Abstract
Ecotourism opportunities in the marine environment often rely heavily on provisioning to ensure the viewing of cryptic species by the public. However, intentional feeding of wildlife can impact numerous aspects of an animals’ behavior and ecology. Southern stingrays (Hypanus americana) provisioned at Stingray City Sandbar (SCS) in Grand Cayman have altered diel activity patterns and decreased measures of health. This study looked at seasonal changes in stable isotope (SI) and fatty acid (FA) profiles of provisioned stingrays at SCS. Plasma δ15N was higher in male stingrays (11.86 ± 1.71‰) compared to females (10.70 ± 1.71‰). Lower values for δ15N in males and females were measured in October during low tourist season, suggesting stingrays may be forced to rely on native prey items to supplement the decreased amount of provisioned squid available during this time. Plasma FA profiles were significantly different between sexes and across sampling time points, with FAs 22:6n3, 16:0, 20:5n3, 18:1n3C, 18:0 and 18:1n9T contributing to dissimilarity scores between groups. Dietary FAs primarily contributed to differences between males and females lending further evidence to differences in foraging patterns at SCS, likely due to intraspecific competition. Further, canonical analysis of principal coordinates (CAP) analysis of FA profiles suggest similar diets during peak tourist season and differences in diet between males and females during the low season. This study demonstrates alterations in feeding ecology in stingrays at SCS which is of critical importance for effective management of the SCS aggregation.
Highlights
Ecotourism that consists of observing wildlife is a thriving business that generates billions of dollars to local economies[1,2,3]
The female stingrays randomly selected for the study averaged 107.2 cm disc width (DW), while the males were considerably smaller, as expected with this sexually dimorphic species (53.8 cm DW)
All animals had a passive integrated transponder (PIT) tag at the initial capture in January (10 males, 10 females) and once it was discovered that re-capture rate in April was poor for males (20% re-capture rate of males [2 individuals], 18 females), animals were sampled opportunistically in the subsequent months of July (7 males, 18 females), and October (7 males, 17 females)
Summary
Ecotourism that consists of observing wildlife is a thriving business that generates billions of dollars to local economies[1,2,3]. Feeding ecology of marine species is difficult to ascertain due to foraging primarily occurring out of sight, and indirect measures of diet and foraging are more commonly u tilized[12] Methodologies such as direct observations, stomach contents and fecal analyses have been utilized, often in c ombination[13]. Southern stingrays are popular animals for tourist-wildlife interactions, usually involving provisioning One such locale is Stingray City Sandbar (SCS), Cayman Islands, where southern stingrays are found year-round in dense aggregations consisting of both sexes at a naturally occurring sandbar in the North Sound lagoon of Grand Cayman[39]. This heavy reliance on provisioning by stingrays at SCS has resulted in altered blood FA profiles compared to non-tourist fed stingrays sampled in Grand Cayman[42]
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