Date of Award

Winter 1-31-2025

Document Type

Thesis: Open Access

Degree Name

MS Marine Science

Department

Environmental and Ocean Sciences

Committee Chair

Dr. Mary Sue Lowery

Committee Member

Dr. Cassondra L. Williams

Committee Member

Dr. Jeffrey A. Seminoff

Committee Member

Dr. Nicholas C. Wegner

Abstract

Sea turtles are air-breathing marine reptiles that spend their lives performing dives to travel, forage, and rest. Several dive types have been previously recorded for sea turtles, each type being associated with a different set of behaviors. U-dives, or Type 1 dives are widely characterized by extensive benthic periods preceded by and concluding with abrupt descent and ascent phases respectively (Minamikawa et al. 1997; Houghton et al. 2002; Seminoff et al. 2006). These dives are widely affiliated with turtle resting behavior though can be indicative of additional activities including benthic travel and foraging. Previous research of green turtle dive behavior has exhibited turtles opting to perform extended duration resting U dives in deeper water offshore; however this behavior cannot necessarily extend to turtles inhabiting areas with significant depth restrictions. San Diego Bay is a uniquely shallow, urban habitat that supports human recreational activities as well as multiple plant and animal species. Members of the resident green sea turtle population prefer the South Bay which comprises some of the shallowest areas of San Diego Bay. Telemetry packages including a Time Depth Recorder (TDR) were placed on five bay resident turtles (n = 5) to further determine baseline dive behavior and further establish the effects of San Diego Bay depth restrictions on turtle diel dive behavior. Deployments lasted between nearly four hours and 10 days collecting a total of 1,020 U-dives for the five turtles. The pattern of turtles exhibiting longer dive durations at night, and resting dive depths and durations 1 being restricted by shallow bay bathymetry was repeatedly observed in this study. Understanding resident turtle baseline dive behavior enables informed determinations of altered behavior due to increasing direct and indirect anthropogenic disturbance and ambient temperature shifts due to the effects of climate change.

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