As stated in the regs,
Catch and Possession Limits – The catch limit is the number of fish you are allowed to catch and keep in one day and includes fish that are not immediately released and any fish eaten or given away. The possession limit is the number you are allowed to have in your possession on hand, in cold storage, in transit, or anywhere. Possession limits are the same as one day’s catch limit except where otherwise specified.
If you catch a fish after reaching the daily catch or possession limit for that species, the fish must be released immediately back to the water (see Ontario’s Catch and Retain Rules, page 9). If the limit is zero, anglers may practise catch and release only, and any fish caught must be released immediately back into the water in a manner that does not harm the fish. For some species there are no limits and no reference will be made to a limit in this summary (see Size Limits, page
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No mention of weather Joe can decide to keep more than his legal limit and decide to give them to Sam at his discretion or not. I think the over limit fish is legally Joe's when he decided not to immediately release it as stated in the regs putting him over his limit and now is at the discretion of the enforcement officer whether or not to charge Joe....if seen. I know you are not even allowed to snap pictures before releasing because that is not an "immediate release". Keep in mind these guys blend in really good from a thread about the Warden up at the Ganny last year.