area. In June they were common out to 2.5 km., 

 and from July through September, when they 

 were most abundant, hirge numbers were 5 to 6 

 km. offshore between Fernandina Beach and Ponte 

 Vedra Beach. The number of females offshore 

 dropped sharply in October, but 62 percent were 

 in sponge compared with 4 percent in the lower 

 32 km. of river. From November to February, fe- 

 male crabs were least common in the sampling 

 area off the mouth of the St. Johns. During this 

 period only one sponge crab was taken (in Janu- 

 a.ry) but the well-developed ova of most of the 

 females mdicated that they would spa^vn in the 

 spring. 



Many if not all female blue crabs spawn twice — 

 in the same season or over two seasons — and they 

 oft#n return to inland waters to develop their sec- 

 ond sponge. Throughout the spawning season, 

 some females reentered the lower 40 km. of the 

 river from the ocean and developed another 

 sponge. These repeat spawners could be distin- 

 guished by the appearance of their shells. Crabs 

 which have not left the river have shiny, clean, 

 bright-colored shells. Crabs which have spent time 

 in the oc«an have dull-colored shells with an en- 

 crustation of fouling organisms — especially the 

 turtle barnacle, Cheloniiia patula. Blue crabs 

 which had previously had sponges also could be 

 distinguished by the ragged apjwarance of their 

 abdominal appendages and the presence of egg- 

 shell remiiants. 



TAGGING AND RECOVERY 



The few tagging studies that have been made to 

 detennine movements of adult blue crabs have 

 been confined largely to bays and to lower parts of 

 estuaries. Fiedler (1930) found that tagged fe- 

 males released in the northern part of Chesapeake 

 Bay migrated to the southern portion and tended 

 to remain there. The direction of movement for 

 males was random. Cronin (1954) detected no 

 clear pattern for movements of crabs in Delaware 

 Bay. Some males and females moved up Delaware 

 Bay after wintering near the mouth ; none of the 

 tagged crabs was returned from other coastal re- 

 gions. Cargo (1958), who tagged only females in 

 Chincoteague Bay, Va., found they moved south- 

 ward to the lower bay even if released in areas 

 where high-salinity water was to the north. Only 

 two crabs were captured outside Chincoteague Bay 



— one at Oyster, Va., the other in Delaware Bay. 

 Fischler and Walburg (1962) released 4,353 

 tagged blue crabs in three estuaries and two off- 

 shore locations in South Carolina. Both male and 

 female crabs moved considerably between the low- 

 er estuaries and adjoining coastal waters. Only 

 seven males and six females were recaptiu'ed in 

 estuaries other than those in which the crabs were 

 released. Crabs that entered estuaries were almost 

 always from the adjacent ocean tagging site. All 

 but two crabs were recaptured within 80 km. of the 

 i-elease area. The authors concluded that, in South 

 Carolina at least, adult blue crabs do not migrate 

 between estuaries but limit their movements to the 

 estuary or adjacent marine area. 



Of the 11,522 blue crabs tagged in the St. Johns 

 Eiver and in the ocean off its mouth, 4,059 (35 per- 

 cent) were recovered. Ninety-seven percent of the 

 recoveries were by commercial gear, which was 

 fished every month of the year ; 3 percent of the 

 recoveries were by sport, fishermen. 



Eetum of tags from 2,839 males and 830 females 

 recaptured after release in the river indicated some 

 movement of both sexes throughout the year. 

 Migrations witliin the river were principally 

 downstream (table 2). Among crabs tagged from 

 Jacksonville to Lake George and recovered at a 

 distance from the tagging site, 89 percent of the 

 males and 96 percent of the females were recap- 

 tured north or downstream from the point of re- 

 lease. Some males moved randomly between New 

 Berlin and Picolata, but nearly all of those tagged 

 south of Picolata were recaptured downstream. 

 Females tagged at all sites during spring and sum- 

 mer usually migrated into the ocean within 1 

 month, but those tagged in late fall and early win- 

 ter entered the ocean after 3 or more months. Only 

 three females were recaptured more than 25 km. 

 upriver from any tagging site. Many females from 

 the upper river congregated near Jacksonville in 

 late fall. They moved downstream to New Berlin 

 as early as January but in greater numbers during 

 March. Early in the spawning season ( February- 

 May) females were slower to spawn and lingered 

 longer at New Berlin before entering the ocean 

 than those of later months (May-September). 



Two hundred thirty-five blue crabs (52 males 

 and 183 females) tagged in the St. Johns River 

 were recovered from other waters (fig. 3). Males 

 entered the Intracoastal "Waterway north of the 



BIOLOGY OF BLUE CRAB IN ST. JOHNS RIVER, FLORIDA 



21 



