622 



Fishery Bulletin 90(3), 1992 



Results 



Overall, 16% (95% CI, 11-21%) of 219 tagged shrimp 

 were returned (Table 1). The return rate of 21% for 

 brown shrimp was greater than the 11% for white 

 shrimp (x^ 4.415, Idf, P<0.05). Reporting rates did 

 not differ between bay systems for brown shrimp (x^ 

 2.081, Idf, P>0.05) or white shrimp (x^ 1.059, Idf, 

 P>0.05). Reporting rates for the two species of shrimp 

 were similar in Galveston Bay (x^ 0.001, Idf, P>0.05); 

 in Aransas Bay, reporting rates were greater for brown 

 shrimp (x^ 6.890, Idf, P<0.05). Sixty-eight percent of 

 shrimp returned were reported found on the same day 

 as placement. 



Mean lengths of placed and returned brown shrimp 

 from Aransas Bay were similar (t - 0.48, P>0.05) (Fig. 

 1), while the mean length of placed white shrimp was 

 smaller than the mean length of those returned 

 (t -4.01, P<0.05). Placed brown shrimp were similar 

 in length to those measured from the unculled catches 

 on commercial shrimp boats (Fig. 2) whereas placed 

 white shrimp were clearly smaller than those measured 

 on commercial boats. 



Discussion 



Tag reporting rates for bay-caught shrimp have been 

 reported by Klima (1974) and Johnson (1981). Tag 

 reporting rates presented in this study are more precise 

 because sample sizes were larger than in previous 

 studies. Moreover, tag return rates in this study are 

 more realistic because the tagged shrimp were placed 

 in the catch before any processing occurred, rather 

 than at dockside during the final processing stages. 



The detection rate, and thus the reporting rate, of 

 tagged shrimp in unculled catches may be influenced 

 by size of tagged shrimp relative to size of other shrimp 

 in the catch and by overall volume of catch being pro- 

 cessed. In the fall shrimping season (15 August-15 

 December), there are no restrictions on the amount of 

 shrimp that can be retained. During 15 August-31 

 October, when white shrimp dominate the catch, the 

 minimum shrimp count size is 50 (heads-on) per pound 

 in major Texas bays (State of Texas 1987-88). Thus, 

 commercial fishermen selectively retain larger shrimp 

 during this interval. Since the TPWD gear used to 

 collect white shrimp for tagging was relatively non- 

 selective, surreptitiously-placed shrimp in Aransas Bay 

 were smaller than those in the catch in which they were 

 placed. In contrast, brown shrimp dominated the catch 

 in summer when there was no count size restriction, 

 and thus placed shrimp were similar in size to those 

 in the commercial catch. Because the placed white 



Brown Shrimp 



Placed (N-56) 

 Returned (N>17} 



65 70 75 80 85 90 95 100105110 115120125130135140145150 



Total Length (mm) 



White Shrimp 



_ 8 

 6 





Placed (N-4g) 

 Relumed (N>4) 





65 70 75 BO [>5 aO aS) 100 105 110 115 120 125 130 135 140 145 160 



Total Length (mm) 



Figure 1 



Length-frequency (TL) of surreptitiously-placed brown and 

 white shrimp, and of returned brown and white shrimp from 

 Aransas Bay, May-November 1984. 



