What is the current population of clams in Hampton-Seabrook Harbor and how has it changed over time?

The most recent clam population in Hampton-Seabrook Harbor in 2015 was 1.4 million clams. The population has declined most years since 1997.

Soft shell clams provide recreational opportunities to state residents as well as visitors from outside the region. Clams consume phytoplankton and other detrital material and therefore have a significant impact on coastal and estuarine ecosystems.
Increase the number of adult clams in Hampton-Seabrook Estuary to 5.5 million clams by 2020.
In 2015, there were 1.4 million clams in Hampton-Seabrook Harbor. Since 2012, clam populations have remained below the PREP goal of 5.5 million clams and below the average level (2.4 million) from 2009 to 2011 (Figure 15.1).

Clams may be limited by a type of cancer (Hemic neoplasia) that affects marine bivalves but is not dangerous to humans. Figure 15.2 shows that the percentage of clams infected with Neoplasia has increased since 2002. Research suggests there are several factors that make clams more susceptible to this disease, especially pollution (mainly heavy metals and hydrocarbons) and warming water temperatures.53

Green crabs eat clams and have also been shown to reduce clam populations. However, Figure 15.3 shows that green crab abundance in Hampton-Seabrook Harbor has steadily declined–for unknown reasons–between 2011 and 2015.

Figure 15.1 Standing stock of adult clams in Hampton-Seabrook Harbor. Number of adult clams is calculated by multiplying clam densities by the acreage of clam flats in Hampton-Seabrook Harbor.

Figure 15.2 Percent of clams with any Neoplasia infection in Hampton-Seabrook Harbor.

Figure 15.3 Green crab abundance in Hampton-Seabrook Harbor. CPUE = catch per unit effort. Crabs are caught in baited traps, twice a month year-round with the exception of February and March.