COS 163-4 - Fishing out nutrients: The spatiotemporal dynamics of marine nutrient extraction caused by industrial fisheries

Wednesday, August 9, 2023

10:45 AM – 11:00 AM PDT

Location: B115

Presenting Author(s)

AG

Adrián Alejandro González Ortiz

Masters Student
Utah State University
Logan, Utah, United States

Coauthor(s)

TW

Timothy Walsworth

Assistant Professor
Utah State University, Utah, United States
EH

Edward Hammill

Associate Professor
Utah State University, Utah, United States
TA

Trisha Atwood

Associate Professor
Utah State University, United States

Abstract: Over the last century, industrial marine fisheries have contributed to a notable decline in marine biomass. While fisheries’ effects on marine life have been acknowledged for decades, we have only recently begun to study how fisheries affect marine nutrient cycles. Specifically, fisheries can alter nutrient cycles through changes to the release and storage of nutrients in living biomass. We examined the magnitude and spatial extent of carbon (C), nitrogen (N), and phosphorus (P) extraction by industrial fisheries to better understand these fisheries’ impacts on biomass-based nutrient storage. To do so, we compiled data on bodily nutrient compositions within fishery-targeted organisms and compiled these with industrial fishery landings to comprehensively quantify and map nutrient extraction over a 69-year period. We found that, between 1950 and 2018, industrial fisheries removed approximately 452 million metric tons (MMT) of C, 115 MMT of N, and 24 MMT of P. Most nutrient extraction occurred at mid-trophic levels (e.g., sardines and herrings), which accounted for 56% of the total extraction of all three nutrients. Nutrient extraction per square kilometer was highest along the western coasts of South America and Africa, the Sea of Japan, and the Norwegian Sea. Although nutrient extraction per square kilometer decreased between the 1990s (time of peak extraction) and 2010s, nutrient extraction per square kilometer in the high seas increased, with the highest rates of extraction from the high seas occurring between 2014 and 2018. Increased extraction from the open ocean is important because these systems are generally nutrient-poor and rely on tight nutrient cycling within the food web. Furthermore, the magnitude of nutrients – approximately 172 MMT of C, 44 MMT of N, and 9.6 MMT of P – extracted from mid-trophic level, pelagic organisms highlights how industrial fisheries disproportionately reduce biomass-based nutrient supplies within these groups. Considering the role fisheries play in the removal or redistribution of marine nutrients is critical for understanding the ecosystem-level impacts of fisheries. Here, we show that fisheries have removed a substantial amount of nutrients from the ocean since the 1950s and that intense extraction of mid-trophic level species could be impacting the exchange of nutrients within pelagic food webs from the middle out.