All About Florida Keys Fishing & Key West Fishing
______________________________________________________________________________________________________________________
Calico scallop, Argopecten gibbus

Calico scallops are patchily distributed from Delaware Bay south into the Caribbean Sea
north to about 20 degrees N latitude. Genetic and morphological similarities between Florida
and North Carolina calico scallop populations and coastal current patterns suggest that larval
dispersal from Florida may be an important source of North Carolina stocks (Krause et al. 1994).
Calico scallops are generally found in waters ranging from about 30 to 1,300 feet deep but have
been reported from shallower waters in Biscayne Bay (Coleman et al. 1993). Spawning occurs
throughout the year but peaks in late fall and in the spring (Arnold 1995). Calico scallops are
hermaphrodites that sequentially release sperm and eggs. In the laboratory, the pelagic larval
phase lasts for 14–16 days after which larvae attach to hard substrate. Calico scallops can reach
0.06” shell height in two months and 0.7”–1.1” in three months (Allen 1979). Scallops reach a
commercial size of 1.87”–2.10” shell height in six to eight months. Maximum life span is about
24 months.
Calico scallops may have similar feeding habits as the closely related bay scallops. Davis
and Marshall (1961) reported that the bay scallop primarily fed on microflora such as detritus,
bacteria, and organic matter. Predation is a major factor affecting survival during various phases
of the calico scallop life cycle. Schwartz and Porter (1977) found that 22 species of
macroinvertebrates and 24 species of fish fed on calico scallops. The invertebrates included sea
stars, gastropod, mollusks, squid, octopus, and crabs. The fishes included sharks, rays, and bony
fishes.
No landings of calico scallops were reported from Florida in 2005. The most recent
landings date to 2003, and were 61,704 pounds. In 2003, landings were made exclusively in
Brevard County on the Atlantic coast (Fig. 1). Total annual landings of calico scallops are
highly variable due to extreme fluctuations in recruitment success, population size, and changes
in market demand. For instance, no landings were reported in Florida during 1996 due to an
apparent switch by the fishery to fishing for rock shrimp. The 2003 total landings of calico
scallops were 95% lower than the average landings in the previous five years (1998–2002) and
were 99% lower than the historical average landings (1982–2003; Fig. 2). At its highest peak in
1984, the Atlantic coast fishery reported landings of more than 40 million pounds (Fig. 2).
Since1989, the statewide landings have ranged from zero to about 7.0 million pounds. Atlantic
coast commercial catch rates were highly variable with occasional peaks, e.g., 1998 (Fig. 3).
Calico scallops are infrequently landed along the gulf coast of Florida except in “boom” years,
e.g., 1994, 1998, 1999 (Fig. 2, Appendix A).
Successful calico scallop recruitment is highly variable. Factors influencing year-class
success probably include coastal upwelling, which drives nutrient rich water to the surface layers
and may aid in retaining larvae over favorable habitat. Biological impacts on year-class strength
Florida Fish and Wildl. Conserv. Comm., FWRI (2006) CALICO SCALLOP - 1
are unknown, but parasitic infestations have caused mass mortalities (Arnold 1995). With these
resource dynamics, the fishery is a "boom-or-bust” type where large annual harvests can be
followed by years with little to no harvest. The present condition of stock in the south Atlantic
region is unknown because of the large fluctuations in calico scallop abundance (South Atlantic
Fishery Management Council and Gulf of Mexico Fishery Management Council 1981). Given
the level of fluctuations in abundance and limited data, no MSY have been specified for calico
scallop in the management plan. It is believed that several scallop beds are not harvested each
year because of the vastness of the scallop beds on the grounds. Commercial fishing catch rate
may regulate the exploitation rate. When catch rates drop below a profitable level, harvesting
ceases, leaving the remaining scallops to contribute to stock recruitment (South Atlantic Fishery
Management Council and Gulf of Mexico Fishery Management Council 1981). No formal stock
assessment of the Florida’s calico scallop stocks is available at the present time.
Download complete report
(including figures)
Status and Trends 2007 Report
Florida’s Inshore and Nearshore Species
by Florida Fish and Wildlife Research Institute