Sanchez-Rubio and Perry: Meteorological and hydrological regimes and their influence on recruitment of Brevoortia patronus 
401 
Table 3 
Linear models fitted to fishery-independent and fishery-dependent data on Gulf menhaden (Brevoortia patronus) in the 
northern Gulf of Mexico during the periods from 1981 through 2008 and from 1964 through 2010, respectively. BPL=beam 
plankton trawl; vtw=vessel ton week in the purse-seine fishery; F=F-test; r 2 =coefficient of determination; AIC=Akaike’s in- 
formation criterion. Adjusted r 2 would be sufficient. 
Explanatory 
Sum of 
Adj usted 
Model 
Response variables 
variables 
df 
squares 
F 
P( >F) 
r 2 
AIC 
r 2 
1 
cube-root-transformed 
5 th component 
1 
15.568 
19.841 
0.000 
0.679 
-21.5 
0.62 
abundance per 
3 rd component 
1 
-0.493 
0.21 
BPL haul 
Intercept 
3.219 
2 
Age-1 landing 
2 nd component 
1 
230.728 
40.740 
0.000 
-2.240 
83.7 
0.46 
per vtw 
Intercept 
7.657 
3 
Age-1 proportion 
2 nd component 
1 
0.501 
12.344 
0.000 
- 0.100 - 
179.7 
0.33 
of total landings 
1 st component 
0.032 
0.01 
per vtw 
Intercept 
0.572 
2 climate periods, a series of years of low river flows 
followed by years of high river flows. Sanchez-Rubio et 
al. (2011a) and Sanchez-Rubio and Perry, 13 using cli- 
matic indices that spanned the time period preceding 
and during the low river flow conditions of Guillory et 
al. (1983) and high river flow period of Govoni (1997), 
characterized the years during their studies as aver- 
age (1964-1970) and high (1971-1994) river flow pe- 
riods. The high river flow regime ended in 1994 and 
was followed by low river flow conditions brought on 
by a change in the phases of AMO and NAO in 1995 
(Sanchez-Rubio and Perry 13 ). 
At the decadal scale, Govoni (1997) found increased 
numbers of Gulf menhaden under conditions of high 
river flow in the years following 1975. He attributed 
this increase to enhanced nutrient availability and 
suggested “discharge of the Mississippi River was posi- 
tively associated with recruitment over decadal scales.” 
A relationship between decadal oscillations of Missis- 
sippi River flow and abundance of another estuarine 
organism, the blue crab ( Callinectes sapidus ), was re- 
ported by Sanchez-Rubio et al. (2011b). Both blue crab 
and Gulf menhaden in northern GOM estuaries appear 
to respond positively to wet regimes, although the fac- 
tors responsible for driving abundances differ between 
the 2 species. Decreased predation, associated with a 
reduced predator guild in waters with lowered salini- 
ties, was found to be responsible for increased numbers 
of juvenile blue crab during wet regimes. In this study, 
decadal abundance of early juvenile Gulf menhaden in 
the BPL surveys was higher during the decadal cold, 
13 Sanchez-Rubio, G., and H. Perry. 2013. Climate-related 
meteorological and hydrological regimes and their influence 
on Gulf menhaden ( Brevoortia patronus) recruitment in the 
northern Gulf of Mexico: final administrative report, 30 p. 
Saltonstall-Kennedy project no. NA10NMF4270195. [Avail- 
able from Office of Management and Budget, Natl. Mar. Fish. 
Serv., NOAA, 1315 East-West Hwy., Silver Spring, MD.l 
wet regime (throughout the coupling of AMO cold and 
NAO positive phases) characterized by high (2.3) cube- 
root-transformed N:P ratio of Mississippi River influx 
than during other considered regimes. 
The importance of nutrients to recruitment was 
evident in this study. The Mississippi River N:P ra- 
tio and north-south wind direction explained 41% of 
variability in abundance of early juvenile Gulf menha- 
den. In Louisiana, northerly winds produce extremely 
low tides, high transport of organic material into open 
waters, and strong upwelling events (Moeller et al., 
1993). The contribution of other environmental fac- 
tors, such as NAO, east-west wind direction in off- 
shore waters, air temperature and river flow in the 
central region, and PDSI, precipitation, and air tem- 
perature in the western region, accounted for 21% of 
the variability. 
Commercial landings also showed decadal fluctua- 
tions in the proportion of age-1 Gulf menhaden in re- 
lation to the total landings, measured as numbers of 
fish per vtw. The proportion of age-1 Gulf menhaden 
in the catch (Alabama-Texas) was significantly higher 
during the decadal cold, wet regime characterized by 
high (0.56) values of PDSI and high (401.6 m 3 /s above 
average) river flows in the central region than during 
the decadal warm, dry regime. A decrease in both early 
juvenile abundance (fishery-independent surveys) and 
the proportion of age-1 fish in the commercial landings 
occurred with the 1995 shift in climate regimes from 
cold and wet to warm and dry, indicating diminished 
recruitment over the warm, dry period. Although the 
abundance of age-1 fish in commercial landings de- 
creased, the numbers of Gulf menhaden of ages 2-6 
remained stable with a slight increase observed for 
age-2 fish (Vanderkooy and Smith 4 ). The increase in 
numbers and relative stability of age-2 fish in com- 
mercial landings indicated continued recruitment to 
the fishery. 
