Using software Vortex as a tool towards conservation actions for sharks

Elasmobranchs, especially sharks, are part of the most threatened group of animals in the world. Among the factors that negatively affect these populations, the environmental degradation and disordered fishing can be highlighted. Although these threats are well known, the responses of most species to these factors are not fully understood, which makes it difficult to predict potential population responses according to conservation actions. The present study aims to develop a theoretical model based on a real population of white sharks (Carcharodon carcharias) that inhabit Gulf of Mexico, using their biological patterns to identify trends for the populations using Vortex (version 10.0.0.3) as a tool. The construction of the model was based on bibliographic data, considering parameters of life history, demographic rates and main known threats. Data were entered into Vortex software, and two population sizes were tested in the population viability analysis, indicating in both cases that the species tends to lose its genetic diversity over 500 years with a 12% and 51% of probability of extinction, respectively, considering exclusively its biological potential. This results can reflect on an mislead assumption of the real subpopulation’s size, which shows that the species is inserted into the vortex of extinction even with the existence of protective measures regarding white sharks on the location of the study, and it must incorporate neonates and juveniles individuals on the analysis to generate a consistent result. Despite this, the study suggests that the utilization of Vortex is capable of generating responses necessary for the conservation of sharks by analyzing stochastic events and life history in a simple way.


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or conserved by any regional or multilateral treaty that aims the management of marine 26 resources (IUCN, 2002). 27 The biology of most species of sharks is little known and there are poor data about  (Lacy, 2005). This analysis predicts the tendencies in population size to 38 increase or decrease in the future according to the life history of the species analyzed 39 and the current situation of the population, taking into consideration the deterministic or 40 stochastic factors that may cause fluctuations in the population size (Gilpin et al.,1986). 41 However, its widespread use is hampered by the scarcity of information on vital rates 42 and lack of ecological information of the species, which are required as input 43 parameters for the models (Pardini, 2001;Beerkircher, 2003). 44 The PVA assesses the risk of a population of wildlife animals to diminish or 45 extinguish due to current or future conditions. Demographic information of the 46 population serve as data to be added to a "Vortex" model with a structure that defines 47 the basic biological characteristics of the species and habitat use patterns, so the model 48 can project the demographic behavior of the simulated population for a specific period 49 of the future, considering the specific conditions assumed. Within these aspects, the preconditions for growth or decline of the population can be determined, as well as the 51 best options for management of the species in order to minimize the risk of extinction 52 (Lacy, 1993). 53 This study aimed to compile biological and population data of white sharks 54 Carcharodon carcharias (Linnaeus, 1758) through literature review, since this species 55 has lots of biology and life history data available of the population that inhabits the 56 northeastern Pacific Ocean based on a theoretical but biologically accurate population 57 tested in different scenarios to analyze if using Vortex as a tool is applicable to identify 58 future shark's population trends. The data obtained from the literature were condensed in Table 1 Table 1. Synthesis of data used in the PVA.

Parameters
Basal value References  According to Ussami (1995) California region.

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The support capacity was considered as 100, taking advantage of the result that       The data of population size to be analyzed was inserted in the software, 166 comprising 106 individuals having 500 independent interactions over 500 years. It was 167 considered that females have their first offspring at age 8 old and males copulate for the The population growth rate is negative, there is an abrupt drop in the first 5 years 183 and it is assumed that this is related to the age distribution from Table 4 obtain and often result in great uncertainty (Caswell, 1998).

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The software has three options to analyze the tendencies of extinction in years,   A more detailed study with representative data on real population size is needed.

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Pursuant to the results shown in the present study, the tendency of diversity genetic loss 247 of the population analyzed reaches 50%, a result reflected on an mislead assumption of 248 the real subpopulation's size, which shows that the species is inserted into the vortex of