M Sc Dissertation(WII)

Now showing 1 - 2 of 2

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, Bivash
Olive 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.
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 area

M Sc Dissertation(WII)

Browse

Filters

Settings

Sort By

Results per page

Search Results