Sticklebacks are small creatures. 9 spined stickleback usually is even smaller than in picture but 3 spined stickleback can be as large as smallest finger. They aren't big and despite their "needles", they get eaten by predators.
These fish spawn in special "nests" and protect them. I guess that their look help them to defend these nests against more peaceful fish but I doubt that a pike would care about that
Omaha, I really don't know what is that goby you are talking about so I won't be helpful in this case.
About ruffe and Great Lakes... Lets look at the Wikipedia (
http://en.wikipedia.org/wiki/Ruffe):
It has been introduced into the Great Lakes of North America, reportedly with unfortunate results
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Seems like you are right. I haven't heard about this case but it sounds interesting and I'm willing to read more. But somehow I don't understand how it can do so great impact on environment...
Average fish size is very small and predators like to eat it. What can it do? It eats fish eggs and thet's the worst thing I can imagine.
ADDED:
I read quickly and article:
http://www.great-lakes.net/envt/flora-fauna/invasive/ruffe.htmlNothing much has been said there but one phrase sounds silly:
Ruffe rarely grow bigger than 5 inches, although the sharp spines on their gill covers, dorsal and anal fins make them difficult for larger fish to eat. Seems like writer hasn't seen this fish and doesn't know much about them. As I said above - predators eat perch and ruffe much and seems like they don't care about their fins. Large pike can eat really large perch and it would eat very large ruffe if there were any (they don't reach such size). Their fins don't differ much.
