An estimated 250,000 loggerhead (Caretta caretta) and leatherback
(Dermochelys coriacea) sea turtles are taken each year as incidental catch by the pelagic
long-line fishing industry. Various gear and bait modifications as well as time/area
closures to fishing, enacted to reduce anthropogenic impacts on sea turtles, have been
ineffective or incompatible with regional fishery interests. Chemosensory and auditory
deterrents have yielded little benefit thus far in repelling sea turtles from long-lines. The
fact that sea turtles are highly visual animals has precipitated studies of the efficacy of
using shark shapes to repulse them from long-lines. Previous shark-shape studies
yielded promising results, but their design lacked statistical rigor. The present study
examined the response of 42 captive-reared loggerhead sea turtles (Caretta caretta) to a
shark-shape model at the NOAA Sea Turtle Facility in Galveston, TX. To measure
repulsive effect, time taken to consume squid bait beneath the shark model was
compared to that for controls in which loggerheads were offered squid beneath a
spherical object or a bare squid (i.e., no object control) in a captive setting. Additional
responses compared among these three treatments were time spent near treatment, number of breaths taken, approaches to the treatment, and avoidance behaviors displayed
(e.g., turning carapace toward treatment).
Loggerheads exhibited anti-predator behavior toward the shark model, taking
significantly more time to consume squid bait beneath the shark model than for the other
two treatments. Turtles also spent significantly more time opposite the tank from the
shark model, approached it less often, and exhibited more carapace turns to the model.
Some avoidance of the spherical control object also was observed, but was not as
pronounced as that displayed toward the shark model.
While a repulsive effect of the shark model was resolved during the
aforementioned trials, application of such models to reducing long-line fishery bycatch
would require further research to identify a plausible application; numerous shapes
attached to long-line hooks would be very cumbersome. However, it may be plausible
to develop a “boy’s day kite” shark model that would unfurl and “fly” underwater, and
could possibly be clipped to buoy float lines.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2010-08-8409 |
| Date | 2010 August 1900 |
| Creators | Bostwick, Angela Sue |
| Contributors | Landry, Jr., Dr. Andre M. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | thesis, text |
| Format | application/pdf |
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