Abstract
The seascapes on which many millions of people make their living and secure food have complex and dynamic spatial features -- the figurative hills and valleys -- that influence where and how people work at sea. Here, we quantify the physical mosaic of the surface ocean by identifying Lagrangian Coherent Structures for a whole seascape -- the U.S. California Current Large Marine Ecosystem -- and assess their impact on the spatial distribution of fishing. We observe that there is a mixed response: some fisheries track these physical features, and others avoid them. These spatial behaviors map to economic impacts, in particular we find that tuna fishermen can expect to make three times more revenue per trip if fishing occurs on strong Lagrangian Coherent Structures. However, we find no relationship for salmon and pink shrimp fishing trips. These results highlight a connection between the biophysical state of the oceans, the spatial patterns of human activity, and ultimately the economic welfare of coastal communities.
Highlights
When quantifying the dynamics of coupled natural-human systems it is vital to consider the ways in which human activity occurs and where it is focused (Levin et al, 2013)
The Kolmogorov-Smirnov tests identified that the tuna and salmon Vessel Monitoring System (VMS)-Finite-time Lyapunov Exponent (FTLE) distributions are significantly different from random, but that there is no significant difference between the shrimp VMS-FTLE and random-FTLE distributions (Figure 2; Kolmogorov-Smirnov p-values are given below the fishery names)
The G-test p-values reflect those from the Kolmogorov-Smirnov tests, that is the fraction of fishing events occurring on FTLE values ≥ 0.1day−1 in the tuna and salmon fisheries are significantly different from random, whereas in contrast, there is no significant difference for shrimp fishing
Summary
When quantifying the dynamics of coupled natural-human systems it is vital to consider the ways in which human activity occurs and where it is focused (Levin et al, 2013). Almost all fisheries management actions are designed to influence the (spatial) behavior of fishermen (Branch et al, 2006; Hilborn, 2007), yet the issue of where they decide to fish and why, remains a key obstacle to achieving sustainable fisheries (Fulton et al, 2011; Hobday et al, 2011). This uncertainty is not for want of effort. In the absence of a full understanding of the factors driving fishermen’s spatial behavior, their actions will continue to surprise fisheries managers, potentially undermining management systems and jeopardizing the sustainability of fisheries (Fulton et al, 2011)
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