The recent research article by Schiller et al. in Science Advances is a novel and useful summary of the key features of fisheries on the high seas – the species captured, the quantities of each targeted species caught, the countries doing most of the fishing, and the destinations of the various products. However, the main conclusion of the article – that high seas fisheries play a negligible role in addressing global food security – needs to be considered with some caution. Context is important – it depends on which countries on the globe we are talking about.
The reason for caution is that one third of the high-seas catch is sold as canned tuna. All skipjack tuna caught from areas beyond national jurisdiction (22.3% of the high-seas catch) is processed in this way, and 70% (9.2% of the catch) of yellowfin tuna caught on the high seas is also likely to be canned (based on the proportion of yellowfin tuna caught by purse-seining in world’s largest tuna fishery). Although much of this low-cost, nutritious food is processed in Asia and destined for Europe and the USA, canned tuna is also commonly found on the shelves of local stores in many developing nations.
Food-insecure Pacific Island countries are a case in point. In these nations, canned tuna provides dietary animal protein when sea conditions are too rough for nearshore fishing or when nearshore fish catches are seasonally low. Canned tuna comprises up to 15% of recommended fish consumption across this region and, even in those Pacific Island countries that process their own tuna, 10-60% of canned tuna is imported. Given that one third of global skipjack and yellowfin tuna catches are taken in areas beyond national jurisdiction, it is reasonable to assume that the canned products derived from these catches help underpin food security in Pacific Island countries with limited access to other sources of animal protein.
As the authors of the study mention, it is also important to consider that present-day patterns of high-seas fish catches are not necessarily a good guide to the future. The latest modelling (see chapter 14) of the expected responses of skipjack and yellowfin tuna in the Pacific Ocean to climate change indicates that greater proportions of the catch are very likely to be made on the high seas in the decades to come. All canned tuna markets are therefore expected to depend more heavily on skipjack and yellowfin tuna caught from the high seas in the years ahead.
A related consideration is that the jury is still out on whether area-based management tools proposed for the high seas will add value to the measures used by the Regional Fisheries Management Organizations to manage skipjack and yellowfin tuna. To answer this question, we need information on the spatial structure of these species, i.e., the distribution of each self-replenishing population (stock). Only then can we evaluate 1) the size and optimal location of a fishing closure required to conserve the target spawning biomass for each stock; and 2) the effectiveness of area-based approaches compared to conventional fisheries management measures. The foundational importance of information on the spatial structure of fish stocks needs to be recognized during the BBNJ discussions by the United Nations, and any decision to apply area-based management for high-seas fisheries deferred until such information is available.
Editor’s note part 2: Though publishing responses in a scientific journal has its function, we support having scientific conversations out in the open. Policy makers and the public should have access to as many credible perspectives as possible. If you are an expert and wish to write for us, contact us here.