Table 5. — Estimates of the production of first protozoeae of 

 P. duorarum on the Tortugas Shelf, August 1962 to 

 October 1964 



Figure 3. — Histograms showing tlie relation between the 

 percentage of the annual catch of first protozoeae 

 taken in each month, and (solid lines) the average 

 bottom water temperature from the Tortugas Shelf 

 area, 1959-64. Broken lines indicate no data. 



An analysis of the distribution of bottom 

 temperatures suggests that temperature plays no 

 significant part in the movement of the center of 

 spawning. During 1963, when the movement into 

 deeper water was most marked, bottom tempera- 

 tures appeared to be almost uniform at any given 

 time throughout the sampling area. Shrimp 

 landing data for 1963 (U.S. Fish and WikUife 

 Service, 1964) showed that small shrimp appeared 

 in the shallow areas of the trawUng grounds about 

 April and again in October. Previous studies of 

 adult shrimp (Iversen and Jones, 1961; Iversen, 

 Jones, and Idyll, 1960; and Iversen and Idyll, 

 1959) have shown that the average size of shrimp 

 increases with increasing depth. Shrimp tagging 

 studies also have indicated a migration toward 

 deeper water. Apparently the maturing shrimp 

 entering the fishery in the early part of the 

 summer begin spawning when they reach a 

 suitable size and continue to spawn as they 

 migrate to deeper water. This theory is compatible 

 with data on maturation and growth provided by 

 Eldred, Ingle, Woodburn, Hutton, and Jones 

 (1961) and by Iversen (1962). 



Cruise 



Date 



First proto- Average num- 

 Length of zoeae produced ber of first 

 intercruise during inter- protozoeae pro- 

 period cruise period duced per day 



6201 

 6202 

 6203 

 6204 

 6205 

 6206 

 6207 



6301 

 6303 

 63M 

 6305 

 6306 

 6307 

 6308 

 6309 

 6310 

 6311 

 6313 

 6314 

 6315 

 6316 

 6317 

 6318 



6401 

 6402 

 6403 

 6404 

 6405 

 6406 

 6407 

 6408 

 6409 

 6410 

 6411 

 6412 

 6413 

 6414 

 6415 

 6416 



Days 



-\ug. 14-16 



Aug. 28-30 



Sept. 11-12 



Sept. 25-28 



Oct. 9-10 



Not. 7-8 



Dec. 4-5 



196! 



Jan. 9-10 



Mar. 11-12 



Mar. 26-27 



Apr. 8-10 



May 7-9 _. 



May 20-23 



June 4-5 



June 18-22 



July 1-2 



July 30-Aug. 1. 



Aug. 13-14 



Aug. 27-28 , 



Sept. 9-10 



Oct. 1-2 



Oct. 15-16 



Nov. 5-6 , 



I96i 



Feb. 17-18 



Mar. 3-4.- 



Mar. 17-18 



Apr. 1-2.. _ 



Apr. 14-15 



Apr. 28-30 



May 12-14 



May 26-28 



June 9-11- 



June 23-25 



July 7-9 



July 21-23 



Aug. 4-5 



Aug. 18-21 



Sept. 1-2- 



Oct. 2-4 



14.0 

 13.8 

 14.3 

 14.0 

 21.0 

 28.0 

 32.0 



48.5 

 38.0 

 14.3 

 21.3 

 21.3 

 13.8 

 14.8 

 13.5 

 20.8 

 21.5 

 13.5 

 13.5 

 17.5 

 18.0 

 17.5 

 64.5 



59.0 

 14.0 

 14.5 

 14.0 

 13.8 

 14.3 

 14.0 

 14.0 

 14.0 

 14.0 

 14.0 

 13.8 

 14.3 

 14.0 

 22.3 

 30 



Calculated number X 10» 



2, 993. 213. 8 



5, 091. 9 369. 



4, 062. 2 284. 1 



8, 886. 2 634. 7 



13, 455. 5 640. 7 



258. 5 9. 2 



6, 423. 200. 7 



3,511.0 



7501 



104.8 



791.6 



2, 746. 6 



2, 794. 7 



177.0 



1, 403. 9 



8, 021. 3 



2, 738. 2 



2, 540. 8 



6, 134. 



6, 002. 7 



7, 184. 2 



4, 287. 6 



11,352.1 



1, 079. 

 327.2 



5, 595. 3 

 11,021.5 



9,004.4 

 1, 792. 6 

 1, 967. 4 

 2,083.1 



6, 793. 4 

 15, 593. 8 



7, 881. 4 



4, 056. 2 



5, 680. 8 

 804.9 

 530.4 



3, 834. 3 



72.4 



19.7 

 7.3 



37 2 

 129.0 

 202.5 



12.0 

 104.0 

 385.6 

 127.4 

 188.2 

 454.4 

 343.0 

 399.1 

 246.0 

 176.0 



18.3 



23.4 



385.9 



787.3 



652.5 



125.4 



140.5 



148.8 



485.2 



1,113.8 



563.0 



293.9 



397.3 



57.6 



23.8 



127.8 



INTRAMONTHLY VARIATIONS IN SPAWNING— 

 THE EFFECT OF MOON PHASE 



The percentage of various larval stages in the 

 total catch varied considerably on successive 

 cruises. We analyzed these variations to determine 

 whether they could in some way be related to the 

 lunar phases. 



The percentage which first protozoeae repre- 

 sented in the total catch of larvae and postlarvae 

 taken on each cruise was calculated and plotted 

 against moon age minus 5 days (table 6). The 

 average age of first protozoeae is 5 days (Ewald, 

 1965), and subtracting 5 days backdates the 

 observation of the relative abundance of protozoeae 

 to the time of spawning. The average of the 

 percentages of protozoeae in all catches was 50.6 

 percent; in 12 of 18 catches taken during the 

 waxing moon (0-14.7 days) the relative abundance 

 of first protozoeae was below average (fig. 5), 

 whereas in 11 of 17 catches during the waning 

 moon the relative abundance was above average. 



PINK SHRIMP ON FLORIDA TORTUGAS SHELF 



171 



