Salmon Farms and Venomous Snakes

Bob - This week on Science Update, we're going to bring you the latest news about how salmon farms may be killing wild salmon. But first, in other fish news, Chelsea tells us that there may be a lot more venomous ones out there than anyone guessed.

Chelsea - When you think about venom, you probably think about snakes. And there are about 450 venomous snakes in the world. But a new study from New York's American Museum of Natural History shows there are at least three times as many venomous fish. That's at least 1,200 venomous fish in the world. Ichthyologists Leo Smith and Ward Wheeler made this estimate by placing the 200 previously known venomous fish on their new evolutionary tree and guessing which other fish species would also have venom. They then confirmed their predictions with dissections. Smith explained that this estimate is very conservative.

Leo - Only when someone had actually published a paper talking about venom in a group did I include them. And, you know, plenty of us have been stung by other ones that are clearly venomous.

Chelsea - Smith says he wouldn't be surprised if the number rises to over six thousand - important news for drug researchers who often use venoms to develop new medicines.

Bob - Thanks, Chelsea. A salmon farm can indirectly kill young wild salmon within a thirty-five mile radius. This according to a two-year study of over fourteen thousand fish, led by Ph. D. student Martin Krkosek at the University of Alberta in Canada. He explains that salmon farms are teeming with sea lice: a parasite that's relatively harmless to adult salmon, but deadly to juveniles.

Martin - These fish are only about an inch long. They weigh about half a gram. They don't have any protective scales, and all it takes is one or two lice to kill them.

Bob - In the wild, juveniles rarely get sea lice, because they grow up far away from adult carriers. But Krkosek found that fish farms along juvenile migration routes can infect and kill up to 95 percent of the young fish that pass by. As a result, he says that farming appears to be depleting the wild salmon population, rather than saving it.

Chelsea - Thanks, Bob. That's it for this week. Next time we'll talk about some prairie dogs who are too busy thinking about you-know-what to look out for predators. Until then, I'm Chelsea Wald.

Bob - And I'm Bob Hirshon, for AAAS, The Science Society. Back to you, Naked Scientists!