"Next Image" on attachement page of gallery links to next image in media library

I have an image gallery on a page using a standard WP gallery. Images are sorted using the gallery menu. Images link to their associated attachment page.

Using the “Next Image” link on the attachment page leads to the next image in the media library, rather than the next image in the image gallery that I’ve defined. Even images that are not included in the gallery are included.

Is that the intended behaviour?

Can the attachment pages links be limited to only image in the gallery?

Should I be looking at alternate gallery plugins?

Images Gallery:
http://www.bethlevin.ca/sculpture/

Thank you!