ALL ANIMALS EXCEPT 

 POLYCHAETA, LAEVICARDIUM. AND PENAEUS 



POLVCHAETA 



^ 



^ 



PENAEUS SPP 

 9-30 MM TOTAL LENGTH 



LAEVICARDIUM MORTON! 



20 - 



\- 



O 10 



z 

 a 



K 

 U 



a. 



30 

 20 



10 







MAY JUN JUL AUG SEP OCT NOV DEC JAN, 

 1965 1966 



Figure 8. --Monthly abundance of Penaeus spp. and 

 associated animals at station 1, Florida Bay. 



juvenile pink shrimp, studies by personnel 

 at Galveston indicate that brown shrimp 

 definitely prefer polychaetes. 



Thomas J. Costello, Project Leader 

 Donald M. Allen 



RELATION OF VARIATIONS IN ABUNDANCE 



OF JUVENILE PINK SHRIMP EMIGRATING 



FROM THE EVERGLADES NATIONAL 



PARK ESTUARY TO THE 



COMMERCIAL CATCH 



This year marked the beginning of the 

 second phase of the study of juvenile pink 

 shrimp in Everglades National Park. Observa- 

 tions on the abundsLnce of pink shrimp leaving 

 this nursery have been increased considerably 

 by establishing a second sampling station at 

 Joe River. 



The abundance of pink shrimp migrating out 

 of Everglades National Park was estimated in 

 previous years by sampling with a large chan- 

 nel net at a single station in Button wood Canal. 

 As knowledge of the changes in abundance 

 and the distribution of the shrimp in the ebbing 

 currents of the canal improved, it was possible 

 to design "wing-net" gear that provided a 



reliable index of the total numbers of shrimp 

 migrating in the canal. The use of the wing 

 net has made it possible to maintain the 

 continuity of observations in Buttonwood Canal 

 with less manpower and at the same time 

 to sample in more remote areas with conri- 

 parable gear. 



The second sampling station in Joe River 

 (in the western outlet of Whitewater Bay) has 

 improved the accuracy of abundance estimates. 

 Wing -net sampling at this station was started 

 on a weekly basis in October 1965. 



"Conical-net" sampling was also started at 

 the Joe River station in October. These nets 

 provide data on the vertical and lateral dis- 

 tribution of the shrimp in the river in relation 

 to moon phase, water velocity, and other fac- 

 tors. This sampling was suspendedtemporarily 

 in late October when shrimp abundance de- 

 clined and insufficient numbers were being 

 caught to determine their distribution in the 

 river. Sampling with conical nets was resumed 

 in May 1966; catches indicate ahighpercentage 

 of the shrimp migrate near the surface and 

 that the largest samples are obtained by 

 sampling in the swiftest currents. These 

 results are similar to those for Buttonwood 

 Canal. 



We recorded a single period of high abun- 

 dance of shrimp migrating out of Buttonwood 

 Canal in 1965. A peak in June tapered off 

 through October, At least two periods of high 

 abundance were observed in 1963 and 1964. 

 The level of abundance in 1965 was slightly 

 greater than that in 1964, and the period was 

 about 2 months shorter. The period of low 

 abundance that started in October 1965 con- 

 tinued at a still lower level foralonger period 

 {5 months) than in previous years. The abun- 

 dance trend was similar in Joe River. 



The relative abundance of juveniles mi- 

 grating out of Buttonwood Canal and the size 

 of commercial catches continue to have little 

 correlation. Periods of high abundance that 

 have occurred, however, during these years 

 of sampling in Buttonwood Canal are con- 

 sistently reflected in increased catches of 

 the smallest commercial shrimp 1 to 2 1/2 

 months later; the lag depends on the size of 

 the emigrating shrimp. Conversely, all major 

 peaks of abundance in the commercial landings 

 of the smallest shrimp can be related to a 

 corresponding period of abundance in Button - 

 wood Canal. The peaks are only roughly 

 comparable, but the extent of agreement with 

 only one sampling station encourages us to 

 believe that dependability of predictions can 

 be improved by adding a second station. 



In 1965-66, as inprevious years, the smallest 

 shrimp collected in Buttonwood Canal were 

 taken during the period of highest abundance. 

 Although shrimp in both Joe River and Button - 

 wood Canal have remained large since October 

 1965, the monthly mean lengths of shrimp 

 caught in Joe River are consistently larger 



11 



