Southern stingrays, Dasyatis americana, have been provided supplemental food in ecotourism operations at Stingray City Sandbar (SCS), Grand Cayman since 1986, with this site becoming one of the world’s most famous and heavily visited marine wildlife interaction venues. Given expansion of marine wildlife interactive tourism worldwide, there are questions about the effects of such activities on the focal species and their ecosystems. We used a combination of acoustic telemetry and tag-recapture efforts to test the hypothesis that human-sourced supplemental feeding has altered stingray activity patterns and habitat use at SCS relative to wild animals at control sites. Secondarily, we also qualitatively estimated the population size of stingrays supporting this major ecotourism venue. Tag-recapture data indicated that a population of at least 164 stingrays, over 80% female, utilized the small area at SCS for prolonged periods of time. Examination of comparative movements of mature female stingrays at SCS and control sites revealed strong differences between the two groups: The fed animals demonstrated a notable inversion of diel activity, being constantly active during the day with little movement at night compared to the nocturnally active wild stingrays; The fed stingrays utilized significantly (p<0.05) smaller 24 hour activity spaces compared to wild conspecifics, staying in close proximity to the ecotourism site; Fed stingrays showed a high degree of overlap in their core activity spaces compared to wild stingrays which were largely solitary in the spaces utilized (72% vs. 3% overlap respectively). Supplemental feeding has strikingly altered movement behavior and spatial distribution of the stingrays, and generated an atypically high density of animals at SCS which could have downstream fitness costs for individuals and potentially broader ecosystem effects. These findings should help environmental managers plan mitigating measures for existing operations, and develop precautionary policies regarding proposed feeding sites.

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Southern stingrays (Hypanus americanus) represent a multimillion dollar ecotourism operation in Grand Cayman, interacting with over a million visitors annually. Over 30 years of stingray provisioning by tour operators has provided a predictable aggregation at the Stingray City Sandbar (SCS). Despite potentially negative effects of provisioning and concerns about declining stingray numbers at SCS, there has never been a formal assessment of the aggregation. In the present study we analysed tagging data from 2002 to 2015 and established structured censuses monitoring the aggregation. The consistently female-dominated aggregation declined between 2008 and 2012, from >100 to <60 stingrays, but has increased since 2012, stabilising at ~90 stingrays. Female site fidelity was high, with ~20% of females resident for ≥10 years, compared with only 3 years for most males. Stingrays were also found to have growth rates similar to those in captivity. The results of the present study suggest the SCS aggregation is highly dependent on individuals arriving from the island-wide stingray population, susceptible to perturbation, and that successful management of activities at SCS will benefit from regular monitoring of the stingray aggregation. We chronicle the historical status of this well-known and economically valuable marine resource and provide suggestions applicable towards sustainable human–marine wildlife interactions for similar resources.

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