Abstract:The occurrence and abundance of cyanobacterial population was monitored monthly in two urban fish ponds in Rajshahi City Corporation area from January to December, 2006. The bloom was observed in March, August and September. Some environmental parameters such as water temperature, transparency, pH, Dissolved Oxygen(DO), free Carbon dioxide(CO 2 ), Biological Oxygen Demand (BOD), NO 2 -N, NH 3-N, NH 4 + , toxic ammonia, Oxidation reduction Index (rH 2 ) were recorded and their relationship with the bloom formation by cyanobacteria are discussed. During the study period 23 species of cyanobacteria were identified. Among which Microcystis, Anabaena, Planktothrix were found to be the dominant genera. Microcystis aeruginosa was the most dominant species during the bloom period. At the peak bloom period, Microcystis aeruginosa comprised 81.64% and 83.24% of total cyanophyceae in pond-1 and pond-2, respectively. The initiation and persistence of natural bloom of cyanobacteria, especially Microcystis was found to be triggered by relatively high temperature (33.21-33.53 o C), alkaline pH (8.8), and nutrient enrichment especially high NO 2 -N, NH 3 -N, and NH 4 + concentration.

The present study compared the effectiveness of the Carp pituitary gland extract (PGE) and the synthetic hormone Ovaprim on spawning success of the stinging catfish, Heteropneustes fossilis during induced breeding. The PGE hormone was administered at 6 mg/kg of body weight for females and 2 mg/kg of body weight for males. In contrast, Ovaprim was administered at 0.3 ml/kg body weight and 0.1 ml/kg of body weight for females and males, respectively. The spawning success was higher in the Ovaprim-induced individuals with better performance recorded at all stages of spawning including latency period, ovulation, fertilization, hatching and incubation period compared to the PGE-induced individuals. In the Ovaprim induced individuals, the latency period occurred within 10 hours while in PGinduced individuals, the latency was after 15 hours. Similarly, ovulation rate was 90% for Ovaprim injected fish but lower 78.7% for PGE injected fish. Higher rate of fertilization was observed in the eggs of Ovaprim treated fishes 86.7% compared to 69.2% in PGE induced fish. On the other hand, hatching rate was 76.9% in eggs spawned from Ovaprim induced individuals compared to 72.7% in PGE induced fish and the incubation period was also shorter at 3.5 h for eggs from Ovaprim-induced fish while the PGE induced fish eggs required a 5-h incubation period. Finally, the results showed that Ovaprim treated fish yielded better results compared the PGE treated fish in terms of ovulation, fertilization and hatching rates of H. fossilis.

Zooplankton constitute important food item of many omnivorous and carnivorous fishes. The study was conducted with an aim to study the zooplankton production including physico-chemical parameters with an emphasis to the existing management practices taken by the operators. The study was carried out in a culture and a non-culture pond of Rajshahi University campus was carried out from September, 2004 to February, 2005. Monthly fluctuations of some physico-chemical parameters were noted. The ponds showed alkaline in nature with moderate bicarbonate alkalinity. Diurnal change of water temperature, free CO 2 and dissolved Oxygen were also studied. Four groups of zooplankton were identified, of which copepods (1260 units/l and 973.33 units/l in pond-1 and pond-2 respectively) were most dominant. A total of 9 genera of zooplankton were identified of which Cyclops (68.25% and 60.28% of total copepods) was most abundant in both ponds. Total zooplankton showed positive correlation with pH, carbonate alkalinity (CO 3 ) and bicarbonate alkalinity (HCO 3 ) in both ponds and DO, carbon dioxide (CO 2 ) in pond-1. Present findings indicated that the culture pond showed better result than that of the non-culture pond regarding zooplankton production.

Paratya australiensis Kemp (Decapoda: Atyidae) is a widely distributed freshwater shrimp in eastern Australia. The species has been considered as an important stream organism for studying genetics, dispersal, biology, behaviour and evolution in atyids and is a major food source for stream dwelling fishes. Paratya australiensis is a cryptic species complex consisting of nine highly divergent mitochondrial DNA lineages. Previous studies in southeast Queensland showed that “lineage 4” favours upstream sites at higher altitudes, with cooler water temperatures. This study aims to identify putative selection and population structure between high elevation and low elevation populations of this lineage at relatively small spatial scales. Sample localities were selected from three streams: Booloumba Creek, Broken Bridge Creek and Obi Obi Creek in the Conondale Range, southeast Queensland. Six sample localities, consisting of 142 individuals in total were sequenced using double digest Restriction Site Associated DNA-sequencing (ddRAD-seq) technique. Among the 142 individuals, 131 individuals shared 213 loci. Outlier analysis on 213 loci showed that 27 loci were putatively under selection between high elevation and low elevation populations. Outlier analysis on individual streams was also done to test for parallel patterns of adaptation, but there was no evidence of a parallel pattern. Population structure was observed using both the 27 outliers and 186 neutral loci and revealed similar population structure in both cases. Therefore, we cannot differentiate between selection and drift here. The highest genetic differentiation was observed between high elevation and low elevation populations of Booloumba Creek, with small levels of differentiation in the other two streams.

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