International Journal of Aquatic Biology
Volume:3 Issue: 1, Feb 2015

Our plankton and semi-plankton collections from twelve floodplain lakes (beels) of Majuli River Island, Upper Assam reveal 124 rotifer species (32 genera and 17 families); these merit biodiversity value as ~52.0% and ~30.0% of species, ~68.0 and ~45.0% of genera and ~74.0 and ~65.0% of the families of the Phylum known from northeast India (NEI) and India, respectively. Two species are new to India with Trichocerca uncinata as new record to the Oriental region. Eleven species are new to the study area and we provide an updated list (144 species) for following meta-analyses of Majuli Rotifera. Biogeographically important elements include one Australasian, four Oriental, four Palaeotropical and one cosmo (sub) tropical species while several species are of regional distribution interest. The rotifer fauna is predominantly tropical and Lecanidae > Lepadellidae collectively include ~53.0% species but it records paucity of Brachionus species. Individual beels record total richness of 60-100 (77 ± 12) species, monthly richness between 24 ± 7-34 ± 7 species and maximum up to 54 species/sample. The results are characterized by high community similarities (59.7-90.4% vide Sørensen’s index), more rotifer homogeneity amongst beels, lack of any pattern of temporal richness variations and much limited influence of abiotic parameters.

This report provides the first record of the exotic sucker fish P. pardalis from the Cauvery river system, Tamilnadu state, India. Information on the assumed presence of this invasive species based on sightings of a hitherto unknown species by local people and fishermen in stretches of Cauvery river have been confirmed by our study. Sailfin sucker fishes are popular among pet traders and aquarists in south east Asian countries and have been regarded as invaders worldwide. Occurrence of P. pardalis in newer habitats due to its potential invasion in the South Indian waters issues threat to native fauna.

The potential of Marine Actinobacteria particularly Streptomyces as a single cell protein (SCP) feed for the growth of ornamental fish, Xiphophorus helleri has been investigated. The Streptomyces strains used as SCP were isolated from the marine sponges, namely Callyspongia diffusa, Mycale mytilorum, Tedania anhelans and Dysidea fragilis. Six SCP feeds were prepared and their effects were compared with those of control diet. After 30 days of feeding trials, the growth parameters including absolute growth rate, specific growth rate and feed conversion efficiency were found to be significantly (P<0.001) higher in groups that received SCP feed than those of control one, whereas feed conversion ratio was lower. Thus it was found that in addition to being effective antibiotic agents against harmful pathogens, Streptomyces could also promote the growth of fish effectively. Marine Actinobacteria, particularly Streptomyces, could play an important role as a single cell protein (SCP) in aquaculture nutrition and is a promising microbe for the development of marine biotechnology.

Garra rufa, a bottom dwelling freshwater fish and native to the Middle East, is distributed in the southwestern of Iran and the Tigris basin. Considering the importance of length-weight relationships data of a species in different habitats, the length-weight relationship of G. rufa from 13 rivers in the Persian Gulf and the Tigris basins was explored. The value of exponent b ranged from 2.74 to 3.19 with average of 2.99 in the Tigris basin and 2.96 in the Persian Gulf basin which was in normal range (2.5-3.5). As the length-weight parameters were concluded for each location separately, this information would be useful for further population dynamics researches.

The histological analysis, disposition and histochemical localization of tryptophan were investigated in the pancreas to compare the cellular organization and histochemical characterization in the pancreas of Labeo rohita (Hamilton, 1822), Mystus vittatus (Bloch, 1790) and Notopterus notopterus (Pallas, 1769) having different feeding habits. Histological analysis demonstrated that the exocrine pancreatic tissues were dispersed within the hepatic parenchyma and spleen in L. rohita. Thin septa of connective tissue separated parenchyma of liver and also the spleen from exocrine pancreatic cells. However, in M. vittatus, the discrete pancreatic tissue formed distinct oval or elongated acini interspersed with small area of islet of Langerhans and blood vessels. In N. notopterus, the rhomboidal acinar cells of discrete pancreatic tissue intercalated with comparatively clear and large islet of Langerhans. The exocrine acinar cells in all the three species were provided with prominent nuclei and densely packed zymogen granules. Histochemical localization revealed that the zymogen granules of exocrine acinar cells of all species exhibited varied intensities of tryptophan reaction, the precursor of various pancreatic enzymes which may be related to the food and feeding habits of the fishes under study.

We collected Silver bream Blicca bjoerkna from March to July 2013 from Aras Dam Lake (North-west of Iran) and investigated its age, size, and some biological characteristics. The maximum age was 5+ years. The total length and weight of specimens ranged 137-278 mm and 26-247 g for male and 134-282 mm and 26-289 g for female, respectively. Length-weight relationship was estimated as W = 1E-06TL3.44 for females, W = 1E-06TL3.45 for males and W = 1E-06TL3.44 for the sexes combined. Sex ratio was 1:1.42 in favor of males. The growth model was positive allometric for males, females and sexes combined. The calculated maximum condition factor was 0.34 in male and 0.37 in female. The most frequent age classes in the samples were 2+ years for males and females.

The fish assemblage and diversity in relation to water quality of three coastal rivers Sita, Swarna and Varahi of Udupi district, Karnataka, India was studied. 71 species representing 7 orders, 20 families and 41 genera were recorded from 21 sites along the three rivers. Species composition varied longitudinally in relation to the environmental factors of the habitat. The downstream change in the three rivers indicates that fish assemblage changed with increasing loss of riparian canopy cover and increasing agricultural land-use. The richness and abundance of fishes were correlated with land-use type, canopy cover, pH and turbidity. Diversion of water, discharge of domestic sewage and agricultural runoff were prominent among the disturbances that alter the habitat quality.

Rapid and accurate identification of microorganisms have a significant impact on strategies and fish health management programs. Hence, in this study a duplex PCR assay based on the 16s rRNA gene for simultaneous detection of Aeromonas hydrophila RTICC 1032 and Escherichia coli RTICC 2325 from pure cultures, and challenged fish tissues was performed and their results were compared with the results of single PCR assays for each bacterium. For this purpose, an experiment with three treatments including artificially infected with A. hydrophila, E. coli and a mixture of them with a control group was designed. Fish were injected intraperitoneally with 1 ml of sterile physiological saline containing 106CFU/ml of the corresponding bacteria. Samples were collected from liver, kidney and spleen 48 hrs post-injection. A duplex PCR based 16S rRNA genes was developed for the simultaneous detection of A. hydrophila and E. coli. The PCR reaction conditions were optimized to permit detection of organisms from agar plates and fish tissues in less than 8 hrs. Each of the two pairs of oligonucleotide primers exclusively targeted 16S rRNA gene of the specific microorganism. When duplex PCR assay was used to simultaneous detection of the pathogens in asymptomatic fish, spleen and liver were negative for A. hydrophila, whereas kidney was positive for two bacteria. Samples that were duplex PCR negative were also negative by the culture method. On the whole, the duplex PCR has advantages in terms of its accuracy, sensitivity, ease of use, time of length analysis and cost-effectiveness compared to the single PCR and traditional method.