Marine reserves help to protect ocean life, but their effectiveness varies. In Australia, researchers studied marine reserves to see how well they work for fish species affected by fishing. They found that, on average, marine reserves had more fish and bigger fish compared to areas where fishing was allowed. Not all reserves were equally effective, though. By looking at factors like how connected and deep the reserves were, the researchers discovered that more connected reserves with greater depth had better results. This means that marine reserves designed to be highly protected, connected, and diverse in depth can be a good strategy for conserving fish in different types of oceans.