89 
National Marine 
Fisheries Service 
NOAA 
Fishery Bulletin 
fb- established in 1881 •<?. 
Spencer F. Baird 
First U S. Commissioner 
of Fisheries and founder 
of Fishery Bulletin 
Modeling the habitat distribution of spiny 
dogfish iSqualus acanthiasX by sex, in coastal 
waters of the northeastern United States 
Email address for contact author: dellapa.andrea@gmail.com 
’ Earth Resources Technology Inc. 
1315 East-West Highway 
Silver Spring, Maryland 20910 
2 Universidade Federal do Rio Grande do Norte (UFRN) 
Department of Ecology 
Campus Universitario s/n, Lagoa Nova 
CEP 59.098-970 Natal (RN), Brazil 
3 Virginia Institute of Marine Science 
College of William and Mary 
P.O. Box 1346 
Gloucester Point, Virginia 23062-1346 
Abstract— A hierarchical Bayesian 
approach was used to model the spa- 
tiotemporal habitat distribution of 
spiny dogfish (Squalus acanthias) 
of both sexes (adults) caught dur- 
ing trawl surveys conducted by the 
Northeast Area Monitoring and As- 
sessment Program in inshore coastal 
waters between New England and 
North Carolina during 2007-2013. 
The best model for predicting catch 
per unit of effort (CPUE) for this 
species includes the following rel- 
evant variables: bathymetry, sea 
surface temperature, salinity, chloro- 
phyll-a (chl-a) concentration, season 
and time of survey, and a random 
spatial effect for both sexes. Predict- 
ed CPUE was related to depth for 
both sexes; females occurred in shal- 
lower waters than those in which 
males occurred. Also, more females 
than males were predicted to oc- 
cur in warmer, less saline and more 
productive (higher chl-a concentra- 
tion) waters. Seasonality and time of 
predicted CPUE indicated that the 
abundance of females was higher in 
inshore coastal waters in the spring 
and in the morning, and the abun- 
dance of males was greater in the 
afternoon and in the fall in the same 
area. Collectively, these results pro- 
vide information that enhances our 
understanding of differences in habi- 
tat selection and spatiotemporal dis- 
tribution of the 2 sexes of this spe- 
cies — information that can help to 
modify present management strate- 
gies for the US. Atlantic fishery. 
Manuscript submitted 15 April 2016. 
Manuscript accepted 17 November 2016. 
Fish. Bull. 115:89-100 (2017). 
Online publication date: 6 December 2016. 
doi:10.7755/FB.115.1.8 
The views and opinions expressed or 
implied in this article are those of the 
author (or authors) and do not necessarily 
reflect the position of the National 
Marine Fisheries Service, NOAA. 
Andrea Dell'Apa (contact author!' 
Maria Grazia Pennine^ 
Christopher Bonzek^ 
The spiny dogfish iSqualus acanthias) 
is a small shark commonly found in 
oceanic and coastal temperate waters 
throughout the world, at depths less 
than 900 m (Compagno et ah, 2005; 
Dell’Apa et ah, 2015). The species is 
sexually dimorphic; adult females, on 
average, are larger than adult males 
(Nammack et ah, 1985). Moreover, 
aggregations of adult individuals are 
segregated by sex and size (Ford, 
1921; Shepherd et ah, 2002; DelFApa 
et ah, 2014) — a common occurrence 
with elasmobranchs (Springer, 1967; 
Sims, 2005). Sexual segregation can 
be the effect of social segregation, in 
which the interaction between the 
sexes is limited by behavioral differ- 
ences between the sexes, or it can be 
the effect of habitat segregation, in 
which the 2 sexes use habitats with 
different physical and environmental 
characteristics. Social segregation 
and habitat segregation can also oc- 
cur simultaneously for the two sexes 
and can lead to differences in spatial 
distribution and habitat associations 
between the sexes (Wearmouth and 
Sims, 2008). Additionally, sexual di- 
morphism may influence feeding 
habits in live-bearing elasmobranchs 
(Sims, 2005), resulting in the 2 sexes 
having evolved specific physiological 
requirements that have led to differ- 
ences in diet and prey preferences 
(Ruckstuhl and Glutton-Brock, 2005). 
Consequently, the 2 sexes may oc- 
cupy different habitats characterized 
by different prey compositions and 
thus reduce intraspecific competition 
(Sims, 2005). 
For commercially important spe- 
cies, such as the spiny dogfish (Lack, 
2006; Dell’Apa et ah, 2013), pre- 
dicting abundance and identifying 
habitat associations in response to 
environmental and spatiotemporal 
factors can be a valuable approach 
to the development of sustainable 
fishery strategies (Perry and Smith, 
1994; Pittman et ah, 2011; Espino- 
za et ah, 2014). For assessments of 
many elasmobranchs, understanding 
habitat associations is complex and 
