METRIC 1 



,009] 



Figure 12. — Internal plastic shrimp tags. 



Sabine Pass, Tex. Between late February and 

 mid-March 1967, postlarval brown shrimp 

 entered Galveston Bay in two major groups 2 

 weeks apart (fig. 13). The large April influx 

 of postlarvae, usually reflected by our sam- 

 pling, did not appear in 1967. Average weekly 

 water temperature remained above 15° C. 

 (59.0° F.) after February 15. 



Postlarval white shrimp were collected in 

 sample catches in late April, but numbers 

 did not increase significantly at either the 

 Galveston or Sabine Pass sampling stations 

 through nnid-June. The early-summer bay 

 crop of juvenile and subadult white shrimp will 

 probably be small. In most years, catches 

 of postlarval white shrinnp increase at bay 

 entrances during the spring and fall. The first 

 group arrives at the tidal passes in May-June 

 and the second in August-September. For the 

 past 4 years, early fall collections have con- 

 tained more postlarval white shrinnp than 

 spring collections, especially at Sabine Pass 

 (fig. 14). 



An apparent limitation of past postlarval 

 shrimp data is the small number of samples 

 taken during periods of greatest abundance. 

 We are building a plankton pumping device 

 that will sample incoming postlarvae at 

 frequent intervals or continuously during 

 periods of peak in-imigration. A working model 

 has been used successfully at the East Lagoon 

 laboratory in preliminary tests. 



Juvenile Shrimp 



Young brown shrimp apparently encountered 

 favorable conditions for survival and growth 

 on the nursery grounds in 1967. By mid-April 

 they were being taken by connmercial bait- 

 shrimp fishermen, and by early May their 



Figure 13. — Weekly water temperatures and indices of 

 abundance of postlarval brown shrimp at Galveston 

 Entrance in early 1967. 



abundance in this fishery appeared to be 

 reaching peak proportions. Indices of abun- 

 dance for postlarval and juvenile brown 

 shrimp indicate a large harvest of adult 

 brown shrimp in the late summer and fall of 

 1967. 



Result of our weekly survey of the bait- 

 shrimp fishery of Galveston Bay indicate that 

 this fishery in 1966 experienced its poorest 

 harvest of young brown shrimp since detailed 

 statistical coverage began in 1959. Juvenile 

 brown shrimp abundance, as reflected by 

 catch-effort statistics, decreasedby 50 percent 

 in 1966 as compared with 1965. This decline 

 may have been caused by the unusually large 

 inflow of fresh water into the Galveston Bay 

 system from the Trinity River and its tribu- 

 taries in May. The resultant lowered salinities 

 for an extended period during the peak growing 

 time for brown shrimp possibly caused nnost 

 shrimp of the year class to move offshore 

 prematurely, thus making them unavailable to 

 the bay fishermen. Early departure of young 

 brown shrimp coupled with a sparse crop of 

 white shrimp in the bay evidently caused the 

 poor catch by bay fishernnen in 1966. 



We continued to prepare monthly summaries 

 of the bait-shrimp fishery of Galveston Bay, 

 including catch, effort, and number of active 

 dealers and fishermen. These summaries are 

 distributed to State agencies, universities, 

 and individuals upon request. 



Inshore Current Patterns 



A 1-year drift bottle and seabed drifter 

 study of inshore current patterns from shore 



17 



