacement by linseed oil: Effect on growth, nutrient utilization, tissue fatty acid composition and desaturase gene expression in silver barb (Puntius gonionotus) fingerlings

Silver barb (Puntius gonionotus) is considered a promising medium carp species for freshwater aquaculture in Asia. This study in silver barb was carried out to evaluate the effects of total or partial substitution of dietary fish oil (FO) with linseed oil (LO) on growth, nutrient utilization, whole-body composition, muscle and liver fatty acid composition. Fish (12.1±0.4g of initial body weight) were fed for 60days with five experimental iso-proteinous, iso-lipidic and iso-caloric diets in which FO (control diet) was replaced by 33.3%, 50%, 66.7% and 100% LO. Final weight, weight gain, percent weight gain, SGR decreased linearly (p<0.001) with increasing LO levels in the diets. Dietary LO substitution levels did not significantly (p>0.05) affect the feed conversion ratio (FCR), protein efficiency ratio (PER) and whole body proximate composition. Furthermore, enhanced level of LO increased α-linolenic acid (ALA; 18:3n3) and linoleic acid (LA; 18:2n6) and decreased eicosapentaenoic acid (EPA; 20:5n3) and docosahexaenoic acid (DHA; 22:6n3) in muscle and liver. To understand the molecular mechanism of long chain-polyunsaturated fatty acid (LC-PUFA) biosynthesis, we cloned and characterized the fatty acyl Δ6 desaturase (Δ6 fad) cDNA and investigated its expression in various organs/tissues following replacement of FO with LO in the diet. The full-length Δ6 fad cDNA was 2056bp encoding 444 amino acids and was widely expressed in various organs/tissues. Replacement of FO with LO increased the expression of Δ6 fad mRNA in liver, muscle and intestine but no significant difference was found in the brain.

Efficacy of water hyacinth compost in nursery ponds for larval rearing of Indian major carp, Labeo rohita

The use of water hyacinth compost as manure in nursery ponds for larval rearing of Indian major carp, Labeo rohita was studied. Better performance with regard to growth and survivability of the larvae was recorded in the ponds treated with water hyacinth compost (Group A) than in either the ponds treated with inorganic fertilizers (Group B) or the ponds where no treatment was applied (Group C). The average percentages of survival in Groups A, B and C were 14.3, 11.2 and 5.0, respectively. Thus about 186% increase in the survivability was recorded in the ponds treated with water hyacinth compost (P < 0.01), whereas the increase was about 124% in the ponds treated with only inorganic fertilizers, when compared with the ponds which were without any treatment.

Short Communication: Stocking Density-Dependant Growth and Survival of Asian Sun Catfish, Horabagrus brachysoma (Gunther 1864) Fry During Hatchery Rearing

The present study was conducted to determine the optimum stocking density of Horabagrus brachysoma fry during fingerling production in the hatchery. For this purpose, four density levels (400, 800, 1200 and 1600 fry/0.6 m3) were considered. The experiment of fry rearing continued for a period of six weeks. The total length and wet weight of fry were significantly highest (P < 0.05) at 400 fry/0.6 m3 density compared to the other three density treatments during the entire rearing period. At harvesting, the length and weight of fry stocked at 1200 and 1600 numbers/0.6 m3 were similar to each other, and both were significantly lower (P < 0.05) than those of fish stocked at 800/0.6 m3. The decreased SGR, percent weight gain, and survival were also observed at the two highest density treatments. But the total biomass was observed to be highest (P < 0.05) at 1600/0.6 m3 density compared to those of the other three densities. If individual size and number of individuals for stocking are not constraints, the maximum number of surviving fry from a minimum rearing space was achieved at a stocking density of 1600 fry/0.6 m3 tank.

Threatened fishes of the world: Clarias batrachus (Linn. 1758)

Common name: Magur, Walking Catfish. Conservation status: Vulnerable (CAMP 1998). Identification: Brownish black in colour. Elongated body with round abdomen and laterally compressed tail. Head with two depressions. Upper jaw slightly longer than lower. The mouth is wide and terminal. Four maxillary and four mandibular barbells. The dorsal fin and anal fin both long, reaching caudal base. Caudal fin homocercal, separated from dorsal and anal fin. D 62–76, P 1/8–11, V 6–7, A 45–58, C 14–17. Illustration by S. Mahali. Distribution: It is native to Indian sub-continent (Jayaram 1981). Habitat and ecology: Inhabits swampy areas and water bodies adjacent to paddy fields. Omnivore with broad feeding habits at different life stages (Hora and Pillay 1962). Reproduction: It breeds in second year of life during the monsoon (June–August) in vegetation under embankments. Parental care exists. The fecundity varies from 4000– 5000 (100 g females) and increases with fish size. The honey colour eggs are adhesive. Threats: Declining population is due to high fishing pressure and habitat loss from rapid urbanization. Conservation action: The Central Institute of Freshwater Aquaculture, India has started working intensively on its propagation and feed development (Sahoo et al. 2005, 2008; Giri et al. 2005). Seven other national Institutes are presently involved on its artificial propagation, sponsored by Indian Council of Agricultural Research, New Delhi. Recommendations: Mass production through hatchery operations, rearing young in natural waters and aquaculture of this species are necessary to restore populations. Remark: Ironically, it is recommended for monoculture in south-east Asia due to its high production potential and market demand. Environ Biol Fish (2010) 88:85–86 DOI 10.1007/s10641-010-9627-8

Effects of Latency Periods and Injection Doses with Carp Pituitary Extract on Spawning Performance and Egg Quality of Asian Catfish, Clarias batrachus (Linn.)

ABSTRACT An experiment was conducted to evaluate the spawning performance and egg quality of Clarias batrachus at variable latency periods (11, 14, 17, 20, and 23 h) and doses of carp pituitary extract (10, 20, 30, 40, and 50 mg/kg). The fish could not be stripped at 11 h latency with 10 or 20 mg carp pituitary extract (CPE). The highest quantity of eggs was obtained at 14 to 23 h latency with 30–40 mg CPE or 50 mg CPE with 14 to 17 h latency, which did not vary significantly (P < 0.05) at a water temperature of 27°C–28.5°C. The eggs did not fertilize and hatch when stripped at 11-h latency period. Over 80% of total eggs stripped from females injected with 30 and 40–50 mg CPE per kg body weight, and stripped at 14 to 23 h and 14- to 17-h latency, respectively, were fertilized. However, the highest (P < 0.05) number of larvae was obtained from females injected with 40 mg CPE and stripped at 14 or 17 h latency periods. Therefore, this CPE dose and 17 h latency period combination was regarded as the best for obtaining the highest number of larvae during induced spawning of C. batrachus.

Molecular characterization, tissue distribution and differential nutritional regulation of putative Elovl5 elongase in silver barb (Puntius gonionotus)

Fatty acid desaturase (Fads) and elongase (Elovl) are two important enzymes involved in the biosynthesis of long-chain polyunsaturated fatty acids (LC-PUFAs) in fishes. Silver barb (Puntius gonionotus) is considered a promising medium carp species for freshwater aquaculture in Asia. Earlier, Δ6 fads cDNA was characterized to understand the molecular mechanism of LC-PUFA biosynthesis in this species. In the present study elovl5-like elongase full-length cDNA was cloned and characterized by RACE (rapid amplification of cDNA ends), and analyzed its basal expression in various organs/tissues by quantitative real time PCR (qRT-PCR) assay. Differential expression of elovl5 cDNA in various tissues following replacement of fish oil (FO) with linseed oil (LO) in the diet also studied. The full length cDNA sequence of silver barb elovl5-like elongase consisted of 1853bp, including an open reading frame (ORF) of 876bp encoding a precursor protein of 291 amino acids possessing the entire characteristic features of Elovl protein. The elovl5 transcript was constitutively expressed in all the tissues examined: muscle, liver, brain, kidney, skin, intestine, gill and eye. The expression of elovl5 gene was upregulated, whereas the serum biochemical constituents were either remain unchanged or lowered following replacement of FO with LO in the diets. We report for the first time, an in silico 3D structure model of elongase protein from silver barb. All these findings may contribute to a better understanding the potential regulatory mechanisms involved and may be useful for enhancing endogenous LC-PUFA production in silver barb.