Salmon and sustainability: The biophysical cost of producing salmon through the commercial salmon fishery and the intensive salmon culture industry.

摘要

Technologies play a critical role in mediating the impact of the human enterprise on the ecosphere. Consequently, the adoption of more biophysically efficient technologies is essential if the sustainability of the human enterprise is to improve as populations and per capita consumption demands increase. Within this context, the biophysical efficiency of two salmon production technology systems were analysed and compared using ecological footprint and energy analysis. The two systems evaluated are the vessel-based commercial salmon fishery and the salmon farming industry, as both exist in British Columbia, Canada. In addition, the relative efficiency of the three harvesting technologies employed within the commercial fishery were also evaluated. The ecological footprint analyses entailed quantifying the marine and terrestrial ecosystem support areas needed to grow salmon, sustain labour inputs, and assimilate CO ₂ equivalent to the greenhouse gases that result from industrial energy and material inputs. The energy analyses focused exclusively on the direct and indirect industrial energy inputs to both systems. The results of both the ecological footprint and energy analyses indicate that salmon farming is the least biophysically efficient, and hence least sustainable system for producing salmon currently operating in British Columbia. On a species-specific basis, farmed chinook salmon (Oncorhynchus tshawytscha) appropriated the largest total area of ecosystem support at 16 ha/tonne. This was followed by farmed Atlantic salmon (Salmo salar) at 12.7 ha/tonne, and commercially caught chinook and coho salmon (Oncorhynchus kisutch) at 11 ha/tonne and 10.2 ha/tonne, respectively. Commercially caught sockeye (Oncorhynchus nerka), chum (Oncorhynchus keta), and pink salmon (Oncorhynchus gorbuscha) had the smallest total ecological footprints at 5.7, 5.2 and 5 ha/tonne, respectively. Results of the energy analyses followed a similar pattern. Farmed chinook salmon required a total fossil fuel equivalent industrial energy input of about 117 GJ/tonne while at the other extreme, total energy inputs to commercially harvested pink salmon amounted to only 22 GJ/tonne. Within both systems, however, opportunities exist to improve the biophysical efficiency of salmon production. Finally, amongst the three commercial fishing technologies evaluated, purse seining, was approximately twice as efficient at harvesting an average tonne of salmon as were either gillnetting or trolling.