M Sc Dissertation(WII)

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Author: search.filters.author.Pandav, BivashSubject: search.filters.subject.Species diversity

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    Assessing the distribution and density of the Fishing Cat in Bhitarkanika mangroves of eastern India by
    (Wildlife Institute of India, Dehradun, 2024) Ashik, C.S.; Mukherjee, Shomita; Gopi, G.V.; Pandav, Bivash
    Identifying the areas of occurrence, population, and the factors affecting the species distribution is critical in conservation and management. The Fishing Cat (Prionailurus viverrinus), a smaller feline native to South and Southeast Asia, is globally vulnerable and adapted to wetland habitats, with a diet primarily consisting of fish. This makes Bhitarkanika, a mangrove ecosystem, an ideal habitat for the Fishing Cat. This study was conducted to estimate the species density, determine the factors affecting its distribution, and assess the effect of lunar illumination and tidal fluctuation on Fishing Cat activity. Despite known occurrences of Fishing Cats in this area, there has been no proper assessment of their population or other ecological studies. Camera traps were deployed in 109 grids, each covering 1km², across a total of 145 km², for 2878 trap nights. Camera trap locations are unbaited, with two cameras used to capture both flanks. Spatially explicit capture-recapture (SECR) was used to estimate the density, resulting in 0.6 ± 0.1 individuals per km². The abundance was also calculated, with an estimate of 99 ± 16 individuals. These density estimates from this study are close to recent high-density estimates for the species. The canopy cover, the width of the creek, canopy cover and the distance to the aquaculture farms significantly influenced the Fishing Cat habitat use, indicating the need for the conservation of natural mangrove habitats and regulation of aquafarms present near the forest. In contrast, the presence of Saltwater Crocodile showed a negative effect on the distribution of Fishing Cats. The Fishing Cats were more active during the brighter nights of the moon phase (μ= 266.783, r= 0.051, p< 0.01) due to better visual detection. The activity was influenced both by the tidal fluctuations in terms of food resources from waterbodies and it is further enhanced by the lunar illumination during the night. Pairwise non-parametric tests showed that the probability distributions of Fishing Cat activity under lunar illumination and tide fluctuation (D= 0.125, p-value = 0.9885 and D= 0.125, p-value= 0.9899) were similar, indicating minimal differences between each probability distribution. This study underscores the importance of protecting the mangrove habitat and controlling aquaculture expansion to ensure Fishing Cat survival in the Bhitarkanika National Park.
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    Estimating sea snake diversity using trawler bycatch along the coast of Goa
    (Wildlife Institute of India, Dehradun, 2003) Lobo, Aaron Savio; Vasudevan, K.; Pandav, Bivash
    The sea snake community off the coast of Goa was studied using trawler bycatch. To obtain a fair idea of species richness .other fishing crafts such as shore seines and sluice nets were visited at regular intervals to check for snakes that were opportunistically caught in them. Catch per unit effort was calculated to compute the sea, snake abundance. Food habits of sea snakes were studied using a gut content analysis, where in the fish families commonly fed on by sea snakes were recorded. An attempt was made to understand the causes of mortalities in sea snakes. This was done relating the magnitude which was the number of dead sea snakes and intensity which was the proportion of dead sea snakes with the duration of the trawl, weight of the catch and mean depth in meters. Sea snakes were measured for several parameters and length-weight relationships were computed. A total of six species were encountered of which four were caught through systematic sampling using trawlers while the remaining two. were obtained through opportunistic searches using shore seines and sluice nets. The total catch per unit effort calculated for the entire study was 1.28 x 10-5 sea snakes per net/hr and the catch per unit efforts calculated for the individual bases varied significantly. The sea snake diversity was seen to be the highest for Vasco followed by Malim, Chapora and Betul. A cluster analysis with complete linkage showing similarities across the four different fishing bases showed that Vasco is most similar with Malim and Betul with Chapora. The composition of sea snake species varied with depth The proportion of Lapemis curtus increased and Enhydrina schistosa decreased with an increase in depth. The proportion of male and female snakes per trawl were similar in all three depths for L.curtus. In E.schistosa, however males did not occur in depths greater than 15 m. In L.curtus most individuals contained food in the stomach. The species was found to feed on five fish families of which families Clupeidae and Cynoglossidae dominated~ The consumption of clupeids decreased with increase in the length of the snake. Consumption of prey families varied slightly with the time of the day and this was mainly with the change in the proportion of Cynoglossids consumed.The mortality of sea snakes was found to be strongly related with the number of individuals caught. The magnitude and intensity of mortality were found to increase with the duration of the trawl, weight of the catch and mean depth. Mortalities of sea snakes varied with species, L.curtus having a larger proportion of dead than live individuals and E.schistosa having a larger proportion of live as compared to dead individuals, thus showing that L.curtus is more susceptible to mortalities- due to trawling as 'compared to E.schistOS8. Betul recorded the highest mortalities and the mortality of sea snakes was found to be significantly influenced by the time of the day and season. Bruises were found to vary significantly in live and dead sea snakes and were higher in dead snakes. Morphometric studies in L.curtus and E.schistosa found that snout vent length bore a strong relationship with the weight and tail length. No sexual dimorphism in terms of size was recorded in both the species which was similar to previous studies in the case of L.curtus.