Acute toxicity of fluoride and aluminium on the freshwater fish, Cyprinus carpio L

Fluoride is a trace element which has beneficial effect at lower concentration but detrimental at higher concentration. The fluoride contamination in ground water is a major global problem. Similarly, aluminium is the most abundant metal of the earth, highly toxic to all organisms. In the present study, we investigated the acute toxicity of fluoride and aluminium on three month old fingerlings of Cyprinus carpio L. in hard water (Hardness 125 mg/L of CaCO3) under static renewal bioassay. The 96 h LC50 value of the fluoride and aluminium were 675.615 and 224.214 mg/L, respectively. There was a significant correlation (P <0.01) between mortality rate of C. carpio with all concentrations of fluoride as well as aluminium. The exposure time (24, 48, 72 and 96 h) and different concentration of fluoride (680, 684, 686 and 692 mg/L) and aluminium (228, 229, 231 and 232 mg/L) was also significantly correlated (P <0.05). The different abnormal behaviour displayed by the fluoride and aluminium exposed fishes were erratic swimming movements, rapid opercular activity and excessive secretion of mucous. The safe level of concentrations of fluoride and aluminium were 6.75 and 2.24 µg/L, respectively. The LC50 values of fluoride and aluminium of the present study may be useful in deriving water quality standards in West Bengal.

Comparative studies on age and growth patterns of cultivated and wild Catla catla (Hamilton)

Catla catla (Hamilton) is one of the fastest growing Indian major carps (IMCs) with increasing market demand. Consistent demand and exploitation invites the attention of ichthyologists for its conservation strategies. Age and growth studies play a pivotal role for managing the fishery stocks in different water bodies. Here, we studied the age and growth patterns using opercula of both farm grown as well as the wild grown C. catla adopting standard methodologies. Wild specimens were caught from Harike wetland (Ramsar site) and the cultivated one from a farm at Dhudike in Punjab. High value of correlation coefficient ‘r’ 0.976 (wetland) and 0.983 (farm) reveals the strong relationship in total length and operculum radius of the fish. C. catla achieved average total length from wetland and farm, respectively at 1st (273.44 mm) 2nd (427.44 mm) 3rd (525.49 mm) 4th (624.52 mm) 5th (744.98 mm) 6th (813.62 mm) and 1st (282.1 mm) 2nd (463 mm) 3rd (601.7 mm) year of age of opercular bones study. The growth parameters such as, index of species average size (?h) 135.6 (wetland) and 200.6 (farm), growth constant (Clt) showed two growth phases from both localities i.e. sexual immaturity up to 2 years and sexual maturity afterwards. Whereas, growth characteristic (Cth) has revealed irregular growth pattern at wetland in comparison to growth of fish from farm. The results of this study concluded that the fish experienced more growth from the farm due to better and controlled conditions but, in wetland surrounding conditions were observed to be unfavourable for survival of the fish C. Catla.

Microsatellite DNA Marker Analysis Revealed Low Levels of Genetic Variability in the Wild and Captive Populations of Cirrhinus cirrhosus (Hamilton) (Cyprinidae: Cypriniformes).

Aims: To reveal the genetic variability of wild and captive populations of the Indian major carp, mrigal (Cirrhinus cirrhosus) based on microsatellite DNA markers analysis. Study Design: Three rivers namely the Halda, the Padma and the Jamuna were selected under wild population category and three hatcheries such as Brahmaputra Hatchery of Mymensingh, Raipur Government Hatchery, Luxmipur, and Sonali Hatchery, Jessore were selected under the captive population category. Place and Duration of the Study: Department of Fisheries Biology and Genetics, Bangladesh Agricultural University, Mymensingh from July 2005 to June 2008. Methodology: DNA was extracted from fin clips of a total of 180 fish, 30 from each of the six populations. Five microsatellite markers MFW1, MFW2, MFW17, Barb54 and Bgon22 were amplified by polymerase chain reaction for each DNA sample and resolved on denatured polyacrylamide gel and visualized by silver nitrate staining. Results: Three of the five loci were found to be polymorphic in all the six populations. The observed (HO) and expected heterozygosity (HE) ranged from 0.233 to 0.633 and 0.406 to 0.664 respectively. The FIS values ranged from 0.032 to 0.635 indicating deficiency in heterozygosity. Except the Raipur Hatchery stock, the other five populations showed nonconformity to Hardy- Weinberg Expectation at least in one locus. Significant population differentiation was observed between the Halda-Jamuna, Jamuna-Brahmaputra Hatchery, Jamuna-Raipur Hatchery and the Padma-Raipur Hatchery population pairs. The UPGMA dendrogram based on genetic distances resulted in two major clusters: the Halda river and the Raipur Hatchery population were in one cluster and the remaining four populations were in the other cluster. Conclusion: The study, as a whole, revealed low levels of genetic variation in terms of allelic richness and heterozygosity in the three major rivers and three selected hatchery stocks of C. cirrhosus in Bangladesh.

Comparative organoleptic quality of Indian major carps collected from pond and reservoir.

An attempt was made to distinguish the possible organoleptic differences between the pond reared and wild fish species of reservoirs and correlate these with the physicochemical characteristics of water bodies. The texture was found to firmer in wild varieties of fishes than pond reared fish, with best in Catla catla followed by Labeo rohita and Cirrhinus mrigala. All the cultured fishes had lighter colour than wild fish species which were darker in appearance. Comparatively, higher dissolved oxygen and transparency levels with low temperature and alkalinity levels were found in reservoirs. Hydrobiologically, the efficient ecosystem of reservoir was responsible for stronger texture and dark colouration in wild fish species. The fishes from reservoir exhibit tendency to lead active and agile life, comparatively the fishes from ponds are docile. Reservoirs have the potential of enhanced quality fish production.

Studies on the identification and control of pathogen Saprolegnia in selected Indian major carp fingerlings at mid hill altitude.

The Indian major carp cultured in ponds in the North Eastern hilly states of India frequently suffer from fungal disease during winter months resulting in mass mortality. This study examined the pathogenic fungi isolated from farmed raised Indian major carp fingerlings and identified as Saprolegnia. For treatment, the diseased fish were exposed to 4g salt per litre of water for 2 min followed by dip treatment with 5ppm KMnO4 for 10 min, thrice every week for a period of 6 weeks. The treatment resulted in recovery from the disease after 6 weeks from the beginning of treatment. Soon after recovery, the pond management practices such as removal of pond bottom soil, application of lime and replenishment with freshwater were followed in the infected ponds. Our study concluded that rapid decrease in pond water temperature from 22 to 8°C that remains low for months together coupled with increased water pH (9) and decreas dissolved oxygen (4ppm) causes saprolegniasis to the fingerlings of Indian major carps.