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Fishery Bulletin 1 10(3) 
T 
Computational group 
(100 x 100 cells) 
Figure 2 
Diagram of one computational group of 25 fishing sets in the independent 
clumping scenario {Turtles ^ )u , Sefs clump _ sets ). A fishing set is a single deploy- 
ment of fishing gear made by a vessel. The grid is 100x100 cells. The dark 
borders of the fishing set clumps indicate the cells that could be fished by 
a set that began at the edge of the interior of its clump (lighter gray cells 
indicate clump interiors). The light gray lines of 5 cells indicate fished cells. 
Turtles were placed in the interior of their clumps (white cells indicate clump 
interiors), and the dark borders of the turtle clumps indicate the cells that 
could be fished by a set that began at the edge of that turtle clump. No part 
of fishing set clumps could overlap. Borders of turtle clumps could overlap, but 
interiors of turtle clumps could not; therefore, sets could not fish in multiple 
turtle clumps. No restriction was placed on how turtle clumps and set clumps 
could overlap each other. 
of the estimation methods that are relevant to other 
problems with the management of natural resources. 
General structure of the simulation model 
Much remains unknown regarding the spatial distribu- 
tions of sea turtles, how fishermen decide where to fish, 
and the nature of interactions of sea turtles with fishing 
sets in time and space. Therefore, we designed several 
spatially explicit scenarios to address the uncertainty 
and variation in interactions of sea turtles and the 
fishery. Five spatial scenarios were modeled (Fig. 1): 
1) co-occurrence clumping {Turtles clump , Sefs clump . turtles ); 
2) independent clumping {Turtles clump> Sefs clump _ sets ); 
3) sets-only clumping {Turtles uniform , Sefs clump . sets ); 4) 
turtles-only clumping (Turtles clump , Sets uniform ); and 5) 
fully uniform distribution {Turtles uniform , Sets uni(orm ). 
Details of model construction 
In each simulation, the number of fishing sets that we 
modeled was 8000, which was approximately the aver- 
age number of sets reported annually to the SEFSC 
from 2005 to 2007 (Walsh and Garrison, 2006; Fairfield- 
Walsh and Garrison, 2007; Fairfield and Garrison, 
2008), the first 3 years after NMFS regulations man- 
dated a change from J-hooks to circle hooks for the 
longline fishery (Watson et ah, 2005). Circle hooks were 
required to reduce the number of sea turtles caught 
and the severity of their injuries. However, rather than 
simulating 8000 sets at once, we divided the 8000 sets 
into computational groups of 25 sets for convenience 
(Fig. 2). The computational groups of 25 sets were 
used to distribute turtles and sets, place observers, 
and simulate bycatch, but bycatch estimates were not 
made at this scale. 
With the Atlantic Ocean, Caribbean Sea, and Gulf of 
Mexico divided into 10 geographic regions and bycatch 
estimates for these statistical areas made by the SEFSC 
for each calendar quarter, bycatch estimates are made 
in 40 quarter-area strata. Bycatch rates were expected 
to vary across these strata; therefore, we also modeled 
strata (Table 2). For each stratum, we calculated the av- 
erage number of sets reported to the SEFSC from 2005 
