Overview of nycthemeral and lunar cycle variations in acoustic detections of small cetaceans in the Mediterranean sea

Presenter Information

Camille Ollier

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Location

Gallaudet University - JSAC Multipurpose Room

Start Date

4-3-2024 3:00 PM

End Date

4-3-2024 3:30 PM

Description

Small cetaceans, as long-lived species, face anthropogenic pressures and are associated with high conservation stakes. Cetacean abundance, which can be estimated either by visual or passive acoustic surveys, is essential for their effective conservation and is highly dependent on detectability. Small cetacean detectability is closely linked to behavioral patterns, such as surfacing behavior, which can be considered to accurately estimate abundance in visual surveys. However, within acoustic surveys, small cetaceans display diel patterns in their emission of clicks during foraging can be influenced by environmental and temporal variables. The study aims to determine the factors that influence the number of acoustic detections within a 24-hour period. We used acoustic data from a vessel-based line transect survey conducted day and night, using a passive towed hydrophone across the Mediterranean in summer 2018. A generalized additive mixed model was used to investigate the effects of temporal and environmental variables. The study revealed that time of day and lunar cycle significantly influence the number of acoustic detections with a higher frequency at night. Understanding the factors that contribute to the variation of acoustic detection production rate could improve the methods to account for detectability biases, leading to more accurate estimates of cetacean abundance.

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Mar 4th, 3:00 PM Mar 4th, 3:30 PM

Overview of nycthemeral and lunar cycle variations in acoustic detections of small cetaceans in the Mediterranean sea

Gallaudet University - JSAC Multipurpose Room

Small cetaceans, as long-lived species, face anthropogenic pressures and are associated with high conservation stakes. Cetacean abundance, which can be estimated either by visual or passive acoustic surveys, is essential for their effective conservation and is highly dependent on detectability. Small cetacean detectability is closely linked to behavioral patterns, such as surfacing behavior, which can be considered to accurately estimate abundance in visual surveys. However, within acoustic surveys, small cetaceans display diel patterns in their emission of clicks during foraging can be influenced by environmental and temporal variables. The study aims to determine the factors that influence the number of acoustic detections within a 24-hour period. We used acoustic data from a vessel-based line transect survey conducted day and night, using a passive towed hydrophone across the Mediterranean in summer 2018. A generalized additive mixed model was used to investigate the effects of temporal and environmental variables. The study revealed that time of day and lunar cycle significantly influence the number of acoustic detections with a higher frequency at night. Understanding the factors that contribute to the variation of acoustic detection production rate could improve the methods to account for detectability biases, leading to more accurate estimates of cetacean abundance.