From the Advisory Body Evaluation:
The waters of the Upper Gulf and Colorado River Delta are shallow (50-200m) and becoming more saline (to 35.5ppm) as a result of the upstream diversions of the
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and silts near the delta, sandy and rocky further south. In this area there are 18 species of marine mammal. One of most important for conservation is the so-called
"vaquita", or Gulf porpoise, which is one of the world’s four rarest marine mammals. There are also sea lion, 5 species of dolphin, 11 species of whales and 161
species of fish, 42 of them endemic. Marine invertebrate include 35 species of mollusc and 190 decapods.