130 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



38 have been made available through the Fish and 

 Wildlife Service of the United States Department 

 of the Interior and are on file in the Department 

 of Oceanography at Texas Agricultural and Me- 

 chanical College where a file-report has been pre- 

 pared. The key in figure 38 shows the period of 

 years in which observations were made and sent 

 in from each station. The study of these shore 

 station data is continuing, and references to addi- 

 tional information of this kind are sought. It is 

 hoped that they may provide a clue to general 

 changes which are occurring offshore where ob- 

 servations are not so readily obtainable. 



Studies of sea surface temperatures in the Gulf 

 of Mexico have been based on some 200,000 ob- 



servations taken on ships in this area over a period 

 of more than 50 years. The majority of these 

 observations were made with the instruments 

 carried as a regular part of each ship's equipment. 

 Due to the possibility of error in the individual 

 thermometers and to errors in reading, the results 

 must be interpreted with care. However, with 

 such a large number of observations the non- 

 systematic errors tend to cancel each other, with 

 resulting averages being not far from the true 

 mean. 



The Weather Bureau of the United States De- 

 partment of Commei'ce has computed average sea 

 surface temperatures in the Gulf of Mexico using 

 the above observations. Table 1 shows the aver- 



Table I. — Monthly average sea surface and air temperatures in the Gulf of Mexico (in degrees Fahrenheit) 



Note.— From Charts 115-126, Atlas of Climatic Charts of the Oceans, U. S. Department of Commerce, Weather Bureau. 



age sea surface and air temperatures for the 12 

 months of the year, the Gulf being divided into 

 eight 5° quadrangles. This information was taken 

 from charts 115 to 126 of the Weather Bureau's 

 Atlas of Climatic Charts of the Oceans. 



Probably the most recently prepared charts 

 showing average sea surface temperatures in the 

 Gulf are those of Fuglister (1947). Isotherms 

 reproduced from his work for the winter month 

 of February and the summer month of August 

 are shown in figures 39 and 40. The main feature 

 of the average winter pattern is a gradual drop 

 from approximately 75° F. in the south to 65° F. 

 in the north in all parts of the Gulf, the gradient 

 being larger in the east portion. In the summer- 

 time the average temperatures are very nearly 

 uniform at 84° F. throughout the region. Cruises 

 of the Alaska indicate that considerable deviation 

 from these average isotherms may occur at cer- 

 tain times. 



The annual range of normal sea surface tem- 

 perature varies from 15° to 20° F. in the northern 



portion of the Gulf, while m the central and 

 southern portions the range is about 10° F. 

 February is normally the coolest month of the 

 year, though January is the coolest month for 

 that portion of the Gulf adjacent to Texas and 

 Mexico. Except for a few scattered areas, 

 August is normally the warmest month of the year. 



In regard to diurnal variation of surface tem- 

 perature in the Gulf, a study by Stommel and 

 Woodcock (1951) presents some data and dis- 

 cusses various methods of computation. It makes 

 recommendations for future investigation of this 

 problem. 



According to Storey (Gunter 1947), there were 

 nine freezes along the west coast of Florida be- 

 tween 1886 and 1936 which killed fishes in large 

 numbers. Intense cold spells, sufficiently severe 

 to kill large numbers of fishes, occurred along the 

 Texas coast on an average of one every 14 years 

 between 1856 and 1940, with less damaging spells 

 coming at shorter intervals. Similar data for 

 other parts of the Gulf coast are not available. 



