A Rocha was speaking after a study by the World Wildlife Fund and the Zoological Society of London found the level of marine life in world's seas has halved since 1970.
Tuna and mackerel - two common foods - have fallen by three quarters since 1970.
The study cited global warming, pollution, overfishing and habitat destruction as the main reasons, and called governments across the world to act urgently.
At a national level, it specifically called governments to agree on protected areas where all or some types of fishing would be banned so wildlife numbers could increase again.
Andy Lester from A Rocha told Premier: "There are always things that we can do... Prayer is a fantastic starting point; prayer moves mountains.
"If you can join up to your local wildlife trust or your local A Rocha group, or take part in local campaigns or activities, or write to government... all those things can practically make a difference.
"The biggest challenge is protecting our oceans, because it's not just about what our oceans can give us, but this is a core part of God's creation. Every little creature plays a part in the order of things and we simply don't know the impact this decline will have long term [if it continues]."
Listen to Premier's Aaron James speaking to A Rocha:
