Browsing by Author "Araya, Miguel"

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    Biphasic growth modelling in elasmobranchs based on asymmetric and heavy-tailed errors
    (2021) Contreras-Reyes, Javier E.; Wiff, Rodrigo; Soto, Javier; Donovan, Carl R.; Araya, Miguel
    Growth in fishes is usually modelled by a function encapsulating a common growth mechanism across ages. However, several theoretical works suggest growth may comprise two distinct mechanistic phases arising from changes in reproductive investment, diet, or habitat. These models are termed two-state or biphasic, where acceleration in growth typically changes around some transition age. Such biphasic models have already been successfully applied in elasmobranch species, where such transitions are detectable from length-at-age data alone, but where estimation has assumed normally distributed errors, which is inappropriate for such slow-growing and long-lived fishes. Using recent advances in growth parameter estimation, we implement a biphasic growth model with asymmetric and heavy-tailed errors. We use data from six datasets, encompassing four species of elasmobranchs, to compare the performance of the von Bertalanffy and biphasic models under normal, skew-normal, and Student-t error distributions. Conditional expectation maximization estimation proves both effective and efficient in this context. Most datasets analysed here supported asymmetric and heavy-tailed errors and biphasic growth, producing parameter estimates different from previous studies.
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    Redescription of the Chilean angel shark Squatina armata (Philippi, 1887) (Squatiniformes, Squatinidae)
    (2024) Kraft, Sebastian; Fernandez-Cisternas, Italo; Araya, Miguel; Concha, Francisco J.
    Angel sharks ( Squatina spp. Dum & eacute;ril, 1805) are a group of coastal benthic sharks distributed worldwide, currently including threatened and understudied species. Two species are formally described along the East Pacific coast, the California angel shark S. californica Ayres, 1859 and the Chilean angel shark S. armata (Philippi, 1887). The latter species occurs in the southeastern Pacific and has historically been understudied. Additionally, the original description of S. armata lacks sufficient data to confidently identify individuals of this species compared to modern descriptions, and no type specimen is currently available to ensure specimen identification. Detailed morphological descriptions for identifying species are an essential resource for solving taxonomic issues in groups of morphologically similar species and to promote the conservation of critically endangered species. Therefore, a neotype from the type locality is here designated for S. armata , and a detailed and standardized morphological characterization based on modern taxonomic works is provided. This work contributes in improving the knowledge on the Chilean angel shark taxonomy and provides an improved frame of reference for identifying angel sharks in the East Pacific, especially in areas where species may occur in sympatry.
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    Using expert knowledge to propose recreational marine reef-fish management measures in Chile
    (2024) Estevez, Rodrigo A.; Godoy, Natalio; Araya, Miguel; Azocar, Cristian; de la Barra, Christian; Bardi, Francisca; Fernandez-Urzua, Francisco; Garcia, Marcelo; Hiriart-Bertrand, Luciano; Lomonico, Serena; Medina, Marianela; Naretto, Javier; Ojeda, F. Patricio; Pequeno, German; Ponce, Francisco; Pulgar, Jose; Perez-Matus, Alejandro; Rivera, Javier; Smith, Andres; Toro Da Ponte, Jorge; Torres-Canete, Felipe; Vasquez, Julio A.; Gelcich, Stefan
    Marine recreational fisheries often lack necessary information to perform assessments and develop sustainable management strategies. In Chile, although reef-fish fisheries have been signaled as overexploited, there are still no commercial or recreational regulations regarding bans, catch limits, or size limits. We implemented an expert elicitation protocol to propose management measures to regulate recreational reef-fish harvests of 17 reef-fish species. Sixteen experts estimated minimum legal sizes, temporal closures, and maximum number of individuals harvested per person per trip (known as "bag limits"). Experts also prioritized management measures for each of 17 reef-fish species. Maximum number of individuals harvested per person per trip varied between 1 and 7. In addition, permanent bans were recommended for some species, such as acha (Medialuna ancietae), pejeperro (Semicossyphus darwini), and San Pedro (Oplegnathus insignis). We concluded that information gathered through expert elicitation can play a key role to inform data-poor recreational fishery management. Expert elicitation protocols that include iterative process, based on individual estimates and an open expert discussion phase, provide the necessary enabling environment to identify a variety of management measures. While future challenges include the development of mechanisms to promote acceptability and compliance for recreational fisheries management, the approach presented here is important to initiate much needed discussions.