| Abstract: | The inland waters of Mexico support a highly diverse groupof freshwater fishes with high levels of endemism that occur
across a broad range of aquatic habitat types. These aquatic
ecosystems provide many direct (e.g., fisheries) and indirect
(e.g., agricultural irrigation) benefits to people, and support
local livelihoods and economies across Mexico. Freshwater
ecosystems are undervalued and receive insufficient funding,
political attention and protection. Developing interests
and funding for freshwater species conservation is crucial
for “bending the curve” to reduce and ultimately reverse
freshwater biodiversity declines. Historical disregard for the
health and sustainable use of freshwater ecosystems has
resulted in alarming rates of loss in the quality and availability
of aquatic habitat. This report presents the most recent
information on the conservation status and distribution of
freshwater fishes in Mexico, and examines the stressors that
are driving their declining conservation status. Important
conservation actions and considerations are also presented.
Five hundred and thirty-six species of freshwater fishes
were assessed against the IUCN Red List Categories and
Criteria, representing the most comprehensive assessment
of freshwater biodiversity in Mexico to date. This assessment
seeks to address the insufficient information available on
freshwater fish conservation status, which has resulted in
their inadequate representation in environmental planning
and management. The full data set, including all species
distribution maps, is freely available through the IUCN Red
List website (www.iucnredlist.org).
Forty percent of all extant species assessed are threatened
with extinction, assuming all Data Deficient species are
threatened in the same proportion as those for which
enough information was available. The most pervasive
threats are related to habitat loss and degradation, which is
driven primarily by unsustainable water use and widespread
agricultural activity. Excessive extraction of groundwater and
diversion of surface water for human consumption, industrial
processes, and plantation agriculture has led to widespread
flow reductions, reduced water tables, and subsequent drying
of aquatic habitat, which is especially prevalent in the arid,
endorheic spring systems of northern and central Mexico.
Mexico’s vast hydroelectric infrastructure has altered the
historical flow regime of many major rivers, blocking natural
migration routes and fragmenting subpopulations of native
fishes. Agricultural runoff, inadequate wastewater treatment,
and industrial discharges have also resulted in increased
levels of pollution. A number of non-native fish species
have been introduced both intentionally and unintentionally
throughout many of Mexico’s natural and artificial surface
waters, with profound impacts on native species distribution
and abundance.
Given the high connectivity of riverine surface waters
and underlying aquifers, the impacts of these threats
spread rapidly throughout freshwater ecosystems. Future
conservation efforts must place greater emphasis on
upstream, downstream, and lateral connectivity within water
catchments. Systematic conservation planning approaches
should be implemented to develop an integrated conservation
action plan for freshwater fishes in Mexico, including
broad stakeholder participation, environmental monitoring
schemes, and the development of protected areas designed
to maintain high levels of aquatic connectivity.
Another priority is to direct additional research effort towards
the high proportion of species assessed as Data Deficient due
to insufficient information on their conservation status and
distributions. This lack of information presents a significant
bottleneck to the effective management and conservation of
Mexico’s freshwater habitats and ichthyofauna.
From a policy perspective, the information presented in this
report will help support the implementation of multilateral
environmental agreements in Mexico, guide conservation
planning and priority setting at the national and international
level, and provide a baseline of conservation success in
subsequent assessments of extinction risk. In addition, this
new information will help efforts to achieve the targets of the
UN Sustainable Development Goals (SDGs), such as: Target
6.6 for protecting and restoring water-related ecosystems;
Target 6.5 on implementing integrated water resources
management at all levels; Target 15.1 for conservation,
restoration and sustainable use of terrestrial and inland
freshwater ecosystems and their services; and Target 15.5
focused on urgent and significant action to reduce the
degradation of natural habitats, halt the loss of biodiversity
and, protect and prevent the extinction of threatened species.
The IUCN Red List is one of the most authoritative global
standards supporting policy and action to conserve
biodiversity. The analysis presented in this report, based
on an assessment of species Red List status, will provide
new information to help guide conservation actions and development planning to safeguard the diversity of freshwater
ichthyofauna in Mexico. Periodic update of IUCN Red List
species assessments will enable calculation of a Red List
Index of change in freshwater species extinction risk over
time, which will inform managers on the conservation
effectiveness of any management interventions.
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