Seafood prices reveal impacts of a major ecological disturbance

Abstract

Coastal hypoxia (dissolved oxygen ≤ 2 mg/L) is a growing problem worldwide that threatens marine ecosystem services, but little is known about economic effects on fisheries. Here, we provide evidence that hypoxia causes economic impacts on a major fishery. Ecological studies of hypoxia and marine fauna suggest multiple mechanisms through which hypoxia can skew a population's size distribution toward smaller individuals. These mechanisms produce sharp predictions about changes in seafood markets. Hypoxia is hypothesized to decrease the quantity of large shrimp relative to small shrimp and increase the price of large shrimp relative to small shrimp. We test these hypotheses using time series of size-based prices. Naive quantitybased models using treatment/control comparisons in hypoxic and nonhypoxic areas produce null results, but we find strong evidence of the hypothesized effects in the relative prices: Hypoxia increases the relative price of large shrimp compared with small shrimp. The effects of fuel prices provide supporting evidence. Empirical models of fishing effort and bioeconomic simulations explain why quantifying effects of hypoxia on fisheries using quantity data has been inconclusive. Specifically, spatial-dynamic feedbacks across the natural system (the fish stock) and human system (the mobile fishing fleet) confound "treated" and "control" areas. Consequently, analyses of price data, which rely on a market counterfactual, are able to reveal effects of the ecological disturbance that are obscured in quantity data. Our results are an important step toward quantifying the economic value of reduced upstream nutrient loading in the Mississippi Basin and are broadly applicable to other coupled human-natural systems.hypoxia | fisheries | coupled human-natural systems | bioeconomics | spatial dynamics F ertilizer use in coastal watersheds and agriculture intensification contribute to a growing incidence of coastal ecological disturbances (1-4). Of particular concern is coastal hypoxia [dissolved oxygen (DO) ≤ 2 mg/L] and potential impacts on marine fauna (1-4). The Western Hemisphere's largest area of seasonal hypoxia is in the Gulf of Mexico (GoM; >20,000 km 2 ) and overlaps with what was once the highest value fishery in the United States (brown shrimp) (www.st.nmfs.noaa.gov/commercial-fisheries/index) (5-7). Because controlling nutrient runoff upstream is costly, identifying and quantifying economic benefits downstream, including benefits to commercial fisheries, are essential for policy analysis (www.st. nmfs.noaa.gov/commercial-fisheries/index) (8-10). Although studies demonstrate ecological effects of hypoxia, economic consequences have not been established in this fishery.GoM brown shrimp (Farfantepenaeus aztecus) provide a unique opportunity to study the economic effects of hypoxia. First, the fishery is concentrated in regions of the GoM that become hypoxic seasonally (7) (SI Appendix, Figs. S1 and S2). Second, the temporal dynamics of brown shrimp and hypoxia match. Within season, harvest and hy...

Causal inference in coupled human and natural systems

“…The additional layer of spatial dynamics allows us to explore the consequences for the CHANS when one zone within the system is affected (treated) by an ecological shock such as hypoxia, a technological disaster such as an oil spill, or a policy intervention such as the creation of an MPA (6). The ecosystem is divided into discrete patches that correspond to fishing zones (23)(24)(25), and fishers make discrete decisions about whether to fish and, if so, which zone to fish in (6,7,21,25). The model generates simulated data on fishing effort and catches from which fish stocks can be estimated (7).…”

“…Similar models have been applied to a broad range of economic scales and of species and ecological conditions (7,(26)(27)(28)(29)(30)(31)(32)(33). Statistical generalizations are often used in empirical applications (28,30,31), but the model is sufficiently complex to produce simulated data that are consistent with the basic choice structure faced by fishers (6,7,25).…”

“…social-ecological systems | marine protected areas | quasiexperiment | bioeconomics | spatial dynamics C oupled human and natural systems (CHANS) are complex, dynamic, interconnected systems that have important feedbacks across social and environmental dimensions (1). Researchers have applied CHANS and precursor bioeconomic models to a wide range of human-environment interactions, including ocean fisheries, lake fisheries, human disease spread, wildfires, coastal landscape change, deforestation, invasive species spread, desertification, eutrophication, large mammal extinctions, and collapse of whole civilizations (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11). In the science of CHANS, related social-ecological systems (SESs), and sustainability more broadly, scholars aim to understand and identify causal relationships (3,12,13).…”

Hypoxic volume is more responsive than hypoxic area to nutrient load reductions in the northern Gulf of Mexico—and it matters to fish and fisheries

“…For example, in the case study developed here, a federal-state-tribal Action Plan for the nGOM (Task Force 2001, 2015 set a goal of reducing the midsummer hypoxic extent to 5000 km 2 . For over three decades, the relative areal extent of the hypoxic region on the Louisiana-Texas continental shelf has drawn scientific and policy attention (Rabalais and Turner 2001, Rabalais et al 2002, O'Connor and Whitall, 2007, Langseth et al 2014, Smith et al 2017. During that time, models ranging from regressions (Turner et al 2006, Greene et al 2009, Forrest et al 2011, Obenour et al 2012 to relatively simple (Scavia et al 2003, 2013, Obenour et al 2015 and more complex biogeochemical models (Hetland and DiMarco 2008, Wang and Justić 2009, Fennel et al 2011, Justić and Wang 2014 have been used to explore hypoxia dynamics and to provide management guidance relating the size of the hypoxic zone to key drivers.…”

Ensemble modeling informs hypoxia management in the northern Gulf of Mexico

“…Policymakers developed hypoxia reduction goals because of ecological, economic, and commercial fisheries impacts (7)(8)(9)(10). However, the goals remain elusive after >30 y of research and monitoring (3,11) and >15 y of assessment and goal-setting (5,(12)(13)(14)(15)(16).…”