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Fishery Bulletin 115(1) 
confounded by sexual segregation that can lead to spa- 
tial or temporal segregation (Conradt, 2005). 
On the northwest Atlantic continental shelf, habi- 
tat use and seasonal movements of spiny dogfish 
have been reported to differ by sex — the key driver 
being seasonal changes in temperatures (Shepherd et 
ah, 2002; Methratta and Link, 2007; Sagarese et al., 
2014a, 2014b). Additionally, it has been suggested that 
the movement of species is influenced by the distribu- 
tion of their prey (Overholtz and Tyler, 1985; Sagarese 
et al., 2014b). In this region, aggregations of mature 
females are commonly found inshore, in shallower and 
warmer waters, and aggregations of mature males 
dominate offshore, deeper and colder waters (Shep- 
herd et al., 2002; Sagarese et al., 2014a). Collectively, 
the spiny dogfish is characterized by north-south sea- 
sonal migrations: fish overwinter off North Carolina 
and migrate northward during the spring to waters in 
New England and Gulf of Maine, where they remain 
between summer and late fall before their southward 
migration (Ruiifson, 2010). 
A regional study in which fishery-dependent data 
were used and that was conducted in inshore coastal 
waters inside and off the peninsula of Cape Cod, Mas- 
sachusetts (Dell’Apa et al., 2014), elucidated the local 
habitat association of spiny dogfish, by sex, and pro- 
vided information on the potential drivers of sexual 
segregation in this species. The results of that study 
indicated that the distribution of the 2 sexes differed 
by location, season, and time. The highest occurrence 
of adult males was found early in the day and between 
spring and early autumn in inshore waters off the east- 
ern side of the sampling area in relatively close prox- 
imity to deep water (>100 m), and highest occurrence of 
adult females was found inshore, in waters (depths <78 
m) shallower than the waters in which adult males oc- 
curred, and farther inside the Cape Cod peninsula than 
the other locations surveyed (DelFApa et al., 2014). 
DelFApa et al. (2014) suggested that adult females may 
actively seek shallow waters as a strategy to elude adult 
males and energy-demanding copulation — a tactic that 
results in spatial segregation. Alternatively, in deeper 
coastal areas, where males are usually more abundant, 
adult females may synchronize their different habitat- 
selection behavior with that of adult males, resulting in 
temporal segregation (DelFApa et al., 2014). 
Overall, the results of that study indicate that sex- 
ual segregation in spiny dogfish, in the Cape Cod area, 
occurs both spatially and temporally and is strongly in- 
fluenced by depth. Different behavioral choices by each 
of the sexes are reflected in their preferred habitat as- 
sociations and indicate that depth and time, but likely 
not temperature, are potential key drivers for sexual 
segregation in spiny dogfish (DelFApa et al., 2014). 
However, that study was based on limited data collect- 
ed through fishery-dependent surveys in a regionally 
restricted inshore coastal area, and the findings may 
not be representative of the entire U.S. Atlantic stock 
of spiny dogfish. Therefore, for fishery management 
purposes it would be useful to analyze existing data 
sets from a larger coastal area, one that encompasses 
the entire range of the current commercial fishery be- 
tv/een New England and North Carolina. 
In addition, it would be beneficial to analyze com- 
parable regional data from fishery-independent inshore 
surveys. In this regard, the nearshore trawl surveys 
conducted by the Northeast Area Monitoring and As- 
sessment Program (NEAMAP) in the mid-Atlantic rep- 
resent the most suitable data source that is available 
for completing a more extensive study on the influence 
of environmental habitat characteristics, season, and 
time of day on the distribution of spiny dogfish in in- 
shore coastal waters of the northeastern United States. 
The aim of this study was to use the NEAMAP sur- 
vey data to model the abundance of spiny dogfish, by 
sex, in inshore coastal waters of the U.S. Atlantic, by 
considering oceanographic (i.e., sea-surface tempera- 
ture [SST], salinity, and chlorophyll-a [chl-a] concen- 
tration), topographic (i.e., depth, slope, and distance to 
land), and temporal (i.e., season and time of day) char- 
acteristics as predictive variables for catch per unit of 
effort (CPUE). This study involved the use of hierarchi- 
cal Bayesian spatiotemporal models and is the first one 
to use a large fishery-independent database as a source 
of data for analysis and prediction of the habitat dis- 
tribution of spiny dogfish along the northwest Atlantic 
inshore coastal area, by sex and by time of day. The 
results of this study provide information on the spatial 
and temporal distribution of adult spiny dogfish that 
will be valuable for fishery managers because it will 
enable the adoption of enhanced management strate- 
gies for the fishery for spiny dogfish in the U.S. Atlantic 
that are based on the sexual segregation exhibited by 
this species. 
Materials and methods 
Mid-Atlantic surveys 
NEAMAP surveys are conducted in the coastal waters 
bounded by the western edge of Cape Cod, Massachu- 
setts, and by Cape Hatteras, North Carolina. From 
Montauk, New York, and southward, sampling is con- 
fined within the 18.3-m depth contour. In the deeper 
nearshore waters off southern New England, the deep- 
est stations extend to about 36.6 m (Fig. 1). NEAMAP 
conducts 2 cruises per year, one each in spring (April- 
May) and fall (September-October), timed to rough- 
ly coincide with offshore surveys carried out by the 
NOAA Northeast Fisheries Science Center (NEFSC). 
Each NEAMAP cruise samples 150 stations distributed 
among 17 regions and 2 depth strata. To allow compari- 
sons with current NEFSC surveys, NEAMAP adopted 
the bottom trawl design developed for the NEFSC by 
the Northeast Trawl Survey Advisory Panel, joint board 
of the Mid- Atlantic and New England Fishery Manage- 
ment Councils. The NEAMAP conducts surveys by fish- 
ing with a 3-bridle, 4-seam bottom trawl with a net of 
400 meshes (of 12 cm width) for a total length of 48 
