34 
Fishery Bulletin 107(1 ) 
cooler months, as reported by DeVries and Chittenden 
(1982). Sand seatrout also may migrate to the deeper 
waters of the GOM in response to either photoperiod 
or temperature extremes of winter and summer (Vet- 
ter, 1982), although they tend to be found at shallower 
depths than those occupied by silver seatrout in the 
gulf areas. The environmental variables for Gulf area 
E formed an exception in our data; there were no cor- 
relations found with the presence of either species. This 
result may have been caused by environmental factors 
that were outside the optimum for both species, which 
resulted in neither species being found in high abun- 
dance in this area. 
Water temperature displayed some correlation with 
the preference of silver seatrout for warmer waters, dur- 
ing the winter season across relevant gulf areas (A-D). 
This correlation, in conjunction with the propensity of 
silver seatrout to be found deep in the water column, 
may indicate that they have less temperature tolerance 
than sand seatrout. 
Distribution of sand seatrout inshore 
Sand seatrout are unique among their GOM congenerics 
in their extensive use of both inshore and offshore areas, 
compared to spotted seatrout (a primarily inshore spe- 
cies) and silver seatrout (a primarily offshore species). 
Therefore the intent of the second objective of our study 
was to relate the abundance of sand seatrout between 
these two locations and further to characterize factors 
that correlated with their inshore distribution. To this 
end, the overall abundance at the offshore and inshore 
locations was compared. Second, the effectiveness of 
direct passes between the inshore and offshore areas 
in predicting sand seatrout abundance was examined. 
Finally, the correlation between abundance inshore and 
offshore was examined in order to demonstrate whether 
increased inshore abundance was predictive of increased 
offshore abundance in the same area. 
Despite using both offshore and inshore areas, sand 
seatrout were significantly less abundant inshore than 
offshore, in all seasons. Additionally, trends in inshore 
abundance appeared to mirror trends in offshore abun- 
dance, with abundance increasing in spring and sum- 
mer and decreasing in fall and winter. These trends 
correspond with spawning cycles followed by spawning 
inactivity, and are comparable to trends suggested by 
Shlossman and Chittenden (1981). For instance, sand 
seatrout migrate offshore from inshore areas during 
temperature extremes (Vetter, 1982) and for spawning 
(Gunter, 1945). Additionally, older fish may become 
more tolerant of higher salinity levels with age, in gen- 
eral resulting in older fish using offshore areas more 
frequently. The offshore abundance of sand seatrout 
may also result from nutritional preferences of mature 
fish. Sand seatrout found offshore are generalists, prey- 
ing on both fish and crustaceans that are found at off- 
shore depths of 3.5-22 m (known white shrimp grounds) 
during June-September and that are most common in 
the depths of 22-91 m (known brown shrimp grounds) 
during January-March (Chittenden and McEachran, 
1976; Byers, 1981). Finally, sand seatrout are found 
in highest abundance inshore during the summer, a 
finding that is similar to what has been indicated by 
Byers (1981). Shlossman and Chittenden (1981) sug- 
gested that this abundance is due to the introduction 
of the recently spring-spawned offspring to the inshore 
population (Shlossman and Chittenden, 1981), which 
thus consists primarily of age-1 individuals that have 
not yet moved offshore. 
Inshore sand seatrout abundance was different 
among locations, and correlated closely with the pres- 
ence or absence of direct access to GOM spawning 
grounds. It has previously been noted that sand seat- 
rout have a higher affinity for bays with direct passes 
to the offshore than to bays with no direct passes. For 
instance, Simmons and Hoese (1959) suggested that 
pass presence is imperative for seasonal sand seatrout 
migration, although they did not directly quantify the 
effect of pass presence on abundance. The data in the 
present study demonstrated a disparity in abundance 
between bays with direct access to offshore water and 
bays with some limitations to offshore water, whether 
it is distance or a barrier by islands. In fact, pass 
presence is the most influential global factor in affect- 
ing abundance among the various inshore bays. Pass 
presence clearly affects movements of fishes offshore 
and inshore; therefore, for a migratory species that 
moves between the two areas annually, pass presence 
is critical to inshore abundance. Shlossman and Chit- 
tenden (1981) suggested that although sand seatrout 
nurseries may be found both in estuarine and offshore 
habitats, estuarine areas may be the most important 
habitat for late summer age-1 fish. Finally, Shloss- 
man and Chittenden (1981) noted that the spawning of 
sand seatrout coincides with onshore winds and surface 
currents that facilitate passive transport of eggs and 
larvae to inshore nurseries; thus pass presence would 
have a significant effect on abundance within bays, 
particularly during early life stages. 
A second factor that significantly indicated inshore 
abundance of sand seatrout was abundance in the con- 
tiguous offshore area. Sand seatrout abundance within 
bays with direct passes is significantly higher in bays 
from Corpus Christi Bay, north, and this high abun- 
dance correlates with the overall abundance of sand 
seatrout offshore, year round. For major bays with low 
sand seatrout abundance, such as the Lower Laguna 
Madre, there is a corresponding lower overall abun- 
dance offshore (i.e., in gulf area E). One exception to 
this finding is the unique assemblage of species found 
in the hypersaline Lower Laguna Madre — species that 
are not seen elsewhere along the Texas coast. In this 
instance, it is likely that both hypersaline conditions 
and low offshore abundance have limited the abundance 
of sand seatrout inshore of Lower Laguna Madre. 
Sand seatrout inshore abundance is thus related to a 
host of different factors. Access to offshore waters is the 
most significant factor, but it is important to note that 
inshore transport of eggs and larvae and offshore mi- 
