Journal of Fisheries

Multiplex-PCR protocol development for rapid screening of white spot syndrome virus (WSSV) in shrimp

2020-11-25T20:31:34+00:00

This study was aimed to develop a faster single step multiplex PCR protocol for the simultaneous detection of white spot syndrome virus (WSSV) with its host (i.e. shrimp) as internal positive control. To do so, four combinations of primer were tested (I. 16S rRNA+Lo F1R1; II. 16S rRNA+Lo F2R2; III. 16S rRNA+Lo F1R2; IV. 16S rRNA+Lo F2R1) which were selected based on two pairs of WSSV specific primer (Lo F1R1 and Lo F2R2) and one pair of shrimp specific primer (16S rRNA). DNA extracted from WSSV infected shrimp were amplified by PCR in a single tube using each of the primer combinations and the thermal cycling conditions as well as reagent compositions were optimized. All the primer combinations yielded their expected band sizes with stronger band resolution intensity that indicated the development of four multiplex PCR protocols. The developed multiplex protocols reduced the chance of cross contamination and these were found to be faster, single step and unique with less effort and resource use. Considering sensitivity and specificity, among the protocols, we suggested the protocols based on 16S rRNA+Lo F1R1 and/or 16S rRNA+Lo F2R2 primer combinations for rapid and routine screening of WSSV in shrimp PL, juvenile and adult.

Are haematological and biochemical properties of freshwater spotted snakehead Channa punctata (Bloch, 1793) season and sex dependent?

2020-11-22T21:06:58+00:00

Freshwater murrel, Channa punctata commonly known as “spotted snakehead” is a popular fish because of its taste and price. Haematological and biochemical profile of fish helps in understanding the fish health and play an important role in fisheries management. The present work was carried out to determine season (summer, monsoon and winter) and sex dependent variations in the blood profile of C. punctata. Haematological [red blood cell counts (RBC), packed cell volume (PCV) and haemoglobin (Hb)] and serum biochemical parameters [blood glucose, total protein, cholesterol, triglyceride (Tg), low density lipoprotein (LDL), very low density lipoprotein (VLDL), high density lipoprotein (HDL), serum calcium levels] of C. punctata were analysed which varied significantly with seasons (p < 0.05). The level of glucose, total protein, Tg, VLDL, RBC, Hb and PCV was low during monsoon season because of the growth and development of gonads compared to the summer and winter season. The level of cholesterol and LDL was high during monsoon. However, haematological and biochemical parameters were not sex dependent. The seasonal haematological and biochemical variations in the fish were mainly due to the physiological acclimatisation of the fish to variations in the environmental condition and feeding regime.

Delineation of seven species of genus Channa from upper Assam region, India using sagittal otolith morphology

2020-10-12T20:07:56+00:00

Morphology of sagittal otoliths of seven species of genus Channa from upper Assam, India was studied to obtain baseline information for their prospective role in taxonomic studies. In the present study, variations were recorded in morphological characteristics of sagittal otolith among the studied species. Of all the studied parameters, otolith shape, sulcus acusticus, ostium, and cauda, in particular, were found to be taxonomically important features for the identification of the species. The pentagonal shape of sagitta in Channa punctata, pseudo-ostiocaudal sulcus acusticus in C. marulius, bent concave ostium in C. stewartii, straight cauda in C. bleheri were found to be species-specific features. Sagitta size was smallest in C. gachua while the largest was recorded in C. striata. The proposed taxonomic keys enumerated through the combination of different otolith characters from the present investigation will be useful in the identification of these species when standard methodologies fail to deliver satisfactory results.

Quality and shelf life of vacuum- and nitrogen-packed dried barb fish (Puntius spp.)

2020-09-26T16:33:16+00:00

Vacuum and modified atmosphere packaging are widely used for preserving food items including fish. In this context, the quality and shelf life of air- (control), vacuum- and nitrogen-packed dried barb fish (Puntius spp.) stored at ambient temperature were evaluated through biochemical and microbial analyses for 90 days. In most of the storage days, significantly lower values of moisture, total volatile base-nitrogen (TVB-N) and peroxide value (PV) were observed in the vacuum pack sample compared to control. However, the TVB-N, PV, total coliforms and faecal coliforms counts were within the acceptable limit in all groups. The total plate count (TPC) increased gradually with time from an initial value of 4.29 log CFUg^–1. However, compared to control, significantly lower TPC were found on and after the 30^th day of storage in vacuum and nitrogen pack samples. Considering the TPC value of 5 log CFUg^–1, the shelf life was determined at approximately 15 days for control, 35 days for nitrogen pack and 45 days for vacuum pack samples. Therefore, the vacuum pack is considered the best packaging, which may be utilised by the processors to produce and retail the dried products with prolonged shelf life.

Relationship between cortisol and glucose as physiological stress indicators during growth season in juvenile Siberian sturgeon Acipenser baerii

2020-09-21T16:15:45+00:00

The relationship between cortisol and glucose was studied in two-year old farmed Siberian sturgeon Acipenser baerii with a body weight of 340±30 g (mean ± SD) and total length of 45±1 cm from August to November 2017. Thirty-six individuals were randomly selected and stocked in some 3×300 L fiberglass tanks. Blood samples were collected monthly from the tagged fish. The mean cortisol in August, September, October and November were 4.7±0.9, 23.5±3.0, 6.3±0.9 and 7.4±0.9 ng mL^–1 respectively whereas glucose concentrations were 44.6±0.4, 27.3±0.6, 49.2±0.7 and 48.5±0.7 mg dL^–1 respectively indicating a significant increase in cortisol and decrease in glucose in September, may be due to the exposure to prolonged high temperature (26–28.5°C). Although it was expected to happen naturally due to hyperglycemia of cortisol but no such phenomena was detected. Our results suggest that the consumption of glucose for maintenance of homeostasis and physiological status is a mechanism against the non-optimal thermal regime. This mechanism consumes glucose at a rate higher than that produced by cortisol, causing significant decrease of plasma glucose. In general, there was a reverse relationship between cortisol and glucose concentration during the experiment in Siberian sturgeons.