Spatial-dynamics of Hypoxia and Fisheries: The Case of Gulf of Mexico Brown Shrimp

Abstract

We analyze the Gulf of Mexico brown shrimp fishery and the potential impacts of a large seasonal area of hypoxia (low dissolved oxygen) that coincides with the peak shrimp season.A spatial-dynamic bioeconomic simulation embeds three biological impacts on shrimp: mortality, growth, and aggregation on hypoxic edges. Hypoxia creates feedbacks in the bioeconomic system, altering catch and effort patterns. System changes propagate over space to affect areas that do not experience hypoxia. Areas that might otherwise be considered controls in a natural experiments framework are contaminated by the ecological disturbance through spatial sorting. Aggregate predictions from simulations are similar to empirical fishery data. Average shrimp size and total landings are negatively correlated, as are hypoxic severity and landings. Shrimp size and hypoxic severity are only weakly negatively correlated. Growth overfishing, which varies with recruitment success and with ecological disturbances, is a key mediating effect. JEL Code Q22.

Seafood prices reveal impacts of a major ecological disturbance

“…Effort response to profitability creates feedbacks between the human (fishing fleet) and natural (shrimp population) systems that undermine quasi-experimental approaches to observational data (10,21). When an area becomes hypoxic, the increased catchability along the edge draws fishing effort into the area and away from nonhypoxic areas (12)(13)(14), changing the fishing effort in both places relative to the counterfactual.…”

“…Within the region most affected by hypoxia, these correlations are weaker and suggest negative effects on large shrimp and positive effects on small shrimp (SI Appendix, Table S2). Because establishing a causal effect of hypoxia requires a valid counterfactual, aggregate fishery landings are insufficient because so many environmental, economic, and institutional factors influence fishery outcomes (3,10,17,18). Economic studies of other, smaller fisheries have found modest economic losses from hypoxia (17)(18)(19)(20).…”

“…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)(9)(10). Although studies demonstrate ecological effects of hypoxia, economic consequences have not been established in this fishery.…”

Modeling the Population Effects of Hypoxia on Atlantic Croaker (Micropogonias undulatus) in the Northwestern Gulf of Mexico: Part 2—Realistic Hypoxia and Eutrophication

“…There are other pathways by which hypoxia could affect croaker population dynamics that were not included in our model simulations. For example, hypoxia avoidance can lead to changes in overlap of croaker and their predators (see Ludsin et al 2009), hypoxia exposure can reduce sperm production by males (Thomas and Rahman 2010), and shifts in shrimp fishery in response to hypoxia (Smith et al 2014) can affect croaker mortality via bycatch. These additional effects can be added to the model simulations (e.g., predation from habitat compression- Adamack et al 2017).…”

Nordic fisheries and aquaculture

“…A number of studies have incorporated environmental externalities into bio-economic models of fisheries (Barbier and Strand, 1998;Simonit and Perrings, 2005;Foley et al, 2009;Udumyan et al, 2010;Foley et al, 2012;Nguyen et al, 2013;Smith et al, 2014;Nguyen et al, 2015). Barbier and Strand (1998) study the effect of changes in mangrove areas on the carrying capacity of shrimp stocks in Mexico, while Simonit and Perring (2005) look at effects of eutrophication on growth of fish in Lake Victoria.…”