International Journal of Aquatic Biology
Volume:3 Issue: 3, Jun 2015

Beluga sturgeon (Huso huso Linnaeus, 1758) fingerlings are released into the Caspian Sea for recruiting and enhancing commercial and recreational fishing purposes. These fingerlings are reared in fresh water, but released to the estuaries that may be caused mortalities due to acute osmotic stress. In this study, the fingerlings in whole (in vivo) or their gill tissue (in vitro) were exposed to three different levels of ‘the stress hormone’ cortisol (3, 5, 7 mg L-1 hydrocortisone sodium phosphate) for 24 hrs. The effects of treatments on blood cortisol levels and the size and numbers of gill chloride cells were monitored. In each case, hormonal treatment significantly increased blood cortisol levels and also the number but decreased the size of the chloride cells. We conclude that bathing in hydrocortisone could promote the survival rate of the fingerlings in brackish water and may be have a positive effect on their osmoregulation potentiality.

Metals bioaccumulation in five organs of Cirrhinus mrigala, Labeo rohita and Catla catla captured from three industrial and sewage polluted downstream sites (Shahdera = B, Sunder = C and Balloki = D) were compared with a non-industrial upstream site (Siphon = A) during high (post monsoon) and low (winter) flow seasons of river Ravi. Mean concentrations of metals were significantly higher in low flow than the high flow season. Pattern of metal accumulation in the studied organs was: Zn > Fe > Mn > Cu > Cr > Pb > Ni > Hg > Cd. Kidneys showed mostly greater metal bioaccumulation than intestines, hearts, eyes and gills. Among fish species, the highest concentrations (µg/g dry weight) of Cr (3.77), Zn (56.22), Mn (8.95), Ni (1.70) and Hg (1.60) and lowest of Pb (2.53) were detected in C. mrigala whereas Cu (7.19), Fe (62.11) and Pb (2.64) appeared higher while Zn (52.69), Mn (7.82) and Ni (1.41) with lowest concentrations in C. catla. In contrast, lower concentrations of Cd (0.15), Cr (3.16), Cu (7.06) and Fe (54.18) were recorded in L. rohita. Accumulation of the metals was significantly different in organs among the different sampling sites. Based on metals accumulation pattern, second downstream site (Sunder) identified as the most polluted site due to untreated industrial and municipal discharges. Measured elevated levels of metals concentrations in fish organs indicated potential health risks for the fish and the food chain.

The research carried out the length-length relationships (LLR), length-weight relationship (LWR) and condition factor of nine freshwater small indigenous species viz. G. giuris, E. Danricus, M. pancalus, L. guntea, C. fasciatus, P. sophore, H. Fossilis, C. punctatus and M. cavasius from the waterbodies of Nageshwari, Bangladesh. Relationships among different body lenght parameters of each species were found highly significant with all “r” values being >0.900. LWRs were obtained on the form of TW = aTLb. The “b” values range from 2.65-3.03. The parameter “b” of the length-weight relationship equation showed higher value (>3) only for G. giuris and C. fasciatus. Rest of the specimens showed lower value (<3) but close to the value of 3 and relationships were found highly significant with all “r” values being >9.00. The Fulton’s condition factors showed positive growth tendency for five specimens viz. G. giuris, C. fasciatus, P. sophore, C. punctatus, M. cavasius; and negative tendency for four specimens viz. E. danricus, M. pancalus, L. guntea, and H. Fossilis.

Herbal medicinal products have attracted significant research interest in recent years. Considering the efficiency of algae products in controlling pathogenic bacteria and also easy access to large resources of algae, this study was conducted to evaluate the effects of methanolic, chloroformic and aqueous extracts of Gracilaria salicornia against Aeromonas hydrophila, a heterotrophic, Gram-negative, rod-shaped bacterium found mainly in warm climate. Algae samples were collected from Qeshm Island coastlines and transferred to the laboratory. Standard methods were used to obtain the algae extract. Antibacterial activities of various extracts were tested against the bacterium using well diffusion assay method. Significant differences were observed in antibacterial activities of different extracts (P<0.05). The diameter of zone of growth inhibition varied in correlation with concentration of the extracts (50, 100, 200 and 300 mg.ml-1). The best inhibition zone was observed at 100, 200 and 300 mg.ml-1 methanolic and 300 mg.ml-1 aqueous extracts.

The early reaction of the plankton communities to environmental changes makes it a useful tool for monitoring the pollution of aquatic environments. Lake Azili is a small water body, the majority of which is strongly influenced by river Ouémé during the floods time. Its ecosystem is one of the most important for the country, due to its rich biodiversity, especially that of halieutics. By following the evolution of its health, due to the strong anthropological pressure, this study aims to estimate the structure and the dynamics of its planktonic biodiversity and to assess its current state. It was carried out for seven months between May to November, 2012, according to the hydrological seasons of Benin. Plankton samplings were monthly, taken in a vertical sense from the lake, from all depths, using plankton net. The diversity indices were calculated for the compartment of zooplankton, that of phytoplankton being a preliminary evaluation. A total of 51 species of phytoplankton and 36 zooplankton species were inventoried. Instability is observed in the seasonal structure of both communities, especially for the period of transition between the floods and the floods recession. Due to the specific composition and the diversity, the ecosystem of Lake Azili is perturbed.

Length-weight relationship and condition factor were investigated in seven fish species, including Barbus cyri, Capoeta gracilis, Alburnoides eichwaldi, Acanthalbarnus microlepis, Ponticola cyrius, Cobitis keyvani and Oxynemacheilus bergianus from Totkabon River. A total of 570 specimens ranging from 25.90 to 146.97 mm in total length and 0.1 to 260.3 g in total weight were collected. Based on the results, growth coefficient values “b” ranged from 2.429 (A. microlpis) to 3.71 (C. keyvani). All length-weight relationships were significant (P<0.05), with r2 greater than 0.856. The four species viz. A. microlepis, C. gracilis, P. cyrius and C. keyvani showed allometric (b<3 Keywords: River, Freshwater fishes, LWR, Allometry, Condition factor