Tagging of Skipjack — Yamashita and Waldron 
347 
Fig. 4. Tagged skipjack recovered 252 days after release with only the jacket portion of the tag still in place. 
Dorsal view showing healed wound (dark area in circle) on the left side. Photograph by E. D. Stroup. 
Honolulu auction markets was carried out 
between October, 1955, and June, 1956. Dur- 
ing this interval, which included periods when 
skipjack were being tagged and released 
within the fishery, stomachs were examined 
from 538 bigeye {Parathunnus sihi), 103 yel- 
lowfin, 128 striped marlin {Makaira audax), 
and 74 black marlin {Makaira ampla) taken 
in the Hawaiian longline fishery. Twenty- 
eight of these stomachs (3.3 per cent) con- 
tained a total of 30 skipjack, none of which 
was tagged. Furthermore, only 9 of the 30 
skipjack were as large as those being tagged, 
i.e., 2 pounds or larger, and the rest were 
estimated to be 1 pound or less. Only one 
large skipjack was taken from the stomach of 
a tuna; the others were from black and striped 
marlins. Unfortunately, there are no com- 
parable data concerning the number of un- 
tagged skipjack from stomachs at the time 
the three tagged fish were found, but on the 
basis of subsequent sampling it seems that 
there was a higher rate of predation on tagged 
than on untagged fish. 
SUMMARY 
A tagging project was inaugurated to study 
migrations and to supplement our knowledge 
of growth of skipjack in Hawaiian waters. 
During the period 1954-1956, California 
type G tags were attached to 1,961 skipjack 
released in Hawaiian waters. The majority of 
these fish weighed less than 10 pounds. 
Only 12 or 0.6 percent of these fish were 
later recovered. This low recovery rate may be 
attributed to tagging mortality, predation, 
and movement out of the fishery. 
The longest interval between release and 
recovery, by pole-and-line fishing, was 252 
days and the shortest interval was 6 days. 
Net movement was limited to 40 miles or 
less and no inter-island travel was shown. 
The tag wounds on recovered skipjack were 
enlarged but well healed after 12 days. When 
used on smaller fish, the free ends of the tag 
caused chafing of the anterodorsal margin of 
the caudal fin. 
One skipjack weighing 14 pounds at re- 
covery grew at an estimated rate of 0.8 pound 
per month over an 8U-month period. 
Predation by large tunas and spearfishes 
may be greater on tagged than on untagged 
skipjack. This conclusion is based on the 
recovery of three tagged skipjack from the 
stomachs of large tuna. 
