Browsing by Author "Wiff, Rodrigo"

Now showing 1 - 20 of 42
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    A multivariate statistical analysis to determine catch intention in the pink cusk-eel (Genypterus blacodes) longline fishery in southern Chile
    (2020) Wiff, Rodrigo; González, G. M.; Contreras, F.; San Martin, M. A.; Canales, T. M.
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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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    A survey-based approach to constructing an abundance index of the pink cusk-eel (Genypterus blacodes) in the fjords of Chilean Patagonia
    (2020) Wiff, Rodrigo; Flores, A.; Queirolo, D.; Ahumada, M.; Apablaza, P.; Gacitúa, S.; Montero Styles, José Tomás; Gelcich, Stefan; Cañete, F. T.; Lima Arce, Mauricio
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    Accuracy of gonadosomatic index in maturity classification and estimation of maturity ogive
    (2019) Flores, Andrés; Wiff, Rodrigo; Ganias, Konstantinos; Marshall, C. Tara
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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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    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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    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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    Changes in the size-structure of a multispecies pelagic fishery off Northern Chile
    (2015) Canales, Mariella T.; Law, Richard; Wiff, Rodrigo; Blanchard, Julia L.
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    Chilean fishing law, maximum sustainable yield and the stock-recruitment relationship
    (2016) Wiff, Rodrigo; Quiróz, J. C.; Neira, Sergio; Gacitúa, Santiago; Barrientos, Mauricio A.
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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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    Estimating consumption to biomass ratio in non-stationary harvested fish populations
    (2015) Wiff, Rodrigo; Roa Ureta, Ruben H.; Borchers, David L.; Milessi, Andrés C.; Barrientos, Mauricio A.
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    Estimating spatio-temporal distribution of fish and gear selectivity functions from pooled scientific survey and commercial fishing data
    (2021) Gonzalez, Guillermo Martin; Wiff, Rodrigo; Marshall, C. Tara; Cornulier, Thomas
    Model-based prediction of fish distribution at fine resolutions in space and time has the potential to inform areabased and dynamic forms of management, such as permanent marine protected areas or real-time temporary closures. A major limitation to the spatial and temporal mapping resolution that is achievable is the amount of high quality, standardised data that can be utilized for fitting statistical models. To achieve an adequate spatiotemporal resolution from sparse data, one option is pooling information from several sources, such as scientific surveys and fisheries data. Because surveys and fisheries data usually use different sampling methods, pooling information from different sources requires cross-calibration of catch rates values across multiple gears. However, the individual gear efficiency and selectivity curves (the ratio between catch and availability at a given length) for all fishing gears and species are typically unknown. Using cod (Gadus morhua) in the northern North Sea as a case study, we developed a new formulation of spatio-temporal generalised additive models (GAM) of relative abundance of fish, combining catch data from multiple sources. Differences in gear efficiency and selectivity were internally calibrated within the model by the estimation of the local spatio-temporal variation in abundance. We show that pooling data sources enables the prediction of multi-annual and seasonal spatial variation in cod relative abundance-at-size, at spatio-temporal resolutions that are relevant for informing fishing strategies, e.g., reducing bycatch in real-time, or management objectives, e.g., real-time closed areas. We also show that GAM models fit to catch and effort data can reveal the relative efficiency and selectivity of different survey and commercial gears. The selectivity curve estimates that emerged as a by-product of our analysis are consistent with expert knowledge of the performance of the gears employed for cod. Our analytical approach can therefore serve two useful purposes: to estimate spatio-temporal variation in relative abundance of fish and to estimate relative gear efficiency and selectivity.
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    Estimating steepness of the stock-recruitment relationship in Chilean fish stocks using meta-analysis
    (2018) Wiff, Rodrigo; Flores, Andrés; Neira, Sergio; Caneco, Bruno
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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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    First report of the hapuku wreckfish Polyprion oxygeneios (Polyprionidae) in Argentinian waters
    (2021) Milessi, Andres C.; De Wysiecki, Agustin M.; Carvalho Filho, Alfredo; Wiff, Rodrigo
    The hapuku wreckfish Polyprion oxygeneios is recorded for the first time in Argentinian waters. Four specimens were caught off Mar del Plata (38 degrees S, Argentina) in depths between 60 and 260 m during austral summer (three by sport fishers and one in a research cruise). Up to the present, this species was consistently misidentified with its congener, the common wreckfish P. americanus, off Argentina. These records represent a connection between previous records from Brazil and the more austral circumglobal distribution of the species.
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    Flexible Bayesian analysis of the von Bertalanff growth functions with the us of a log-skew-t distributions
    (2017) López, Freddy; Contreras, Javier; Wiff, Rodrigo; Arellano Valle, Reinaldo Boris
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    Growth estimates of young-of-the-year broadnose sevengill shark, Notorynchus cepedianus, a top predator with poorly calcified vertebrae
    (2022) Javier Jaureguizar, Andres; Cortes, Federico; Matias Braccini, J.; Wiff, Rodrigo; Milessi, Andres C.
    The broadnose sevengill shark, Notorynchus cepedianus (Peron, 1807), is a large marine top predator in temperate coastal ecosystems. Some aspects of its life history have been determined, but its growth pattern is yet to be fully understood. The authors used a multi-modelling approach and a sensitivity test to estimate growth parameters from young-of-year (YOY) length data collected off San Antonio Cape (SAC), Argentina, a critical habitat in the Southwest Atlantic Coastal Zone (SACZ). The best selected model, a sex-combined logistic growth model, estimated an asymptotic length (L-infinity) of 92.58 cm TL (95% C.I.: 86.48-105.89 cm), a growth coefficient (K) of 0.006818 days (-1) (95% C.I.: 0.004948-0.008777) and a size at birth (L-0) of 40.73 cm. The predicted annual growth (i.e., L1 - L-0) was 43.2 cm TL. Males had smaller L-0, higher K and achieved larger sizes after 1 year. The YOY in SAC attained a larger L-1 and grew faster than their Australian and South African wild counterparts. The consistent year-round presence of YOY in the SAC highlights the importance of this area as a pupping ground and potential nursery for N. cepedianus; this has direct implications for the allocation of research and management effort for the conservation of this species in the Southwest Atlantic.
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    Highest catch of the vulnerable broadnose sevengill shark Notorynchus cepedianus in the south-west Atlantic
    (2018) De Wysiecki, A.M.; Milessi, A.C.; Wiff, Rodrigo; Jaureguizar, A.J.