Cod may have had it's chips and tuna could be off the menu soon if we don't cut down the number of fish we catch.
Research shows that big fish like tuna, marlin, sharks and cod are declining fast and could soon be wiped out completely.
Killed too young
Millions of fish are caught and killed every day - over the last 50 years 90 per cent of all large fish populations have disappeared from our seas.
Scientists reckon the problem is that we're catching the fish when they're too young.
Large fish take a long time to grow up and don't have many babies so they have trouble keeping their numbers up.
Serious warning
The study took 10 years to complete, and although it's not the first warning we've had, it's the first time a big worldwide study of fish stocks has been done.
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