Yes, they're rivers. They flow into the ocean, and have very small populations. Not only are they hard to assess, but there are so many of them that, practically, it is probably not that useful to assess every one. There are key rivers we can assess within a region, and use those as index rivers to manage an area. I think that's a more practical way to look at management questions such as that.
On May 10th, 2016. See this statement in context.