There are various environmental factors that affects, renewable resource extraction and flows of non-extractive ecosystem services for instance temperature variation, proliferation of large dad zones, technological disaster and ocean acidification. Scientists can easily identify these problems for instance by tracking the ocean temperatures and pH .there has been a study to analyze the brown shrimp fishery and potential impacts of a large seasonal area of hypoxia that coincides with the height of the shrimp season. According to the study; shrimp fishery is large while the spatial extent of hypoxia is substantial. However the scientists have encountered difficulties in linking large scale seasonal hypoxia to fishery losses.
According to the natural scientists there has been a comparison between hypoxic severity and aggregate fish catch but no causal inference studies to the phenomenon. Economists did the same using micro data and then exploring the potential effects with empirically grounded bio economic simulations which was successful. They focused on estuaries along the east coast of the US. They saw that shrimp tend to congregate on the edges of hypoxic areas making it easier to catch them.
Causal inference studies of non-random interventions are usually done using spatial characteristics as a source of identification by economists. This system can still be used to study the impacts of hypoxia using spatial and temporal variation though causal approaches to observational data requires separation between treatment and control groups.in order to pursue a particular treatment effect one has to understand how spatial-dynamic bio economic system would affect the data generating process and the extent to which a hypoxic signal would be transmitted in observational data.
In accordance to the experiments the effects of hypoxia on fisheries are more obvious since understanding hypoxic effects on fisheries and controlling cost of nutrient pollution are parts of estimating benefits of these reductions.an examination of potential effects of hypoxia using a spatial-dynamic bio economic simulation shows that mortality and growth effects of hypoxia will lead to decreased harvests. While the catchability effects increases harvests. Empirical data and simulations of brown shrimp fishery seemed consistent with pattern of persistent growth overfishing
For the treatment experiments (effects) the results were not good since ambiguity occurred about shrimp quantities even when the ecological system was observed. This was due to contamination of control sites through re-sorting of the fishing fleet.
Time series analyses of price is another alternative approach used.Theoratical predictions on this method are much sharper because all the biological effects of hypoxia predict a relative increase in small shrimp, which in turn, predicts a decrease in relative prices of small to large shrimp.in that sense the market ultimately becomes a better determinant of the severity of an ecological disturbance compared to an analyst’s attempts to construct a counterfactual.
Another alternative is to harness the structural information in a bio economic simulation model as identifying assumptions. Biologists should have enough baseline parameters to use this simulation to predict outcomes and estimate structural hypoxia parameters
In the Gulf of Mexico the aggregate predictions from simulations are similar to empirical fishery data. The average shrimp size and the total landings are negatively correlated, this also happens to hypoxic severity and landings. Growth overfishing varies with recruitment success and with ecological disturbances while shrimp size and hypoxic severity are only weakly negatively correlated.
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