This has been ongoing for some time. Entire flocks of birds dropping out of the sky dead, mass amounts of fish and other sea animals washing ashore. There has been no definite cause of this yet, but it is strange and disconcerting, and has only been happening over the last couple years.
Speculation on causes: For the birds, the changing magnetosphere and magnetic lines of the earth, likely due to the interference from the sun has been making migrations difficult. It may be that other animals rely on these magnetic influences for navigation on the water as well.
Personal Theory: ALIENS! Well maybe not aliens per se, but at least exotic tech. If anti-gravity craft function in the way I understand it, they exude intense electromagnetic radiation. They have also been known to function underwater as well as in the air and have been observed various times transitioning between the two. I have personally witnessed this. So if an unfortunate flock of birds or fish encounters one of these devices, particularly a large one, they would likely be stunned or possibly killed by the intense resonating electromagnetic fields given off by the craft.
Of course, for the fish and other marine life, it could also be the US Navy testing new and more powerful sonar equipment, which could be intense enough to cause what amounts to blunt force trauma to the fish’s bodies.