coefficient ranged from 62.8 to 138.1%, averaging 104.2%. 
Frequency distributions of abundance from pooled data of all 
cruises also demonstrate the patchy nature of the distribu- 
' tions. Small or modest catches were observed most fre- 
quently (Figs. 5-7), but very high abundances or concen- 
_ trations of organisms occurred at a few stations during each 
cruise. Frequency distributions for individual cruises, 
though not illustrated here, closely resembled those for the 
pooled data, demonstrating that the patchy nature of the 
distributions is not a seasonal phenomenon but occurs 
throughout the year. 
Seasonality of Abundance 
Zooplankton volumes and spawning by fishes show a 
distinct seasonality in the eastern Gulf (Table 2; Figs. 8-10). 
Plankton volumes are largest and fish eggs and fish larvae 
are most abundant in the spring and summer months (May 
through September cruises). Fall and winter (November 
through March cruises) abundance is less, but the decrease 
is more apparent for eggs and larvae than for zooplankton 
volumes. Mean fall-winter zooplankton volumes were less 
than 125 ec/1,000 m; while spring-summer means increased 
to 200 cc/1,000 m? or more. A sharp drop in mean zoo- 
NUMBER OF STATIONS 
x 
PLANKTON (cc per I000M®>) 
Figure 5.—Frequency distribution of zooplankton volumes, based on 
samples from all stations made during 12 eastern Gulf of Mexico cruises, 
1972-74. 
i" 
Y 
g 
Z 
Y 
60 
Gg 
Z 
g 
g 
Z 
NUMBER OF STATIONS 
Z 
y 
Z 
Z 
Z D 
Z Z 
j 
j 
500 
Z 
ay 
YY 
AY 
AY 
100- 
200 
y 
Y 
Z 
a 
n 
; AUBAUY Y AA 
100 38° 398 $88" 288° SOS E88" $63 BBS 8S" woe BES 1S isos" os" IFS too 9 
EGGS (No per 10 M7) 
Figure 6.—Frequency distribution of fish egg abundance based on 
samples from all stations made during 12 eastern Gulf of Mexico cruises, 
1972-74. 
NUMBER OF STATIONS 
Figure 7.—Frequency distribution of fish larvae abundance based on 
samples from all stations made during 12 eastern Gulf of Mexico cruises, 
1972-74. 
bey 
a 
es 
MEAN (+1 Standard Error) PLANKTON VOLUME (ce per 1900m3) 
on 
[e} 
PRMPARMG Jans Alcs, -OUNIND ISIE IMMATIM: al 1° TAS Sh OT INSDieU im Foi) Anni 
1972 1973 1974 
DATES OF CRUISES 
Figure 8.—Mean zooplankton volumes for 12 eastern Gulf of Mexico 
cruises, 1972-74. 
SH EGGS (under 10m2 sea surface) 
se 8 8 8 8 38 8 3 
MEAN NUMBER (+1 Standard Error) 
FEFMAMJIJIASONODOSF MAMJJSASONODS FMAM 
1972 1973 1M 
DATES OF CRUISES 
Figure 9.—Mean fish egg abundance for 12 eastern Gulf of Mexico 
cruises, 1972-74. 
