9)=TRANSECTS 

 s; =STATION NUMBER 



Figure I.— Transects with stations occupied 

 during the National Marine Fisheries Service's 

 investigation of the continental shelf waters of 

 the northwestern Gulf of Mexico, 1963-65. 



water depths recorded originally in fathoms but con- 

 verted herein to the nearest meter. Operations were con- 

 ducted around the clock, and the time required to com- 

 plete a cruise ranged from 10 to 24 days; the average 

 cruise was completed in 14 days. Occasionally some 

 stations could not be occupied because of adverse 

 weather conditions or mechanical breakdowns. 



Temperatures were measured with mechanical bathy- 

 thermographs that were allowed to sound bottom on all 

 casts. Surface bucket temperatures were taken for cor- 

 rection purposes with stem thermometers graduated to 

 0.1°C. In the laboratory, temperature and depth correc- 

 tions were calculated for each slide before photography, 

 and bathythermogram profiles were aligned by the 

 average correction process as outlined by LaFond (1951). 

 For tabulation purposes, temperatures at a station were 

 recorded at (surface), 3, 11, 24, 43, 70, 107, and B (bot- 

 tom) meters, depending on total water depth. 



Samples of surface water for salinity determinations 

 were obtained from the bucket samples used for bathy- 

 thermograph reference temperatures. Samples of sub- 

 surface waters were taken at depths of 3, 11, 24, 43, 70, 

 and 107 m with Nansen bottles. The deepest sample at 

 any station was 3 m above the bottom. Depths were 

 determined from the wire angles and precalculated 

 length-of-wire tables. Regardless of the method of col- 

 lection, all samples were drawn into 200-ml culture tubes 

 with Polyseal caps. Chlorinity was determined in the 

 laboratory by the Knud.sen method as soon as possible 

 after each cruise. 



All temperature and salinity values obtained at each 

 station during this survey are listed by station and 

 grouped by transects in Tables 1-10. 



RESULTS 



Temperatures and salinities of waters over the con- 

 tinental shelf of the Gulf of Mexico are affected by a 



number of factors such as air temperatures, surface 

 winds, oceanic currents, and freshwater inflow. Of these, 

 one significant factor in the area under consideration is 

 the discharge from the Mississippi River which has a 

 more pronounced or immediate effect on waters off 

 Louisiana than on those off Texas. For this reason and 

 because State agencies in Louisiana and Texas are con- 

 cerned with natural resources off their respective coasts, 

 the data have been grouped for 1) Louisiana waters 

 (Tables 3-6), and 2) Texas waters (Tables 7-10). Data 

 generated from east of the Mississippi River (Tables 1-2) 

 and from 110 m of water (Table 6, Station E6 and Table 

 7, Station W6) are listed for informational purposes only. 



Louisiana Offshore Waters 



Monthly average surface and bottom temperatures 

 (averaged for observations at stations of like bottom 

 depths) over the 3-yr period are plotted for five depth 

 zones in Figure 2. Within each depth zone, the trends 

 were similar between years, and differences between 

 depths were consistent. Surface and bottom water tem- 

 peratures closely approximated one another at the 7-m 

 stations, but the yearly range from a low of about 13.0°C 

 to the high of 30.5°C was greater at this depth than noted 

 at the deeper zones. As depth increased, the differences 

 between surface and bottom temperatures increased and 

 were greatest at the 73-m stations. Surface tem- 

 peratures at all stations generally dropped during the fall 

 and winter, warmed during the spring, and attained 

 highest values in the summer. Bottom temperatures at 

 depths greater than 7 m, however, only approximated 

 this general cycle inasmuch as highest values frequently 

 occurred when surface waters were cooling. This was par- 

 ticularly pronounced at the two deepest (46 to 73 m) 

 zones. 



Monthly average surface and near-bottom salinities 

 lor five depth zones are presented in Figure 3. Also in- 



