how do you measure a clam?


New member
When people talk about the size of a clam, are they measuring by the length of the shell or the mantle?
I go by the length of the shell. which for bivalves is from the anterior end to the posterior end. With giant clams, this is the longest length that can be measured across the shell.

For me, length of the shell is most appropriate. Curious to hear if there are different answers to this.
I agree the length of the shell is most appropriate, but some people measure the mantle lenght (or they must, because the clam i got was a half inch short). I don't have a problem with mantle lenght, as long as the vendor states they are measuring the mantle and not the shell.
Well, the reason for my asking was because a LFS was measuring it by the mantle, for sure. They marked a clam as 3" that was a full inch smaller than my 3" clam! I guess they aren't misrepresenting since you can see what you get regardless of what it says.
And I was going to suggest a ruler...

And I was going to suggest a ruler...


And my response reminds me of the new United Way commercial where the NFL player is teaching the class, and a child asks where lightning comes from. The NFL player starts explaining ions and electrons to this 6 year old kid, who interrupts and says "Doesn't it come from the sky?" :lmao: :jester: :spin3:
Scientific method: Clams (and all other bivalves) are measured (correctly) along the longest axis of the shell. This is because it means that dead and live specimens can be compared.

I see no reason that aquarists should do any different, it is the logical way...and possibly why LFS do it differently :rolleyes: .
Yep from shell edge to edge, I really don't like how lfs call them 3" when they're really like 2", or 2" when they're like 1", I've seen that at lfs around here as well.