FISHERY BULLETIN: VOL. 81. NO. 4 



Nitrogen 

 S.Tx. 



6 l5 N° r 6 34 S 



*4 + 8 + I2 + I6 +20 





N.Tx. 

 8 La 



• •«•» ■>• 



X X XX 



o 



o 



Fla. 



Sulfur 



X 



0= estuarine dependent shrimp 

 collected in estuary 



• estuarine dependent shrimp 

 collected offshore 



X= nonmigratory offshore 

 resident shrimp and 

 stomatopods 



S.Tx. 



• •• 09 • • p* 



x M« 



N.Tx. 

 8 La. 



r#^-« 



>* XX XXX X X. x 



XXX x* x 



Fla. 



• • • • 5P • • 



+4 +8 i2 + I6 +20 



5 l5 Nor 534 s 



Figure 6. — Regional 5"N and iy 4 S values of benthic shrimp and stomatopods. Most samples are 

 composites. Estuarine collections were made in seagrass meadows in south Texas and Florida, but in 

 both open bays and Spartina marshes along the Louisiana and north Texas coasts. 



averaged less than values of offshore residents in all 

 three regions of the Gulf. The only striking regional 

 difference in these two smaller data sets was not 

 among the estuarine dependent animals but in the 

 S ls N data for offshore resident species. Residents 

 collected in offshore Florida waters averaged +8.3%o, 

 significantly less (P < 0.05) than the +11.8 and 

 + 12.2%o means of the western Gulf. While mean 

 offshore values may thus vary by region, the regional 



794 



uniformities in # 5 N and ^ 4 S values of estuarine 

 dependent species did not suggest striking regional 

 differences in the isotopic compositions of estuarine 

 foods. 



Estuarine Sampling 



To clarify the regional patterns observed in the # 3 C 

 data and also to establish £ 15 N and ^ 4 S values of 



