Replying to the Question; 'Why are fisheries complex to regulate?'

 Fish numbers expand and decline in response to environmental changes like increasingly warm sea temperatures and acidification as well as human predation intensity. Competition for fish drives fishermen to take as many fish as they can even if the high rate of capture sends stocks below reasonable levels of sustainability. Politicians locally and internationally dispute about quotas of fish that may be taken; sometimes leading to conflict. Mining interests may destroy spawning ground health with water spills from tailings ponds. Even hard rock mining can lead to centuries of toxic metal pollution in water that reaches rivers. People develop homes along shorelines of bays and rivers adversely impacting the quality of fish spawning beds. Fish habit was steadily destroyed along the coastal zones of much of the 48 U..S. states and for a while Alaska may have some better protection, though it too will probably eventually have very poor fisheries because of human impact on habitat.

Norway has a multi-billion dollar salmon farming business while the numbers of wild salmon pitiful. Alaskan salmon runs are often canceled as not enough fish exist to return. The snow crab fishery was canceled because deep warm waters kick started too rapid of a population growth with not enough food to eat and the crab cannibalized themselves crashing the stock. Even the loss of sea plankton can harm fish stocks, and off course open sea harvesting of chinook salmon that circle about four years dwindles the number of fish available to return to national waters. New technology such as fish finders and satellites make fish tracking and capture too easy to allow any to escape except those protected by laws. Regulating individual boats would require so much at sea policing to be completely effective that large holes exist very likely in fish numbers reported captured.