Bycatch Loggerhead Satellite Tagged

 STUDYING THE AFFECT OF ATTACHED SATELLITE TAGS ON THE GROWTH OF JUVENILE LOGGERHEAD TURTLES

 

 A concern that exists regarding the attachment satellite tags to the carapace of a hard shelled sea turtle is how that attachment would affect the growth of scutes under the tag.  There is little to no evidence regarding the effect of these tags because very few of them are ever recovered in order to see if there was any impact on the growth. In addition, when a turtle with a satellite tag stops transmitting (and the battery is still good), we don't know if it was because the turtle was predated, died from some other cause of if the tag "fell" off?  

How hard shelled sea turtles grow:

 The internal structure of the carapace (the dorsal covering of the turtle) is made of approximately 50-60 bones including the turtle's ribs and vertebrae, which are fused together. These bones grow primarily at their edges along "suture lines," which are zip-zagging seams similar to those in a human skull.  As the turtle grows, new bone material is added at these seams to expand the overall surface area of the shell.  

The bony shell is covered by a layer of scutes, which are protective plates made of keratin (the same protein as human fingernails) Because keratin does not stretch, new, larger layers areproduced underneath the existing scutes by a thin layer of tissuecalled the epithelium. In hard-shelled sea turtles, the old, smaller outer layers of these scutes periodically peel and shed in individual pieces to make room for the larger layers beneath.

In order to study the affect of tag attachment on the growth of the carapacial bones and scutes we procured 2 "mock" tags from Wildlife computers to put onto 2 turtles and keep them at the Port of Nagoya Public Aquarium.

On June 20, 2024 while the STRETCH team was in Nagoya attaching satellite tags to the 28 juvenile loggerhead turtles of Cohort II, we attached a "mock" tag to a similar sized juvenile loggerhead to be kept at the Port of Nagoya Public Aquarium.  The purpose of this was to see how long the tag will stay attached and what affect the tag attachment would have on the grow of the scutes (scales) under the polyester resin and fiberglass cloth of the attached tag.  

The juvenile loggerhead turtle (tag #5333) was kept in a large tank at the aquarium during the trial. 

 

images captured on 12/24/25 a short time before the tag detached and fell to the bottom of the tank.

As indicated on the main blog page, the rate of growth and the scute form appears to be very normal indicated that, at least for a tag attached for 567 days, there was little impact on the turtle.