270 
NOAA 
National Marine 
Fisheries Service 
Abstract— In the Aleutian Islands, 
patterns of distribution and abun- 
dance of Pacific ocean perch ( Se - 
bastes alutus ) are influenced by 
oceanographic processes and bio- 
genic structures. We used general- 
ized additive modeling (GAM) to ex- 
amine relationships between these 
predictors and patterns of settled 
juvenile and adult distribution and 
abundance from bottom trawl sur- 
veys conducted from 1997 through 
2010. Depth, temperature, and loca- 
tion had the greatest influence, and 
biogenic structures co-occurring with 
this species improved predictions. 
Model results confirmed previously 
reported depth- and temperature- 
dependent patterns of Pacific ocean 
perch and revealed the elevated 
presence and abundance of this 
fish in proximity to Aleutian pass- 
es. Adults were more common and 
abundant in deeper (-225 m) water 
than were juveniles (-150 m), and 
the probability of encountering ei- 
ther life stage increased in the pres- 
ence of fan- and ball-shaped sponges 
over moderate slopes and decreased 
with increasing tidal velocities. The 
GAMs accounted for one-quarter of 
the deviance for juvenile presence- 
absence (24.9%) and conditional 
abundance (25.0%) and accounted for 
38.7% and 42.5% of the deviance for 
the same adult response variables. 
Although depth, temperature, and 
location were the dominant predictor 
variables of both juvenile presence 
and abundance, our results indicate 
that biogenic structures that provide 
vertical structure in otherwise low- 
relief, trawlable habitats may repre- 
sent refugia for Pacific ocean perch 
juveniles and adults. 
Manuscript submitted 18 August 2014. 
Manuscript accepted 20 April 2015. 
Fish. Bull. 113:270-289 (2015). 
Online publication date: 7 May 2015. 
doi: 10.7755/FB. 113.3.4. 
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. 
Fishery Bulletin 
& established 1881 «<?. 
Spencer F. Baird 
First U S. Commissioner 
of Fisheries and founder 
of Fishery Bulletin 
Correlating environmental and biogenic 
factors with abundance and distribution of 
Pacific ocean perch C Sebastes alutus ) in the 
Aleutian islands, Alaska 
Edward A. La man (contact author) 
Stan Kotwicki 
Christopher N. Rooper 
Email address for contact author: ned.laman@noaa.gov 
Alaska Fisheries Science Center 
National Marine Fisheries Service, NOAA 
7600 Sand Point Way NE 
Seattle, Washington 98115 
Describing essential fish habitat 
(EFH), defined by the Magnuson-Ste- 
vens Fishery Conservation and Man- 
agement Act (Magnuson-Stevens Act) 
as “those waters and substrate neces- 
sary to fish for spawning, breeding, 
feeding or growth to maturity,” has 
been the focus of much recent habi- 
tat research. Laidig et al. (2009) used 
the Delta submersible to conduct vi- 
sual surveys on the central Califor- 
nia shelf and found that demersal 
fishes associated with boulder and 
cobble substrata occurred in greater 
numbers than they did with mud or 
brachiopod beds. Other studies have 
observed denser and more diverse as- 
semblages of rockfishes in the pres- 
ence of increased boulder coverage 
(Marliave and Challenger, 2009) or in 
association with rocky ridges (Roop- 
er et al., 2010). Greene et al. (2011) 
demonstrated that rugged seafloor 
geomorphologies in southeast Alas- 
ka can be used to identify suitable 
habitat for demersal shelf rockfish 
( Sebastes spp.). Living substrata can 
also modify seafloor habitats in ways 
that impact EFH. Others have con- 
sidered biogenic structures, such as 
sponges, corals, and bryozoans, to be 
important habitat-forming organisms 
in Alaska (Heifetz et al., 2005; Male- 
cha et al., 2005; Stone et al., 2011) 
and other waters (e.g., Barthel, 1997 
[Weddell Sea]; Beazley et al., 2013 
[the northwest Atlantic]; and Coker 
et al., 2014 [warm-water coral reefs]). 
In this study, we attempt to add to 
the growing body of knowledge used 
to identify and describe EFH for spe- 
cies of Sebastes in Alaska. 
The Resource Assessment and 
Conservation Engineering (RACE) 
Division of the NOAA Alaska Fisher- 
ies Science Center (AFSC) has con- 
ducted periodic bottom trawl surveys 
in the Aleutian Islands since 1980 
(von Szalay et al., 2011). These sur- 
veys are designed to collect fisher- 
ies-independent data on the status 
and trends of fish and invertebrate 
species to support formal stock as- 
sessments. One of the most abun- 
dant commercially harvested species 
landed from trawl fisheries in the 
Aleutian Islands is the Pacific ocean 
perch ( Sebastes alutus ) (Zenger, 2004; 
Rooper and Wilkins, 2008; von Sza- 
lay et al., 2011), and Pacific ocean 
perch biomass from this region has 
been increasing over the last decade 
