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Calico Scallops - Research

In Florida, fishing grounds for calico scallops are located off both coasts in deeper water, usually 50 to 120 feet. Calico scallops within those shellfish beds were once abundant enough to support a commercial fishery. Landings (pounds of meats harvested) peaked in 1984 at 42.7 million pounds but declined in 2000 to 139 thousand pounds, and since that time have been too low to support a commercial fishery. Several factors led to the population collapse, including loss of habitat, reproduction failure, parasitic infection and increased predation by marine snails.  

From 2004 to 2008, Fish and Wildlife Research Institute biologists compared the abundance and distribution of calico scallops to historic data to determine if the amount of habitat currently available is limiting juvenile settlement and adult abundance. They  also determined the preferred substrate (scallop shell, other mollusc shell or live rock) of juvenile calico scallops  on two calico scallop fishing grounds.  

Historically, the fishing beds were based along the 20-fathom contour line around Cape Canaveral and the Florida Panhandle, but in much shallower water along the southwest Florida coastline, within one to five miles of shore. Based on historic records and verbal accounts from fishers, scientists devised a sampling plan for each coast that consisted of four zones each with 60 stations. The east coast study region extended from Daytona to Sebastian Inlet and the west coast study region extended from Anna Maria Island to Ft. Myers Beach. On each coast, scientists sampled 15 randomly selected stations in each zone during spring and fall for two consecutive years. At each station, they towed a 0.6-meter (2-foot) dredge for five minutes and then counted and weighed all live organisms collected. Scientists also recorded the weights of calico scallop shell and other mollusc shell, and recorded the number of juvenile scallops and the type of substrate (surface) they were attached to.

At times, high numbers of calico scallops were collected at both fishing grounds, but abundance was highly variable. Calico scallop shell, considered to be the species’ essential habitat, was abundant in many east coast sites, but the shells of other molluscs were more common in west coast samples. Most of the scallops collected were below a maximum shell diameter of 1.5”. Parasitic infection was detected in every scallop examined.

View the final report