Theses and Dissertations
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Item Understanding Aggregations Sites of Elasmobranchs in selected islands of the Lakshadweep archipelago(Wildlife Institute of India, Dehradun, 2025) Sawant, Chinmay Prakash; Ghanekar, Chinmaya; Johnson, J.A.This Study shows the identification of the aggregation sites of the elasmobranchs, i.e., sharks, rays, and skates, belonging to the Lakshadweep archipelago, emphasising the identification of aggregation places and traditional knowledge regarding related habitats and species. The presence of elasmobranch aggregations is biologically important as it addresses essential life processes like feeding, reproduction, and nursery grounds. Semi-structured interviews were conducted with 120 respondents, including fisherfolks and scuba divers at four selected Islands of Kavaratti, Kadmat, Bitra, and Agatti on traditional ecological knowledge and information about the presence of elasmobranch species and their aggregation sites. Sixteen aggregation sites were reported, nine for rays and eight for sharks. These aggregations occurred most frequently during the post-monsoon season and the early morning hours. The major habitats ecountered with these aggregations were shallow sandy lagoon, coral and rocky reef, sand, and open ocean pelagic zone. The interviews conducted for assessing species composition included a collective 24 species of sharks and 13 species of rays, with dominant encountered species such as the Whale shark, Blacktip Reef Shark and Tawny nurse shark, for rays Spotted eagle ray, Porcupine ray and Oceanic manta ray. 14 species of sharks are aggregating: Whitetip reef shark, Blacktip shark, and Blacktip reef shark are dominant in the aggregation sites. For the ray aggregation site total of 10 species were reported as they formed aggregations from the Porcupine ray, Spotted eagle ray, Cowtail Ray, and Indian Ocean blue-spotted mask ray. Key aggregation sites are such as Cheriyapani, Valiyapani, and Suheli Par, were identified as key elasmobranch aggregation hotspots. Pole and line, hook and line the traditional fishing practices in the islands. The result of the habitat surveys confirmed these findings, showing that lagoon areas are particularly important for the aggregation of rays, whereas coral reefs in Kadmat, Kavaratti, and Bitra host potential shark populations. In Bitra, rays were observed feeding on a locally frequent prey species called "Muchroli," suggesting distinctive trophic interactions. Moreover, drone surveys validated the presence of huge aggregations of rays in pristine reef habitats, such as Cheriyapani, Valiyapani, and submerged banks offshore, including Suheli Par and Perumal Par. These locations are likely to serve as refugia, with the best possible conditions for feeding, resting, and potential nursery grounds, primarily due to minimal human disturbance. This research provides the first comprehensive understanding of the ecological knowledge of sharks and rays, including their species and key habitats. The results highlight the imperative necessity for continuous long-term monitoring, understanding their ecology of specific fisheries management and habitat, to protect these ecologically specialised and at-risk species in the Lakshadweep archipelago.Item Ecology of Seagrass Habitats and its associated macrobenthic invertebrates in Andaman islands, India(Wildlife Institute of India, Dehradun, 2024) Gole, Swapnali; Sivakumar, K.; Johnson, J.A.; Das, HimansuThe diversity, composition, and growth of species in plant communities are shaped mainly by their complex interactions with local environmental settings. Owing to the unprecedented global decline of seagrasses, it is crucial to understand in-situ ecological interactions for informing mitigation measures. However, several ecological aspects of seagrass ecosystems are under-studied in the tropical Indian waters, which fall in the highly productive Indo-Pacific seagrass distribution bioregion, offering many socio-ecological services. In this context, my study aimed to address the ecological gaps in India's unique seagrass biodiversity hotspot, the insular archipelago called the Andaman and Nicobar Islands (ANI). Objectives of the study were 1) To assess the spatial distribution patterns of seagrass habitats and associated macrobenthic invertebrates in the Andaman Islands, 2) To understand the seasonal variation in seagrass meadows and associated macrobenthic invertebrates, 3) To understand the structural diversity of seagrass meadows and its influence on associated macrobenthic invertebrates, and 4) To document the Traditional Ecological Knowledge on seagrass habitats. The field study was carried out between 2018 and 2022, with a significant sampling period between January and May, as it is the best feasible season for fieldwork in ANI. The spatial diversity, distribution, and growth of seagrasses in the present study were primarily governed by the water depth, habitat heterogeneity, substrate types, and availability. The study suggests that any alterations in the benthic habitat profile of these meadows are likely to affect the species distribution patterns and overall ecological services offeredItem The Effect of Land-use Changes on Odonate Assemblages in the Central Western Ghats(Wildlife Institute of India, Dehradun, 2024) Gowda, H.N. Rakshit; Gautam, Ritesh; Johnson, J.A.Odonata, the only apex insect predator in both terrestrial and aquatic life forms, are widely used as biological indicators of the health of aquatic ecosystems across the globe. The Riparian land uses such as commercial plantations negatively impact the Odonata assemblages, causing the homogenisation of habitats with generalist species and the extinction of specialist species. These land uses affect the riparian vegetation, habitat structure, and water quality parameters, which are crucial for Odonates to complete their life cycle. To understand the impact of commercial plantations on stream-associated Odonata assemblages at the sub-order level, three treatments comprising a combination of forest and areca plantations on either bank of streams were selected. The habitat variables, such as ambient temperature and canopy cover, along with stream parameters like flow and water quality parameters such as pH and water temperature, significantly influenced the Odonate assemblages. The sub-orders, Dragonflies and Damselflies, differed in their response to altered (Areca plantations and plantation-forest edge) and preserved sites (forested sites). These outcomes highlight the importance of the dependency of Odonata on particular sets of variables and the consideration of suborders of Odonata separately as indicator groups for the quality of aquatic ecosystems.Item RISK ASSESSMENT OF POTENTIALLY TOXIC ELEMENTS IN THE HABITAT, AND DIET OF SMOOTH-COATED OTTER (Lutrogale perspicillata) IN TUNGABHADRA OTTER CONSERVATION RESERVE (TOCR), KARNATAKA(Wildlife Institute of India, Dehradun, 2024) Ahmed K., Niyaz; Johnson, J.A.; Hussain, S.A.; Sah, RuchikaSmooth-coated otter (Lutrogale perspicillata), is a vital indicator species for freshwater ecosystems, playing a crucial role in maintaining ecological balance. Despite their essential place in the food web, they are always neglected compared to other terrestrial carnivores. This study explores the distribution, diet, and, ecotoxicological exposures to smooth-coated otters in Tungabhadra Otter Conservation Reserve, Karnataka. The study area, encompassing a 36km stretch of the Tungabhadra River (TOCR), is a unique habitat facing significant anthropogenic pressures, including mining activities and pollution, which threaten the local biodiversity and otter populations. The distribution of smooth-coated otters in TOCR was assessed through intensive sign surveys, revealing a clumped distribution pattern. Otter signs, including spraints, pugmarks, and grooming sites were dominant signs found in the landscape. Dietary analysis was examined by analysing the spraints (scat), using two methods frequency of occurrence method, and the score bulk estimate method revealing a predominantly piscivorous diet. The diet consisted of about 14 species out of which 69.53% is constituted of non–native fish species (Oreochromis mossambicus, Labeo rohita, Cyprinus carpio, and Cirrhinus cirrhosus). Ecotoxicological assessments were performed on water, sediment, fish, and spraint samples to evaluate the presence of potentially toxic elements (PTEs). While PTE concentrations in water and sediment were generally below harmful thresholds, their presence poses a long-term risk through bioaccumulation. Risk assessment indicated significant potential health risks from metals like mercury and arsenic, which could impact otter heal