140 
Fishery Bulletin 109(2) 
Table 1 
Meteorological and hydrological parameters and sources for juvenile blue crab (Callinectes sapidus) abundance data used in data 
analyses. Data for climate-related hydrological regimes, oceanic-atmospheric indices, and Mississippi and Pascagoula river flows 
were adopted from Sanchez-Rubio et al. (2011). 
Parameter Annual period 
Source 
Kessler east-west and north-south wind Sep-Aug 
momentum, ( dynes/cm 2 )h 
http://cdo.ncdc.noaa. gov/qclcd/QCLCD?prior=N&state=MS&w 
ban=13820 (accessed Mar 2007). 
Coastal Louisiana and Mississippi Palmer 
drought severity index and precipitation, mm 
http://www7.ncdc.noaa.gov/CDO/CDODivisionalSelect.jsp 
(accessed Mar 2008). 
Louisiana coastal water level, m 
http://www.mvn.usace.army.mil/eng/edhd/watercon.htm (accessed 
Feb 2008). 
Trawl sampling salinity, ppt 
Louisiana Department of Wildlife and Fisheries, Gulf Coast 
Research Laboratory-Mississippi Department of Marine Resources 
Catch per unit of effort Jan-Dec 
al., 2001). The ability to predict adult population size 
and thus annual available harvest has been limited 
by an incomplete understanding of the impact of biotic 
and abiotic variables as they relate to recruitment and 
survival of juvenile blue crabs. Although the oceanic- 
atmospheric oscillations have been associated with the 
amount of Mississippi River and Pascagoula River dis- 
charge (Sanchez-Rubio et al., 2011), they have not been 
related to the periodicity of blue crab population levels 
in the northcentral GOM. The purpose of the present 
study is to examine the relationship between nonlinear 
oceanic-atmospheric oscillations and juvenile blue crab 
abundance in the northcentral GOM and to elucidate 
underlying mechanisms involved in that association. 
This article also addresses the relevance of this study 
for the management of blue crab in the northcentral 
GOM. 
Materials and methods 
Data acquisition 
Sanchez-Rubio et al. (2011) examined combinations of 
oceanic-atmospheric oscillations related to river flow in 
the northcentral GOM and determined that two regime 
occurred during the period covered in this study: I) the 
AMO (cold)-NAO (positive [=high water flow]) and II) the 
AMO (warm)-NAO (negative [Mow water flow]). These 
regimes were used to examine the relationship between 
climate and juvenile blue crab abundance. Individual 
oceanic-atmospheric indices and river-flow anomalies 
were also adopted from that study. Other meteorologi- 
cal (wind momentum) and hydrological (precipitation, 
Palmer drought severity index [PDSI] , water level, and 
salinity) data and the biological data (crab abundance) 
used in the present study are described and illustrated 
in Table 1 and Figure 1, respectively. The annual envi- 
ronmental data were calculated from September to 
August because that period incorporates the time of peak 
settlement of megalopae in the northern GOM and these 
megalopae are an important link in determining early 
year-class strength. Perry and Stuck (1982) noted that 
the large catches of blue crab megalopae in August and 
September were followed by an increased catch of juve- 
nile crabs (10.0 to 19.9 mm) in October or November in 
Mississippi estuaries. Thus the chosen period for exami- 
nation follows the dominant modal group responsible for 
year-class strength. Blue crabs recruit to trawls at ~30 
mm CW and are abundant at this size in the winter. 
The January to December time frame covers the period 
of juvenile development and it is this period when year- 
class success is established. 
Daily coastal water-level data were obtained from two 
U.S. Army Corps of Engineers gauges along the Louisi- 
ana coast (Fig. 1: see Cocodrie [1969-2000], and Rigo- 
lets [1966-2005]). Daily water-level data from the Rigo- 
lets gauge were averaged to obtain monthly water-level 
values. The monthly water-level values were averaged 
to obtain an annual water-level data set for the years 
1973-2005. An annual water level anomaly was cal- 
culated by subtracting the average value by year from 
the yearly values of water level. Hourly wind data were 
obtained from the National Climatic Data Center, Ash- 
ville, NC. Hourly records of wind speed and direction 
were taken from the Kessler Airport, Biloxi, MS, with 
an anemometer mounted at 10 m height. The direction 
of the winds was subdivided into winds from the east 
(67.5-112.5°), west (247.5-292.5°), north (337.5-22.5°), 
and south (157.5-202.5°). Wind stress values were cal- 
culated for the four directions in dynes/cm 2 . For each 
direction of the winds, the monthly average of wind 
stress was multiplied by the number of hours (wind 
momentum = [dynes/cm 2 ]h) and then, annual values 
of wind momentum were calculated from 1973 through 
2003. To compare climate-related periods of blue crab 
