Vaquita - Threats

Incidental mortality, great losses...

Directed fishing, accidental bycatch in nets set for fish and reduction of food supplies due to fishing threaten this species.

In addition, the vaquita is possibly affected by reductions in water flow into the Gulf of California from the Colorado River, and pesticide pollution is suspected as a potential problem.

Fisheries bycatch
Commercial and artisanal fishing being intensive in the upper Gulf, notably for shrimp, sharks and scombrids, the vaquita is particularly vulnerable to incidental mortality in gill nets. Since they need to surface to breath air, when they get entangled in fishing nets they cannot surface to breath and they drown.

Even though it is known that vaquitas die in all types of nets, it has been difficult to estimate the exact mortality in each type. A study by CEDO of the upper Gulf of California determined that the fishing effort is different in each community in the region, and that the fisheries are dynamic and respond to changes of tides, seasons and other environmental factors, as well as economic factors.
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Habitat loss and degradation
This porpoise's habitat has been drastically altered by damming of the Colorado River in the United States. Long-term changes due to the reduced freshwater input are matters of concern and should be investigated.

Throughout the upper Gulf, coastal development is growing and uncontrolled. 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 such as marinas.

The dragging of trawl nets to capture shrimp results in the 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.
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Pesticide pollution
The tributaries of the Colorado River drain through the agricultural lands of Southern California and the Mexicali valley. A potential problem is the presence of organic compounds and chemical fertilizers, which concentrate in the watershed. High levels of pesticides have been related to reproductive incapacity in various marine mammals. 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 on the species cannot be overlooked.
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Natural factors
White sharks, mako, blacktips as well as other shark species have been found with vaquita parts inside their stomachs. Some vaquita tangled in nets showed scars on their flukes from teeth that could be shark or killer whale, and there have been sightings of killer whales and also of other species of sharks, like the tiger shark (Galeocerdo cuvier), scalloped hammerhead sharks (Sphyrna spp.) and bull shark (Charcharhinus leucas), among others. However there have been no direct reports of attacks on vaquita by these species of sharks or by killer whales.