Yarns and fishing lines are made by a process that includes the step of exposing an opaque yarn made from ultrahigh molecular weight, gel spun polyolefin filaments to a temperature within the melting point range of the filaments for a time sufficient to at least partially fuse the contact surfaces of adjacent filaments. For ultrahigh molecular weight, gel spun polyethylene, this temperature is preferably within the range from about 150.degree.-157.degree. C. The surface fusion between and among filaments imparts desirable handling characteristics to the ultrahigh molecular weight, gel spun polyolefin yarns and fishing lines that are similar to those of a conventional monofilaments. Preferably, the temperature, residence time, and stretching ratio at the selected temperature are chosen to provide a fishing line exhibiting a tensile modulus within the range from about 230 g/d to about 780 g/d with a tenacity of at least 15 g/d.