Callihan et al.: Effect of demography on the spatial distribution of the Albemarle Sound-Roanoke River stock of Morone saxatilis 
135 
A; = AIC ; - AIC min , 
where AIC \ - the AIC value of a given model (/); and 
AlC m i n = the AIC value of the best model (mini- 
mum AIC). 
As a general guideline, models with A; close to zero 
have considerable empirical support, models with A; 
of 4-7 have much less support, and models with A; of 
9-14 have little support (Anderson, 2008). The follow- 
ing equation was used to calculate uq values: 
expl-^Ai) 
w i = r— i v 
Note that R refers to the set of models being evaluated. 
Values of uq can be interpreted as the probability that 
a particular model (i) is the best model for the data set 
given that one of the models must be selected as the 
best (Anderson, 2008). 
We based our inferences on parameter estimates 
from the model (i.e., on the combination of explanatory 
variables) deemed most parsimonious from AIC diag- 
nostics. For example, if the third model (length effect 
only) was determined to be the best model, values of 
the parameters (i.e., regression coefficients) that repre- 
sented the effect of fish length were used to calculate 
the predicted relative probability of Striped Bass being 
recovered in each recapture area as a function of their 
size at tagging. We assessed the fit of the best model 
through the use of both Pearson and deviance good- 
ness-of-fit tests. Because explanatory variables were 
continuous, it was necessary to group data for these 
tests (Agresti, 1996). For this purpose, we used 100-mm 
bins and abundance bins of 0.1 million fish. All statisti- 
cal analyses were performed in SAS, vers. 9.1.3 (SAS 
Institute, Inc., Cary, NC) with a. =0.05. 
Results 
Tag return summary 
From 1991 to 2008, 1197 tagged Striped Bass were re- 
ported as having been recaptured within their first 9 
months at liberty (late April-December); analyses con- 
ducted for this study were based on data from these 
individuals. Hook-and-line (recreational) anglers ac- 
counted for a majority (84%) of tag returns. Although 
most returns (80%) were from fish 400-600 mm TL (at 
tagging), fish lengths ranged from 287 to 1105 mm TL. 
Moreover, nearly all tag returns (154 of 156) of larger 
Striped Bass (>600 mm TL) were from years in which 
stock abundance exceeded 1.5 million fish (Table 1). 
Temporal recapture trends 
The AR stock of Striped Bass increased their move- 
ment outside of the Albemarle Sound estuary as the 
TabSe 1 
Number of tag returns of Striped Bass ( Morone saxatilis) per combination of total annual stock abundance (millions of 
fish) and interval of total length (TL) at tagging. Annual abundance estimates (1991-2008) of Albemarle Sound-Roanoke 
River Striped Bass were obtained from a statistical catch-at-age model (NCDMF and NCWRC 2 ). Only those tag returns 
occurring after the first 2 weeks but within the first calendar year at liberty were included in data analyses and are enu- 
merated here. “-”=no tag returns for that year. 
Abundance 
(millions) 
Year 
Number of returns per size (mm TL) interval 
<400 
400-499 
500-599 
600-699 
700-799 
800-899 
900-999 >1000 
1.035 
1993 
— 
37 
15 
— 
— 
_ 
_ _ 
1.101 
1991 
10 
17 
5 
- 
- 
- 
- 
1.104 
1992 
2 
48 
7 
1 
1 
- 
- - 
1.388 
1995 
- 
4 
17 
- 
- 
- 
- _ 
1.518 
2005 
1 
68 
36 
7 
2 
- 
6 
1.569 
1996 
4 
7 
13 
1 
- 
- 
— - 
1.673 
2004 
- 
17 
8 
- 
1 
3 
1 
1.752 
1997 
6 
38 
28 
4 
1 
- 
- - 
1.803 
2006 
- 
54 
80 
6 
5 
3 
9 3 
1.828 
2003 
7 
20 
36 
7 
2 
1 
3 
1.829 
2001 
1 
35 
38 
12 
2 
2 
— _ 
1.836 
2000 
1 
29 
16 
4 
2 
- 
- - 
1.860 
2002 
2 
27 
39 
4 
7 
1 
1 
1.877 
1998 
4 
41 
23 
7 
3 
- 
- - 
1.895 
2008 
38 
42 
13 
3 
- 
3 
5 6 
1.907 
1999 
1 
29 
17 
5 
1 
- 
— — 
2.051 
2007 
— 
19 
40 
11 
3 
1 
5 2 
