An analysis of the spatial distribution of freshwater fishes of Mexico, their conservation status, and the development of a conservation strategy for species with imminent risk of extinction based on contemporary theories and practices.

Contreras Macbeath, Einar Topiltzin (2014) An analysis of the spatial distribution of freshwater fishes of Mexico, their conservation status, and the development of a conservation strategy for species with imminent risk of extinction based on contemporary theories and practices. Doctoral thesis (PhD), Manchester Metropolitan University.

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Abstract

Due to human activities freshwaters are experiencing declines in biodiversity far greater than those in the most affected terrestrial and marine ecosystems, consequently freshwater fishes are by far the most affected group of vertebrates. This situation stands true for Mexican freshwater fishes and their corresponding ecosystems. In this respect, Mexico has a long history of environmental policy, and seeking to protect its biodiversity, the country has carried out a series of important initiatives in response to the adoption of the Convention on Biological Diversity (CBD), such as the creation of the National Biodiversity Commission in 1992, the elaboration of the National Biodiversity Strategy, regional action plans, as well as conservation strategies for terrestrial and marine species and environments, but unfortunately, little has been done in relation to the conservation of freshwater species, nor the ecosystems they live in. With this in mind, the main aim of this study is to analyze the spatial distribution of the Freshwater Fishes of Mexico, their conservation status, and to develop a conservation strategy for species with imminent risk of extinction. In order to develop the strategy four basic phases were taken: (1) assessment of the freshwater fishes of Mexico, (2) determination of conservation priorities, (3) identification and diagnosis of problems, and (4) planning solutions. These were achieved through a series of different methodologies for each particular case. The first part of the assessment phase consisted in developing an updated species list of Mexican freshwater fishes that resulted in a working list of 616 fish species grouped in 61 families for Mexican freshwaters (265 are Mexican endemics). Globally there are approximately 12,000 described freshwater fish species, so results show that Mexico holds 5.1% of the global freshwater fish diversity. This is a large figure considering that the Mexican territory represents only 1.3% of the world global land area. The second part of the assessment phase consisted in developing a study of richness and endemism which was crucial for identifying hotspots and consequently for directing conservation efforts. This was done by mapping and overlaying individual species distributions by means of geographical information systems based on museum data. The results of this study confirmed several previously proposed centers of freshwater fish richness (Southeastern Mexico, the Mesa Central, the Bravo-Conchos river system and the Panuco and Tuxpan-Nautla rivers). Seven areas with high CWEI endemism values were identified, but the valley of Cuatrociénegas was recognized as a true center. An alarming result was the identification of a “Ghost” center of endemism (Llanos El Salado) in Southwestern Nuevo León, where the six endemic Cyprinodont species that were present in this center are all extinct or extinct in nature. 49 single site endemics were identified that are distributed all over Mexico, but it is noteworthy to mention Chichancanab lagoon in the border between Yucatan and Quintana Roo, where a flock composed of 6 endemic Cyprinodonts is present. Three hotspots of richness + endemism were identified for Mexico, the most important of which is the Mesa Central where impacts by human activities have had a detrimental effect on fish populations. In order to determine conservation priorities the risk of extinction for each of the 616 species was assessed according to the IUCN Red List Categories and Criteria: Version 3.1. Results show that 218 species (36%) in 25 families are classified as threatened, 49 are critically endangered (8%), 82 are endangered (14%), 88 are vulnerable (14%). With a total of 160 threatened species, five families compromise 73% of the total, these are Cyprinidae with 55 threatened species, Goodeidae with 38, Poeciliidae with 23, Atherinopsidae with 22 and Cyprinidontidae with 21. Lost fishes, both extinct and extinct in the wild represent 3% of the total with 20 species, 15 of which are Mexican endemics. There are only 18 species (3%) classified as Near Threatened, these belong to 9 families, most diverse of which is Poeciliidae with 7 species. Data Deficient species account for only 2% of the total. Over half of the species (56%) are considered as Least Concern. These figures are very similar to those found for European freshwater fishes, but differ (are worse) from what has been found for Africa, and for global data. Once these phases were completed, an assessment was carried out on the Mexican legal and institutional framework related to freshwater fish species conservation, as well as the effectiveness of ongoing biodiversity conservation strategies by means of on ex-post analysis based on the two Mexican governmental policies related to ecosystem and biodiversity conservation, which are those related to Protected Areas and Conservation of species at risk, implemented by the National Commission on Protected Areas. Results show that even though there have been many successful strategies in the terrestrial realm, over the past 16 years there is a tendency of more freshwater fish species being imperiled. So it is fair to say that conservation programs have not had a positive impact on freshwater fishes. Due to the large number of threatened freshwater fish species found, within such a large country, with limited economic resources for species conservation actions, a decision was made to identify as conservation targets, those species with imminent risk of extinction. After applying a prioritization method, 45 species within nine families, distributed in 30 different sites were identified as those with the highest extinction risk. With the information produced in the previous sections a conceptual model was developed that included scope, vision, and the conservation goal of preventing imminent extinctions. Direct threats were then identified for these sites (recreational activities, water management/use, water pollution and invasive species), and from these contributing factors. Based on the former, 10 general actions are proposed to minimize the impact of these contributing factors, and a case study with Notropis boucardi from the higher Balsas river basin is presented as an example of how these actions can be applied to achieve conservation results. In general terms it can be said that by collating and analyzing data in a systematic manner, by using geographical information systems, and by discussing the results in the context of contemporary theories or views related to conservation practice, the present study has not only contributed to the knowledge of Mexican freshwater fish species, their conservation status and threats, but has set the basis for the implementation of specific conservation actions for species with imminent risk of extinction. It is clear that much work is still needed in order to change the precarious situation of Mexican freshwater fishes and their habitats, but while the Federal Government needs to work harder in aspects such as water treatment and sanitation, there is an opportunity in State and Local governments, that could take the lead in protecting their critically endangered freshwater fish species. Fortunately the database produced for this study, as well as the ten conservation actions identified can serve as the starting point for specific local conservation initiatives.