Hard Clams Research
To gain a better overall understanding of Florida’s wild clam populations, Fish and Wildlife Research Institute (FWRI) scientists have studied clam biology and behavior. In one study, they documented distribution and growth patterns of the northern hard clam (Mercenaria mercenaria) and southern hard clam (Mercenaria campechiensis), and their natural hybrids, to determine how the two species and their hybrids manage to co-occur in similar habitats. Scientists have also documented a type of cancer called neoplasia that affects the reproductive system; it tends to occur more frequently in hybrid clams. In another study, scientists developed a technique to track hard clam larvae, which helps them better understand how clams repopulate an area and identify the physical and biological factors that affect redistribution, or how far the clams spread and where they settle.
Hard clams once supported a large and productive fishery on the east coast of Florida, but the number of clams harvested today is a fraction of what it once was. Because of those declines, which were likely a result of decreased water salinity (salt content), FWRI scientists evaluated several methods designed to increase the number of wild clams in the Indian River Lagoon along the east coast of Florida. Those methods included spawner transplants, juvenile seeding and larval releases. Each was designed to boost the clam population by increasing the odds of reproductive success.
For the spawner transplant method (1998-2000), scientists harvested adult clams and replanted them in a smaller area, concentrating the potential spawners. Similarly, researchers planted juvenile clams – a technique called seeding – in select areas at high concentrations (1998-1999). The third method involved releasing recently fertilized eggs instead of juveniles or adults; FWRI scientists released several million of these larval clams directly into the Indian River Lagoon (2001). Unfortunately, scientists were unable to document any immediate increases and further funding to continue the research was unavailable.
In addition to evaluating methods to boost the reproductive success of wild clams, FWRI scientists have looked into the effects of aquaculture, which is the large-scale raising of clams in a hatchery. As the commercial fishery declined, the hard clam aquaculture industry escalated. FWRI scientists helped develop Geographic Information System (GIS)-based maps describing areas that are suitable for clam aquaculture and evaluated how hard clam aquaculture affects the genetic structure of natural clam populations.