The present report summarizes the 

 results of 13 months' field observations. 

 Several factors, such as weather, mar- 

 kets, season, and size of boats, were 

 expected to affect the results of this 

 research. As the work progressed, other 

 factors, unsuspected originally, were 

 shown to influence the size -depth rela- 

 tionship and the distribution of fishing 

 effort. In the following analysis the effect 

 of the important variables on the results 

 is described, and where possible meas- 

 ured. The results are then presented, and 

 their significance in relation to the man- 

 agement of the fishery is discussed. These 

 data cover a single year, and one that was 

 not altogether "typical." The tempera- 

 tures of southern Florida during the winter 

 of 1957-58 were extremely low, and this 

 may have had some effect on the behavior 

 of the shrimp. 



ACKNOWLEDGMENTS 



Numerous people have contributed their 

 services in the collection and analysis of 

 the data presented in this report. U. S. 

 Bureau of Commercial Fisheries per- 

 sonnel, D. Aldrich and E. Arnold; Marine 

 Laboratory, University of Miami person- 

 nel, W. Cummings, A. Volpe, J. O'Neill, 

 R. Manning, J. Vogel, D. Marra, J. Tweedy, 

 H. FouUc, J. Iversen, W. Saenz, and A. C. 

 Jones are due thanks. Dr. George A. 

 Rounsefell and nnembers of his staff re- 

 viewed the manuscript and provided help- 

 ful suggestions. 



METHODS AND MATERIALS 



VESSELS AND GEAR 



Data were gathered from catches made 

 by chartered commercial shrimp trawlers 

 and from observations made from airplane 

 flights over the grounds. The boats used, 

 the Captain Mack, the Danny Boy, and th.e Joanie, 

 are typical "Florida -type" shrinnp 

 trawlers. They are 63, 55, and 69 feet in 

 length, respectively. The Captain Mack was 

 used from September 1957 to mid-April 

 1958 (table l). She was then sold and the 

 Danny Boy secured and used until late 

 September 1958, when she was acciden- 

 tally rammed and capsized. The last two 

 cruises were made on the Joanie. 



During the first six cruises positions 

 were determined by the radio direction 

 finder on the chartered vessel. A small 

 portable directionfinder was also acquired 

 for use in case of the failure of the ves- 

 sel's instrument. During subsequent 

 cruises the dead-reckoning navigation was 

 improved by the use of a portable pelorus 

 for obtaining more accurate visual fixes 

 on navigation aids. Positions on the 

 northern portion of the area were difficult 

 to locate accurately, owing to the geo- 

 graphical location of the radio stations. 

 After cruise 10 celestial navigation was 

 used to supplement the radio direction 

 finder since fishing is carried on at night. 



Depths were determined chiefly by use 

 of a fathometer. During the first several 

 cruises depths were checked by leadline 

 soundings and by bathythermograph lower- 

 ings, and the fathonneter was repaired and 

 checked to correspond. Fathometer tapes 

 were nnarked and retained. 



The gear ennployed in sampling con- 

 sisted of standard commercial trawls, as 

 described by BuUis (1951) and Knake. 

 et al. (1958). On cruises 1-5 and 7-15, a 

 90-foot "two-seam flat" trawl was used. 

 On cruise 6 a 90-foot balloon net was 

 employed to avoid loss of the regular net 

 on the rough bottom. On cruises 16-21, 

 two 45-foot "double-rig" trawls were 

 used; and on cruises 22 and 23, two 50- 

 foot double -rig trawls. In addition to the 

 big trawls described above, 15 -foot try 

 nets were used regularly. On some tows 

 of cruises 1-11 a large try net, measuring 

 about 30 feet, was used in place of the 

 main trawl. Descriptions of all nets used 

 on the various cruises are given in table 1. 



The research plan provided for two 

 cruises each month, starting in November 

 1957 and ending in November 1958. (Two 

 prelinninary cruises were made during 

 September 1957 by Bureau of Commercial 

 Fisheries scientists.) This plan was ac- 

 connplished in all months except June, 

 October, and November 1958 (in which 

 one cruise was made each month) despite 

 the unusually bad weather experienced 

 during the study period. A total of 23 

 cruises was made. Sampling stations are 

 depicted in figure 2. Fishing was done at 

 night and tows were ordinarily limited to 

 1 hour instead of the usual 3 hours nnade 

 by fishermen. 



