Warraich, Natasha

Loggerhead and leatherback sea turtles are often caught as longline bycatch in fisheries
worldwide. These species of sea turtle differ greatly in life history, morphology, and the ways
they are hooked. Leatherbacks tend to be “foul hooked,” externally in the shoulder or flippers,
while loggerheads tend to be hooked in the mouth or they swallow the bait so that hooking is
internal esophagus or stomach. The numbers of loggerheads and leatherbacks caught decreased
after changes in gear, bait and time of sets. However the proportion of leatherback mouth
hookings increased while foul hooking decreased. We described and compared prey approach
and attack behavior of both species in the presence and absence of visual targets. Waterborne
squid and jellyfish odors were used to elicit feeding behavior in the two species. Visual targets
were necessary to elicit biting. Loggerheads approach their prey with the mouth wide open, have
exceptionally good aim and usually bite their intended target. This accuracy is consistent with
the mouth and internal hooking. Leatherbacks frequently overshoot, miss their intended target
then have to re-approach the target multiple times before making contact. Leatherback feeding
behavior is disrupted easily if the body or flippers are touched during prey approach. This reapproach
behavior may make leatherbacks more prone snagging on lines rigged with J-hooks.
The shift by some fisheries to circle hooks, which are less prone to snagging, by give the
leatherbacks multiple chances to attack the bait and ingest it without getting hooked externally.

Two species of sea turtle, loggerheads (Caretta caretta) and leatherbacks (Dermochelys
coriacea) are caught frequently as bycatch in longline fisheries. These fisheries use
hooks baited with fish or squid. Yet, leatherbacks feed on gelatinous prey while
loggerheads are carnivores. I investigated the responses of these two species to bait
odors in controlled laboratory experiments to better understand their feeding behavior
and why they interact with longlines. Both species initiated feeding behavior in the
presence of squid bait odors and just C. caretta showed feeding behavior with sardine
odors; neither responded to mackerel odors. The turtles are hooked differently on
longlines. Loggerheads are usually hooked in the mouth while leatherbacks are usually
hooked in the shoulder or flippers. Comparisons of prey attack behavior and accuracy in
apprehending a stimulus in the presence of waterborne food odors identified speciesspecific differences that may predispose the turtles to particular kinds of hooking.