Mobs spawning rates seem increased

Ok, so it started with me realizing that there were a few more creepers than usual showing up (sorry I have no pictures of the creepers).  I didn't feel like anything was wrong.  Then I exited a cave to see like 10 squid and salmon in a small portion of a river...  Not only is this an issue for survival players with creepers, but the extra mobs could really cause lag.