Edwards and Perkins: Estimated tuna discard from dolphin, school, and log sets 
217 
Dolphin School Log 
Figure 4 
Estimated expected tuna discard per set by the U.S. tuna 
purse-seine fleet fishing in the eastern tropical Pacific 
Ocean, 1989-92, in specified geographic strata (Federal 
Register, 1989) and in all areas pooled. Standard errors 
indicated by vertical bars. 
Estimated Case 1 Case 2 Case 3 
Figure 5 
Estimated annual tuna discard by the US tuna purse-seine 
fleet fishing in the eastern tropical Pacific Ocean, 1989- 
92, under observed effort patterns and redistributed effort 
patterns where all dolphin sets were redistributed exclu- 
sively to school sets (case 1), equally to school and log sets 
(case 2), and exclusively to log sets (case 3). 
purse-seine fleet in the ETP was probably relatively 
minor (although local effects might have been large 
at some times). From the fishery’s inception in the 
early 1960’s through the mid-1980’s, the majority of 
U.S. vessels (which during that period represented 
over 90% of the international fleet) targeted tuna 
associated with dolphins, a strategy that generates 
very little tuna discard. 
The situation has changed dramatically in the past 
few years, in particular since 1 ) passage, in 1988, of 
stringent new amendments to the Marine Mammal 
Protection Act, 2) the decision by U.S. canneries in 
April 1990 to buy only “dolphin-safe” tuna, and 3) 
the passage of the International Dolphin Conserva- 
tion Act of 1992 (IDCA). The 1988 amendments re- 
quired non-U. S. fleets to meet strict comparability 
criteria related to dolphin mortality rates in order to 
export tuna to the U.S. The cannery decision for dol- 
phin-safe tuna (adopted also by European Commu- 
nity nations in 1993) means that the canneries in- 
volved will now buy only tuna that is certified not to 
have been caught either in association with dolphins 
or by drift gill nets on the high seas. The IDCA places 
increasing pressure on both U.S. and non-U. S. fleets 
to reduce dolphin mortality and to eliminate it alto- 
gether by 1999. 
Largely in response to these events, most U.S. ves- 
sels have left the ETP, either to change flags, retire 
from fishing altogether, or to fish in the western Pa- 
cific Ocean under license from various island nations. 
Of those U.S. vessels remaining (4 vessels in 1994), 
all fish on school and floating logs. This change to 
school and log fishing will have greatly increased the 
U.S. discard of small immature tuna, although the 
overall effect on the tuna stocks due to changes in 
fishing practices by the U.S. fleet is probably small 
because very few U.S. vessels are currently fishing 
for tuna in the ETP using any of these set types. 
However, the decrease in the size of the U.S. fleet 
has been offset by increases in the sizes of non-U. S. 
fleets so that the overall size of the international fleet 
has remained relatively constant since the mid- 
1980’s. Although many of the non-U. S. vessels are 
still fishing “on dolphin,” increasing numbers of ves- 
sels changed during the study period to school and 
