Browsing by Author "Queirolo, Dante"

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    A pilot tagging program on southern rays bream (Brama australis): methodology and preliminary recaptures
    (2023) Wiff, Rodrigo; Flores, Andres; Gacitua, Santiago; Donovan, Carl R.; Canales, T. Mariella; Ahumada, Mauricio; Queirolo, Dante
    The southern rays bream (Brama australis) is a highly migratory, epi-mesopelagic species supporting an important artisanal fishery off central-southern Chile. Despite its importance, several questions exist about this species's demography and migratory routes. The first step in understanding the migratory behavior of B. australis is to test the feasibility of a conventional tagging program, a standard mark-recapture method, to infer migration in fish. Between February 2020 and December 2021, conventional tagging was conducted during 21 fishing trips on board artisanal vessels off Lebu harbor ( Biobio Region, Chile) using gillnets, longlines, and handlines. Three thousand nine hundred forty-six individuals of B. australis between 30 and 55 cm fork length were tagged using external T-anchor bar labels (commonly known as "spaghetti"). Approximately 100 and 200 fish were tagged per fishing trip using longlines and gillnets, respectively. The size distribution of the tagged individuals was consistent with those retained in the catch, with 90% of tagged fish being longer than the fork length at 50% maturity. Eight tags have been recovered off the coast of Lebu up to May 2022. With times at liberty between 50 and 537 days. These preliminary recaptures are also analyzed in the context of the conceptual model for demography and migration proposed for this species in Chile. The main conclusion of this research is that a conventional tagging program is feasible for B. australis in Chile.
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    Catch efficiency of trawl nets used in surveys of the yellow squat lobster (Cervimunida johni) estimated by underwater filming records
    (2021) Ahumada, Mauricio; Queirolo, Dante; Apablaza, Pedro; Wiff, Rodrigo; Flores, Andres
    Catch efficiency is an important index to relate observed density to the size of a population in the context of bottom trawl surveys. The estimation of catch efficiency is challenging because it involves independent measures of animals in the path of the bottom trawl. We estimated catch efficiency using an underwater camera system on three trawl fishing vessels used for estimating the density of the yellow squat lobster (Cervimunida johni) off central Chile. During 2015 and 2018, 54 hauls were analyzed, and a total of 20 h of filming were recorded. A total of 4,155 yellow squat lobster individuals were analyzed approaching the net in the path of the trawl, of which 2,330 (56%) were captured and 1,825 escaped underneath the groundrope. The median estimated ranges of catch efficiency varied between 0.81-0.90 for vessel 1, 0.15-0.72 for vessel 2 and 0-0.58 for vessel 3. According to a hierarchical generalized linear model (HGML), fishing vessels and mean depth of hauls showed significant differences in catch efficiency (p<0.05). The results were comparable with estimates available for other crustacean species, and differences among vessels can be associated with differences in rigging configurations. Discussion was focused on the processes affecting catch efficiency and how differential catchability among sampling vessels may bias the construction of spatially explicit density maps and further abundance estimates of yellow squat lobsters in Chile. (C) 2021 Elsevier B.V. All rights reserved.
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    Coping with El Nino: phenotypic flexibility of reproductive traits in red squat lobster determines recruitment success
    (2021) Flores, Andres; Wiff, Rodrigo; Ahumada, Mauricio; Queirolo, Dante; Apablaza, Pedro
    Many organisms display changes in behaviour and life-history traits when facing variabilities in environmental conditions. A subset of these changes comprises reversible within-individual variations, known as phenotypic flexibility. Using red squat lobster (Pleuroncodes monodon) individuals harvested at the Humboldt Current Ecosystem (HCE), we evaluated how changes in habitat temperatures associated with warm El Nino (EN) conditions and cold La Nina conditions induce phenotypic flexibility in reproductive traits and how this flexibility affects recruitment success. The biological data were obtained from swept area surveys conducted between 2015 and 2020. Remotely sensed sea surface temperature (SST) data were used to compute anomalies (SSTA). Our results showed that females facing warmer environmental conditions carried more eggs with smaller sizes, and under cold conditions, females carried fewer eggs with larger sizes. The recruitments lagged by. year correlated positively with the egg density and negatively with the egg size. Our evidence shows that for phenotypic flexibility to be expressed in recruitment success, the warm conditions experienced by females should match good food availability for the planktonic stages. We discussed how climate change predictions for HCE will amplify responses of the reproductive traits of red squat lobster with strong impacts on recruitment likely.
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    Estimation of natural mortality in two demersal squat lobster species off Chile
    (2019) Canales, T. Mariella; Wiff, Rodrigo; Quiroz, Juan Carlos; Queirolo, Dante
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    Influence of Growth and Recruitment Parameters in the Assessment and Management Variables of the Yellow Squat Lobster (Cervimunida johni)
    (2020) Canales, T. Mariella; Quiroz, Juan-Carlos; Wiff, Rodrigo; Queirolo, Dante; Bucarey, Doris
    Fitting length data in age-structured stock assessment is a common method for evaluating hard-to-age animals, such as crustaceans. Growth specification and the uncertainty in the stock recruitment relationship are key issues in length-based assessment models. We conducted sensitivity analyses to evaluate the impact of growth and recruitment parameters on the stock assessment and management variables of the yellow squat lobster (Cervimunida johni) caught off the Chilean coast. Nine different scenarios of the length at first capture (L-a=1) and the coefficient of variation at age (cv(a)) were tested for six combinations of values for the steepness parameter (h) and the recruitment variance (sigma(2)(R)). We also investigated the reliability of these estimates using an operating model. Our findings indicate that the parameter related to growth, L-a=1, has the greatest impact on the assessment and management variables of this fishery resource, with cv(a) having a lesser effect. Recruitment and fishing mortality estimates were the main variables affected. Parameters h and sigma(2)(R) did not profoundly impact the variables assessed. In addition, L-a=1 was the most biased estimated parameter. We discuss that the high influence of growth parameters is related to model structure, and thus implications for determination of the status of yellow squat lobster should be addressed in the future. We recommended developing simulation protocols for the selection of growth parameters when using an age-structured model with length observations, and we believe that our findings are relevant for all Chilean fisheries with a similar stock assessment framework.
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    Modelling density on historical aggregation areas improves biomass estimates in yellow squat lobster off Chile
    (2024) Cusba, Jose; Queirolo, Dante; Ahumada, Mauricio; Apablaza, Pedro; Paramo, Jorge; Wiff, Rodrigo
    Yellow squat lobster fishery is one of the most important extractive activities in the central zone of Chile that occurs between 100 and 300 m deep. One of the difficulties in the management of the fishery is the high variability of the indices of abundance, which depends on the spatial distribution of the resource, among other things. Given the limited knowledge of spatial distribution patterns and spatiotemporal changes in yellow squat lobster density and biomass, the information collected during trawl survey assessments between 1999 and 2019 in central Chile was analyzed. Using the criteria of presence, persistence, distance, and discontinuity, 23 areas of aggregation between 26 degrees 42 ' and 36 degrees 54 ' S were identified and used to model the catch per unit area by a generalized additive models. The model explained 21.4% of the deviance and allowed us to show the population growth from 2001 onward between the regions of Valpara & iacute;so and Biob & iacute;o, which was consistent with the extractive closure implemented by the managers from 32 degrees 10'S to the south. Most of the biomass of Cervimunida johni (similar to 75% of the biomass) was located in the Coquimbo, Puerto Oscuro, La Ligua, Valpara & iacute;so, Pichilemu, and Biob & iacute;o aggregations, corresponding to 57% of the total surface where the resources were distributed. The present work provides information on the places that have been persistently occupied by Cervimunida johni, suggesting to managers an evaluation of the spatial limits that are currently being used in the surveys and their influence on the performance of the population evaluation model.