High predation of marine turtle hatchlings near a coastal jetty

Growing human populations are driving the development of coastal infrastructure such as port facilities. We used acoustic telemetry to examine the effects of a jetty and artificial light on the rates of predation of flatback turtle (Natator depressus) hatchlings as they disperse through nearshore waters. When released near a jetty, around 72% of the tagged hatchlings were predated before they could transit the nearshore, irrespective of the presence or absence of artificial light. Evidence for predation was provided by rapid tag detachment due to prey handling by a predator or the extensive movement of the tags within the receiver array suggesting that the tag (and hatchling) was inside the stomach of a predator. We found that 70% of the fish predators that consumed tags used the jetty as a refuge during the day and moved along nearshore waters at night.
By providing daytime refuges for predators, nearshore structures such as jetties have the potential to concentrate predators and when these structures are located near turtle nesting beaches, they can increase the predation rate of hatchlings. The potential for elevated rates of predation on hatchlings must be taken into consideration when assessing the environmental impact associated with these structures.