Threats to Vaquita's habitat that could affect recuperation

Given the limited geographic distribution of Vaquita, the condition of that habitat plays an important role in determining the status of the population. Any change in the habitat could affect the well being and recovery of the Vaquita.

Reduction in Colorado River flow
The flow of water from the Colorado River has been greatly reduced by dams and other water projects in Southwestern U.S. and to a lesser extent, in Northwestern Mexico. Today freshwater flows from the Colorado River reach the Delta only in years of heavy precipitation. Some investigators assume that this reduced flow has caused a drastic change in the ecosystem. For example, the low salinity estuarine conditions that prevailed prior to these flow reductions have been replaced by negative hypersaline estuarine conditions in the Delta, and these changes could have caused alterations in the food web and in biological diversity. However, there isn't sufficient information to confirm this hypothesis. The available evidence suggests that the Colorado River Delta acts like a very fertile coastal lagoon, maintaining abundant populations of crustaceans and mollusks, and other species use this habitat for feeding and as a refuge.

Contaminants:
The tributaries of the Colorado River drain through the agricultural lands of Southern California and the Mexicali valley. This causes concern about the extensive use of organic compounds and chemical fertilizers on these farmlands, which concentrate in the watershed. High levels of pesticides have been related to reproductive incapacity in various marine mammals. The presence of contaminants like DDT in bivalves collected at the mouth of the Colorado River confirms that these compounds are entering the upper Gulf food web. However, the most recent analyses indicate that the chlorinated organic compounds and pesticides found in mollusks collected in El Golfo de Santa Clara and near San Felipe are in low concentrations.

The accumulation of contaminants in Vaquita and other organisms that inhabit the delta remains a concern. While the results of eight samples of blubber, liver, heart and kidneys from Vaquita suggest that the levels of contaminants are low, the presence of possible effects from these contaminants in Vaquita cannot be overlooked. Levels of these contaminants still appeared to be much lower than those found in marine mammals in any other part of the world.

Destruction of coastal habitats
Throughout the upper Gulf coastal development is growing and uncontrolled. In some places wastes are discharged directly into the sea. Uncontrolled growth can alter and destroy habitat important for different life stages of species in the food web. The coastal zones of estuaries are especially important for the growth of larvae of both non-commercial and commercially important fisheries species. Unfortunately estuaries are the targets for development as marinas.

Degradation of sea floor ecology
In the Gulf of California the Mexican Pacific shrimp fleet harvests brown and blue shrimp in an intensive effort along the coast of Sonora, from Guaymas to the Delta of the Colorado River and to San Felipe. The dragging of trawl nets to capture shrimp results in a destruction of the sea floor and its ecology. The removal of enormous tonnage of fauna, in many cases containing juvenile stages of many species of fish, has disturbed the benthic food web. Investigators believe that this effect is drastic, considering that shrimp bycatch is many times greater than the amount of shrimp captured. Most of the shrimp bycatch, predominantly fish, die on the boats and are discarded. Part of this waste could have been food for the vaquita and many other marine organisms.