Doctor eating last bit of halibut — or some other fish? (8)

I believe the answer is:
sturgeon
'some other fish?' is the definition.
'sturgeon' can be an answer for 'fish?' (type of fish). I am not certain of the 'some other' bit.
'doctor eating last bit of halibut' is the wordplay.
'doctor' becomes 'surgeon' (surgeon is a type of doctor).
'eating' indicates putting letters inside.
'last bit of' suggests the final letters.
The last letter of 'halibut' is 't'.
'surgeon' enclosing 't' is 'STURGEON'.
'or' acts as a link.
Can you help me to learn more?
(Other definitions for sturgeon that I've seen before include "swimmer" , "Shark-like fish" , "So urgent to find caviar-bearing fish" , "Our gents caught a large fish" , "supplier of delicacy" .)
