Browsing by Author "Flores, Andres"

Now showing 1 - 9 of 9
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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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    Applying machine learning to predict reproductive condition in fish
    (2024) Flores, Andres; Wiff, Rodrigo; Donovan, Carl R.; Galvez, Patricio
    Knowledge of reproductive traits in exploited marine populations is crucial for their management and conservation. The maturity status in fish is usually assigned by traditional methods such as macroscopy and histology. Macroscopic analysis is the assessing of maturity stages by naked eye and usually introduces large amount of error. In contrast, histology is the most accurate method for maturity staging but is expensive and unavailable for many stocks worldwide. Here, we use the Random Forest (RF) machine learning method for classification of reproductive condition in fish, using the extensive data from Chilean hake (Merluccius gayi gayi). Gonads randomly collected from commercial industrial and acoustic surveys were classified as immature, mature-active and mature-inactive. A classifier for these three maturity classes was fitted using RFs, with the continuous covariates total length (TL), gonadosomatic index (GSI), condition factor (Krel), latitude, longitude, and depth, along with month as a factor variable. The RF model showed high accuracy (>82%) and high proportion of agreement (>71%) compared to histology, with an OOB error rate lower than 15%. GSI and TL were the most important variables for predicting the reproductive condition in Chilean hake, and to lesser extent, depth when using survey data. The application of the RF shows a promising tool for assigning maturity stages in fishes when covariates are available, and also to improve the accuracy of maturity classification when only macroscopic staging is available.
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    Baited remote underwater video stations as a potential tool for assessing coastal rocky fishes in Chile
    (2024) Irigoyen, Alejo J.; Flores, Andres; Gacitua, Santiago; Merlo, Pablo; Wiff, Rodrigo; Canales, T. Mariella
    Coastal rocky fish species support important fishing activities, but basic information is lacking for many before catches decline. Monitoring and management of coastal rocky fish species is urgently needed in Chile, but knowledge of these species is fragmentary at best. Performance of Baited Remote Underwater Video Stations (BRUVS) for assessing rocky fish assemblages was evaluated in south-central Chile. Seven medium- to large-sized exploited species dominated fish assemblages in the survey area, including five small cryptic rocky reef fishes, one agnathan and a catshark species. These seven species represented 78% of the species targeted by commercial fishing in the survey area. Furthermore, this tool provided new information on behaviour of rocky fish species. The simple, inexpensive and light nature of single-camera BRUVS may be crucial for maintaining monitoring programs along remote areas of 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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    Monitoring data poor small-scale estuarine fisheries: a proposal from the striped mullet (Mugil cephalus) fishery in the Rapel River, Chile
    (2024) Wiff, Rodrigo; Flores, Andres; Peralta, Leonardo; Estevez, Rodrigo A.; Gacitua, Santiago; Gelcich, Stefan
    Chile has a relatively long history of monitoring and managing large-scale commercial fish stocks. However, many other small-scale fisheries, particularly those operating in estuaries, usually lack basic fisheries and biological information. International experience indicates that a monitoring system designed for large-scale stocks cannot simply be resized to address the complexity, relatively low total economic value, and the large number of actors and supply chains in small-scale fisheries. This article proposes a strategy to monitor data-poor fisheries operating in estuaries. The striped mullet (Mugil cephalus), locally known as "lisa", in the Rapel River, central Chile, was selected to establish a pilot monitoring program for small-scale fish resources. From May 2022 to May 2023, fisheries information, including fleet description, catch and effort data, and fish biological attributes such as length and weight, were collected and described for the first time in the region. Drawing insights from this case study, we propose developing a generic monitoring system tailored specifically for monitoring fish stocks in estuaries. This conceptualization is based on: i) change agents, who are individuals trained to work with both the social and biological dimensions of each coastal fish stock; ii) experienced fisheries scientists outside government agencies; and iii) local fishers' knowledge to provide constant feedback for adapting temporal and spatial scales for monitoring. This monitoring scheme is cost-effective and can be efficiently replicated in other estuarine fisheries in Chile.
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    New records of Bramidae in Chilean waters: the sickle pomfret (Taractichthys steindachneri) and the rough pomfret (Taractes asper)
    (2023) Carvalho Filho, Alfredo; Wiff, Rodrigo; Milessi, Andres C.; Flores, Andres
    Artisanal fisheries in center-southern Chile targeted a large amount of southern ray bream (Brama australis), whereas other species of Bramidae are negligible in the catches. During a small-scale fishing trip targeting B. australis off the coast of Lebu Harbour (38 degrees S) in August 2021, two specimens of other Bramidae species were also caught, but the fishermen did not identify them. The first corresponded to a sickle pomfret, Taractichthys steindachneri, the first record of the species in Chilean waters. The second specimen corresponded to the rough pomfret, Taractes asper, already reported from the Chilean coast, but with only one previous record from the eighties. We discussed how the occurrence of T. steindachneri and T. asper provide insights regarding the B. australis demography in the south Pacific.
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    Reproductive ecology of the female pink cusk-eel (Genypterus blacodes): evaluating differences between fishery management zones in the Chilean austral zone
    (SPRINGER, 2014) Baker, Laurie L.; Wiff, Rodrigo; Quiroz, J. C.; Flores, Andres; Cespedes, Renato; Barrientos, Mauricio A.; Ojeda, Vilma; Gatica, Claudio
    The pink cusk-eel (Genypterus blacodes), a benthic-demersal fish confined to the southern hemisphere, supports an important commercial fishery in Chile where it is exploited over an extensive geographic area. Although the fishery was originally divided into a northern (41A(0)28'aEuro"47A(0)00'S) and southern (47A(0)00'aEuro"57A(0)00'S) zone for the purposes of fisheries management, recent studies have reported significant differences in life history parameters between these zones. Individuals from the southern zone reached larger asymptotic sizes and possessed higher survival rates compared to the northern zone. We estimate and compare the gonadosomatic index (GSI), shape of the maturity ogive, and length at 50 % maturity (L (50%)) of female G. blacodes between management zones and across time using biological data collected from the industrial fleet between 1985 and 2009. Females in the northern zone had higher monthly mean GSI than females in the southern zone. Our analyses also revealed L (50%) to be significantly higher in the southern zone than in the northern zone from 1985 to 2009. The significant differences in life-history traits between fishery management zones agree with the trade-offs predicted by Charnov's life history theory. Together these results provide additional support for the hypothesis that two separate stocks exist and suggest that females from the northern zone have developed a life-history strategy, which favours early maturation and a proportionally greater investment in reproduction than females from the southern zone.
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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 .