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Most of the observed seasonality in larval fish abundance 
was attributable to changes at stations shallower than 50 m 
(Fig. 14). 
Specific Areas of Abundance 
The patchy nature of zooplankton distribution in the 
eastern Gulf made it difficult to determine if any areas 
consistently had high biomass. The contour charts (Fig. 2) 
do suggest that an area on the southwest Florida shelf, 
encompassed by lat. 25°30'N to 27°30'N and long. 82°30’W 
to 84°00’W, usually had high zooplankton volumes. This 
observation is similar to that of Bogdanov et al. (1968) and 
Khromov (1969) who observed year-round high plankton 
standing stocks in this area during 1963 and 1964. 
Another area of relatively high plankton volumes was 
located on the shelf in the northeast Gulf (lat. 28°N to 29°N 
and long. 84°W to 85°W). Our data show this area to be 
rich in zooplankton at all seasons but richest in summer, 
thus differing from data of Bogdanov et al. (1968) and 
Khromov (1969), who reported high plankton biomass 
there only in winter. Because their observations apparently 
included phytoplankton biomass, as well as zooplankton, our 
data may not be directly comparable. Austin and Jones 
(1974) also reported a high zooplankton biomass in this 
region and cited possible influences of the Loop Current and 
shelf circulation on production. Their data, based on 
monthly collections from June 1969 through August 1970, 
showed plankton biomass for this area of the Gulf to be 
lowest in February and March, then increasing rapidly 
through May and June, and reaching a peak in fall. 
Zooplankton volumes frequently were high in small 
areas near the coast, but none of these areas had consis- 
tently high volumes. Such areas included coastal stations 
west of Charlotte Harbor (lat. 26°30 N), Tampa Bay (lat. 
27°30'N) and Cedar Key (lat. 29°00'N). Nutrients from local 
terrestrial runoff may have a major influence on plankton 
production in these areas. 
Contour charts of fish egg abundance (Fig. 3) show less 
uniformity than those for zooplankton volumes. Egg abun- 
dance was low during fall and winter; the only area that had 
relatively high numbers of eggs at those seasons was located 
between Charlotte Harbor and Tampa Bay at depths of 20 to 
100 m. During spring and summer, spawning is intense but 
no areas of unusually great spawning activity were located. 
Patches of high abundance (>1,600 eggs under 10 m’) often 
occurred and these usually were found where depths ranged 
from 20 to 50 m. 
Abundance of fish larvae (number under 10 m’) was 
greatest at depths from 50 to 100 m (Fig. 4). Contour lines of 
larval fish abundance tended to lie parallel to isobaths. 
Greatest abundance of larvae occurred between lat. 26°30'N 
and 28°30'N. Localized patches of great abundance some- 
times were observed for larvae, but these were less common 
than for fish eggs. 
Relationships Among Biological Variables 
Complex statistical analyses were not undertaken to 
examine relationships among the plankton and ichthyo- 
plankton categories. Simple correlation coefficients among 
pairs of variables for each cruise were calculated, however, 
to determine if any of them had a significant linear associa- 
tion (Table 5). All of the correlations were calculated using 
log 1. -transformed data because most of the cruise frequency 
distributions for abundance or concentrations were nearly 
normally distributed after transformation. 
atf/ 
Table 5.—S of simple correlations among biological variables. 
ae correlation coefficients were calculated using log ,. -transformed 
ta. 
Plankton Plankton Fish eggs 
(ec/1,000 m3) (ce/1,000 m°) (No./10 m2) 
by by by 
fish eggs fish larvae fish larvae 
Cruise (No./10 m*) (No./10 m?) (No./10 m?) 
8B 7201 & 
GE 7202 +0.281 +0.218 +0.389* 
GE 7208 +0.631** +0.097 +0.087 
GE 7210 -0.172 +0.727** -0.329 
IS 7205 +0.283 +0.109 +0.610** 
IS 7209 +0.038 -0.179 +0.021 
IS 7303 +0.022 -0.118 +0.172 
IS 7308 +0.205 -0.056 +0.070 
IS 7311 -0.074 +0.347* +0.252 
IS 7313 +0.171 -0.241 -0.012 
IS 7320 +0.211 -0.000 +0.376** 
CL 7405 -0.044 +0.450** +0.346 
CL 7412 +0.309* +0.359* +0.258 
* Significant; P<0.05 
** Highly significant; P<0.01 
The correlations between zooplankton volumes and fish 
egg abundance were positive for nine cruises,. but signifi- 
cantly so (P< 0.05) for only two of these. This suggests that 
there is a relationship between areas of intense spawning 
and high zooplankton abundance at some times. The 
correlations between fish egg abundance and fish larvae 
abundance, though positive on 10 of the 12 cruises, were 
significant in only three cases. The fact that only positive 
correlation coefficients were significant among those that 
were calculated (Table 5) supports the belief that there is at 
times a real association among these variables in the eastern 
Gulf. 
Relationships of Biological Variables to 
Temperature and Salinity 
There were no obvious associations among temperature 
and salinity conditions and the distribution of organisms. 
Such associations almost certainly would be species depen- 
dent; because we did not identify organisms to the species 
level or sample discrete depth strata, these associations 
were not observed. Even in summer 1973, when a lens of low 
salinity water (<30%..) was located over part of the shelf 
study area, predominantly from Mississippi flood runoff, the 
effects on the plankton were not obvious. Zooplankton 
volumes, fish egg abundance, and larval fish abundance 
were all reduced during the June-July 1973 cruise (Figs. 
8-10), but had recovered by August 1973, although surface 
salinities remained low in the area. Because this low salinity 
water was present only from the surface to 15-m depth, it is 
