MyOMy

For what is allowed to be bring in thru airport, you can check this CBSA link :   http://www.cbsa-asfc.gc.ca/fpa-apa/law-loi-eng.html

Specifically for fish and seafood:  All species except puffer fish and Chinese mitten crab (Eriocheir) are allowed.

The CBSA tell you what's allowed but won't tell you what's not allowed. So they have you to declare what you are bringing in so that they can make the decision.   

For meat, it is a NoNo. I think everybody knows about it.  For birds nest case, birds nest is an animal by product and has a very high price tag, CBSA wil not relax about it.  I know if you import birds nest, each shipment you need to provide a pound or so birds nest (non-returnable)  for lab inspection / testing. (wonder those lab techs can 餐餐冰糖燕窩。 )