2015 Regional Estuary Assessment for the Northern Gulf of Mexico
Dates
Metadata Creation Date
2016-02-23
Citation Creation Date
2016-02-09
Start Date
1991-01-01
End Date
2015-01-01
Assessment Date
2015
Summary
The Regional Estuary Assessment for the northern Gulf of Mexico represents an effort to develop, test, and implement a new assessment methodology for marine habitats that improves the analytical basis for identifying impacts to estuary fish habitats. Building from work completed for the National Estuary Assessment, this approach includes: 1) information on fish and shellfish presence/absence from over 70,000 sampling events collected over two decades, to better relate fish habitat condition to natural and anthropogenic variables; 2) data on natural factors, to better incorporate information on the natural susceptibility of individual estuaries; and 3) regional datasets not available on a nationally-consistent basis. Methods for the [...]
Summary
The Regional Estuary Assessment for the northern Gulf of Mexico represents an effort to develop, test, and implement a new assessment methodology for marine habitats that improves the analytical basis for identifying impacts to estuary fish habitats. Building from work completed for the National Estuary Assessment, this approach includes: 1) information on fish and shellfish presence/absence from over 70,000 sampling events collected over two decades, to better relate fish habitat condition to natural and anthropogenic variables; 2) data on natural factors, to better incorporate information on the natural susceptibility of individual estuaries; and 3) regional datasets not available on a nationally-consistent basis. Methods for the assessment were developed through a collaborative process with regional partners. First, indicator screening models are used to rapidly screen a large number of potential stress variables against each species found in Gulf estuaries and identify the most important variables for further investigation. The models use the probability of fish presence (by species) to assess the significance of each estuary-level stress variable one at a time. These models also control for natural variables, such as temperature and salinity (collected concurrently with fish samples), which might otherwise obscure the effects of the stress variables. Once the most significant stress variables were identified from the screening models, they were tested using multi-stressor models for each fish species. Here, backwards selection eliminates variables one at a time from the model based on statistical significance, until only variables that are highly significant (i.e. at a 95% confidence level) remain. Using these more refined models, current conditions were then compared to the Least Disturbed Condition (LDC) - defined as the minimum observed value of each significant stressor across the entire region. By comparing against LDC, we can estimate the current impact of stressors and avoid extrapolating beyond the range of conditions for which the models were developed. Overall, this process allowed us to identify the most influential habitat stressors for each fish species and overall for estuaries in the northern Gulf of Mexico.
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2015RegionalEstuaryAssessment-GoM.xml “Metadata” Original ISO Metadata
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Purpose
The results represent the absolute difference in current condition from the Least Disturbed Condition (LDC). Comparing against LDC provides a relative benchmark and allows estimation of the effects of anthropogenic stress on individual species and on entire estuaries, relative to the LDC. This provides a conservative estimate of anthropogenic impacts to estuaries in the northern Gulf of Mexico. Understanding how human activities are impacting fish habitats is important so resource managers can better manage these impacts, and ultimately, sustain estuaries and the fish populations they support. Identifying estuaries with the best and worst relative condition, as well as the key impacts, us useful to help prioritize conservation and restoration efforts.
