During the late 1920's and 30's Canadians came up with a novel use for surplus bombs from the recent European War.
According to a post in the February 1930 edition of Popular Mechanics, attributed in the marginal notes to John Spicer of Owen Sound, Ontario, (p. 216) the Quebec Department of Game and Fisheries were seeking to aid commercial fishers in the lower St. Lawrence estuary. The agency felt that the fishery was in danger of collapse from the effects of the "voracious appetites of porpoises". It seems the marine mammals had an unfair advantage (their existence as part of the ecosystem that included the fish being "harvested" in the commercial fishery; the evolutionary adaptations that allow the animals to cooperate in capturing the fish that sustain them).
After using sharpshooters to address the problem ("..they made no headway") the QDGF escalated by trying airplanes with "depth bombs". This was not successful however, as the pesky porpoises would simply "scatter as soon as the bombs hit the water". The obvious solution - bombs that explode on striking the surface! This proved to be the most effective method as "several bombs dropped on a school kill many outright, injure others, and send the survivors scurrying in all directions."
If true, this episode adds valuable context to the historical practices of seal hunting carried out in this same region for nearly 300 years.
