Fishing gear has long been function over form. And that may be just the reason brands want a piece.

Late last year, Jonas Clark reached out to the owner of Vintage Fly Tackle, an online dealer of ultrafine rods, reels and other fly-fishing equipment coveted by the sport’s most ardent collectors.

Over the years, merchandise and services have included bamboo fly rod appraisals, turkey call makers, custom fishing lures, vintage fishing lures and tackle, vintage and new bamboo fly rods ...