I would not give them house room.
Billingsgate market sometimes has sales of fish very near it's sell by date - they have to move it quickly as restaurants/fishmongers will not touch it.
Worse - the Billingsgate Inspectors are very dilligent - if the fish is not up to standard due to being not fresh enough, basically it is within a smidge of being 'off' , or a batch falls on the floor, they condemn the whole stall and it has to be thrown away or used for animal feed etc.
Now some of this rejected fish does get thrown away...but an unscrupulous porter could well - for a 'backhander' - put it in the back of someones van.
Door to door fish anyone?