NurkaLurks are a type of Mirelurk or Mirelurk Hunter that has been exposed to large amount of strontium isotope which is used to color Nuka-Cola Quantum. There are only 9 in Fallout 3 and they can all be found in the Nuka-Cola Plant.
The NukaLurks are no difference from standard Mirelurks or Mirelurk Hunters in terms of Strength or Endurance. They glow bright blue because of the strontium isotope which makes Nuka-Cola Quantums appear purple. The only difference between them and Mirelurks is the NukaLurk Meat you get from NukaLurks, this gives you a +10 Action Point boost.