As individuals, I think that we can spread the word about returnnig fish whenever we're posting on other web boards or just chewing the fat down the pub.
Things can change. 30 years ago, I was argunig with a salmon fishing relative about returning salmon as they were a species in decline. At the time he's have none of it saying that a caught fish was a dead fish anyway. Today, he gets very huffy about anybody who doesn't return a salmon.
As a club, we could think about voluntary catch limits (yes, I know how to become unpopular!). Seriously, in the US a lot of saltwater fishing is governed by bag lmits, it is beyond me as to why we don't do the same here [RANT OVER!]