Biological Resources Shown on ESI Maps

Under the Environmental Sensitivity Index (ESI) method, species that are especially vulnerable to the effects of oil spills have been classified into seven general categories, such as Bird, Fish, and Marine Mammal. The categories are then further divided by grouping species together by similar taxonomy, morphology, life history, and/or sensitivity to spilled oil.

The table below lists all of the categories and subcategories for biological resources, and it also includes some information about how they are displayed on ESI maps. When a biological resource exists in a small area (such as a bird nesting site), it is indicated on an ESI map by a symbol. When a biological resource encompasses a larger area, it is represented on ESI maps by a polygon with a specific pattern and color.

Category/Sub-Category	Symbol	Locations Shown on Maps
Marine Mammal
Dolphin		Concentration areas
Manatee		Concentration areas, cold weather refuge areas
Polar Bear		Concentration areas
Sea Otter		Concentration areas
Seal/Sea Lion		Haulouts, concentration areas
Whale		Migratory or other concentration areas
Terrestrial Mammal
Bat		Locations of threatened, endangered, or species of significance
Bear		Intertidal feeding or aquatic/wetland concentration areas, areas hazardous to spill responders
Deer		Intertidal feeding or aquatic/wetland concentration areas
Small Mammal		Aquatic fur-bearer concentration areas, locations of threatened, endangered, or rare species
Bird
Alcid/Pelagic Bird		Rookeries, roosting, and other concentration areas
Diving Bird		Rookeries; forage/wintering areas; roosting concentration areas
Gull/Tern		Nesting sites; other concentration areas
Passerine Bird		Locations of threatened, endangered, or rare species, especially nesting areas
Raptor		Nesting sites; migratory/feeding concentration areas
Shorebird		Nesting sites; migratory, wintering, and roosting concentration areas
Wading Bird		Rookeries; feeding and roosting concentration areas
Waterfowl		Wintering and migration concentration areas; nesting sites
Reptile/Amphibian
Alligator/Crocodile		Concentration areas, especially nesting locations
Other Reptiles/Amphibians		Locations of threatened, endangered, or rare species, especially aquatic/wetland concentration areas
Turtle		Nesting beaches; concentration areas
Fish
Anadromous Fish		Spawning and nursery areas; locations of threatened, endangered, or rare species
Diadromous Fish		Spawning and nursery areas; locations of threatened, endangered, or rare species
Estuarine Nursery Fish		Spawning, nursery, and other concentration areas
Estuarine Resident Fish		Spawning or other concentration areas; locations of threatened, endangered, or rare species
Freshwater Fish		Spawning and nursery areas; locations of threatened, endangered, or rare species
Marine Benthic Fish		Spawning and nursery areas; reefs, kelp beds, or other concentration areas
Marine Pelagic Fish		Spawning or other concentration areas
Shellfish/Insect
Bivalve		Harvest areas; abundant beds; locations of threatened, endangered, or rare species
Crab		Nursery areas; areas of high concentrations
Echinoderm		Harvest areas
Gastropod		Harvest areas; high concentrations, locations of threatened, endangered, or rare species
Insect		Locations of threatened, endangered, or rare species
Lobster/Crayfish		Nursery, spawning, and harvest areas; locations of threatened, endangered, or rare species
Shrimp		Nursery areas; locations of high concentrations
Squid/Octopus		Harvest areas; areas of high concentrations
Habitat/Rare Plant
Coral/ Hardbottom Reef		Generally restricted to water and tidal flats
Floating Aquatic Vegetation/Intermittent Coastal Wetlands		Areas of floating aquatic vegetation
Rare Plant/Terrestrial Plant/Native Plant		Locations of threatened, endangered, or rare species or communities
Submerged Aquatic Vegetation		Areas of submerged aquatic vegetation; seagrass beds, kelp, algae

For More Information

Complete ESI Species List List of species that may be shown on ESI maps. Not all species are shown on every ESI map.

Anatomy of ESI Maps Brief introduction to the basic elements of ESI maps.

Shoreline Sensitivity Rankings Shorelines are ranked according to their sensitivity to oil, the natural persistence of oil, and the expected ease of cleanup after an oil spill.

Human-Use Resources Resources and places important to humans and sensitive to oiling, such as public beaches and parks, marine sanctuaries, water intakes, and archaeological sites.