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MAPPING THE DISTRIBUTION OF HARVESTED ESTUARINE BIVALVES WITH NATURAL HISTORY-BASED HABITAT SUITABILITY MODELS
Citation:
DeWitt, Ted, N. Lewis, AND EricW Fox. MAPPING THE DISTRIBUTION OF HARVESTED ESTUARINE BIVALVES WITH NATURAL HISTORY-BASED HABITAT SUITABILITY MODELS. Joint Meeting of the Pacific Estuarine Research Society and California Estuarine Research Society, Coos Bay, OR, March 16 - 19, 2017.
Impact/Purpose:
EPA scientists at NHEERL/WED have developed ecological models using readily obtained environmental data, that accurately generate maps of the best (e.g., “most suitable”) and worst habitats for locating populations of harvested species of bivalve shellfish within Pacific NW estuaries. Whereas these bivalves are valued in the recreational and commercial fisheries, and are thus an important final ecosystem good for coastal communities, maps of their distribution are also useful to State and local decision-makers for land-use planning applications. A highlight of the new modeling approach is that disparate, independent sets of existing data were sufficient to produce and validate maps of habitat suitability. While not all estuaries may have the necessary data readily available, environmental parameters included in the models can be measured at relatively low cost, especially when compared to the expense of collecting bivalve population data. The research was conducted as part of SHC Project 2.61, Task 3: Ecological Production Functions for Quantifying Final Ecosystem Goods and Services.
Description:
Maps of harvested bivalve populations are invaluable for the management of fisheries species, yet the cost to produce them typically limits their availability. Here, we demonstrate a relatively low-cost approach to generate habitat maps for five species of bivalves found in many Pacific estuaries. Using natural history information, rule-based habitat suitability models were constructed in ArcGIS for each bivalve species. Species tolerance limits, based on habitat characteristics, were determined through a literature review of four easy-to-sample parameters: salinity, depth, sediment grain size, and the presence of burrowing shrimp. Spatially-explicit habitat maps were produced for Yaquina and Tillamook estuaries (Oregon) using environmental data from multiple studies ranging from 1960 to 2012. Suitability of a given location was ranked on a scale of 1-4 (lowest to highest) depending on the number of variables that fell within a bivalve’s tolerance limits. Models were tested by comparing the distribution of each suitability class with the observed distribution of bivalves reported in benthic community studies (1996-2012). Areas of highest habitat suitability within models coincided with the greatest proportion of bivalve observations and highest population densities, for each species. The principle advantage of this approach is that disparate, independent sets of existing data were sufficient to parameterize the models, and to produce and validate maps of habitat suitability. While some estuaries may not currently have those data, the model’s environmental parameters are cost less to measure than bivalve population data.