Sagarese et al. : Spatiotemporal overlap of Squalus acanthias and commercial fisheries within the northeast U.S. marine system 
15 
0 5 10 15 20 
log (Abundance of mature females [number per survey tow]) 
Figure 6 
Relationship between log e -transformed abundance of mature female (to- 
tal length >80 cm) spiny dogfish (Squalus acanthias ) in the northeast 
U.S. shelf large marine ecosystem and their availability to (A) the otter 
trawl fishery during autumn (availability=22.269 log e [catch per unit of 
effort (CPUE)]+10.954, coefficient of multiple determination [f? 2 ]=0.48, 
P=0.0005) and (B) the sink gillnet fishery during spring (availabil- 
ity^. 867 log e [CPUE]+24.217, R 2 = 0.24, P=0.024) between 1989 and 
2009. Data points reflect annual observations. Solid lines indicate fitted 
logarithmic trends. 
(ASMFC 2 ). Higher spatial overlap after 1998 indicates 
increased availability of the stock to each fishery. Al- 
though this observation seems counterintuitive given 
that the fishery in the 2000s was strictly one of by- 
catch, it is possible that this increased overlap is re- 
lated to distributions of species targeted by fisheries 
and spiny dogfish (i.e., predation). 
The use of commercial statistics in tracking abun- 
dance trends is often discouraged because of nonran- 
dom fishery behavior, particularly because fishing 
crews search for concentrations of fish rather than 
fish at random (Paloheimo and Dickie, 1964; Salthaug 
and Aanes, 2003); however, fishery-dependent data 
have provided a rare opportunity to examine fishery 
behavior and investigate how fisheries are distributed 
with respect to a marine resource. Clustering of spiny 
dogfish CPUE in the SGN fishery indicated that this 
fishery, compared with the OT fishery, targeted spiny 
dogfish more directly. Annual Moran’s I values revealed 
relatively high clustering of CPUE during the 1990s 
as fishing effort spread inshore in SNE and Mid-At- 
lantic Bight. During this same time period, a shore- 
ward shift in distribution, predominantly of mature 
males but also of mature females, was documented by 
the bottom trawl survey (NEFSC 3 ). Trends for the OT 
fishery indicated more random catches of spiny dogfish 
compared with trends for the SGN fishery, supporting 
the notion that OT catches are likely bycatch. Further 
