Browsing by Author "Mariella Canales, T."

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    Comparing growth curves with asymmetric heavy-tailed errors: Application to the southern blue whiting (Micromesistius australis)
    (2014) Contreras-Reyes, Javier E.; Arellano-Valle, Reinaldo B.; Mariella Canales, T.
    Von Bertalanffy growth models (VBGMs) have been used in several studies of age, growth and natural mortality. Assuming that the residuals about this growth model are normal is, however, questionable. Here, we assume that these residuals are heteroskedastic and follow a log-skew-t distribution, a flexible distribution that is asymmetric and heavy-tailed. We apply the proposed methodology to length-at-age data for the southern blue whiting (Micromesistius australis) collected from Chilean austral continental waters between 1997 and 2010. The estimates of the VBGM parameters were L-infinity = 57.042 cm, K = 0.173 yr(-1), t(0) = -2.423 yr for males, and L-infinity= 61.318 cm, K = 0.163 yr(-1), t(0) = -2.253 yr for females. The BIC criteria suggest that females grow significantly faster than males and that length-at-age for both sexes exhibits significant heteroskedasticity and asymmetry. (C) 2014 Elsevier B.V. All rights reserved.
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    Considerations for management strategy evaluation for small pelagic fishes
    (2021) Siple, Margaret C.; Koehn, Laura E.; Johnson, Kelli F.; Punt, Andre E.; Mariella Canales, T.; Carpi, Piera; de Moor, Carryn L.; De Oliveira, Jose A. A.; Gao, Jin; Jacobsen, Nis S.; Lam, Mimi E.; Licandeo, Roberto; Lindegren, Martin; Ma, Shuyang; Oskarsson, Gudmundur J.; Sanchez-Marono, Sonia; Smolinski, Szymon; Surma, Szymon; Tian, Yongjun; Tommasi, Desiree; Gutierrez, Mariano T.; Trenkel, Verena; Zador, Stephani G.; Zimmermann, Fabian
    Management strategy evaluation (MSE) is the state-of-the-art approach for testing and comparing management strategies in a way that accounts for multiple sources of uncertainty (e.g. monitoring, estimation, and implementation). Management strategy evaluation can help identify management strategies that are robust to uncertainty about the life history of the target species and its relationship to other species in the food web. Small pelagic fish (e.g. anchovy, herring and sardine) fulfil an important ecological role in marine food webs and present challenges to the use of MSE and other simulation-based evaluation approaches. This is due to considerable stochastic variation in their ecology and life history, which leads to substantial observation and process uncertainty. Here, we summarize the current state of MSE for small pelagic fishes worldwide. We leverage expert input from ecologists and modellers to draw attention to sources of process and observation uncertainty for small pelagic species, providing examples from geographical regions where these species are ecologically, economically and culturally important. Temporal variation in recruitment and other life-history rates, spatial structure and movement, and species interactions are key considerations for small pelagic fishes. We discuss tools for building these into the MSE process, with examples from existing fisheries. We argue that model complexity should be informed by management priorities and whether ecosystem information will be used to generate dynamics or to inform reference points. We recommend that our list of considerations be used in the initial phases of the MSE process for small pelagic fishes or to build complexity on existing single-species models.
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    Influence of climate variability on anchovy reproductive timing off northern Chile
    (2016) Contreras-Reyes, Javier E.; Mariella Canales, T.; Rojas, Pablo M.
    We investigated the relationship between environmental variables and the Gonadosomatic Monthly Mean (GMM) index of anchovy (Engraulis ringens) to understand how the environment affects the dynamics of anchovy reproductive timing. The data examined corresponds to biological information collected from samples of the landings off northern Chile (18 degrees 21'S, 24 degrees 00'S) during the period 1990-2010. We used the Humboldt Current Index (HCI) and the Multivariate ENSO Index (MEI), which combine several physical-oceanographic factors in the Tropical and South Pacific regions. Using the GMM index, we studied the dynamics of anchovy reproductive timing at different intervals of length, specifically females with a length between 11.5 and 14 cm (medium class) and longer than 14 cm (large class). Seasonal Autoregressive Integrated Mobile Average (SARIMA) was used to predict missing observations. The trends of the environment and reproductive indexes were explored via the Breaks For Additive Season and Trend (BFAST) statistical technique and the relationship between these indexes via cross-correlation functions (CCF) analysis. Our results showed that the habitat of anchovy switched from cool to warm condition, which also influenced gonad development. This was revealed by two and three significant changes (breaks) in the trend of the HCI and MEI indexes, and two significant breaks in the GMM of each time series of anchovy females (medium and large). Negative cross-correlation between the MEI index and GMM of medium and large class females was found, indicating that as the environment gets warmer (positive value of MEI) a decrease in the reproductive activity of anchovy can be expected. Correlation between the MEI index and larger females was stronger than with medium females. Additionally, our results indicate that the GMM index of anchovy for both length classes reaches two maximums per year; the first from August to September and the second from December to January. The intensity (maximum GMM values at rise point) of reproductive activity was not equal though, with the August-September peak being the highest. We also discuss how the synchronicity between environment and reproductive timing, the negative correlation found between MEI and GMM indexes, and the two increases per year of anchovy GMM relate to previous studies. Based on these findings we propose ways to advance in the understanding of how anchovy synchronize gonad development with the environment. (C) 2016 Elsevier B.V. All rights reserved.
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    Regulation of fish stocks without stock-recruitment relationships: The case of small pelagic fish
    (2020) Mariella Canales, T.; Delius, Gustav W.; Law, Richard
    Small pelagic fish lack clear stock-recruitment relationships. This is a problem because such relationships are taken to be the primary descriptors of density dependence, responsible for regulating population density. In this paper, we show that small pelagic fish species, anchovy (Engraulisspp., Engraulidae), living in a stochastic environment, can be strongly regulated without a stock-recruitment relationship emerging. This is done through numerical analysis of a size-spectrum model, in which fish grow by eating and die in part from being eaten, with the result that birth, growth and death are all density-dependent. The model includes cannibalism, and growth-dependent larval mortality, both of which have been suggested as regulatory mechanisms in anchovy, together with growth and reproduction later in life. Despite the lack of a clear stock-recruitment relationship in the presence of stochasticity, signals of density dependence in the vital rates remain clear, suggesting that they might prove to be better indicators of density dependence than stock-recruitment relationships in small pelagic fish.
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    Spatial and bathymetric occurrence of Brama australis off the Chilean Coast and in the South Pacific Ocean
    (2017) San Martin, Marcelo A.; Leal, Elson; Mariella Canales, T.
    Data about Brama australis distribution along the Chilean coast and the South Pacific is scarce and varied. The aim of this study was to provide new information concerning the spatial and bathymetric occurrence of B. australis in the Southern Pacific Ocean. To do this, all data and information available in scientific literature regarding Chile and the South Pacific Ocean were collected, including fishery dependent and independent as well as bycatch data. B. australis could be present in a wider latitudinal range from the 27 degrees S to 57 degrees S, including fjords, open ocean, and along a band in the Pacific Ocean, from New Zealand up to the Chilean coast. Thus, B australis shows a wider distribution compared to previous studies especially towards the Southern Chile. Bathymetrically the species occurs with a higher frequency in depths between 100 and 250 m, however a low occurrence was recorded over 500 m depth. A potential association of B. australis with the West Wind Drift, which could influence the distribution of the species in the Pacific Ocean and off the Chilean coast, is hypothesized. Further work includes taxonomic studies to confirm the presence of the same species in the distributional area proposed here.
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    The Interaction Between Stock Dynamics, Fishing and Climate Caused the Collapse of the Jack Mackerel Stock at Humboldt Current Ecosystem
    (2020) Lima, Mauricio; Mariella Canales, T.; Wiff, Rodrigo; Montero, Jose
    The collapse of marine fisheries had caused a cascade of ecological, social and economic consequences. Recognizing the complex nature of the fisheries collapses is essential for understanding the impact of human activities on natural systems. The rapid and abrupt shifts in abundance exhibited by some marine fish populations can be driven by the fishing fleet behaving like generalist predators. Here, we propose that fishing fleet has a s-shaped functional predator function that, combined with economic factors and ENSO variability could cause rapid and abrupt transitions in the of jack mackerel (Trachurus murphyi) fishery in the south-eastern Pacific. Our results showed that fishing fleet predator functional response is well described by a s-shaped function, where ENSO variability (El Nino/La Nina years) appears to decrease/increase the fishing rate. Our model predictions were able to accurately forecast independent data of jackmackerel acoustic survey estimates. We show that the population trend and collapse of jack mackerel stock at the Humboldt Current Ecosystem (HCE) can be explained by the changes in fishing effort, which seem to be driven by economic forces and El Nino climatic variability. Our simple model allows us to explore some management responses in a heuristic manner. The most critical element seems to be the combination of an n-shaped isocline for fish stock growth, modulated by ENSO variability, and a horizontal isocline of fishing effort which is highly sensitive to changes in the profitability of the fishery. Therefore, the implementation of management policies based on simple theoretical models will be increasingly required to harvest fish stocks in these times of growing demographic demands and climate change.