Browsing by Author "Ahumada, Mauricio"

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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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    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.
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    Reproductive strategy of yellow squat lobster (Cervimunida johni Porter, 1903): re-evaluating the maturity criteria
    (2021) Flores, Andres; Wiff, Rodrigo; Brown, Donald I.; Ahumada, Mauricio; Larrea-Meza, Sebastian
    Studying the basic biology of heavily fished marine species is essential to achieving conservation and sustainable exploitation. Yellow squat lobster (Cervimunida johni) is a demersal crustacean with a long fishing history in the Southeast Pacific. However, knowledge of its reproductive biology is still fragmented, and these traits have never been validated at the gonad level. In this context, we assessed the reproductive traits of this species for the first time based on gonadal development using data from a research survey conducted during 2018 off the Chilean coast. A total of 117 and 376 gonads were assessed based on histological and macroscopic analyses, respectively. The functional and effective criteria (a combination of functional and physiological maturity) were used to estimate the maturity ogives. Using a total of 113 females, fecundity (F) and relative fecundity (RF) at length were estimated using the autodiametric method. We determined that females of yellow squat lobster possess group-synchronous ovary development with indeterminate fecundity. Histological analysis revealed that 59% of non-ovigerous females had mature ovaries and were therefore misclassified as immature based on the functional criterion. Similarly, maturity ogives derived from the effective criterion were displaced to smaller sizes and varied significantly from those estimated using the functional criterion (P < 0.05). In addition, the effects of female size on F and RF were significant (P < 0.05). A warning on the use of functional criteria for assessing maturity status is issued, and the importance of adult females on the per capita contribution to population renewal in this crustacean species is discussed .