Dunton et al.: Abundance and distribution of Acipenser oxyrinchus within the Northwest Atlantic Ocean 
453 
CA). Map base layers were obtained from 
the United States Geological Survey Coastal 
and Marine Geology Program GIS catalogue. 
Atlantic sturgeon captures were plotted by 
using graduated symbols in the following 
categories: 1, 2, 3—4, 5—10, 11-14, and >15 
Atlantic sturgeon per tow. 
Habitat preferences 
We estimated the habitat preference of Atlan- 
tic sturgeon by using the catch-weighted 
methods of Perry and Smith (1994) for cor- 
recting bias that arises in stratified sur- 
veys where sampling effort differs between 
strata. With this method, a comparison of 
a catch-weighted cumulative distribution of 
available (all habitat sampled) and occupied 
(habitat where Atlantic sturgeon were cap- 
tured) habitat was made and a randomization 
routine was used to estimate whether the 
occupied habitat was significantly different 
from available habitat. Habitat variables 
analyzed included temperature, dissolved 
oxygen, and salinity. 
The cumulative distribution function (cdf) 
of the environmental variable was calculated 
with the following function: 
0.35 
0.30 - 
I 
fe °' 25 - 
Q. 
= 0.20 - 
'o 
<5 
| 0.15 - 
c 
LU 0.10 - 
Z3 
CL 
O 
0.05 - 
0.00 T 1 1 T 1 1 1 1 1 
NYBTS NJDEP ME-NH NMFS MADMF 
Figure 2 
Catch per unit of effort (CPUE) for Atlantic sturgeon ( Acipenser 
oxyrinchus) during the New York bottom trawl survey (NYBTS), 
New Jersey Department of Environmental Protection finfish survey 
(NJDEP), Maine-New Hampshire inshore bottom trawl survey 
(ME-NH), National Marine Fisheries Service bottom trawl surveys 
(NMFS), and Massachusetts Division of Marine Fisheries bottom 
trawl survey (MADMF). 
, w 
f(t )= X H—KXhO’ (1) 
h , n h 
where W, 
n. 
the proportion of the survey in stratum /z; 
the number of tows in stratum h ; 
the habitat variable in tow i and stratum 
h; and 
an indicator function where 
| 1 , if Hi^t 
0, otherwise 
(2) 
The following function relates the catch weighted cdf 
to the habitat variable: 
*<*>=XX 
n h y st 
I(x lu ), 
(3) 
Significance is determined by randomizing for 1000 
trials the pairings of x hl and ( W h /n h ) (y hi - y st )!y st ) and 
by dividing the number of trials that are greater than 
the test statistic by the total number of trials. 
Results 
The NYBTS had the highest CPUE (0.291 fish/tow), 
followed by the NJDEP finfish survey (0.072 fish/tow), 
ME-NH inshore bottom trawl survey (0.024 fish/tow), 
NMFS bottom trawl survey (0.004 fish/tow), and the 
MADMF bottom trawl survey (<0.001fish/tow), in the 
latter of which only one Atlantic sturgeon has ever been 
captured (Table 1; Fig. 2). The details of the CPUE by 
depth (Fig. 3) and seasonal distribution and abundance 
(Fig. 4-7) for each survey are reported in detail below. 
Total length of Atlantic sturgeon captured within the 
surveys ranged from 56 to 269 cm (mean=108 cm) (Table 
2; Fig. 8). 
where y hi = the number of fish captured in tow i in 
stratum h ; and 
y st = the stratified mean abundance. 
The strength of the association is measured by the dif- 
ference between the available and occupied cdf: 
c|g(U-/'(U| = 
max 
XX— 
h i n h 
f — \ 
y -y , 
hi st 
V st J 
(4) 
NMFS bottom trawl survey 
A total of 107 Atlantic sturgeon were captured in 27,420 
bottom trawls (Table 1). The depth distribution of com- 
pleted tows ranged from 5 to 542 m deep, and 5214 peak 
tows occurred between 20 and 40 m (Fig. 3A). CPUE of 
Atlantic sturgeon was highest for the 10 -m depth stra- 
tum (0.0273/tow) and decreased with each depth interval 
(Fig. 3A). A total of 71.30% of the Atlantic sturgeon 
were captured in 20 m or less and no individuals were 
captured in water deeper than 30 m (Fig. 3A). Atlantic 
