Tagging Bigeye Tuna off of Kona, Hawai'i,  Cruise 99-01

January 5 - January 29, 1999
     The TOWNSEND CROMWELL was working off the Kona Coast of Hawai'i and at Cross Seamount (130 nautical miles southwest of the Big Island). This cruise, the ship's mission was to capture tuna (specifically bigeye tuna) for a tag and release study. In the past, fish tags were mainly used to mark a fish, enabling scientists to compare the fishes size with the time and location of the fish between captures. The tags we placed in the bigeye tuna are more sophisticated. They record depth, seawater temperature, the fish's body temperature, and the amount of sunlight. By comparing the amount of sunlight with the depth and time, the scientists can determine a rough idea of where the fish traveled in between captures. Another important item contained on the tags, is a phone number which fisherman can call for instructions on how to return the tags to the NMFS Honolulu laboratory. For each tag returned, the fisherman receive a monetary reward. Unfortunately, many tags are never seen again as natural predators eat the fish or the fish are caught by fisherman who don't notice the tags.

     The TOWNSEND CROMWELL uses longline fishing gear to capture the fish. As the 8.5 mile line is hauled in, each fish is carefully lifted out of the water using a specially designed "hammock" and placed upon a cushion on the deck. Assistants cover the fish's eyes to keep it calm and gently hold it still while Fisheries Scientist, Rich Brill, inserts the electronic tags within the back of the fish. The tags have been proven to hinder the fish very little and the incision quickly heals around the tag with the light collecting "antennae" protruding out. An Identification tag is also attached which records where and when the fish was caught and it's size. The incision is sewn and glued closed and the fish is than quickly released.
     Bigeye tuna are an important commercial species in Hawaii. The scientists hope the data recovered from the tags will be useful in studying the ranges of these fish and ultimately gain an idea of how much fishing their population can support.