@article {130536, title = {Temporal variability of a soundscape near a mid-oceanic atoll in the northern Indian ocean}, journal = {PROGRESS IN OCEANOGRAPHY }, volume = {214}, year = {2023}, month = {06/2023}, pages = {103033}, abstract = {

Soundscape ecology in the context of physical oceanographic features is an emerging area of research revealing interactions between physically, biologically and anthropogenically driven sounds and their sources. Sound-scapes can shape and reveal distributions of a range of species, from fish larvae to whales, within marine eco-systems. The northern Indian Ocean is a region of high environmental variability driven by seasonally reversing monsoonal winds. The mid-oceanic islands within these waters consist of steep slopes forming a crucial interface between shallow reef and deep oceanic habitats. Studies on soundscape are limited in these waters. The aim of this study was to characterize major sound sources off the southern and northern side of the Kavaratti atoll in Lakshadweep islands, India, located at the northern part of the Laccadive-Maldives-Chagos Ridge. A first look at shallow water soundscapes are provided here using passive acoustic monitoring, and how they correlate with satellite-derived oceanographic variables. Geophonic and biophonic sources across different frequency bands are identified with three major choruses - a dusk fish chorus, a midnight chorus that is speculated to be produced by myctophids, and a snapping shrimp night chorus. Low frequency biophonic choruses peaked in inter-monsoon months (January to March), while low frequency geophonic sound levels peaked during monsoon months (June to October) and increased with wind speed. The dusk fish chorus and the midnight chorus (at the south site) decreased with increasing sea surface salinity, while the snapping shrimp chorus (at the south site) increased with increasing sea surface salinity. Snapping shrimp chorus levels increased with decreasing wind speed. The dusk fish chorus peaked during full and waning moon, and the midnight and snapping shrimp choruses peaked during new moon periods. The sources and patterns described in this study will help compare with future soundscape and sound pressure level measurements within this region. This will be useful in the context of a changing climate and for planning future developmental projects on the islands. Reef choruses link with peak larval recruitment, spawning, or feeding activities, and further investigation into the peak calling times reported here will help uncover the function of choruses. Expanding the collection of passive acoustic monitoring data and oceanographic measurements over longer timescales will significantly advance {\textquoteright}soundscape oceanography{\textquoteright}.

}, doi = {DOI10.1016/j.pocean.2023.103033}, author = {Panicker, Divya and Stafford, Kathleen M.} } @article {108042, title = {Fine-scale spatial and temporal acoustic occurrence of island-associated odontocetes near a mid-oceanic atoll in the northern Indian Ocean}, journal = {MARINE ECOLOGY PROGRESS SERIES}, volume = {683}, year = {2022}, month = {02/2022}, pages = {195-208}, abstract = {

Temporal patterns of oceanic predators can provide valuable information on both lunar and diel influences not just on the distributions of these predators, but also on prey patches that are often difficult to study. Mid-oceanic island chains in the northern Indian Ocean have high odontocete occurrence, but the ecology of these animals is not well characterized. We investigated fine-scale spatial and temporal patterns of island-associated odontocetes using passive acoustic monitoring from January 2019 to January 2020 around Kavaratti Island, Lakshadweep, India. Based on opportunistic recordings in the presence of odontocetes, the majority of the detected whistles were likely made by spinner dolphins Stenella longirostris. We identified a resident population whose whistle occurrence was significantly influenced by month, site, and diel and lunar cycles. More acoustic detections were made in the northeast monsoon month of November and fewer during pre-monsoon and southwest monsoon periods. Distinct day-night differences along with fine-scale temporal variability were also observed, suggesting that delphinids use nearshore waters as a daytime resting habitat. Odontocete detections were highest during the new moon period and lowest during the first quarter phase. Detection rates were higher on the south side of the island. Our study shows that solar and lunar cycles modulate odontocete vocal occurrence, presumably through influences on their prey. Similarities of odontocete occurrence around Lakshadweep to other mid-oceanic island chains suggests that an island-associated micronekton community may exist around Lakshadweep that may also be important to other pelagic species targeted by local fisheries.

}, doi = {10.3354/meps13947}, author = {Panicker, Divya and Baumgartner, Mark F. and Stafford, Kathleen M.} } @article {72068, title = {Cetacean Distribution and Diversity in Lakshadweep Waters, India, Using a Platform of Opportunity: October 2015 to April 2016}, journal = {AQUATIC MAMMALS}, volume = {46}, year = {2020}, month = {01/2020}, pages = {80-92}, abstract = {

Prior stranding records suggest that at least 12 cetacean species occur within the Lakshadweep archipelago off the southwest coast of India. These islands consist of coral atolls and form the northern part of the undersea Chagos-Laccadive ridge. Distinct oceanographic features, seasonal monsoon cycles, and high productivity make this region a potentially rich cetacean habitat. In this article, we report findings from the first systematic visual cetacean surveys, which were conducted from high-speed passenger ferries that sail between nine Lakshadweep islands. The surveys were carried out between October 2015 and April 2016 during both the northeast monsoon (October to December) and inter-monsoon (January to April) seasons. We used a line-transect survey framework to record sightings as well as group size estimates. We documented 139 sightings over 3,880 km of which 78 sightings were during systematic survey effort. Eight odontocete species were confirmed from these sightings: Stenella longirostris, S. attenuata, S. coeruleoalba, Tursiops spp., Globicephala macrorhynchus, Pseudorca crassidens, Grampus griseus, and Feresa attenuata. One Balaenoptera sp. was also encountered during this survey. S. longirostris was sighted the most often (n = 22) followed by Tursiops spp. (n = 18) and G. macrorhynchus (n = 13). We documented significantly higher sightings in the northeast monsoon season compared to the inter-monsoon season. Along ferry routes, cetacean species differed significantly from each other with respect to their associations with seafloor slope gradients and distances to nearest landmass. We encountered mixed species assemblages of G. macrorhynchus with Tursiops sp. and S. attenuata with Tursiops sp. Given the confirmed high cetacean diversity and occurrence in this region, there is a need for in-depth, long-term studies on biogeography, ecology, and population status of cetaceans here.

}, doi = {10.1578/AM.46.1.2020.80}, author = {Panicker, Divya and Sutaria, Dipani and Kumar, Ajith and Stafford, Kathleen M} } @article {30081, title = {Indian Ocean humpback dolphin (Sousa plumbea) estuary-use patterns in Kochi harbor, India}, journal = {MARINE MAMMAL SCIENCE}, volume = {34}, year = {2018}, month = {01/2018}, pages = {208-219}, doi = {10.1111/mms.12438}, author = {Panicker, Divya and Haris, Asad and Sutaria, Dipani} }