8000 kHz lies in the same "allocation type" as 6765-7000 kHz ("fixed/mobile") which means a grab bag of all sorts of stuff. The pescadores seem to like these allocations (or bands, I should say) so that would support Chris' theory. The use LSB mode sort of does as well.
Also, 8000 is an easy-to-remember frequency. It seems like the pescadores/freebanders like to do this. 6919 kHz, 6900 kHz, 6888 kHz, 8000 kHz, etc.
Wouldn't surprise me if there's fishermen using 7777 kHz and 8888 kHz somewhere