144 
Fishery Bulletin 109(2) 
(Sanchez-Rubio et al., 2011). Mississippi, Atchafalaya, 
Pearl, and Pascagoula river flows and blue crab abun- 
dance were higher during AMO cold and NAO posi- 
tive phases than during AMO warm and NAO negative 
phases. Other studies have linked blue crab abundance 
to river flow and salinity. Guillory (2000) noted juvenile 
blue crab abundance was positively related to river flow 
and negatively related to salinity in fishery-independent 
(crabs <40 mm CW) trawl survey data for Louisiana. 
High commercial landings of blue crabs were associated 
with increased river flow by More (1969) in Texas bays, 
Wilber (1994) in Apalachicola Bay, Florida, and Guillory 
(2000) in Louisiana estuaries. Hydrological conditions 
associated with phases of AMO and NAO in conjunction 
with the north-south wind may influence blue crab pre- 
dation dynamics through predator exclusion. Under an 
annual positive north-south wind regime with flooding 
rain events, greater availability of low-salinity habitats 
increases the survival of juvenile crabs by diminishing 
intra- and interspecific predation. Under an annual 
negative north-south wind regime (inshore water move- 
ment), low-salinity habitats are reduced and there is a 
greater suite of predators and an increased opportunity 
for predation. 
Although long-term climatological patterns influence 
the abundance of estuarine organisms, there is also 
evidence that an interannual oceanic-atmospheric os- 
cillation (ENSO) can affect population levels. In mic- 
rotidal Louisiana estuaries, ENSO-related hydrological 
conditions were found to influence the abundance of 
estuarine organisms over limited time periods (Childers 
et al., 1990). High (or low) rates of local precipitation 
and Mississippi River discharge were gener- 
ally associated with anomalously high (or low) 
marsh inundation, respectively, that coincided 
with ENSO warm (or ENSO cold) phases. The 
ENSO warm and cold phases generally coin- 
cided with the lowest abundance of organisms, 
and the ENSO neutral phase was related to 
high abundance. Sanchez-Rubio et al. (2011) 
found that the effect of ENSO phases on river 
discharge was most evident in the last climate- 
related hydrological regime (drought) in the 
Pascagoula River and flow from this river was 
significantly higher during ENSO warm and 
ENSO neutral phases than during the ENSO 
cold phase. Although the ENSO was found to 
affect river flow, the limited number of ENSO 
phases (warm, cold, neutral) occurring dur- 
ing the last hydrological regime precluded any 
meaningful analysis of the abundance of crabs 
in relation to ENSO events. 
Implications for management 
Management of any fishery requires some 
knowledge of the factors that contribute to 
year-class strength. Initial population levels 
are established by recruitment. In the northern 
GOM, recruitment success (measured as the 
number of megalopae at settlement) was found 
to be dependent on interannual variations in 
wind stress patterns coupled with basin-scale 
events, such as Loop Current spin-off eddies, 
generated during critical periods of larval devel- 
opment (Johnson and Perry, 1999; Perry et al., 
2003). Seasonality of spawning coincided with 
climatological inner shelf water circulation pat- 
terns that transported larvae offshore initially 
but then acted to return them to shore at the 
appropriate developmental stage. Although 
annual temporal periodicity of settlement was 
similar, settlement was highly episodic and 
there were large annual variations in numbers 
of megalopae (Perry et al., 1995; Perry et al., 
2003). Perry et al. (1998) noted that regard- 
'd =5 
a) O 
as Q- 
O) o 
OS 
-C X 
CD CD 
=3 TD 
O C 
■5 ' >» 
CD Fn 
-4 J 
Ulnmn 
lOnnlnniinln 
nmnnnnnn 
n 
n Flnl 
L _ 
■urn 
ILI 1 ’ U‘- J ' 
' ' ~ UU 1 1 1 ' 
_=Oo □□□ On CL 
—I— 1 Ql-I 
1 yu 1 
^ 1 < ^uj u ' 1—1 
~ E 
.9- E 
60 
-60 J 
nfln 
u 
•PpPj-pO. 
Inn 
flr 
euQ= 
i -i 
-l J 
I 1 1 I f~l r-ir-in n fl i ii — i i — il ll I 
-fl 
TT 
SO) — roihhO'-mio 
t^'P-r^r^-ooooooooooo><^'ON 
On On On On On On On On On On On ON 
Figure 3 
Weighted catch per unit of effort (CPUE = average crab catch per 
ten minute trawl) of juvenile blue crabs ( Callinectes sapidus ) 
related to highly influential hydrological and meteorological 
factors (salinity, PDSI, precipitation, and north-south wind 
momentum) in the northcentral Gulf of Mexico within two climate- 
related hydrological regimes (AMO cold-NAO positive: gray bars, 
and AMO warm-NAO negative: white bars). AMO=Atlantic 
Multidecadal Oscillation and NAO=North Atlantic Oscillation. 
