than those in Buttonwood Canal. The meain 

 carapace length of shrin-ip from Joe River in 

 January 1966 was 19.6 mnn.; these shrimp were 

 the largest collected from either station. 



C. P. Idyll, E. S. Iversen, and 

 B. Yokel, Project Leaders 



Institute of Marine Science, 

 University of Miami 

 (Contract No. 14-17-0002-140) 



SEASONAL CHANGES IN RELATIVE 



ABUNDANCE OF POSTLARVAE OF 



PINK SHRIMP ENTERING THE 



EVERGLADES ESTUARY 



Studies began on the abundcuice and seasonal 

 distribution of postlarval pink shrimp entering 

 the Everglades nursery area. 



Two sampling stations have been established, 

 one in Buttonwood Canal about 0.8 km. (0.5 

 mile) from its end at Florida Bay and one in 

 the Little Shark River about 0.8 km. (0.5 mile) 

 fronn the Gulf of Mexico. These stations 

 represent the eastern and one of the western 

 access routes to the Whitewater-Coot Bay 

 system. 



A 1-m. nylon plcuikton net with 471 -micron 

 mesh is used as the sampling gear. Surface 

 and bottonn samples are taken simultaneously 

 from a small boat which is run against the 

 tidal current at a constant speed. The plankton 

 nets are equipped with Tsurumi Precision 

 Instruments Company "TSK-Type" flowmeters 

 to permit the calculation of the cubic meters 

 of water strained per tow. 



Observations on tidal current velocity, water 

 temperature, salinity, and depth of water have 

 been recorded to determine their importance 

 in the movement of the postlarvae. Moon-phase 

 and meteorological conditions have also been 

 recorded to learn their effect on migration 

 and abundance. 



Sampling began at the Buttonwood Canal 

 station in July 1965 and at the Little Shark 

 River station in January 1966. When post- 

 larval abundcince was high, sampling was con- 

 ducted in all phases of the moon; during 

 periods of low abundance, sampling was lim- 

 ited to new- and full-moon phases. The abun- 

 dance of shrimp in Buttonwood Carnal showed 

 a bimodal distribution that had a major peak 

 in July-August and a minor peak inNovember. 

 Abundamce was relatively low in 1966 from 

 January to the first of April; catches of 

 postlarvae began to increase by mid-April at 

 both stations. 



A preliminary analysis of the data indicates 

 that several factors may affect the relative 

 abundance and movennent of postlarvae: (l)the 

 abundance of shrimp during a single tide is 

 correlated with water velocity; (2) shrinnp are 

 most common during night flood tides; (3) the 

 greatest numbers of shrimp are taken in 

 bottom hauls; (4) more shrimp are caught in 

 Buttonwood Canal than in Shark River; and 

 (5) shrimp are most abundant during the 

 waning moon and least at the full moon. 



C. P. Idyll and Martin Roessler, 

 Project Leaders 



Institute of Marine Science, 



University of Miami 

 (Contract No. 14-17-0002-141) 



SHRIMP DYNAMICS PROGRAM 



The research responsibilities of this pro- 

 gram include studies to deternnine the most 

 appropriate means for n-ianaging shrimp fish- 

 eries and investigations of methods to predict 

 the catch of shrimp. The program includes 

 three projects at this Laboratory aind contract 

 research at the University of Southwestern 

 Louisiana. Each of these activities has been 

 in operation between 3 and 6 years and is now 

 well established. Although progress toward 

 our eventual aims already has been substantial, 

 we continually find reasons to review and 

 revise our methods. We have made several 

 changes in the past year and contemplate 

 others. 



The orgauiizational structure of the program 

 was altered during the year to incorporate a 

 former project. Commercial Catch Sampling, 

 into another existing project entitled Population 

 Studies. This change marks the end of studies 

 designed to evaluate the accuracy of published 

 data on shrimp landings and an expansion of 

 research on how commercial fishing affects 



stocks of shrimp. Conclusions drawn from 

 the appraisal of landing data are included in 

 the present report. Other work within the 

 Population Studies Project, but not reviewed 

 here, includes a detailed study of howtheTor- 

 tugas pink shrimp stock and the commercial 

 fishery interact; investigations of the selec- 

 tivity of shrimp nets; and studies of seasonal 

 changes in the size composition of shrimp 

 off the central Texas coast. 



The report for the Mark-Recapture Project 

 centers on many recent improvements in the 

 design of equipment for staining shrimp. Use 

 of the new equipment makes it possible to mark 

 large numbers of shrimp and thereby increase 

 the reliability of resulting estimates of shrimp 

 growth, mortality, sind movements. Whereas 

 earlier experiments had included about 3,000 

 marked shrimp, between 7,000 and 12,000 

 stained shrimp were released during the past 

 year. 



The Postlarval and Juvenile Shrimp Project 

 has succeeded in measuring the abxindance of 



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