Tuesday, June 4, 2013

Tuna trap tagging takes teamwork!

Our tagging efforts, initially scheduled to commence on May 14th, following the ICCAT SCRS Meeting, were delayed due to heavy winds and anxious seas, which posed too much risk for both the divers and the tuna.  After waiting five days for the winds to subside and the seas to calm, we headed to the port town of Larache on May 19 and attempted to initiate the tagging operation.  Although the winds had calmed, the swell remained high, and still posed too much risk for the team, but weather forecasts appeared promising for the following morning. 

Waiting for a calm weather window.
Image: George Shillinger
Anchors await deployment at the Société Maromadraba offices in Larache, Morocco.  
Image: Pablo Cermeño  
We decided to divide the tag deployment efforts into two different methodologies to examine for any bias in movement behavior that might be associated with the tagging procedures.  One-half of the PAT-tagged fish (n=7) would be tagged on board and the other half would be tagged in the water while the fish were in the chamber.




Diver guides tuna into the ‘tagging chamber’.
Image: George Shillinger


Artisanal fishermen assist with the tag deployment effort.
Image: George Shillinger

Fishermen prepare the trap for tagging.
Image: George Shillinger
The trapped fish were lead into a smaller chamber, surrounded by the fishermen. The fishermen worked to manually lift the nets, and brought the tuna to a depth (~ 20m) accessible to the divers.  Divers manually captured each tuna and shepherded them into slings, where they rolled over underwater, belly side up.    


Fishermen draw the nets while divers await access to the trapped fish.
Image: George Shillinger


Lowering the giant tuna sling into the tagging chamber -- to awaiting divers and fish.
Image: George Shillinger


Tuna and diver square off in the trap.
Image: George Shillinger

A skilled tuna trap diver captures and rolls a bluefin, in preparation for maneuvering the fish into the sling.
Image: George Shillinger
A huge stretcher and a crane were used to hoist the tuna onboard the tagging vessel. The remainder of the tagging operation followed standard TAG deployment procedures used in North Carolina, Canada, and elsewhere around the world.  The team double-tagged seven fish (ranging from ~215-250 cm CFL) with seven Wildlife Computer mini-PATs and seven VEMCO V16 acoustic tags. An additional tuna was tagged with a single Vemco V16 acoustic tag.  The following morning, another seven fish were tagged in the water with Wildlife Computer mini-PATs.




A bluefin is released from the sling following a successful double-tag (mini-PAT and acoustic) deployment.
Image: George Shillinger


Carefully coordinated teamwork is essential for successful tag deployments on Moroccan trap tuna.
Image: George Shillinger
This year’s Moroccan trap tagging effort was an outstanding success and an excellent example of collaborative research linking together artisanal fishermen, scientists, and fisheries managers. 


Dr. Pablo Cermeño smiles as another tagged tuna departs the trap.
Image: George Shillinger

The 2013 Morocco Atlantic bluefin tagging team.
Image: George Shillinger
The ancient Moroccan trap fishery presents a unique opportunity to expand the state of knowledge about bluefin tuna research and conservation, and TAG is proud to contribute to this effort!