Human Impacts on Hawksbill Sea Turtles
I) Impacts in the nesting environment
- The greatest threat on nesting beaches is poaching. Poaching of hawksbill eggs is a serious problem in Puerto Rico , and also occurs at lower levels in St. Thomas and St. Croix . Adult females are still butchered for their tortise shell, but the practice is decreasing with better enforcement.
- Removal of sand for construction aggregate or renourishment of other beaches is a serious threat throughout the Caribbean. Sand removed from above the tide line is replaced very slowly from subtidal areas, a process which can take decades. Subtidal sand removal results in beach sand moving offshore.
- Exotic plants can damage or destroy nests through root action.
- Artificial lighting can cause disorientation or misorientation of both adults and hatchlings. Turtle hatchlings are attracted to light, ignoring or coming out of the ocean to go towards a light source, increasing their chances of death or injury. In addition, as nesting females avoid areas with intense lighting, highly developed areas may cause problems for turtles
- The most serious threat of nighttime use of a beach is the disturbance of nesting females. Heavy utilization of nesting beaches by humans may also result in lowered hatchling success due to sand compaction.
- The use of off-road vehicles on beaches is a serious problem in many areas. It may result in decreased hatchling success due to sand compaction, or it directly kills hatchlings. Tire ruts may also interfere with the ability of hatchlings to get to the ocean.
- A variety of natural and introduced predators such as hogs, mongooses, ghost crabs and ants prey on hawksbill eggs and hatchlings.
II) Impacts in the marine environment
- The extent to which hawksbills are killed or debilitated after becoming entangled in marine debris is unknown, but it is believed to be a serious and growing problem. Hawksbills have been reported to be entangled in monofilament gill nets, "fish nets", fishing line and rope.
- Hawksbill turtles eat a wide variety of debris such as plastic bags, plastic and styrofoam pieces, tar balls, balloons and plastic pellets. Effects of consumption include interference in metabolism or gut function, even at low levels of ingestion, as well as absorption of toxic byproducts.
- Incidental catch during fishing operations is an unquantified and potentially significant source of mortality. Gill nets, longlines and shrimp trawls all take turtles in Gulf of Mexico waters. In Puerto Rico , hawksbills are captured by a variety of fishing gear, including driftnets, gillnets, seines and spearguns. Gillnets and seines are widely deployed and are a particularly serious problem; these nets are sometimes set specifically for turtles.
- In areas where recreational boating and ship traffic is intense, propeller and collision injuries are not uncommon.
- In Puerto Rico , damage to coral reefs and other shallow water benthic systems from sedimentation and siltation has not been assessed as yet, but is known to be a serious problem in some areas, with some coral reefs completely destroyed by siltation.
- Pesticides, heavy metals and PCB's have been detected in turtles and eggs, but their effect is unknown.
- The illegal take of hawksbills at sea has not yet been fully quantified, but it is a continuing problem.
- Marine turtles are at risk when encountering an oil spill. Respiration, skin, blood chemistry and salt gland functions are affected.
- The hawksbill's dependence on coral reefs for shelter and food link its well-being to the condition of reefs. Destruction of reefs from vessels anchoring, striking or grounding is a growing problem. Cruiseships and yachts are destroying portions of coral reefs with their anchors and anchor chains in the US Virgin Islands, Puerto Rico , the British Virgin Islands , Belize and elsewhere. There is also damage from recreational, diving and fishing boats anchoring indiscriminately on reefs.
- International commerce in hawksbill shell (bekko) is the single most significant factor endangering hawksbill populations around the world. Japanese imports of raw bekko between 1970 and 1989 totalled 713,850 kg, representing more than 670,000 turtles; more than half the imports originated in the Caribbean and Latin America . While hawksbills are protected under CITES, trade continues for several reasons:
In nearshore waters, hawksbills are periodically captured in the colling water intakes of industrial facilities. In addition, illegal use of explosives for fishing is a concern, especially off the southeast coast of Puerto Rico .
- Not all countries have ratified CITES;
- Some treaty signatories participate in trade by falsifying documents of origin;
- Some treaty signatories ignore the treaty and trade openly in hawksbills and hawksbill products; and
- Some treaty signatories have exercised their right to take exemption to treaty provisions as they affect sea turtles.
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