Cutting the head off is legal:
http://www.env.gov.bc.ca/fw/fish/regulations/#SaltwaterSalmon and Saltwater Fishing
Freshwater Salmon Regulations
The management of salmon fisheries in B.C., in both tidal and freshwater, is the responsibility of Fisheries and Oceans Canada (DFO). Unlike previous years, DFO's regulations for salmon fishing in freshwater are not included in this Synopsis. This year, for conservation and fisheries management reasons, this information will be published by DFO in a supplement to this Synopsis, which will be available where you purchase your licence, or at any DFO office.
Barbless hooks are required for salmon fishing in all freshwater, as well as all tidal waters in B.C.
Please note that when freshwaters are closed to fishing or have gear restrictions outlined in this Synopsis, these regulations apply to salmon as well as to non-salmon species.
For information on all the salmon regulations,
please contact the Department of Fisheries and Oceans (DFO)
Updated freshwater salmon regulations are listed in the Freshwater Salmon Supplement( http://www.pac.dfo-mpo.gc.ca/recfish/KeyPoints/packaging_e.htm ). as well as information on salmon identification and packaging salmon for transport.