Transshipment Fishery Description
Trends in Vessels by Nation
Since 1989 the island of Guam has become an important port for both the Japanese and Taiwanese longline fleets and together they annually landed 9,927 t of fresh fish for the Japanese market.
The Japanese and Taiwanese longline vessels annually averaged more than 99% of the landings of Guam fresh tuna transshipment fishery with a very minor contribution from the Korean fleet. The Japanese vessels spent a median of 22 days at sea of which 17 were fishing days. The median number of days at sea for the Taiwanese longline vessels was 21 of which 11 days were spent fishing. Most of the reported fishing by both fleets was centered between the 2-5°N latitudes and 140-160°E longitudes.
Seasonally, the Japanese longline vessels made proportionately more trips to Guam during the first half of the year; conversely more trips were made by the Taiwanese fleet during the later half of the year.
The Japanese fleet size declined significantly from 106 vessels in 1989 to 51 vessels in 1996. The number of Japanese trips to Guam fell from a high of 817 trips in 1990 to 131 in 1996 with an annual average of 517.25 trips/year.
Although the drop in the landings appear to suggest declining fishing effort in the Western Pacific, reported catches of bigeye and yellowfin within the SPC affiliate areas remained relatively unchanged during the period between 1989-95 at an average annual landing of 42,668 tons. A possible explanation for this is that the Japanese vessels are using other ports to transship fresh tuna to the market in Japan. These could include ports in the Federated States of Micronesia which are closer to the fishing grounds.
In contrast, the number of Taiwanese vessels rapidly increased from 118 to 364 during the same period. As a result, the number of reported Taiwanese fishing trips also increased from a low of 274 in 1991 to a high of 1542 trips in 1995, a greater than 300% increase with an annual average of 750.75 trips.
Trends in Tuna Catch by Nation
In 1991, a total of 9,627 t of fresh fish was transshipped from Guam to Japan with yellowfin and bigeye tuna comprising 96% of the total. Landings from the Japanese and Taiwanese longliners accounted for 84% (8,058 t) and 14% (1,310 t) of the catches respectively. The newest addition to the fishery was the Korean fleet that landed 241 t or 2% of the total catch.
Annual landings of bigeye tuna (Thunnus obesus) by the Japanese averaged 3,798 t but have since declined from a high of 7,170 t in 1989 to 1,253 t in 1996. Similarly, Japanese yellowfin tuna (Thunnus albacares) landings have also declined during the same period from a peak of 5,719 t in 1989 to a low of 620 t by 1996.
Taiwanese caught bigeye tuna remained relatively constant with an annual average of 1,273 t. Taiwanese yellowfin landings, however, increased over six fold during the same period from 870 t to 6,336 t.
Together, both of the fleets landed an average of 137,500 bigeye tuna per year. The number landed ranged from a high of 247,000 in 1989 to a low of 59,000 in 1996. This is a significant downward trend in the number of fish landed. The annual number of yellowfin tuna landed ranged from 140,000 to 267,000 and averaged 194,000 with no detectable trend.
The Japanese longline fleet annual landings of bigeye tuna declined severely from a high of 212,217 in 1989 to 33,537 by 1996. Like bigeye, the number of yellowfin tuna landed by the Japanese has also declined from a high of 242,238 in 1989 to 24,759 in 1996, with an average of 109,901 fish per year.
The number of bigeye landed by the Taiwanese vessels remained relatively unchanged with the annual mean count of 28,154 fish with a range of 11,150 to 38,781. The Taiwanese landings of yellowfin tuna dramatically increased from a low of 24,808 in 1989 to 184,740 by 1996, with an annual average 82,854 fish landed. The disparity in landings by the Taiwanese of the two major tuna species could be the result of the fleet targeting yellowfin tuna with monofilament gear which tend to fish shallow.
Trends in Tuna Size and Reject Rate by Nation
Through the years the mean sizes of bigeye and yellowfin tuna have remained unchanged with the Taiwanese landing the larger fish.
The mean weight of bigeye tuna that met the market grading were 36.65kg from the Japanese fleet and 45.32 kg from the Taiwanese fleet. The average size of yellowfin tuna air transshipped to the market was 28.6 kg from the Japanese and 38.73 kg from the Taiwanese vessels.
A possible explanation for the disparate sizes is the Taiwanese fishing practices. The Taiwanese fleet generally fish for quantity over quality and as a result their catches were priced lower on the fresh fish market. Consequently, the Taiwanese were inclined to be more selective against unloading fish that were either small or of a lower quality as these fish that would be rejected for Transshipment. These fish were kept on board were sold in Taiwan where a better price could be acquired.
The annual quality rejection rate average of Japanese bigeye tuna was 6.04% and ranged from 1.3% to 12.4%. The overall mean rejection rate of bigeye tuna from the Taiwanese fleet was 7.1%. The average weight of rejected fish was significantly lower than market grade fish.
Despite the declining yellowfin landings, the annual rejection rate for yellowfin tuna increased from a low of 5.7% in 1989 to a high of 42.6% in 1995 with an average of 20.3% for the Japanese. Similarly, the annual rejection rate of Taiwanese caught yellowfin tuna increased significantly from 4.5% to 33.5% during the same period.
In recent years an industry has developed a market for the rejected tuna. Rejects were bought and stored frozen for later export to foreign canneries. The prices of rejected fish have improved over the past and partially explain the increase landings of rejected fish.