Effects of C/N controlled periphyton based organic farming of freshwater prawn on water quality parameters and biotic factors

The effects of C:N controlled periphyton based organic farming of freshwater prawn on water quality parameters and biotic factors were investigated. The experiment had two treatments: T1 and T2 each with three replications. Stocking density was maintained at 20,000 juveniles ha-1. In T1, only commercially available prawn feed was applied and in T2, a locally formulated and prepared feed containing 24% crude protein with C:N ratio close to 20 was used, and maize flour and bamboo side shoots were provided for maintaining C:N ratio 20. Mean values of water quality parameters did not vary significantly (P>0.05) between treatments. Periphytic biomass in terms of dry matter, ash free dry matter (AFDM) and chlorophyll a showed significant difference (P<0.05) among different sampling months. Individual harvesting weight, individual weight gain, specific growth rates, gross and net yields of prawn were significantly higher (P<0.05) in T2 than T1. Therefore, it was concluded that freshwater prawn might consume periphyton biomass in C:N controlled periphyton based organic farming practices resulted a significantly (P<0.05) higher production of freshwater prawn than traditional farming

Study on the Socio-Economic Condition of Fishermen of the Punorvaba River under Sadar Upazila, Dinajpur

The present study was conducted to evaluate livelihood status of fishing community of the Punorvaba River under Dinajpur Sadar Upazila during the period from January to August, 2013. The livelihood status of fishermen were studied in terms of age structure, family size and type, occupation status, educational status, housing condition, drinking water facilities, sanitary facilities, health facilities, credit facilities and monthly income. It was found that most of the fishermen were belonged to the age groups of 36-45 years (40%), represented by 90% Muslim. The family size of fishing community is usually consisted of 5-7 members. Over 45% of the fishermen primarily engaged in fishing. Among them 50% was illiterate and 7% was SSC and above group. About 40% of the fishermen received health service from village doctors, 23% from upazila health complex and remaining 7% got health service from MBBS doctors. Some management strategies such as prohibition of catching brood fish, control of destructive gears, establishments of fish sanctuaries, release of fish fry have been suggested by the fishermen to stop the decreasing trend in the fish catch and to enhance fish production

Morphological relationships, growth patterns and some aspects of reproductive biology of Sind Danio Devario devario (Hamilton 1822)

This study examined the morphological relationships, growth population factors and reproductive biology of Devario devario collected from the Atrai River of Dinajpur, Bangladesh, for sustainable management and conservation aspects. The length-weight relationships (LWRs) commonly indicated the isometric growth. The Fulton’s condition factor (CFf) and relative body weight (BWr) varied across sexes. A positive correlation was found in length-length relationships (LLRs); among total length (TL), standard length, head length and fork length. The asymptotic lengths were 7.5, 7.2 and 7.5 cm, with growth rates of 0.78‒1.8, 0.6‒3.4 and 1.8‒3.6 year–1 while total mortality was 1.22‒3.06, 0.97‒7.07 and 3.70‒6.09 year–1; fishing mortality was –0.87 to –1.04, –0.97 to 1.09 and –0.05 to –0.23 year–1; natural mortality was 2.26–3.93, 1.94–5.98 and 3.93–6.14 year–1 for female, male and combined sexes respectively. The highest probability of capture (L50) was 5.74‒6.15 cm. The gonado-somatic index ranged from 32.75±1.82 to 44.12±2.73, with a peak in April to May. Fecundity was recorded from 3253±289 to 4831±342, with a significant correlation among TL, BW, gonad length (GL) and gonad weight (GW). These initial findings on D. devario will serve as the basis for future research and management

Evaluation of production performance and profitability of hybrid red tilapia and genetically improved farmed tilapia (GIFT) strains in the carbon/nitrogen controlled periphyton-based (C/N- CP) on-farm prawn culture system in Bangladesh

Performance of hybrid red tilapia (Mutant, Oreochromis niloticus × Oreochromis mossambicus) and GIFT tilapia strain (Oreochromis niloticus) in C/N-CP prawn (Macrobrachium rosenbergii) farming system was evaluated at the farmers' pond at Bailor union under Trishal upazilla of Mymensingh district, Bangladesh. The on-farm trial had two treatments: TR and TG (named according to the tilapia strains) with three replications. Six rectangular ponds of varying sizes (400–880 m2) were used for this experiment. Hybrid red and GIFT tilapia stains were stocked with prawn at the stocking densities of 1 tilapia fingerlings (either red or GIFT strain) and 3 prawn juveniles m-2 in both treatments. Bamboo side shoot were posted vertically as periphyton substrate. This resulted in an additional substrate surface area of 1067 m2 for periphyton development equaling 147% of the pond surface area. Considering the body weight of freshwater prawn only, feeding rates were 10% of body weight at the beginning of the study (up to 30 days), and feeding application was gradually reduced to 3% in the last month assuming 80% survival. The abundance of total benthos and periphyton as well as total periphytic biomass were significantly higher (P < 0.05) in TR than TG treatment and they were also differed significantly (P < 0.05) among different months with a decreasing trends (exception to some extent) over the experimental period. The individual harvesting weight, individual weight gain, specific growth rate, Food Conversion Ratio (FCR), survival (%), gross and net yields of prawn were similar in two treatments. In contrast, the GIFT tilapia strain showed a higher (P < 0.05) individual harvesting weight, individual weight gain, specific growth rate ((SGR, % bw d-1), survival, gross and net yields (1935 and 1825 kg ha-1, respectively) combined gross and net yields (2952 and 2784 kg ha-1, respectively), and economic return (3755 US$ with BCR 0.82) than the hybrid Red tilapia