Hernandez et al.: Variability in ichthyoplankton abundance and composition in the northern Gulf of Mexico 
195 
Table 1 
Station data for ichthyoplankton samples collected during a larval fish monitoring survey at a site located approximately 18 km 
south of Dauphin Island, Alabama (October 2004-October 2006). Seasonal classification is based on historic (10-year average) 
and observed monthly mean temperatures for the region (see Fig. 2). 
Year 
Cruise date 
Survey type 
Seasonal classification 
Number of samples 
2004 
22 Oct 
monthly 
Summer 
54 
2004 
16-17 Nov 
diel 
Fall 
41 
2004 
29 Nov 
monthly 
Fall 
47 
2004 
08 Dec 
monthly 
Fall 
47 
2005 
06-07 Jan 
monthly 
Winter 
48 
2005 
18-21 Jan 
diel 
Winter 
76 
2005 
16 Feb 
monthly 
Winter 
50 
2005 
29 Mar 
monthly 
Spring 
23 
2005 
05 Apr 
monthly 
Spring 
18 
2005 
19 Apr 
monthly 
Spring 
47 
2005 
09-13 May 
diel 
Spring 
72 
2005 
17 May 
monthly 
Spring 
48 
2005 
09 Jun 
monthly 
Summer 
47 
2005 
13 Jul 
monthly 
Summer 
48 
2005 
09 Aug 
monthly 
Summer 
46 
2005 
14 Sep 
monthly 
Summer 
48 
2005 
27-29 Sep 
diel 
Summer 
72 
2005 
11 Oct 
monthly 
Summer 
31 
2005 
09 Nov 
monthly 
Fall 
32 
2005 
29 Nov-02 Dec 
diel 
Winter 
71 
2005 
16 Dec 
monthly 
Winter 
40 
2006 
12 Jan 
monthly 
Winter 
44 
2006 
07-10 Feb 
diel 
Winter 
60 
2006 
17 Feb 
monthly 
Winter 
43 
2006 
16 Mar 
monthly 
Spring 
39 
2006 
12-13 Apr 
monthly 
Spring 
38 
2006 
01-04 May 
diel 
Spring 
70 
2006 
17 May 
monthly 
Spring 
43 
2006 
15 Jun 
monthly 
Summer 
42 
2006 
05 Jul 
monthly 
Summer 
46 
2006 
10 Aug 
monthly 
Summer 
46 
2006 
08 Sep 
monthly 
Summer 
46 
2006 
19-22 Sep 
diel 
Summer 
66 
2006 
12 Oct 
monthly 
Summer 
47 
oblique sample were collected with 202-pm mesh nets 
at dawn, noon, dusk, and midnight (local time) over 
the course of three diel periods for a nominal total of 
84 samples per quarterly cruise. Contents of nets were 
rinsed with seawater, sieved, and preserved in 4% forma- 
lin for 48 hours before being transferred to 70% ethanol. 
A conductivity-temperature-depth probe (CTD) (SBE19, 
Sea-Bird Electronics, Inc., Bellevue, WA) was integrated 
into the BIONESS system and provided temperature, 
salinity, and depth profiles for each plankton tow. A flow- 
meter (General Oceanics, Miami, FL) mounted within 
the BIONESS frame estimated the volume of water 
filtered for each sample. Filtered volume estimates for 
each sample were compared with measurements from a 
second, externally mounted flowmeter to estimate filtra- 
tion efficiency. In all, 1634 ichthyoplankton samples were 
processed and used in subsequent analyses. Although all 
fish larvae were collected from a single station, Alabama 
has a relatively short coastline (<85 km), thus the larval 
fishes collected likely represent the ichthyofauna of the 
entire Alabama inner shelf region. 
Preparation of environmental data 
CTD data were processed using the manufacturer’s 
software (SEASOFT, Seabird Electronics, Inc., Bellevue, 
WA) and averaged into 0.5-m bins. Seasonal patterns 
in water temperature were examined using depth-inte- 
grated monthly mean temperatures recorded during each 
sampling month. For historic comparisons, the 10-year 
