Managing conflicts between economic activities and threatened migratory marine species toward creating a multiobjective blue economy

Abstract

Harnessing the economic potential of the oceans is key to combating poverty, enhancing food security, and strengthening economies. But the concomitant risk of intensified resource extraction to migratory species is worrying given these species contribute to important ecological processes, often underpin alternative livelihoods, and are mostly already threatened. We thus sought to quantify the potential conflict between key economic activities (5 fisheries and hydrocarbon exploitation) and sea turtle migration corridors in a region with rapid economic development: southern and eastern Africa. We satellite tracked the movement of 20 loggerhead (Caretta caretta) and 14 leatherback (Dermochelys coriacea) turtles during their postnesting migrations. We used movement-based kernel density estimation to identify migration corridors for each species. We overlaid these corridors on maps of the distribution and intensity of economic activities, quantified the extent of overlap and threat posed by each activity on each species, and compared the effects of activities. These results were compared with annual bycatch rates in the respective fisheries. Both species' 3 corridors overlapped most with longline fishing, but the effect was worse for leatherbacks: their bycatch rates of approximately 1500/year were substantial relative to the regional population size of <100 nesting females/annum. This bycatch rate is likely slowing population growth. Artisanal fisheries may be of greater concern for loggerheads than for leatherbacks, but the population appears to be withstanding the high bycatch rates because it is increasing exponentially. The hydrocarbon industry currently has a moderately low impact on both species, but mining in key areas (e.g., Southern Mozambique) may undermine >50 years of conservation, potentially affecting >80% of loggerheads, 33% of the (critically endangered) leatherbacks, and their nesting beaches. We support establishing blue economies (i.e., generating wealth from the ocean), but oceans need to be carefully zoned and responsibly managed in both space and time to achieve economic (resource extraction), ecological (conservation, maintenance of processes), and social (maintenance of alternative livelihood opportunities, alleviate poverty) objectives.

Multi-Decadal Humpback Whale Migratory Route Fidelity Despite Oceanographic and Geomagnetic Change

“…Migratory animals face an uncertain future (Cotton, 2003;Wilcove and Wikelski, 2008;Hazen et al, 2013;Hof et al, 2017;Cohen et al, 2018). Global change, climate change, development, resource extraction, habitat fragmentation, and other human-induced perturbations combine to present unprecedented challenges to the sustainability of migratory populations and the ecosystem services they provide (Peñuelas et al, 2002;Harris et al, 2009Harris et al, , 2018Roman and McCarthy, 2010;Thackeray et al, 2016;van Doren et al, 2017). Ensuring that sustainable populations of migratory animals persist into the future requires knowledge of how migrants respond to Earth system dynamics (Schwenk et al, 2009;Bowlin et al, 2010).…”

Species distribution modelling of Bryde’s whales, humpback whales, southern right whales, and sperm whales in the southern African region to inform their conservation in expanding economies

“…Worldwide, cetaceans are increasingly threatened by anthropogenic activities ( Williams et al, 2014 ; Braulik et al., 2017 ). These activities are likely to increase in South Africa with the initiation of Operation Phakisa ( Harris et al, 2018 ; Purdon et al, 2020b ). Operation Phakisa is a South African government initiative created to unlock the economic potential of the country’s oceans through increasing industry in five focal areas: marine transport and manufacturing; offshore oil and gas exploration; aquaculture; tourism and small harbour development and infrastructure ( Van Wyk, 2015 ; Findlay, 2018 ).…”

Impact of Tropical Cyclones on Inhabited Areas of the SWIO Basin at Present and Future Horizons. Part 1: Overview and Observing Component of the Research Project RENOVRISK-CYCLONE

“…Sea turtles are known to generally swim in rings and frontal areas in between, and often travel by moving from one ring to another [98]. These rings and eddies are numerous in the Mozambique Channel [99,100], but less common north of Réunion Island, which During this experiment, two species of late juvenile sea turtles (loggerhead and Olive Ridley) were equipped with Argos TD tags.…”

“…Sea turtles are known to generally swim in rings and frontal areas in between, and often travel by moving from one ring to another [98]. These rings and eddies are numerous in the Mozambique Channel [99,100], but less common north of Réunion Island, which may explain that loggerhead STs released from there generally tend to follow a straight trajectory (Figure 9)-another explanation (currently under investigation) is that STs rarely feed during their reproductive migration, so as to reach their breeding areas as fast as possible.…”