months after release. Three females were recap- 

 tured during the third spawning season, 20 to 24 

 months after they were tagged; and two males 

 were recaptured after 33 and 36 months. If these 

 periods are added to the approximately 12 months 

 required to attain adult size, the maximum age of 

 St. Johns crabs is estimated at little more than 4 

 yeai-s. 



LARVAL STAGES 



Newly hatched blue crabs pass through two 

 larval forms, zoea and megalops. Rearing of larvae 

 in the laboratory has shown that crabs have seven 

 zoeal stages over a period of 31 to 49 days and 

 a subsequent megalops stage of 6 to 20 days (Cost- 

 low and Bookhout, 1959) . 



Call'mecfes zoeae were found from April through 

 October in samples taken l>etween buoys 11 and 38, 

 3 to 11 km. above the mouth of the river. Peak 

 abundance occurred earlier in 1962 than in 1961 

 (table 3). The number of zoeae per cubic meter 

 of water ranged from to 460.9. More CalUnect^s 



T.^BLE 3. — Number of Callinectes zoeae collected per cubic 

 meter of water in the St. Johns River between buoys 11 and 

 38 (3-11 km. above mouth of river) 



zoeae were collected near the surface than at the 

 bottom regardless of tidal direction. No evidence 

 appeared of retention of GalUnectes zoeae within 

 the estuary, as more were obtained during outgoing 

 tides than during incoming tides. 



Most of the larval CalUnectes captured were 

 first-stage zoeae, but some second-stage zoeae and 

 some megalops also were caught. The proportion 

 of second-stage to first-stage zoeae was 1 to 323. 

 The second-stage form occurred in one surface 

 sample in May (1.5 per 1 m.^) and in four surface 

 and four bottom samples in August (0.6-2.6 per 

 1 m.^). The proportion of megalops to zoeae was 

 1 to 164. Megalops were found in three July sam- 

 ples (0.5-1.1 per 1 m.^), two August samples (1.1- 

 18.6 per 1 m.^), and two September samples (0.4 

 and 0.5 per 1 m.'). Ninety-six percent of the meg- 

 alops were taken in bottom collections. 



Zoeae of 22 kinds of crabs and megalops of 5 

 genera were collected between buoys 11 and 38. In 

 1961, Callinectes zoeae ranked third m abundance 

 after Vca. and Sesarma (table 4), and in 1962 Cal- 

 linectes ranked second to Uca (table 5). Megalops 

 of four other genera were collected from May 

 through October. Sixteen samples contained Uca 



Table 4. — Estimated average number of crab zoeae per cubic 

 meter of water, between buoys 11 and 38 {3-11 km. above 

 mouth of St. Johns River) in May, June, and August- 

 December, 1961 



[Number of samples each month In parentheses] 



1 Less than 0.06. 



24 



U.S. FISH AND WILDLIFE SERVICE 



