32 
Fishery Bulletin 107(1 ) 
Gulf area A 
Gulf area B 
Gulf area C 
Gulf area D 
Gulf area E 
(Logio) water depth x (logio) abundance 
Q6 
Q4 
02 
Q0 
-02 
-04 
-06 
F] i 
_in 1 i 
In . 
iL 
iDI 
I 
A 
n 
■ 
a « 
■ I 
□ 
ITT- 
‘ 1 II 
r 
'C' 
(Logio) salinity x (logio) abundance 
I Q 6 
O Q4 
0 02 
J i . 1 
S . .0 
l 
B 
c .02 
'cS 
2 -Q6 
o -08 
o 
IB 
1 
I 1 
' i TU 
: nr ■ 
(Logio) temperature x (logio) abundance 
0.6 
0.4 
0.2 
1 
| 
1 i 
. . 1 
Li jL 
i 
■ i 
C 
-0.2 
-0.4 
-0.6 
1 1 
® * 
■“1 
I 
1 1 
nVr 
A' 
/V 
n/- /v* 
^ ^ cf 
<vvy 
a ^ n 
Figure 8 
Correlation coefficients (r) describing the relation between annual mean abundance (indi- 
viduals collected/hr), averaged over twenty years of trawl data (1987-2006) for sand seatrout 
(Cynoscion arenarius ) and silver seatrout (C. nothus ) collected across all sampling areas in 
the Gulf of Mexico (A-E) (black bars = sand seatrout, gray bars = silver seatrout) and (A) water 
depth (m), (B) water salinity (psu), and (C) water temperature (°C). 
mesh sizes, and therefore a direct comparison of data 
cannot be made. Depending on their ability and size, 
fishes attempt to avoid contact with trawl gear by either 
maintaining position at the net opening (Wardle, 1983) 
or by falling back along the taper of the body panel 
of the trawl net towards the codend opening (Wardle, 
1983), as discussed by Broadhurst et al. (2000). Thus 
trawl configuration can play a role in limiting the size 
and condition of fishes that are captured. In contrast to 
silver seatrout, sand seatrout are found offshore within 
gulf areas in highest abundance during the spring and 
summer seasons. Increased spring abundance may be 
due to both the mature-size individuals emigrating from 
bays to the offshore in order to spawn as well as to the 
presence of recently spawned young of the year during 
May- July (Fig. 3). In any case, the relative abundance 
of sand seatrout off the coast of Texas is dramatically 
lower than that of silver seatrout, in all seasons other 
than summer. 
There is a difference in the distribution of both sand 
and silver seatrout in offshore gulf areas. Whereas sil- 
ver seatrout are found predominately along the middle 
coast, sand seatrout, although lower in overall abun- 
dance, appear to decrease in abundance from north to 
south. Moore et al. (1970) described somewhat similar 
results, namely a higher abundance of sand seatrout 
within Louisiana waters and more silver seatrout in 
Texas waters. The distributional distinctions between 
species in our study correlated well with both salinity 
and water depth. Sand seatrout were shown to have a 
preference for lower salinities, whereas silver seatrout 
prefer higher salinities (ranging from 7.5 to 38.6 psu) 
(Swingle, 1971). In addition, Ginsburg (1931) and Miller 
(1965) have reported the water depth preferences for 
sand seatrout (shallower depths) and silver seatrout 
(deeper depths). Gulf area A, because it is shallower 
and less saline than the other gulf areas, appears to 
be ideal habitat for sand seatrout, whereas silver seat- 
rout prefer the deeper and more saline gulf areas C 
and D. Correlation between depth and abundance also 
occurred locally, within selected sampling areas. For 
instance, within gulf area A, silver seatrout were found 
specifically within the deepest grids, for all seasons. 
Also, silver seatrout were found in deeper waters during 
fall and winter, across most sampling areas, indicating 
the occurrence of an offshore winter migration during 
