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Fishery Bulletin 109(2) 
coverage among and within CSAs were variable from 
1967 through 1981 and more equally distributed be- 
ginning in 1982. A regional data set of yearly overall 
abundance (all size classes) was constructed. The vast 
majority of the crabs collected were less than one year 
old. Crabs <50 mm CW represented 61.7% of the catch 
and crabs <90 mm CW represented 82%. To obtain 
a yearly catch per unit of effort (CPUE), the average 
catch by station in each study area was calculated by 
dividing the total catch by the total number of samples. 
The annual CPUE for each station within a study area 
was added and then divided by the number of stations 
to obtain a yearly CPUE for each of the eight CSAs. 
The annual CPUE of each CSA was multiplied by the 
number of samples taken annually and the products for 
all CSAs were added and then divided by the total num- 
ber of samples collected in the eight CSAs. The yearly 
regional CPUE was a weighted average by sample size, 
which gives the CSAs with few collected samples less 
weight than those with a large number of samples in 
the calculation of the regional CPUE. 
Climate-related hydrological regimes 
and crab abundance 
Over the period of the biological surveys (1967-2005), 
two climate-related hydrological regimes (1973-94 and 
1997-2005) were identified (Sanchez-Rubio et ah, 2011). 
To evaluate the response of blue crab abundance to 
these hydrological regimes, a /-test was used. Relation- 
ships among crab abundance and oceanic-atmospheric 
oscillations and hydrological and meteorological param- 
eters were determined by using correlation analysis. 
To identify models of oceanic-atmospheric oscillations 
and meteorological and hydrological parameters that 
contribute to the variability in blue crab abundance 
in the northcentral GOM, multiple linear regression 
analysis (Statistical Package R, vers. 2.7.0, http://www.r- 
project.org/) was used. To find the best-fitting model, an 
Akaike’s information criterion (AIC; Akaike, 1981) and 
Bayesian information criterion (BIC; Raftery, 1996) were 
calculated for each model. To check model reliability, the 
models with the lowest BIC and AIC values were com- 
pared after having been corrected for small sample size 
(McQuarrie and Tsai, 1998). Multiple linear regression 
in SPSS (IBM, Somers, NY) was used on the selected 
models to determine their r 2 values. 
Results 
Climate-related hydrological regimes 
and crab abundance 
Two long-term climate-influenced hydrological regimes 
were found to be related to two distinct periods of blue 
crab abundance in the northcentral GOM. Significance 
differences in blue crab mean abundance (/=3.196, 
P= 0.003; Fig. 2) were found within regimes that were 
associated by Sanchez-Rubio et al. (2011) with wet and 
dry conditions. During regime I (wet), there were higher 
catches of juvenile crabs than during regime II (dry). 
The regime with the highest blue crab abundances had 
a significantly higher mean of the north-south wind 
momentum (/=2.187, P= 0.038) and a lower mean of AMO 
(/=-7.276, P<0.001) than did the regime with low crab 
abundance (Table 2). 
Correlation analysis showed that blue crab abun- 
dance was positively correlated with the north-south 
wind momentum (Pearson /-= 0.406, P= 0.023) and PDSI 
(Pearson r=0.356, P=0.042) and was negatively related 
to salinity (Pearson ?•=(). 345, P=0.053). According to 
the regression models developed from AIC and BIC, 
the north-south wind momentum in concert with either 
salinity, precipitation, or the Palmer drought severity 
index, or the combination of the NAO and precipitation 
were influential in determining 22% to 28% of the vari- 
ability in blue crab abundance (Table 3). Figure 3 shows 
histograms of the variables that were associated with 
blue crab abundance by year. 
Discussion 
Early investigations into factors affecting population 
dynamics of blue crabs attempted to relate fluctuations 
in abundance to physiological tolerances to temperature 
and salinity. Livingston (1976) was among the first to 
Table 2 
Juvenile blue crab (Callinectes sapidus) weighted catch-per-unit-of-effort data and climatological factors showing significant 
differences in mean values during two hydrological regimes in the northcentral Gulf of Mexico. AMO: Atlantic Multidecadal 
Oscillation and NAO: North Atlantic Oscillation. 
Climate-related hydrological regimes 
AMO cold-NAO positive AMO warm-NAO negative 
Average values 1973—94 1997—2005 
Weighted catch per unit of effort 7.207 4.395 
AMO -0.147 0.201 
North— south wind momentum, (dynes/cm 2 )h 0.083 -0.082 
