Tolan and Fisher: Biological response of Lut/anus griseus to climate patterns in Texas bays and estuaries 
37 
99°0'0"W 98”0'0"W 97WW 96°0'0''W 95WW 94WW 93*0'0''W 
of the major estuarine systems sampled as part of the Resource Moni- 
toring Program conducted by the Texas Parks and Wildlife Department 
from 1978 through December 2006. The fine line trailing the coastline 
represents the outline of the barrier island that runs from the pass 
at Sabine to Brazos-Santiago Pass, just north of Rio Grande. 
of mangrove snapper). Because of 
their affinity for hard bottom sub- 
strates, gray snapper are especially 
common on the numerous artificial 
reefs, such as oil and gas platforms, 
and on other man-made structures 
located on the northern gulf conti- 
nental shelf from Alabama to Texas 
(Fischer et ah, 2005). 
Studies of the life history char- 
acteristics of gray snapper (Ruth- 
erford et ah, 1989b; Burton, 2001) 
have revealed this species to be 
both euryhaline (they have been 
observed in salinities ranging from 
0 to 67) and thermally tolerant (in 
temperatures ranging from 12.8° to 
31.7°C). The lower lethal tempera- 
ture limit is reported to be 11-14°C 
(Starck and Schroeder, 1971) and 
increased mortalities accompany 
sudden temperature drops. Cold 
kills of gray snapper (along with 
other estuarine and coastal fishes) 
have been reported at numerous 
times along the Texas Gulf coast 
(Gunter, 1941, 1951; McEachron et 
al., 1994). These cold kills of tropi- 
cal species in Texas waters have 
previously been associated with 
warmer than usual summer and 
fall temperatures that stimulate 
tropical species either to move in- 
shore or to remain inshore much 
later into the winter than would 
otherwise occur, thereby leaving 
them more vulnerable to sudden 
cold spells (Moore, 1976, Holt and 
Holt, 1983). 
Texas Parks and Wildlife Depart- 
ment (TPWD) has used various 
gears systematically in Texas estu- 
aries since 1975 to assess changes 
in the abundance and size of organ- 
isms, their spatial and temporal 
distributions, species compositions of the community, 
and selected environmental parameters known to in- 
fluence their distribution and abundance. The purpose 
of this study was to examine the relationship between 
water temperature and population trends in juvenile 
and adult gray snapper within the seven major estuar- 
ies along the Texas gulf coast. 
Methods and materials 
Gray snappers were collected from November 1978 
through December 2006 with bag seines, otter trawls, and 
gill nets as part of a survey conducted by the Resource 
Monitoring Program of the Texas Parks and Wildlife 
Department within each of the seven major estuaries 
on the Texas Gulf coast: Sabine-Neches, Trinity-San 
Jacinto, Lavaca-Colorado, Guadalupe, Mission-Aransas, 
Nueces, and Laguna Madre (further subdivided into an 
Upper and Lower section, see Fig. 1). Bag seines (18.3 
m wide, 1.8 m deep, and equipped with 1.3-cm stretched 
nylon multifilament mesh in the 1.8-m wide central bag 
and with 1.9-cm stretched mesh in the remaining web- 
bing) were pulled parallel to the shoreline for 15.2 m for 
a total area swept of 0.03 ha. Sampling frequencies of the 
bag seines have not been uniform since the inception of 
the Routine Monitoring Program. Before 1981, only six 
bag seine samples were collected in each month in each 
bay (except for June 1978 when none was collected). From 
January 1982 through August 1984, 10 samples were 
