I would take that with a huge grain of salt . . .
Yeah, a depth charge is going to kill fish if they are in the pressure zone . . . but its not like a guy in a rowboat tossing dynamite. The ship has already come banging around in the area and there would be a lot of other noise to drive off the sea life. The pings surface ships were using to detect subs are different IIRC than what is used now that are claimed to cause whales to beach.
Sharks, squid and octopus were probably no more active than before, there were just more folks spread out to observe their activity- previously they had been a tree falling in the forest with no one to hear.
I shied away from this, but bluntly sunken cargoes and lost crews would provide for the cycle of life.