Browsing by Author "Wiff, Rodrigo"
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- ItemAccuracy of gonadosomatic index in maturity classification and estimation of maturity ogive(2019) Flores, Andrés; Wiff, Rodrigo; Ganias, Konstantinos; Marshall, C. Tara
- ItemApplying machine learning to predict reproductive condition in fish(2024) Flores, Andres; Wiff, Rodrigo; Donovan, Carl R.; Galvez, PatricioKnowledge 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.
- ItemBaited 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. MariellaCoastal 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.
- ItemBayesian modeling of individual growth variability using back-calculation: Application to pink cusk-eel (Genypterus blacodes) off Chile(2018) Contreras-Reyes, Javier E.; Lopez Quintero, Freddy O.; Wiff, Rodrigo
- ItemBiphasic growth modelling in elasmobranchs based on asymmetric and heavy-tailed errors(2021) Contreras-Reyes, Javier E.; Wiff, Rodrigo; Soto, Javier; Donovan, Carl R.; Araya, MiguelGrowth 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.
- ItemCoping 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, PedroMany 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.
- ItemEstimating 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.
- ItemEstimation of natural mortality in two demersal squat lobster species off Chile(2019) Canales, T. Mariella; Wiff, Rodrigo; Quiroz, Juan Carlos; Queirolo, Dante
- ItemIncorporating sea surface temperature into the stock-recruitment relationship: Applications to jack mackerel (Trachurus murphyi) off Chile(2016) Espíndola, Fernando; Quiroz, Juan Carlos; Wiff, Rodrigo; Yáñez Rodríguez, Eleuterio
- ItemInfluence 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, DorisFitting 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.
- ItemModelling 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, RodrigoYellow 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.
- ItemNew 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, AndresArtisanal 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.
- ItemOtolith shape as a stock discrimination tool for ling (Genypterus blacodes) in the fjords of Chilean Patagonia(2020) Wiff, Rodrigo; Flores, Andrés; Segura, Ángel M.; Barrientos, Mauricio A.; Ojeda, Vilma
- ItemReproductive biology of female cardinalfish, Epigonus crassicaudus de Buen, 1959(2015) Flores, A.; Wiff, Rodrigo; Díaz, E.; Gálvez, P.
- ItemReproductive 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, ClaudioThe 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.
- ItemRole of the preferred habitat availability for small shark (Mustelus schmitti) on the interannual variation of abundance in a large Southwest Atlantic Coastal System (El Rincón, 39°–41°S)(2016) Jaureguizar, A. J.; Wiff, Rodrigo; M. Luz Clara
- ItemThe invariance of production per unit of food consumed in fish populations(2017) Wiff, Rodrigo; Barrientos, Mauricio A.; Segura, Ángel M.; Milessi, A. C.