Kurt Schaefer and Dan Fuller, scientists with the Inter-American Tropical Tuna Commission La Jolla, California, completed the 7th annual Tagging of Pacific Pelagics (TOPP) yellowfin tuna tagging cruise aboard the San Diego based long-range sportfishing vessel Royal Star (images provided) during the period of December 10-20, 2008. Those tagging cruises have been conducted on regularly scheduled 10-d trips aboard the Royal Star with the cooperation and assistance of co-owner and captain Tim Ekstrom and approximately 22 paying passengers aboard the vessel whom have all enthusiastically participated in the project through providing yellowfin specimens for implanting LOTEK LTD 2310 geolocating archival tags before release. During each cruise a seminar has been provided to the passengers and crew aboard the vessel while transiting to the fishing grounds, describing the objectives, methods, results, and implications of the TOPP yellowfin tuna tagging project regarding research, conservation, and management considerations.

The San Diego-based long-range sportfishing vessel Royal Star

During this year’s cruise just one day after departing San Diego south-bound for the designated fishing area off southern Baja California Mexico all aboard were fortunate to observe a most unusual sight. At about 2 PM on December 11th we observed an estimated 100-150 sperm whales (images provided) within a 2 to 3 nautical mile (nm) area about 6 nm north-west of San Benitos Islands (28°24.8’N-115°34’W). We do not know the reason for this large aggregation of sperm whales but it was a beautiful calm afternoon and the whales appeared to be milling about the area with no set direction. We spent about an hour in the area observing these remarkable whales, whom were very curious about the vessel and would come very close while we were drifting amongst them. At one point there was a tight group of about 10 whales nearby the vessel with the largest an estimated 40 to 50 feet total length as well as a calf of an estimated 8 to 10 feet. We observed several such groups in the area before resuming our course southbound, with all aboard enchanted by our fortunate timing and encounter with such an aggregation of sperm whales.

Passengers on the bow of the Royal Star gazing at sperm whales

This years tagging cruise aboard the Royal Star was successful, as the 43 archival tags scheduled for deployment were implanted in the peritoneal cavities of yellowfin tuna (images provided) ranging in length from 65 to 94 cm (mean = 74.2 cm). Thirty yellowfin were captured and released near the 13-Fathom Bank (25°43’N-113°08’W) and 13 yellowfin were captured and released near Punta Tosca (24°12’N-111° 30’W). All of these fish were associated with common dolphins. All specimens in which archival tags were implanted were also tagged with conventional green plastic dart tags. There is a US$250 reward offered for the return of these archival tags.

Kurt Schaefer of the IATTC surgically implants an archival tag in the peritoneal cavity of a yellowfin tuna being held in a tagging cradle aboard the Royal Star.

The timing of this years TOPP yellowfin tagging cruise was scheduled to occur during the time period in which a closure to purse –seine fishing was being observed by the Mexican fleet, with vessels tied up in port until around the middle of January 2009. This should allow for the fish to disperse somewhat from these areas where they were tagged and released, and hopefully lead to some long periods of time at liberty. Recoveries of archival tags from this years tagging experiment should provide a remarkable opportunity for comparative evaluations of the temporal variation in the movements, behavior, and habitat utilization of yellowfin from this highly productive oceanographic region within the eastern Pacific Ocean.

From left to right: Captain Tim Ekstrom, Kurt Schaefer and Dan Fuller after completing an archival tag surgery of a yellowfin tuna, before releasing the fish back into the sea