Flea - The following link will take you to the actual regulation book which also serves as our permit. http://wdfw.wa.gov/publications/00290/wdfw00290.pdf
You will notice that in water work timing is listed on a per stream or drainage basis with most seasons opening July 1 and closing August 31...that's a total of 60 day. to work out of the entire year. Some seasons are longer, lasting thru September and some are very short, being open only 2 weeks. These seasons are created by the WDFW with extensive input from their Biologists and consider not only the spawning cycles of salmon and steelhead but also trout and other aquatic species.

Dredging does benefit the stream and that is a proven fact. The modern day suction dredge is the most environmentally friendly mining method ever devised. In addition to gold, it efficiently collects a variety of toxic heavy metals including mercury, lead, copper and steel that current lie in the bottom of our streams, constantly leaching into the water. State and federal studies indicate that a modern suction gold dredge is capable of removing 98% of mercury in the stream. There is no other device in existence that will remove heavy metals from the stream as efficiently as a suction gold dredge.
(State of California, California Water Board (2005), Mercury Losses and Recovery )
(US Geological Survey (2010) The Effects of Sediment and Mercury Mobilization in the South Yuba River )

Dredging also loosens compacted gravel. You may not have encountered this unless you have dredged but the gravel strata in a riverbed can become so densely compacted that you have to use pry bars or pick hammers to break it up. This cemented layer can be inches or many feet think and it is impossible for fish to spawn in it. Dredging loosens this and allows it to be redistributed by the river so it will create suitable spawning areas downstream.

Refuge - Imagine a cross section of a stream where the water is 6 feet deep. The depth of water flow is actually much deeper because water permeates through the gravel all the way to bedrock. This sub-aggregate flow of water tends to be significantly cooler than surface water. A dredge will create pockets in this layer of gravel that fill with cool water from the substrate and create holding pools for fish called a cold water refugia. A highly compacted stream does not easily allow the surface waters to mix with the cooler sub-aggregate waters so you get warm and low oxygen conditions in the upper layers that are not good for fish.

Permitting fees - That actually has attracted the attention of one lawmaker, Rep Gael Tarleton, who proposed a bill to close most wates and place a $150 fee on everything else. This fee is designed to be prohibitory, high enough o force out the small prospector. I was on the committee that worked with the WDFW to create the original Gold & Fish. We offered to pay a reasonable fee for a prospecting permit and the WDFW declined because the administration would have cost them more than the revenue.

Gold Rush Alaska has certainly increased interest in prospecting. Unfortunately, this show is a great example of what not to do. Most of the people inspired by the show are very new and inexperienced so they are beginning at an entry level with small hand operated gear like pans and shovels. They are also not working at the scale necessary for a HPA permit.
I offer classes to the public to teach them how to prospect for gold. I focus on proper technique and best practices for environmental responsibility. I try to instill a respect for the land and other users and leaving a small footprint. Last summer a local vocational high school hired me to take the entire Environmental Sciences class out and teach them the methods of modern prospecting and how it can impact the environment. Since they were very pro-environment they came with a lot of negative assumptions about mining and asked a lot of tough questions. At the end they had a great time and learned a lot including that gold prospecting is not a bad thing for the environment if done properly.