Speaking in ideal terms, a business exists to make money while a government exists to serve the interests of the populace. Thus, in an ideal world, I would rather place the trust in the government, yes.
Of course, nothing is ever ideal, and trust me, I'm just as fed up with our government right now as you are, albeit for somewhat different reasons. But I do not think that the fact that our government is currently not serving the purpose it should logically leads to the conclusion that government should not be regulating the environmental impact of businesses. That said, I completely agree with you that the focus of most "environmentalism" is off-base and unconvincing - yes, saving the environment for the environment's sake is desirable (to an extent to which it doesn't adversely affect large numbers of people), but it is not the main reason for environmental conservation. Environmental conservation is important because of the potential impact on human society if we don't, and that concern should always have the priority.
To be honest, though, the amount of regulation required to save the global fisheries at this point simply isn't feasible - it would require massive international cooperation which would never, ever happen. I just hope we don't get to the same point with various other environmental concerns (deforestation is a big one - look at Haiti if you want to see what cutting down all the trees can do to a country).