M Sc Dissertation(WII)
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Item Spatial Dynamics and Drivers of Nearshore Aggregations in Olive ridley Sea Turtles along the Gahirmatha Coast by(Wildlife Institute of India, Dehradun, 2024) Sarkar, Arnab Dey; Prabakaran, Nehru; Kumar, R.S.; Pandav, BivashOlive ridley sea turtles (Lepidochelys olivacea) exhibit a well-documented phenomenon known as nearshore aggregation during their breeding season. These aggregations, comprising large numbers of turtles in shallow coastal waters, are a common feature observed along most of the mass nesting beaches. The ecological benefits of such aggregations are multifaceted, potentially including enhanced predator avoidance and increased opportunities for mate encounter. The importance of studying these nearshore aggregations stems from their vulnerability during this period. Olive ridley turtles within these aggregations are susceptible to various threats, including bycatch mortality from fishing gear. Understanding the spatial and temporal dynamics of these aggregations is crucial for developing effective conservation strategies. The Gahirmatha nesting site presents a unique case due to the influence of the Brahmani-Baitarani River system. The substantial freshwater inflow and sediment discharge from this river system have resulted in a vast area of shallow seabed compared to other nesting grounds. This distinct ecological setting necessitates a dedicated investigation into the dynamics and influencing factors of nearshore aggregations specific to Gahirmatha. The study examined the distribution and density of olive ridley sea turtles near Gahirmatha, India, a critical nesting site, with a particular focus on how environmental factors influence the location of these nearshore aggregations. Surveys were conducted throughout the breeding season, recording turtle sightings and environmental data. The findings reveal that olive ridley turtles are not distributed randomly in the nearshore waters. Instead, they form concentrated aggregations in shallow depths (less than 5 km offshore and 5-15 meters deep) before nesting. The location and density of these aggregations were not static but shifted throughout the breeding season. During the pre-nesting season, turtles were more dispersed across a wider area. As the season progressed and nesting approached, the aggregation grew denser and shifted closer to the nesting beach. The study also identified distance from the coastline and the nesting beach as the key factors influencing the distribution of these nearshore aggregations. Additionally, the unique shallow seabed near Gahirmatha, created by the discharge from the Brahmani-Baitarani River, might influence the preferred depth range of turtles compared to other nesting sites. Understanding these dynamic aggregation patterns is crucial for effective conservation efforts. Protecting these areas is essential for the well-being of this globally significant olive ridley population. However, it's important to acknowledge that the exact locations of these aggregations can vary between years. This year's lower nesting numbers suggest fewer turtles arrived in the nearshore waters, potentially impacting the size and distribution of the observed aggregations. This study emphasizes the need for long-term studies to gain a more comprehensive understanding of these variations and the factors influencing them. The study suggests a targeted approach of focusing on areas with high turtle usage. By implementing stricter patrolling measures within these zones, the forest department can significantly reduce threats like bycatch mortality from fishing activities. This targeted approach would be more effective in safeguarding the turtles compared to focusing on reducing illegal fishing in the entire sanctuary, considering the limited resources available.Item Age Estimation of a Breeding Population of Olive Ridley Sea Turtle (Lepidochelys olivacea) Along the Odisha Coast, Eastern India: Using skeletochronology(Wildlife Institute of India, Dehradun, 2013) Baburam, Anupya D.; Pandav, Bivash; Kumar, R.S.A migratory population of olive ridley sea turtle (Lepidochelys olivacea) forms huge reproductive congregations in the coastal waters of Odisha every winter. This breeding population of olive ridley has been subjected to heavy fisheries related mortality for the past two and half decades. Although a number of studies have been carried out on olive ridleys congregating and nesting along the Odisha coast, the impact of such large scale mortality on the demography of this breeding population has been least understood. The effect of this continued mortality on the age class of olive ridleys nesting along Odisha coast is not known. In order to understand the age class of this breeding population I carried out this study from December 2012 till May 2013. I used skeletochronological analysis to estimate the age class of this breeding olive ridley sea turtle population. Although this technique has been applied for marine turtles mostly in North Pacific, Atlantic and Gulf of Mexico coast of United States of America, no studies of this kind have been carried out on sea turtles of Eastern Pacific as well as Indian Ocean region. This study provides the information needed to bridge this gap and establish baseline for future skeletochronological studies on the breeding population of olive ridley. Humeral samples from 85 dead turtles (29 males and 56 females) washed ashore the Odisha coast was collected for skeletochronological studies. Cross sections were taken from the mid-diaphysis, just distal to the deltopectoral crest and beneath the insertion scar on the humerus were taken using first a Dremel 4000 round saw, then a freezing stage microtome. These sections were processed according to standardized histological techniques; growth rings on the stained humeral cross sections were counted to estimate age of dead turtles. Two age estimation protocols were used; the correction factor protocol and the ranking protocol; which yielded age estimates of 19.9 - 51.8 and 24 – 49 years respectively; for a size class of 56 - 74 cm (SCL). No correlation between size class and age was obtained from this analysis. This relationship was not established because the samples collected were from an adult breeding population, whereas, in the previous studies, sample collection represented individuals that greatly varied in size (hatchlings to adult). This study suggests that adult breeding population size class has no correlation with age; however, age can be correlated with size class of a younger population. This breeding population is sustaining a wide age group even though mortality rates are high in this areaItem Estimating sea snake diversity using trawler bycatch along the coast of Goa(Wildlife Institute of India, Dehradun, 2003) Lobo, Aaron Savio; Vasudevan, K.; Pandav, BivashThe 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.Item Diurnal and Seasonal Activity Pattern of Water Monitor (Varanus salvator) in Bhitakanika Wildlife Sanctuary, India(Wildlife Institute of India, Dehradun, 1993) Pandav, Bivash; Choudhury, B.C.This study investigated the diurnal and seasonal activity pattern of water monitor, Varanus salvator in Bhitarkanika Wildlife Sanctuary, India. The study was conducted in an intensive study area of 17 sq.km selected after a pre sampling survey in the Sanctuary. The methodology involved to record the activity pattern of water monitor was monitoring of two permanent standard paths every three hours on diurnal basis. Sightings of water monitors were recorded while walking on the standard path. Behaviour of water monitor was divided into four categories such as basking, foraging, resting and non-foraging. Microhabitat of water monitor was recorded on each sighting. Ambient and substrate temperatures and ambient relative humidity were recorded along with diurnal activity pattern of water monitors. Results show a shift in diurnal activity pattern with season. The activity pattern of water monitor was unimodal in winter and uniform in summer. Basking was the major activity of water monitor in winter, whereas all the activities were evenly spread out in summer.The lizards used different microhabitats for different activities. Maximum lizards were recorded active at cooler substrate temperatures (29°C). The relation of ambient and substrate temperatures with activity was curvilinear. At low ambient temperature basking was prevalent. With increase in temperature other activities, such as foraging and resting were recorded. At high ambient temperature lizards selected cooler substrates. Ambient temperature and ambient relative humidity varied inversely. The activity was low at high levels of humidity It is concluded that behavioural thermoregulation plays a major role in water monitor’s activity.