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Fishery Bulletin 113(4) 
principal components (PC) of climate-related meteoro- 
logical and hydrological parameters in years t with t 
equal to 1981-2008 for recruits to age 0 and 1964-2010 
for recruits to age 1, 
flat = bo + bi PCi,t + b 2 PC 2 ,t + £ and (3) 
fll,t+i = bo + bi PC t _! + b 2 PC 2 , t-i + £, (4) 
where bo, b\, and b 2 are estimated parameters; and 
error e is normally distributed e ~M0 ,g 2 ). 
To find the best-fitting model, the model selection meth- 
od of best subsets was used with Akaike’s information 
criterion (AIC; Akaike, 1981). The models with the low- 
est AIC values were considered most reliable and their 
coefficients of determination (r 2 ) were recorded. 
Results 
Climate-related meteorological and hydrological regimes 
and population levels of menhaden 
Analyses of fishery-independent data Influence of decadal 
and interannual climate-related meteorological and hy- 
drological regimes on early juveniles of Gulf menhaden 
was evident. Early juvenile abundances from the BPL 
surveys in the central region (Z= -2.212, P= 0.027; Fig. 
2A) and the N:P ratio of the Mississippi River influx 
(Z= -2.520, P=0.012; Fig. 2B) were higher during the 
decadal wet regime than during the decadal dry re- 
gime. During the wet regime, Mississippi River waters 
had an average N:P ratio closer to the Redfield (1958) 
ratio of 16:1, a ratio that indicates no limitation in N. 
During the dry regime, Mississippi River waters had 
an average N:P ratio of less than 10, a value that usu- 
ally indicates conditions under which phytoplankton 
production is nitrogen limited (Ram and Plotkin, 1983; 
Sakshaug and Olsen, 1986). 
Abundance of early juveniles from seine surveys was 
higher in the central region than in the western region 
(Texas, Z= -5.938, P<0.001), supporting the need for a 
regional analysis of data. Mean ranks of seine catches 
(% 2 =8.814, P=0.012) and air temperature (% 2 =7.066, 
P=0.029) in the western region and of PDSI in the 
central and western regions (x 2 >9.858, P<0.007) were 
different among ENSO events. Seine catches of early 
juveniles in the western region (Z< -2.441, P<0.016; 
Fig. 3A) and of PDSI in the central region (Z< -2.620, 
P<0.010; Fig. 3B) were higher during wet and average 
ENSO years than during dry ENSO years. In addition, 
PDSI in the western region was higher during wet 
ENSO years than during dry ENSO years (Z= -2.928, 
P=0.003; Fig. 30. 
With principal component analysis we extracted 5 
components of climate-related meteorological and hy- 
drological parameters associated with BPL catches of 
Gulf menhaden (Table 2). Correlation analysis of BPL 
catches with the 5 extracted principal components 
showed that catches of early juvenile Gulf menhaden 
Wet regime Dry regime 
Figure 2 
Box plots of (A) cube-root-transformed abundance of 
postlarval Gulf menhaden (Brevoortia patronus ) in beam 
plankton trawl (BPL) surveys, measured as numbers per 
BPL haul (1981-2008), and (B) cube-root-transformed 
N:P ratio of the Mississippi River influx in the central 
region of the Gulf Coast (1981-2008) under 2 contrast- 
ing climate-related hydrological regimes: the wet regime, 
or the cold phase of the Atlantic Multidecadal Oscilla- 
tion (AMO) and the positive phase of the North Atlan- 
tic Oscillation (NAO) in 1981-1994, and the dry regime, 
or the AMO warm-NAO negative phase in 1995-2008. 
Horizontal lines for each box plot indicate the 5th, 25th, 
50th (median), 75th, and 95th percentiles. Outliers are 
shown as dots, and they are labeled by year. 
in BPL hauls in the central region were correlated 
with the third (r= -0.494, P=0.010) and fifth (r- 0.624, 
P=0.001) extracted components. In order of importance, 
the variables loaded on the third extracted component 
were air temperature from the central region, north- 
south and east-west wind directions from offshore 
waters, NAO from the North Atlantic Ocean, air tem- 
perature from the western region, river flow from the 
central region, and PDSI and precipitation from the 
western region. In order of importance, the variables 
loaded on the fifth component extracted were cube- 
