The blue mussel (Mytilus edulis) is known as a robust bivalve species, although its larviculture appears to be highly susceptible to diseases. In this study, we isolated 17 strains from induced mortality events in healthy wild-caught blue mussel adults and demonstrated that they caused between 17% and 98% mortality in blue mussel larvae in a newly developed, highly controlled immersion challenge test model. Eight of the isolates belong to the Splendidus clade of vibrios, while the other isolates belong to the genus Photobacterium. The genomes of the most virulent Vibrio isolate and the most virulent Photobacterium isolate were sequenced and contained several genes encoding factors that have previously been linked to virulence towards bivalves. In vitro tests confirmed that all 17 isolates were positive for these virulence factors. The sequenced genomes also contained a remarkably high number of multidrug resistance genes. We therefore assessed the sensitivity of all isolates to a broad range of antibiotics and found that there were indeed many strong positive correlations between the sensitivities of the isolates to different antibiotics. Our data provide an ecological insight into mass mortality in blue mussels as they indicate that wild mussels contain a reservoir of pathogenic bacteria.
The main aim of this study was to assess the effect of water depth on the growth performance (length and weight) of table size Indian major carp (Gibelion catla, Labeo rohita, and Cirrhinus mrigala) fi shes. Fishes were recorded under different depth (1.20 m, 1.80 m and 2.80 m) for about eight months from February 2016 to September 2016. Water depth was considered as treatment 1 (T 1 ) for 1.20 m, treatment 2 (T 2 ) for 1.80 m and treatment 3 (T 3 ) for 2.80 m, respectively. Randomized Complete Block Design (RCBD) with two replications of each treatment was differentiated at signifi cant level 0.05. Various water quality parameters such as water temperature, dissolve oxygen, transparency, and pH were also recorded. The survival rate was found maximum (99.23±0.4%) for Labeo rohita fi sh at 2.80 m water depth and lowest (95±2.1%) survival rate was observed for Gibelion catla fi sh at 1.20 m water depth. Results of this study showed that Gibelion catla, Labeo rohita and Cirrhinus mrigala fi sh cultivated at four feet depth of water produces lowest average weight of 1398 g, 1048 g and 1050 g, respectively with an average length of 47 cm, 49.2 cm and 46.4 cm, respectively. The maximum average weight of fi sh 3667 g, 2700 g and 2800 g were obtained at 2.80 m depth of water with the maximum average length of 63.2 cm, 60.0 cm and 58.6 cm for Gibelion catla, Labeo rohita and Cirrhinus mrigala fi sh, respectively. From this study, it can be observed that the fi shes cultivated at low depth of water yielded lowest, and shorter in length in contrast to the carps cultivated at higher depth of pond water. However, growth of Gibelion catla was notably high among other carps.
This study was conducted to assess the growth performances of cage reared GIFT strain of tilapia (Oreochromis niloticus) fingerling using length-weight (LW) relationship technique. Along with this, condition factor (K) of fish and pond water quality parameters were also brought under this study to have broader understanding. For LW relationship and K, a sample size of 120 fingerlings was made from randomly selected three different cages in a pond at Tarala village in Kaharole Upazila of Dinajpur District, Bangladesh. The length-weight relationship of tilapia fingerlings reared in cages managed by Adivasi people was significant. The value of correlation coefficient (r) and the coefficient of determination (r2) were 0.97 and 0.94 respectively. This suggests that growth of tilapia from fry to fingerling was normal in cages. The condition factor of different size group of fish was almost closed to 2, indicating fish health as satisfactory. All the water quality parameters including temperature, transparency, dissolved oxygen,ammonia-nitrogen, phosphate-phosphorus, nitrate-nitrogen and pH were within suitable range both in cages and outside the cage in pond. About 5 phyla and 25 genera of phytoplankton from Bacillariophyceae, Cyanophyceae, Chlorophyceae, Euglenophyceae and Rhodophyceae groups and one phylum and 5 genera of zooplankton from Rotifera group were found in cage installed in ponds. These all indicate the growth of tilapia fingerling in cages was satisfactory which was technically sound for landless adivasi households. DOI: http://dx.doi.org/10.3329/jbau.v10i1.12107 J. Bangladesh Agril. Univ. 10(1): 149155, 2012
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