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3.1.2 Clams
3.1.2.1 General Information About Clams
Clam is a common name for several kinds of bivalve molluscs. The word is often
applied only to those that are edible and live as infauna, spending most of their lives
halfway buried in the sand of the seafloor. Clams have two shells of equal size connected by two adductor muscles and have a powerful burrowing foot. Clams in the
culinary sense do not live attached to a substrate (whereas oysters and mussels do)
and do not live near the bottom (whereas scallops do). In culinary usage, clams are
commonly eaten marine bivalves (Wikipedia 2019e).
Clam production and aquaculture are important economic resources in a worldwide context (Fiz da Costa 2013). Clams are an important food item, especially in
Mediterranean countries. In Italy, Christmas Eve is the day of the year with highest
seafood consumption, including clams and anchovies that are generally used in
appetizers (FAO-Globefish 2019).
Although the amount of production is lower than other bivalve species, clams
have an important place in world trade. International trade of clam was stable during
the first 9 months of 2017 compared with the same period in 2016. Around 170,000
tonnes were exported, and 180,000 tonnes were imported. The main importing
countries continued to be Japan and the Republic of Korea, both buying mainly
from China. China is in the main clam exporter globally, accounting for about 70%
of world clam exports. Most clams are traded in live or fresh form (FAO-Globefish
2018a). FAO reported the amount of capture production to be 591,265 tonnes for all
of clams, cockles, and ark shells in 2016 (FAO 2016).
There are several bivalve families in the Clam category. This book will include
families with economic importance in terms of fisheries and aquaculture.
Biology of Clams
Clams are a very diverse group of bivalves in that there is notable variation in the
shape, size, thickness, colour, and degree of sculpturing of the shell from one species to the next. The one feature that all clams have in common is that they burrow
into the seabed. Consequently, both shell and body display modifications necessary
for this type of existence. The quahog clam M. mercenaria has a thick, triangular
shell. It is grey or brown with a sculpturing of numerous shallow concentric rings
that run around the shell, parallel to the hinge. Annual rings are clearly visible on
the shell exterior and thus ageing in this species, and indeed in many of the other
commercially important clam species, is an easy task. There are three conspicuous
teeth on each valve and each tooth fits into a corresponding socket on the opposing
valve. This ensures an intimate fit when the valves are closed. The shell interior is
marked by an anterior and posterior adductor muscle scar, a distinct pallial line, and
a short pallial sinus. The depth of the pallial sinus is a very reliable indicator of the
3 Molluscan Shellfish
3.1.2 Clams
3.1.2.1 General Information About Clams
Clam is a common name for several kinds of bivalve molluscs. The word is often
applied only to those that are edible and live as infauna, spending most of their lives
halfway buried in the sand of the seafloor. Clams have two shells of equal size connected by two adductor muscles and have a powerful burrowing foot. Clams in the
culinary sense do not live attached to a substrate (whereas oysters and mussels do)
and do not live near the bottom (whereas scallops do). In culinary usage, clams are
commonly eaten marine bivalves (Wikipedia 2019e).
Clam production and aquaculture are important economic resources in a worldwide context (Fiz da Costa 2013). Clams are an important food item, especially in
Mediterranean countries. In Italy, Christmas Eve is the day of the year with highest
seafood consumption, including clams and anchovies that are generally used in
appetizers (FAO-Globefish 2019).
Although the amount of production is lower than other bivalve species, clams
have an important place in world trade. International trade of clam was stable during
the first 9 months of 2017 compared with the same period in 2016. Around 170,000
tonnes were exported, and 180,000 tonnes were imported. The main importing
countries continued to be Japan and the Republic of Korea, both buying mainly
from China. China is in the main clam exporter globally, accounting for about 70%
of world clam exports. Most clams are traded in live or fresh form (FAO-Globefish
2018a). FAO reported the amount of capture production to be 591,265 tonnes for all
of clams, cockles, and ark shells in 2016 (FAO 2016).
There are several bivalve families in the Clam category. This book will include
families with economic importance in terms of fisheries and aquaculture.
Biology of Clams
Clams are a very diverse group of bivalves in that there is notable variation in the
shape, size, thickness, colour, and degree of sculpturing of the shell from one species to the next. The one feature that all clams have in common is that they burrow
into the seabed. Consequently, both shell and body display modifications necessary
for this type of existence. The quahog clam M. mercenaria has a thick, triangular
shell. It is grey or brown with a sculpturing of numerous shallow concentric rings
that run around the shell, parallel to the hinge. Annual rings are clearly visible on
the shell exterior and thus ageing in this species, and indeed in many of the other
commercially important clam species, is an easy task. There are three conspicuous
teeth on each valve and each tooth fits into a corresponding socket on the opposing
valve. This ensures an intimate fit when the valves are closed. The shell interior is
marked by an anterior and posterior adductor muscle scar, a distinct pallial line, and
a short pallial sinus. The depth of the pallial sinus is a very reliable indicator of the
3 Molluscan Shellfish