Oysters 



Over 90% of Florida's oyster production is from the Apalachicola River 

 estuary; the oyster industry is second only to shrimp in Northwest Florida. 

 Income from the landings is a major source of income in Franklin County. In 

 1980, landings of 6.6 million lb yielded a dockside value of $5.9 million. 

 Since 1977, the annual production of oysters has slowly increased. Some of 

 the increase may be attributed to opening June, July, and August for oyster 

 fishing. The potential for oyster production throughout the region is threat- 

 ened by further coastal development for marine transportation, and for resi- 

 dential, business, and industrial purposes. 



The monthly landings of oysters on the west coast of Florida in 1965, 

 1970, and 1975 are given in Table FSH-39. 



Oysters usually spawn April -October and individuals may spawn several 

 times in a season. Fertilization is external and requires simultaneous 

 release of sperm and eggs by animals in close proximity. Fertilized eggs sink 

 rapidly, and the trochophore larval stage is reached in 4 to 6 hours. This is 

 followed in 24 to 28 hours by the vel iger (larval) stage. These ciliated 

 pelagic forms drift for 2 to 3 weeks and distribute the oysters. When mature 

 larvae, known as spat, contact suitable hard substrate, they settle and attach 

 permanently. 



Oysters grow rapidly after settling on suitable substrate. In Florida, a 

 marketable oyster is generally less than 18 months old. Besides suitable sub- 

 strate, oysters require adequate water flow, salinity, and temperature for 

 growth and survival. Good water circulation not only aids in their dispersal, 

 but assures transport of nutrients and removal of wastes. Wide salinity 

 fluxes tolerated by oysters may be beneficial in controlling the abundance of 

 predators that require high salinities. Permanent communities do best in a 

 salinity range of 10 to 20 ppt. Oysters also have a wide temperature toler- 

 ance, but best growth is near 75°F. 



Bay and Callico Scallops 



Landings of callico scallops ( Argopecten irradians ) in Northwest Florida 

 vary greatly from year to year, ranking from none early in the century to over 

 1.8 million lb in 1976. 



Many marine species vary widely in abundance, but annual fluctuations for 

 scallops are even more extreme. Although scallops have only limited mobility, 

 it has been conjectured that mass movement of a population might possibly ex- 

 plain the disappearance of a large bed. Mass movements have not been scien- 

 tificially verified, and the periodic disappearances of a major portion of the 

 population may simply be a result of high natural mortality. 



Bay scallops ( Argopecten qibbus ) spawn during fall and early winter in 

 bays, sounds, and other protected areas. Calico scallops spawn offshore in 

 spring and early summer; some spawn year-round. Scallops are hermaphroditic 

 (contain both male and female reproductive organs), but the release of eggs 

 and sperm at different times for the same individual during spawning prevents 

 self-fertil ization. 



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