Size Range (mm) 



10-50 



51-90 



91-130 

 131-170 

 171-200 



0.2 



21.0 



69.0 



9.6 



0.2 



n = 16,000+ 



Table 41. Size range distribution 

 of pink shrimp in the 

 controlled area off 

 Key West, Florida 

 (adapted from Ingle 

 et al. 1959). 



smaller, younger shrimp to congre- 

 gate in shallower waters along the 

 south/southeast boundary of the 

 grounds and larger shrimp in the 

 deeper waters (Iversen et al. 1960). 

 The smaller shrimp are believed to 

 be the year's early recruits from 

 the estuarine nursery areas. These 

 same authors note that there is not 

 only a size/depth correlation but 

 also an increasing size gradient in 

 a northerly direction from Key West 

 irrespective of a depth increase. 

 Controlled release and recovery of 

 shrimp over the Tortugas grounds 

 confirms that a general northwest- 

 erly movement of individuals takes 

 place, but this is by no means 

 always the case (Iversen and Jones 

 1961). An average migration rate 

 (in all directions) of about 8 

 km/day (5 miles/day) is reported. 

 Numbers of shrimp at the surface and 

 mid-depth generally decrease from 

 midnight to mid-day and increase 

 from mid-day to midnight (Roessler 

 et al. 1969). 



Predicting the timing and 

 extent of shrimp abundance on the 

 Tortugas grounds is of primary 

 importance in making management 

 recommendations for the fishery. 

 Consequently, research has focused 

 on trying to understand the growth 

 and migratory patterns of the pink 

 shrimp and the factors which control 

 their seasonal and yearly fluctu- 

 ations. Although there still remain 

 many gaps in this knowledge, Figure 

 59 represents a simplified model of 

 the pink shrimp life cycle and 

 migratory patterns in the area. 

 The following discussion follows 

 this model through one loop in the 

 cycle. 



As adults, various size classes 

 of shrimp are rather broadly disper- 

 sed all over the Tortugas grounds 

 but with some distinct tendency for 



While on the Tortugas grounds, 

 female pink shrimp tend to grow 

 faster, and ultimately, larger than 

 male shrimp (Iversen and Idyll 

 1960). The effect of temperature on 

 growth of pink shrimp is believed to 

 be relatively small. Iversen and 

 Jones (1961) report that, in cage 

 experiments, growth during the warm 

 months is not significantly greater 

 than during the cooler months. In 

 fact the high summer temperatures 

 appear to slow the growth of shrimp 

 relative to springtime growth rates. 



It is believed that the gradual 

 movement of older, larger adults 

 into deeper waters corresponds to 

 the onset of spawning in the pink 

 shrimp. Female shrimp become capa- 

 ble of reproducing when they reach 

 about 90 mm (3.5 in) in length 

 (Ingle et al. 1959). Spawning 



occurs all year round in warm south 



202 



