Table 5. — Number, size (carapace length, millimeters), and sex of pink shrimp caught in Old Tampa Bay, Fla., at difference hours 



salinities on a few occasions and concluded 

 that size was related more closely to locality 

 than salinity. This finding is not in agreement 

 with other reports on size in relation to loca- 

 tion and salinity of an estuary. Gunter, Christ- 

 mas, and Killebrew (1964), Williams (1955a, 

 b), Tabb, et al. (1962), and Saloman (1965) 

 concluded that an increase in shrimp size 

 usually accompanies an increase in salinity. 

 Obviously the relative influence of various 

 factors on the size of shrimp captured will 

 not be easy to determine. 



The 16 sampling series were conducted 

 during periods of moon phases as follows: 

 new moon, 11 series; first quarter, 2; full 

 moon, 2; and last quarter, 1 series. Although 

 cloud cover at night was not recorded and re- 

 sults are not conclusive, greater numbers of 

 pink shrimp were caught during the dark 

 phases (new moon, first quarter, and last 

 quarter) of the lunar cycle than during the 

 light phase (full moon)--table 6. 



Various authors have mentioned that avail- 

 ability of pink shrimp varies with moon 

 phases --that more are caught during the 

 dark or new moon phase (Iversen and Idyll, 

 1959; Fuss, 1964; Idyll, Iversen, and Yokel, 

 1965). Perhaps the greatest effect of the 

 moon on shrimp behavior is through the 

 intensity of light (Wheeler, 1937; Fuss and 

 Ogren, 1966). In that event a correlation be- 

 tween catch and moon phase would be ex- 



Table 6. — Pink shrimp caught at Egmont Key 

 and in Old Tampa Bay, Fla., (data combined) 

 during various moon phases 



pected since light intensity in the first and 

 last quarters is only one-ninth of the moon's 

 total intensity. 



SEASONAL CHANGES IN ABUNDANCE 

 AND SIZE OF PINK SHRIMP 



The mean size (CL) of pink shrimp caught 

 in Tampa Bay showed an average increase of 

 1.2 mm. per month from August 1962 through 

 May 1963 (fig. 3). Small shrimp started to 

 appear again in June and July. The mean size 

 at Egmont Key steadily increased from July 

 to mid-December 1963. In Old Tampa Bay 

 mean sizes increased from a low of 5.5 mm. 

 CL in June to 19.5 mm. CL in August 1963 

 and then decreased slightly. 



Growth rates at Egmont Key were similar 

 in both years; shrimp gained about 0.7 mm. 

 per month from August through December 



1962, and 0.4 mm. per month from July 

 through December 1963. The size increase 

 was greatest from December 1962 through 

 May 1963 when the rate was about 1.5 mm. 

 per month. Mean sizes of pink shrimp at 

 Egmont Key caught during October through 

 December of both 1962 and 1963 were almost 

 identical (fig. 3). 



Mean size of pink shrimp reached a peak at 

 both stations in April or May but decreased 

 sharply by June or July (fig. 3). The absence 

 of large pink shrimp in Tampa Bay in June, 

 after a gradual increase ending in April and 

 May, appears to have resulted from the move- 

 ment of shrimp to offshore waters. Eldred, 

 et al. (1961) found that larger shrimp (85-140 

 mm. total length) migrated out of Tampa Bay 

 from April through July. Commercial shrimp 

 boats seen offshore by Eldred, et al. (1961) in 

 1958, by Saloman (1965) in March and April 



1963, 1964, and 1965, and by the author again 

 in 1966 also give evidence of a migration from 

 Tampa Bay in the spring. 



Catches of pink shrimp increased as tem- 

 perature decreased to 14° C, but declined at 

 temperatures below this level (fig. 4). Eldred, 

 et al. (1961) and Williams (1955a) suggested 

 that pink shrimp remain in the sediment dur- 

 ing cold periods, and Williams also mentioned 



