Weirs and fish traps are a well-known fishing method for much of the Northwest coast of North America. The Stó:lō used fish weirs on streams, rivers and shallow estuaries. Some large rivers were also fished using weirs, such as the Chilliwack River. Large fish weirs were communally maintained and used by an entire village. Smaller fish traps were also used, but these were usually owned by an individual or family, and stored indoors when not in use.
River-based fish weirs tend to involve the creation of an impassable object that forces the fish, mostly salmon in the case of the Stó:lō, towards a hole, or breach, in the weir, which usually has some form of fish trap or fisher person waiting to catch the fish. Tidal fish weirs tend to rely on the ability of the ebb (low) tide to create pools and small streams flowing back out to the ocean. Weirs are placed to block the fish, which came up the beaches with the high (flood) tide, from returning to the sea with the lowering of the tide. Traps and fishers with spears caught what was left in the weir when the tide receded.
Traditionally, fish weirs were constructed using a lattice network of wood, which was temporarily placed between a permanent structure of thick branches of wood. The thick branches were the main structure of the weir, but also maintained the position of the weir in a favourable location. The structure also provided the fisher with a marker, which allowed him not to have to remember the specifics of the behaviour of the river or stream when the water was high, or, more importantly, the tidal behaviour of a beach.
Fish weirs also provided an interesting scenario for neighbourly relations. Due to the ability of a weir to completely block a river, those that were further down the river could block all fish moving upstream, thus preventing them from getting to weirs and fishers further upstream. To counter this behaviour, an upstream neighbour could send a large log down the stream to damage or destroy any traps or the weir itself, getting revenge for such greedy behaviour. River weirs also exposed their owners to land management issues, to which casual anglers may not have been exposed. Due to the strong inclination of salmon to return to their place of birth, care had to be given not to block the return of too many fish, as this might disrupt the spawning patterns. Building a fish weir in a spawning habitat could reduce the number of fish that returned to the rivers and streams each year.