Viability of Natural Populations of Hypancistrus zebra (Siluriformes, Loricariidae), Xingu, Brazil

[Baron Ätzmolch]

Abstract
Hypancistrus zebra is an endemic fish species from the Middle Xingu River and recently included in the Critically Endangered (CR) category in the Red Book List of Endangered Brazilian Fauna that follows IUCN criteria. Given these impacts and the lack of information about the species, it is difficult to assume the viability of natural populations. Thus, this work aims to evaluate the effect of the variation of intrinsic parameters on the population viability of H. zebra. For this, an Individual Based Model (MBI) was created of the type Agent Based Modeling (MBA). To create the model, we considered “individuals” as an entity and the following variables of interest: longevity, age of sexual maturity, annual reproduction number, instant birth rate (b0), instant mortality rate (d0), interference of each individual in population growth (b1), interference of each individual in population mortality (d1), time (t), radius, richness (S), tolerance (tol) and population size (N). The model showed that natural populations today, even not taking human impacts in account, are at the limit of viability. However, any factor that causes a reduction in resource availability, even if not evident, can lead to a steep population decline, affecting the viability of the populations.

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--Michael