Changes in fish diversity at La Silla River, Nuevo León, Mexico: biological collections as witness of the ecosystems quality

Authors: Erick González, María Ramírez, Deborah Barocio

Year: 2019

Abstract

Mexico is considered a Megadiverse country because its geographical position into the Neotropical and Nearctic biogeographic regions, due to the variety of climates, the great orographic diversity, being surrounded by two different oceans, presenting different types of soil, inland waters and different types of vegetation, generating a high fauna richness. However, biodiversity has been diminished due to anthropogenic activities, as well as environmental changes that have affected populations. To mitigate the effects of these factors, it is necessary to be aware on how this diversity has changed over time, making biological and ecological comparisons at different time and geographic scales. The aquatic systems in Mexico are used for the disposal of wastewater, which generates ecological disturbances in the rivers and the surrounding ecosystem. La Silla river, in Nuevo León, Mexico, is considered one of the aquatic ecosystems with the highest ecological priority in North America, due to its biodiversity, as well as the different environmental services it offers as a system, in addition to the potential risk due the human settlements around. It is at this point that the importance of Biological Collections arises, considered as libraries of specimens that are stored in special conditions to guarantee their integrity over time, and providing biological information at historical, geographical, genetic, ecological, anatomical and morphological levels. Fish species lists of Nuevo León have demonstrated the presence of several national or international protected species, and some of these species are distributed in La Silla river. However, for many of them there is not enough information about their biology and ecology to assess their vulnerability to adverse ecosystem conditions. The current conditions of the La Silla river allow us to infer that the fish populations will present unfavorable conditions, both ecological, demographic and genetic, that will increase the need for their protection. At the Ichthyological Collection of the Biological Sciences Faculty from the Autonomous University of Nuevo León, specimens from almost all the States of Mexico and from other countries of the world are present. From La Silla River, there are records dating since 1966, with the Catostomidae, Centrarchidae, Cyprinidae, Characidae, Cichlidae, Poecilidae and Ictaluridae families being the oldest recorded for the area. In this way, for different locations of La Silla river, there are records from 1966, 1969, 1981, 1982, 1988, 1995, 1996, 1998 and 2011, where, in addition, the families Clupeidae, Percidae and Cyprinodontidae are included. During the second half of 2019, a weekly monitoring is carried out in different locations of La Silla river, to analyze the current diversity of species, with the main goal of temporary comparisons and assessing how diversity has changed, both in richness of species as functional, in order to understand how anthropogenic changes, affect the health of the freshwater ecosystem. So far, it a tendency in the decrease of the specific richness is observed, produced, possibly, by the contamination of the river, as well as the decrease of the tributaries and the quality of the water.