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|Snowbirds of the Sea: Environmental Associations of Migratory Cownose Ray (Rhinoptera bonasus) Presence in their Summer and Winter Habitats along the U.S. Atlantic Coast
|Presenting Author Name
|Presenting Author Affiliation
|Smithsonian Environmental Research Center
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|marine highly-migratory species
|Type of Presentation
Identifying the mechanistic drivers of migration can have important implications for conservation and management policies. The Cownose Ray (Rhinoptera bonasus) is a relatively poorly-understood elasmobranch species that undergoes large-scale seasonal migrations along the U.S. Atlantic coast. To better understand the drivers and timing of Cownose Ray migration, we used telemetry detections of 51 mature Cownose Rays (38 female, 13 male) tagged with acoustic transmitters in Chesapeake Bay. Detections in their summer habitat within Chesapeake Bay and winter habitat in the vicinity of Cape Canaveral were matched with publicly-available sea surface temperature (SST) data recorded by data buoys representative of the area of tag detection, and with local photoperiod and day of year. These variables were used in boosted regression tree models of ray presence (all rays combined, females only, and males only) in each seasonal habitat. Models were developed for presence during the entire season, and during the time period of arrival and departure from summer and winter habitats. Presence in both summer and winter habitats was associated with distinct temperature, photoperiod, and date ranges, but males arrived in the upper Chesapeake Bay later and departed earlier than females. Southward migration from Chesapeake Bay was most strongly associated with SST for all rays, but northward departure from Cape Canaveral was most strongly associated with SST for females and with day of year for males. These findings allow for prediction of the timing of Cownose Ray presence in their seasonal habitats, and suggest possible responses to changing ocean temperatures.