NATURAL HISTORY OF REDFISH, ETC., OF TEXAS 133 



The Gulf of Mexico is the fundamental source of all the marine life found within 

 the intercoastal waters. Without the incoming tides the shallow bays and lagoons 

 would be subject to such extreme temperatures and salinities as to render the exist- 

 ence of much marine life highly improbable. At the present time Laguna Madre, a 

 long, narrow lagoon having poor circulation of water with the Gulf of Mexico, often 

 reaches such high salinity through excessive evaporation in summer as to kill thou- 

 sands of fish trapped in the lagoon by shallow water. In spring large quantities of 

 Gulf water pour into the bays, bringing along a new supply of marine oi-ganisms, 

 which usually linger within the intercoastal waters until the approach of cold weather. 



Water from the Gulf enters the bays by the passes or inlets through the barrier 

 islands. Because of the relatively slight tidal action, many of the more remote bays 

 and lagoons do not attain a salinity equal to that of the Gulf and approach the charac- 

 ter of brackish water. Two passes — Aransas and Corpus Christi — are included in 

 the section of Texas coast represented in Figure 1 . 



Aransas Pass is an artificial or dredged channel, which has been enlarged from 

 a relatively shallow, natural inlet to a deep, jettied pass, through which merchant 

 ships go on their way to the inland port of Corpus Christi. The pass is about 2 

 miles long, 1,000 feet wide, 30 feet deep, and is protected against erosion by a pair 

 of rock jetties stretching out into the Gulf about a mile from the shore line. Many 

 observers believe that natural entrance of schools of fish into the bays is hindered 

 by these barriers along the shore line. While no data exist to support or deny this 

 contention, the writer found that the rocks at Aransas Pass had a decided tendency 

 to impede the entrance of many larval and young croakers and spots into the bays. 

 The deepened condition of the pass, resulting from continual dredging, allows more 

 water to enter than would be possible if the pass were continualh' filled with sand, 

 such as is the case with most of the natural passes along the coast. The effect of the 

 dredging in the pass, however, could hardly be called beneficial to the particular 

 species of fish found to spawn at the mouths of the passes. 



Corpus Christi Pass, lying at the head of Laguna Madre and about 20 miles 

 south of Aransas Pass, is a small, natural channel through which not even a small 

 power boat can navigate on account of the ever-present sand bars in and about the 

 pass. At the time of the investigation in 1926 and 1927 this pass was about 1,000 

 feet long, 100 feet wide, and about 6 feet deep in the middle of the channel. It may 

 change its shape and depth after each severe storm and at times may be almost 

 closed by sand bars. 



Tidal action usually gives the passes along the coast but one strong incoming 

 tide a day, and little or no water enters if the tide is opposed by strong winds. With 

 the passes serving as main highways between the Gulf and the intei-coastal waters, 

 their condition is of the utmost importance if a continual interchange of water is to 

 be maintained." 



' According to Marmer (1927. p. 434), the range of the tide at Galveston, Tex., averages but 1 foot, as compared with 4H feet 

 at New York and 9 feet at Portland, Me. On the Atlantic coa.st the two high waters and also the two low waters of a day are ap- 

 proximately the same, the morning and afternoon tides resembling each other in all respects. In the Gulf of Mexico , however, the 

 two high waters do not differ much, but morning and afternoon low waters are so strikingly different that frequently the higher 

 of the two low waters merges witii one of the high waters, and at such times there is iiut one iiigh water and one low water in 

 a day. 



