By Atuna
A study done by Spanish and Canadian scholars over the environmental impacts caused by Spanish purse-seiner tuna fisheries concluded that vessels fishing in the Pacific Ocean had the highest global warming potential based on a life cycle assessment (LCA).
The title of the report is “Life cycle environmental impacts of Spanish tuna fisheries†and it’s a joint research between University of Santiago de Compostela and Dalhousie University, Halifax, Canada.
“By combining the highest average fuel consumption rates with relatively long post-harvest transport distances, vessels operating in the eastern tropical Pacific gave rise to consistently higher life cycle emissions in comparison with operations in either the Atlantic or Indian Oceans†stated the document.
The use of larger amounts of fuel increases costs in that area and as a result, an increasing fraction of Pacific caught tuna is being partially processed at plants in Central-America so that only those portions of the fish suitable for canning (the pre-cooked loins) are transported to Galicia for final processing.
One of the most important uses of LCA is the identification of environmental “hot spots†or activities that contribute disproportionately to the total environmental impact of the system under study. In this study, both fishing-related inputs of diesel fuel (its production and its use) and the use of anti-fouling paint emerge as hot spots of concern.
It has been evaluated the life cycle environmental impacts that result from the industrial processes associated with contemporary Spanish purse seine fisheries for Skipjack (Katsuwonus pelamis) and Yellowfin tuna (Thunnus albacares) undertaken in each of the Atlantic, Pacific and Indian Oceans.
Pacific tuna fishing also achieved the highest marks in ozone depletion potential, acidification potential, human and marine toxicity potential.
Nevertheless, in burning just less than 440 liters of fuel per ton of tuna landed, Spanish purse seiners targeting Skipjack and Yellowfin tuna are relatively energy efficient when compared with many other fisheries for human consumption, which could not be explained by the study.
However, reducing the fuel intensity of contemporary Spanish tuna fisheries could, in theory, be achieved in a number of ways.
Further technological advances, for example in the areas of long-range target identification or the thermal efficiency of engines, are both possible. Alternatively, increasing the general abundance and availability of the targeted species could also result in lower fuel inputs.
Unfortunately, many technologically driven pathways to improved energy performance can work against the stock rebuilding option as they often reduce the economic costs of fishing making it possible to fish longer and harder.
The study also concluded that efforts to rebuild stocks, particularly in the Atlantic Ocean would not only help reverse the decline of aquatic ecosystems but could result in marked improvements in the environmental performance of the Spanish tuna fishery.
Globally, catches of Skipjack and Yellowfin tuna together represent over 70% of total tuna landings.
Not surprisingly, Spanish catches of Skipjack and Yellowfin traditionally came from Atlantic waters with smaller quantities taken in the Pacific. Beginning in the mid-1980s, however, Spanish vessels began pursuing Skipjack and Yellowfin in the Indian Ocean.
Landings from these operations increased rapidly to the point that they now represent approximately two thirds of Spain’s total catch of these species. Regardless of where they are taken, an important share of all Spanish tuna catches are eventually shipped home, possibly after first being loined and cooked in low cost labor countries, and then for final canning processing and distribution to ports in Galicia.