Which Nikon lenses should I have?

I have got a Nikon D90 camera body and I'm pretty happy with it right now and am not looking to upgrade.

I also have 4 lenses:
Nikon 18-200mm f3.5-f5.6 VR lens
Nikon 10.5mm f2.8 fisheye lens
Nikon 105mm f2.8 macro VR lens
Nikon 50mm f1.8 standard lens

I'm fairly happy with my lenses, but I can't decide whether I need to swap my 18-200mm for an 18-55mm and a 70-300mm.

I would love to shoot more wildlife and find my 18-200mm isn't brilliant when I want to get close ups from a distance.

Do I have the right collection of lenses? Perhaps I don't need to change anything?

If you want to see some of my photos, visit my Flickr page

Those are incredible shots.
If you're strictly shooting wildlife, telephoto/teleconverters are the way to go.
And yes you have the right collection of lenses. There wouldn't really be a point of having a 70-300mm lens when you could swap the telephoto for your shorter lenses.

You have all you need to create amazing photos.

At some point you may want to invest in a 200-400 mm for your wildlife shooting, but for now keep what you have.

The 18-200 mm is NOT a lens I would get rid of in any case. I did that once and within six months, I bought a new one

If you're wanting better results for wildlife then the 70-300 won't add much to your capability as it's still F5.6 at the long end. Ken Rockwell doesn't rate it much.http://www.kenrockwell.com/nikon/70-300-vr.htm

There's less and less choice available in DX lenses - Nikon's moving steadily to FX and other lens makers (Tamron, Sigma) are following suit. No need to change kit yet but start saving for a FX format camera and lenses in a few years time.

If you want to try the 70-300 without spending the money then have a look at http://www.lensesforhire.co.uk/ and you can have one for seven days for £30.

Depending on how much time you think you'll use a long lens, then maybe hiring a 500mm or even the 200mm at F2 on occasion is an option?

That's a good range - I wouldn't change any of them. If you find yourself wanting more reach, then consider either a longer Nikon lens 200-400mm or have a look at Sigma's 150-500mm (I have one on a D300). This is one of my shots with it;

I don't use it much - I don't do much wildlife shooting.

I see you are taking water drop shots. Invest a little cash in a manual flash & triggers (cheaper than a Nikon speedlight). Ok you won't have the TTL control you'd have with SB speedlights, but TTL can be inconsistent anyway.

A Yongnuo YN560 & set of RF602's will cost you around £60 + £25. I can highly recommend Cotswold Photo on eBay (UK seller, stuff guaranteed & arrives next day). I'm not connected with them just a satisfied customer.
Ha! Sorry you were asking about lenses not flash, but I thought I chuck this in having seen your 'stream!

What lenses you should have is really depending on what you are going to shoot.

You've got a good portrait, studio and landscape setup, but it's not really useful for shooting nature and sports.

The 70-300mm f4.5-5.6 G VR IF-ED is a good lens to have. The 70-200mm f2.8 is a nicer lens to have. The 18-55mm lens isn't great because it's not an IF lens, but it's a functional.