Fishery, growth, mortality, and stock assessment of endangered Tor putitora from Tehri dam reservoir, Uttarakhand, Himalayan foothills of India in relation to environmental variables.

The current study determined Tor putitora (Hamilton, 1822) fishery, growth, mortality, and population characteristics using length-frequency data assembled monthly from the Tehri dam reservoir in Uttarakhand from January to December 2022. The estimation data was separated into 40-mm class intervals, and population parameters were investigated and computed using the FiSAT-II software tool. W = 0.0101 L2.996, where a = 0.0101 and b = 2.99, were determined as the length-weight relationships, and the growth performance index (ϕ) was computed to be 5.40. Tor putitora commercial catches in the Tehri dam reservoir were dominated by length groups of 360-399 and 320-359 mm. Different growth parameters were estimated using length-frequency data as L∞ = 987.00 mm, K = 0.26 yr-1, and t0 = -0.0003 years. Z, M, and F mortality coefficients were estimated to be 1.01, 0.27, and 0.73, respectively. At the end of the first, second, third, fourth, fifth, sixth, and seventh years, the fish measured 226, 400, 535, 638, 718, and 780, and 827, respectively. The estimated value of the exploitation rate (E) was 0.73 using the length-converted catch curve approach, which was determined to be somewhat higher than the optimum value (0.50). Tor putitora recruitment patterns from the Tehri dam reservoir reveal that the species only has one recruitment pattern every year, and that solely occurs from June to September. The current exploitation level (0.73) has already exceeded the maximum fishing pressure (Emax = 0.508), indicating that there is a decline in the catch at the current fishing pressure, and a further increase in fishing efforts may lead to a decline in the stock, which may be detrimental to the sustainable fishery of Tor putitora in the Tehri dam reservoir, Uttarakhand, India.

Probing river health status: a study based on index of biotic integrity (IBI) in Tapti River of Deccan plateau, India.

Anthropogenic activities impacted the ecological health of rivers by altering the physical habitat and water flow as well as by pollution. Monitoring of biotic groups for gauging the river health is a prerequisite for assessing the extent of degradation and formulating management guidelines for river restoration. An assessment using fish-based index of biotic integrity (IBI) was carried out in the Central Indian river, Tapti, for probing its health status. For the multimetric index, twelve metrics were adopted under five categories: taxonomic richness, habitat composition, tolerance indicators, species resilience, and trophic composition. Among the studied sites, Betul in the upper stretch was selected as the reference site for River Tapti, which almost meets the upper expectation of the metrics explored. Continuous scoring method was applied to evaluate the biotic integrity in the selected sites of the river. The IBI score based on the pooled fish abundance data in River Tapti ranged from 33 to 60. Assessment of the ecological health revealed that three-fourth of the river stretch was moderately impaired (25-50% of impairment) and the most deteriorated site was Kamrej with 45% of impairment which might be due to its location in the urban area with high influx of domestic sewage and industrial effluents. The IBI scores were plotted and compared with an independent estimate of water quality. The CCA with environmental and IBI variables revealed higher correlation with each other and the functional groups such as carnivores, herbivores, and fishes with high population doubling time (PDT) were found in close association with nitrate-N, total alkalinity, and specific conductivity. The study urges the need for the adoption of proper management and mitigation measures to restore the health and wealth of aquatic ecosystem.

New record of two isopods Alitropus typus and Tachaea spongillicola from riverine freshwater fishes in the river Tapti.

The present paper deals with the infestation of freshwater fishes Labeo boggut, Oreochromis niloticus, Systomus sarana, and Xenentodon cancila by the parasitic isopods Alitropus typus and Tachaea spongillicola in Tapti, a westward freshwater flowing river of India. The isopods Alitropus typus H. Milne Edwards, 1840 and Tachaea spongillicola Stebbing, 1907 were identified with the taxonomic keys of Milne Edwards (1840) and Stebbing (1907), respectively. It is the first record of the infestation of parasitic isopods Alitropus typus, and Tachaea spongillicola in the freshwater fishes of river Tapti with new hosts' species Labeo boggut, Oreochromis niloticus, and Systomus sarana.

Isopod parasite, Nerocila depressa Milne Edwards, 1840 infestation in Thryssa stenosoma Wongratana, 1983, as a first record from Narmada estuary, West Coast of India.

The study reported Thryssa stenosoma, as a new host of isopod Nerocila depressa infestation. Furthermore, the record of Nerocila depressa from the Narmada estuary is of first kind in the West Coast of India. Thryssa stenosoma, commonly known as slender thryssa forms an important commercial fish species at Bhadbhut, a part of the Narmada estuary. The prevalence of N. depressa infestation was 17.39% with a mean intensity of 2.8. in T. stenosoma, showing a low rate of infestation. The present information would form a new addition of isopod infestation to the list of parasitic diseases of estuarine fishes in India.

Population structure and genetic diversity of Indian Major Carp, Labeo rohita (Hamilton, 1822) from three phylo-geographically isolated riverine ecosystems of India as revealed by mtDNA cytochrome b region sequences.

The population structure and genetic diversity of Rohu (Labeo rohita Hamilton, 1822) was studied by analysis of the partial sequences of mitochondrial DNA cytochrome b region. We examined 133 samples collected from six locations in three geographically isolated rivers of India. Analysis of 11 haplotypes showed low haplotype diversity (0.00150), nucleotide diversity (π) (0.02884) and low heterogeneity value (0.00374). Analysis of molecular variance (AMOVA) revealed the genetic diversity of L. rohita within population is very high than between the populations. The Fst scores (-0.07479 to 0.07022) were the indication of low genetic structure of L. rohita populations of three rivers of India. Conspicuously, Farakka-Bharuch population pair Fst score of 0.0000, although the sampling sites are from different rivers. The phylogenetic reconstruction of unique haplotypes revealed sharing of a single central haplotype (Hap_1) by all the six populations with a point mutations ranging from 1-25 nucleotides.