Two bettas, divided
Three mystery snails
Seven female bettas
Four oto cats
Five juvenile female guppies
One goldfish (temporary)
One dwarf gourami
Six tiger barbs
Honestly, not trying sound rude or start anything, but unless any of you are goby experts, experienced in the biology of British Columbian lakes, or happened to genetically test the fish in question, I don't think anyone here is qualified to say definitively whether or not this was, for certain, an invasive species. There are endangered goby species too- Who's to say this wasn't one of them?
That's why you shouldn't take any fish out of a body of water without knowing 100% what it is. It's probably just as bad to remove an endangered species from a lake as it is to re-release an invasive species.
This is why Australia has so many restrictions on allowable fish species. People don't realise the possible ramifications of releasing fish that have been kept in captivity back into the wild. Imagine if the goby was exposed to a harmful pathogen that its release then introduced into the lake or wherever it was caught.
In OZ, we nearly got the import of anabantoid fish stopped because of the threat of iridovirus being brought in and introduced to native fish. It was so close to happening, and the threat of such legislation being brought in is still there.
I think its a eurasian goby. Invasive non native fish that is wreaking havocfrom great lakes to north canada. I love fish, but this one is a real problem. Destroying yellow perch and walleye populations. I would never suggest to anyone to kill a fish but...
I think what he did by releasing it back into the lake was the right thing to do. Obviously he had it in a jar with water from the lake. He didn't introduce the fish to any other water and he obviously didn't feed it and decided to let it go rather than use a beloved shrimp or take that one hour drive to buy more. I'm happy the little guy is back home. :)