the extent of coastwise intermingling of mature shrimp after they pass through 

 the fishery and (2) the origin of larvae nurtured in specific estuary systems. 



Mortality Studies of mortality in pink shrimp populations are scheduled to 



begin in late 1961. Further application of the staining technique to facilitate 

 mortality measurement has been encouraged by the generally good results ob- 

 tained from the Bottle Key and Pine Island Sound experiments. 



Growth Attempts to describe pink shrimp growth over an increasingly wider 



range of developmental stages continued during the year. Two mark- recapture 

 experiments involving shrimp ranging in total length from 47 to 77 mm. were 

 initiated in Biscayne Bay in August I960 (11, 000) and April 1961 (2, 775), re- 

 spectively. Marking agents consisted of three dyes (Trypan blue, Trypan red, 

 fast green) applied by "feeding" (ingestion) and injection. As only four recap- 

 tures (3 blue, 1 green) were reported by Biscayne Bay commercial bait fish- 

 ermen, both experiments may be considered to have ended in failure. The sin- 

 gle green recapture did, however, provide a good indication of how rapidly 

 shrimp will grow during juvenile stages. A female, 70. 5 mna. long at release 



in mid-April, had increased in total 

 length at the rate of 27. 5 mm. per 

 30-day period over the 65 days pre- 

 ceding recapture. 



The dearth of recoveries 

 from either experiment was most 

 likely due to a combination of (1) rel- 

 atively small releases of marked 

 shrimp and (2) rapid movement of 

 marked populations beyond the range 

 of effective fishing. A possible ex- 

 planation for no recoveries in cases 

 where Trypan red was used as the 

 marking agent is that this stain did 

 not present enough contrast to the 

 shrimp's normal color to be readily 

 noticed by fishermen or dealers. Try- 

 pan red in all individuals comprising 

 a sample held in captivity for 3 months 

 was, however, still detectable at the 

 end of that period. 



An additional mark- 

 recapture experiment involving slight- 

 ly over a thousand small (50-75 mm. 

 total length) pink shrimp marked with various stains and held in a small sea- 

 water pond yielded, after a lapse of 5 weeks, the results graphed above. These 

 compare favorably with the results of earlier experiments conducted in the same 



70- // 



UNSTAINED 



• - Male 

 o - Femole , 



— I — V~ 



20 30 

 APRIL 



— 1 r- 



20 30 

 MAY 



n 1 1 



10 20 30 

 JUNE 



Growth of pink shrimp in a small sea- 

 water pond, Virginia Key (Miami), 

 Florida, April-June 1961. 



20 



