Ski-Boat — May-June 2017

research permit by DAFF to carry out
cruises within a 100 nautical mile
radius of Hout Bay in order to tag yel-
lowfin, bigeye and skipjack tuna.
At the time of publishing a total of
89 skipjack and 25 yellowfin tuna had
been tagged with yellow or red
spaghetti tags. This may seem like a
slow start, but the violently strong
south-easter winds only allowed the tag-
ging team to fish for 19 days in
February and even fewer days in March.
Even the Cape Argus Cycle Tour was
cancelled due to these winds. But fin-
gers are crossed that they will have
enough time on the water to tag more
fish, for you, our readers and anglers, to
recover.

DIFFERENT TAGS
Four types of tags are currently being
deployed during the program:

• Yellow conventional or spaghetti
  tags — these tags are inserted on
  the left hand side of the fish adja-
  cent to the dorsal fin. In some cases
  fish will be “double-tagged” (left and
  right side) in order to measure tag

shedding rates. This is the most

common type of tag deployed.

• Red spaghetti tags (chemical mark-
  er) — only 10% of the fish caught
  for tagging will be tagged using red
  tags. Fish with red tags are injected
  with oxytetracycline (OTC), a chem-
  ical marker that, once recovered,
  will allow scientists to precisely cal-
  culate how fast the fish grew
  (between tagging and recapture) by
  looking at the amount of calcium
  carbonate deposited on their bones.


• Red spaghetti tags (internal elec-
  tronic archival) — in addition to the
  chemical markers, tuna with the red
  tags will also have internal electron-
  ic archival tags surgically implanted
  in their body cavity. These tags can
  record up to 600 days of data such
  as depth, temperature and salinity
  preferences of tuna to help under-
  stand how tuna survive in the vast
  pelagic environment.


• Pop-up Satellite Archival Tags
  (PSATs) — these are surgically fixed
  adjacent to the dorsal fins of large
  yellowfin and bigeye tuna and are

attached in such a way to minimise

any effects on the fish’s swimming

performance. The PSATs are pre-

programmed to detach from the fish

after a set number of days. The tags

will be fitted with a buoy in order to

enable them to float to the surface

and, once there, they will begin

relaying data via satellite. If these

tags are recovered then valuable

additional data can be uploaded

from the tag itself.

The Awareness and Tag Recovery

Program team at CapMarine and DAFF

are seeking tag recovery information

from the main ports and landing sites in

South Africa, as well as catch reports

from the commercial, recreational and

charter tuna vessels. The success of the

AOTTP is dependent on the reporting

of tagged fish once they are caught by

commercial and recreational fishermen.

CapMarine has already been hard at

work spreading the awareness of this

campaign throughout the coastal fish-

ing towns of the Western Cape, up the

Eastern Cape coastline and into

KwaZulu-Natal as well.

SKI-BOAT May/June 2017 • 41

Above: Tags ready to be deployed.

Right: A tagged tuna is measured before

being released.