Yeah, streamers are pretty common on pikes, especially on the Saxatilis pikes. Not completely sure about males, but as you pointed out, females definately get them.
Our 13" male atabapo red (sp. lugubris) has really nice 'streamers' on his dorsal & anal fins. Our 12" male red tapajos doesn't! only some Pikes get the streamers - both sexes!