Effect of substituting live feed with formulated feed on the reproductive performance and fry survival of Siamese fighting fish, Betta splendens (Regan, 1910)

This study aimed to elucidate the effect of partial or complete replacement of live feed (LF) (Tubifex) with formulated feed (FF) on the reproductive performance of Betta splendens. Three hundred B. splendens fry (average weight 0.19 ± 0.01 g) were equally distributed into five different groups, each with three replicates. They were fed for 105 days with following different diets: control (C)—100% LF; T1—75% LF, 25% FF; T2—50% LF, 50% FF; T3—25% LF, 75% FF, and T4—100% FF. Results showed that the average number of hatched larvae (654 ± 101) and fry survival after 2 weeks of rearing (428 ± 70), after completion of three spawning, were recorded highest in the control group, which was, however, not significantly different from the T1, T2, and T3 groups. At the end of the feeding trial, the highest hatching percentage (90.3%) was registered in the T2 group, which was not significantly different from the control and T1 groups. The T2 group also recorded highest fry survival (65.54%) after completion of three spawning, which was not significantly (P < 0.05) different from the T1 and T3 groups. Control diet contained higher saturated fatty acid (63.23%) than formulated diet (29.80%). In the whole-body tissue, highest level of EPA (0.42%) and DHA (3.13%) were found in the T4 group followed by T3 group. The DHA/EPA ration was recorded highest in the T2 group (10.96%), which did not differ significantly from the T1 and T3 groups. Significant positive correlation was observed between saturated fatty acid levels in fish whole-body tissue and number of hatched larvae (Y = 30.81 × −825.3, R ² = 0.968) and fry survival after 2 weeks of rearing (Y = 21.38 × −580.9, R ² = 0.967). Considering all these factors, it can be concluded that the live feed Tubifex can be replaced up to 50% without any adverse effect on the reproductive performance and fry survival of B. splendens.     

Replacement of live feed by formulated feed: effect on the growth and spawning performance of Siamese fighting fish (Betta splendens,Regan, 1910)

Partial replacement of live feed (LF) with formulated feed (FF) was performed in Betta splendens to evaluate their growth, survival and reproductive performance. Three hundred B. splendens fry of uniform size (mean weight 0.19 g±0.01) were equally distributed in five treatment groups with each of three replicates in glass aquaria of 35 L capacity. Fish were offered diets of different ratio of LF and FF like T1 (control) – 100% LF; T2 – 75% LF, 25% FF; T3 – 50% LF, 50% FF; T4 – 25% LF, 75% FF and T5 – 100% FF. Highest (P<0.05) body weight gain (% BWG) (67.1±1.03) and specific growth rate (2.34±0.02) were observed in the T2 group. Best feed conversion ratio was also found in T2 (2.40±0.11), which was similar to T1 and T3. The highest survival rate (%) was recorded in T1, T2 and T3 groups (97±1.7), which was similar to T4 and the lowest in T5 (49±2.0). The highest gonadal weight (0.12 g±0.01) and gonadosomatic index (15.17±0.50) was observed in the T3 group during the first sampling after 63 days. No significant changes in spawning performance were observed in the second sampling after 21 days after first sampling. However, T4 group registered the highest fecundity and fertilized eggs at the end of 105 days of experiment. From the present study, it concludes that LF can be successfully replaced to the extent of 25% by FF without any detrimental effect on the growth, survival and spawning performance of B. splendens.     

Effect of alternate day feeding strategy of sub-optimal protein level on haemato-biochemical responses in Labeo rohita (Hamilton) juveniles

A feeding trial was conducted for 60 days to delineate the effect of alternate day feeding strategy of sub‐optimal protein level on haematological parameters, serum parameters and phagocyte respiratory burst activity (NBT) in Labeo rohita juveniles. One hundred and thirty‐five fingerlings (1.87 ± 0.01–2.26 ± 0.05 g) were distributed in triplicate groups of each treatment, and fish were fed at 5% body weight daily. Three experimental isocaloric (401.32–410.28 kcal/100 g) diets of 30%, 25%, and 20% crude protein designated as diet A, diet B, and diet C respectively, were prepared, using locally available feed ingredients. Three different feeding schedules of normal protein diet continuously (diet A‐30%), alternate feeding of 1‐day diet A followed by 1‐day diet B (1A/1B) and alternate feeding of 1‐day diet A followed by 1‐day diet C (1A/1C) were tested. The total erythrocyte count and haemoglobin content was significantly (p < 0.05) enhanced in the group T1 fed (1A/1B), and the lowest count was recorded in the group T2 fed (1A/1C). Total leucocyte counts, total serum protein, and serum globulin were higher in the group T1 fed (1A/1B) and lower in the group T2 fed (1A/1C) as compare to control. The respiratory burst activity (NBT) of blood phagocytes and serum A‐to‐G ratio was recorded significantly difference in among the treatment groups. Based on the results of the present study, it is concluded that alternate feeding of 1‐day diet A followed by 1‐day diet B (1A/1B) is equally effective and promote the immunity in Labeo rohita juveniles.     

Aquaculture practices in Northeast India: Current status and future directions

The northeast region of India, comprised of the states of Arunachal Pradesh, Assam, Manipur, Meghalaya, Mizoram, Nagaland, Sikkim, and Tripura, is blessed with rich biodiversity and fisheries resources. With more than 90% of population being fish eaters, there is heavy demand for fish but a wide gap exists between supply and demand. The region produces over 0.214 million tons of fish annually, with almost 50% coming from aquaculture. Aquaculture development in the region is taking place at a rapid rate. However, efforts are necessary to increase the present level of production through both horizontal and vertical expansion. The region has rivers, coldwater streams, floodplain wet lands, reservoirs, lakes, ponds, paddy fields, and mini-barrages to support large-scale aquaculture activities, which can not only produce fish to meet regional requirements, but also export the surplus. This paper describes and discusses the current status of aquaculture, production level, constraints, and future directions towards achieving “fish for all” in the region.     

Effect of dietary supplementation of periphyton on growth,immune response and metabolic enzyme activities in Penaeus monodon

A 60‐day indoor trial was conducted to study the effect of periphyton supplementation on metabolic and immune responses in tiger shrimp, Penaeus monodon. Periphyton developed over bamboo substrate in outdoor tanks (15 m²) was used as dietary supplement for P. monodon (2.02 ± 0.04 g) reared in 1000 L FRP tanks. Graded levels of periphyton were included in shrimp basal diets: 0% (P0), 3% (P3), 6% (P6), 9% (P9) and P0 diet with natural periphyton (NP) over bamboo substrate. At the end of the trial, P6 and NP showed significantly higher (P < 0.01) growth rate, 23.9% and 20%, respectively, compared with control, P0. Comparatively, lower level of metabolic enzymes, such as lactate dehydrogenase, malate dehydrogenase, aspartate aminotransferase and alanine aminotransferase, was recorded in treatments P3, P6 and NP compared with control, P0. The periphyton‐supplemented group, P3 had significantly higher (P < 0.05) superoxide dismutase (15.83 ± 0.96) and catalase activity (15.73 ± 0.69) compared to 6.88 ± 2.84 and 9.15 ± 0.67 unit mg^?1 protein min^?1_, respectively, in P0. Similarly, higher total haemocyte counts, 32.58 ± 1.30, 28.51 ± 3.12 and 27.26 ± 4.43 × 10⁶ cells mL^?1_, were recorded in P6, NP and P3, respectively, compared to P0, 23.57 ± 1.80 × 10⁶ cells mL^?1. After challenge with Vibrio harveyi, P3 recorded the highest relative percentage survival 67% followed by NP (58%) and P6 (42%) compared with control. However, treatment with highest periphyton inclusion (P9) did not differ significantly with P0 on growth and immunological parameters. This study indicates that periphyton supplementation at 3–6% level improves growth, immune response and metabolic activities in P. monodon.     

Higher water temperature enhances dietary carbohydrate utilization and growth performance in Labeo rohita (Hamilton) fingerlings

A 60-day experiment was conducted to delineate the effect of three dietary levels of gelatinized carbohydrate (GC) on growth, nutrient-utilization and body composition of Labeo rohita fingerlings (avg. wt 6.5 ± 0.3 g) reared at two water temperatures (ambient-AT (26 ± 0.8 °C) and 32 °C). Two hundred and sixteen fingerlings were randomly distributed into six treatments in triplicates. Three semi-purified isonitrogenous diets were prepared with graded levels of GC viz. D(1) : 40%, D(2) : 50% and D(3) : 58%. Growth rate, feed efficiency and protein efficiency ratio were significantly (p < 0.05) higher in 50% GC and 32 °C reared groups than their AT counterparts. Hepato Somatic Index was higher in AT reared groups compared to 32 °C reared counterparts. Apparent digestibility co-efficient of carbohydrate was significantly (p < 0.05) higher at 32 °C reared groups but decreased with increasing carbohydrate (GC) levels. Fish reared at 32 °C showed significantly (p < 0.05) higher amylase, protease and hexokinase activities while glucose-6-phosphate dehydrogenase and glucose-6-phosphatse were significantly (p < 0.05) higher at ambient temperatures. The results obtained in present study indicated that L. rohita could utilize higher level (50%) of dietary carbohydrate at 32 °C.     

Metabolic and digestive enzyme activity of Pangasianodon hypophthalmus (Sauvage, 1878) fingerlings in response to alternate feeding of different protein levels in the diet

A feeding trial was conducted for 90 days to assess the metabolic and digestive enzyme activity in response to alternate or mixed feeding of different protein levels in the diet of Pangasianodon hypophthalmus fingerlings. One hundred and forty four fingerlings with an average weight of 5.0–5.5 g were distributed into four experimental groups each with triplicate. Four iso‐caloric diets with varying level of crude protein viz., 35%, 30%, 25% and 20% were made and designated as diet 35P, 30P, 25P and 20P respectively. Four treatments were maintained based on four different feeding schedules such as continuous feeding of diet 35P (35P/35P), alternate feeding of 1 day diet 35P next day diet 30P (35P/30P), alternate feeding of 1 day diet 35P next day diet 25P (35P/25P) and alternate feeding of 1 day diet 35P next day diet 20P (35P/20P). As a result, specific growth rate (SGR) and weight gain percentage were relatively higher in treatment (35P/25P) followed by (35P/35P) and (35P/30P). The metabolic enzymes such as lactate dehydrogenase (LDH), malate dehydrogenase (MDH), glucose‐6‐phosphate dehydrogenase (G6PDH), Glucose‐6‐phosphatase (G6Pase), alkaline phosphatase (ALP), acid phosphatase (ACP), alanine aminotransferase (ALT), aspartate aminotransferase (AST) were expressed better in (35P/35P) group followed by (35P/25P) and (35P/30P) groups. The digestive enzymes, protease and lipase activities were higher in (35P/35P) and (35P/25P) groups. The present study revealed that the better nutrient utilization and growth of 35P/25P group is because of their balanced digestive and metabolic enzyme activities through alternate level of higher and lower protein diet.