The EXIF data is stripped and you provide limited information to make any determination.
What ISO and shutter speed was used?
It sort of looks like hot pixels from high ISO long exposure, but again with the limited information that’s just a stab in the dark. Another possibility is specular highlights off the water, but again limited information.
Thanks all. I will try long exposure noise reduction the next time I do a long exposure. I'm not sure it's necessary because I don't see the noise when I look at a print at normal viewing distance. Do most people not use it because it doubles the time to take the image and they are not bothered by the noise?
I don't know whether most people use it or not. Under most circumstances, I use it. After all, you are presumably already working slowly and deliberately since you're taking long exposures. What's the difference if they take twice as long?
There are exceptions, of course. If you have a need to take as many shots as possible in the available time or don't want time gaps between shots (shooting star trails comes to mind), perhaps you would rather have the hot pixels than the dead time between shots. But to me, those are exceptional cases.
>Thanks all. I will try long exposure noise reduction the next >time. Do most people not use it because it doubles the >time to take the image and they are not bothered by the >noise?
It depends.If you are only taking one or two shots, then the in camera dark frame subtraction (what Nikon calls Long Exposure Noise Reduction) is not to bad. But as already suggested, if you need many long exposure shots in a row and can't wait for that second dark frame time, then you could just take your own single dark frame during the shoot at the same exposure time, and then do the dark frame subtraction as needed later in an editor such as Photoshop.
Usually I take several images with varying exposure times. I think I will give the long exposure noise reduction a try. I am happy that all of the responders helped me to identify the problem as I was not sure what I was dealing with. It didn't look like dirt or noise and I was unfamiliar with 'hot pixels' . Thanks all. Steve