The "Greased Line" presentation is a cast with a sub-surface fly. The caster mends the line in order to control the speed and depth of the fly as it is presented broadside. So what does this mean to the fish? It sees the body and not the back-end of a fly. If I am wrong, then I will forever be a student of the mend and swing.
A few seasons back I found a written editorial about Harry Lemire. His flies are called the Grease Line caddis and Harry's photos struck a cord with me. My muddlers never look perfect to me. It was like a ray of sunshine and I began to follow the templates that Harry made. Stepping into the Bulkley River with a Lemire caddis is the perfect balance between aquatic entomology and the history of spey fishing.
Big bug hatches normally occur when we have an increase or rise in the barometric air pressure. This is why somedays the skated fly works and other days fish are slow to respond. It is the rising air pressure that stimulates the bugs to swim to the surface. So if you understand the effects of air pressure on an ecosystem, you can utilize it in your favour.
Before I step into the fabled Bulkley I stop, and read her like a book. Jet boats may pass and people may flog the water, but when she is ready to hatch you will witness fishing like no other place in the world. My heart skips a beat every time a bug falls from the sky. Scores of books have been written about this topic, but if you can't read the beautiful literature that is the Bulkley River you will never truly understand how lucky we are to have this amazing ecosystem.