The coastal state of Orissa, India, harbours three important mass-nesting beaches of the olive ridley sea turtle Lepidochelys olivacea. During a survey of sea turtle nesting beaches from December 1993 to May 1994, 5282 dead olive ridleys were counted along the 480 km coastline of Orissa. Almost all the deaths were due to incidental capture in offshore fishing nets. Increased fishing activities in the coastal waters near important sea-turtle nesting beaches pose a serious threat to the survival of this endangered sea turtle. It is therefore suggested that coastal waters adjacent to major sea-turtle nesting beaches be declared as closed areas for commercial fishing activities in order to ensure the sea turtle's long-term survival.
The coastal state of Orissa, India, harbours three important mass‐nesting beaches of the olive ridley sea turtle Lepidochelys olivacea. During a survey of sea turtle nesting beaches from December 1993 to May 1994, 5282 dead olive ridleys were counted along the 480 km coastline of Orissa. Almost all the deaths were due to incidental capture in offshore fishing nets. Increased fishing activities in the coastal waters near important sea‐turtle nesting beaches pose a serious threat to the survival of this endangered sea turtle. It is therefore suggested that coastal waters adjacent to major sea‐turtle nesting beaches be declared as closed areas for commercial fishing activities in order to ensure the sea turtle's long‐term survival.
Abundance estimation of marine mammals requires matching of detection of an animal or a group of animal by two independent means. A multimodal detection model using visual and acoustic cues (surfacing and phonation) that enables abundance estimation of dolphins is proposed. The method does not require a specific time window to match the cues of both means for applying mark-recapture method. The proposed model was evaluated using data obtained in field observations of Ganges River dolphins and Irrawaddy dolphins, as examples of dispersed and condensed distributions of animals, respectively. The acoustic detection probability was approximately 80%, 20% higher than that of visual detection for both species, regardless of the distribution of the animals in present study sites. The abundance estimates of Ganges River dolphins and Irrawaddy dolphins fairly agreed with the numbers reported in previous monitoring studies. The single animal detection probability was smaller than that of larger cluster size, as predicted by the model and confirmed by field data. However, dense groups of Irrawaddy dolphins showed difference in cluster sizes observed by visual and acoustic methods. Lower detection probability of single clusters of this species seemed to be caused by the clumped distribution of this species.
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