Institute Fomento Pesquero IFOP

A. Blanco, Chile

Institute Fomento Pesquero IFOP

A. Blanco, Chile
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Contreras-Reyes J.E.,Institute Fomento Pesquero IFOP | Contreras-Reyes J.E.,Federico Santa María Technical University | Cortes D.D.,Institute Fomento Pesquero IFOP
Entropy | Year: 2016

Mixture models are in high demand for machine-learning analysis due to their computational tractability, and because they serve as a good approximation for continuous densities. Predominantly, entropy applications have been developed in the context of a mixture of normal densities. In this paper, we consider a novel class of skew-normal mixture models, whose components capture skewness due to their flexibility. We find upper and lower bounds for Shannon and Rényi entropies for this model. Using such a pair of bounds, a confidence interval for the approximate entropy value can be calculated. In addition, an asymptotic expression for Rényi entropy by Stirling's approximation is given, and upper and lower bounds are reported using multinomial coefficients and some properties and inequalities of Lp metric spaces. Simulation studies are then applied to a swordfish (Xiphias gladius Linnaeus) length dataset. © 2016 by the authors; licensee MDPI, Basel, Switzerland.

Flores A.,Pontifical Catholic University of Valparaíso | Wiff R.,University of Santiago de Chile | Diaz E.,Institute Fomento Pesquero IFOP | Carvajal B.,Institute Fomento Pesquero IFOP
Journal of Sea Research | Year: 2017

Fecundity is a key aspect of fish species reproductive biology because it relates directly to total egg production. Yet, despite such importance, fecundity estimates are lacking or scarce for several fish species. The gravimetric method is the most-used one to estimate fecundity by essentially scaling up the oocyte density to the ovary weight. It is a relatively simple and precise technique, but also time consuming because it requires counting all oocytes in an ovary subsample. The auto-diametric method, on the other hand, is relatively new for estimating fecundity, representing a rapid alternative, because it requires only an estimation of mean oocyte density from mean oocyte diameter. Using the extensive database available from commercial fishery and design surveys for southern blue whiting Micromesistius australis australis in the Southeast Pacific, we compared estimates of fecundity using both gravimetric and auto-diametric methods. Temporal variations in potential fecundity from the auto-diametric method were evaluated using generalised linear models considering predictors from maternal characteristics such as female size, condition factor, oocyte size, and gonadosomatic index. A global and time-invariant auto-diametric equation was evaluated using a simulation procedure based on non-parametric bootstrap. Results indicated there were not significant differences regarding fecundity estimates between the gravimetric and auto-diametric method (p > 0.05). Simulation showed the application of a global equation is unbiased and sufficiently precise to estimate time-invariant fecundity of this species. Temporal variations on fecundity were explained by maternal characteristic, revealing signals of fecundity down-regulation. We discuss how oocyte size and nutritional condition (measured as condition factor) are one of the important factors determining fecundity. We highlighted also the relevance of choosing the appropriate sampling period to conduct maturity studies and ensure precise estimates of fecundity of this species. © 2017 Elsevier B.V.

Salgado P.,Institute Fomento Pesquero IFOP | Salgado P.,FARO | Riobo P.,CSIC - Institute of Marine Research | Rodriguez F.,FARO | And 2 more authors.
Toxicon | Year: 2015

Among toxin-producing dinoflagellates of the genus Alexandrium, Alexandrium ostenfeldii is the only species able to produce paralytic shellfish poisoning (PSP) toxins, spirolides (SPXs) and gymnodimines (GYMs). In this study we characterized and compared three A. ostenfeldii strains isolated from the Baltic, Mediterranean, and southern Chile Seas with respect to their toxin profiles, morphology, and phylogeny. Toxin analyses by HPLC-FD and LC-HRMS revealed differences in the toxin profiles of the three strains. The PSP toxin profiles of the southern Chile and Baltic strains were largely the same and included gonyautoxin (GTX)-3, GTX-2, and saxitoxin (STX), although the total PSP toxin content of the Chilean strain (105.83 ± 72.15 pg cell-1) was much higher than that of the Baltic strain (4.04 ± 1.93 pg cell-1). However, the Baltic strain was the only strain that expressed detectable amounts of analogues of GYM-A and GYM-B/-C (48.27 ± 26.12 pg GYM-A equivalents cell-1). The only toxin expressed by the Mediterranean strain was 13-desmethyl SPX-C (13dMeC; 2.85 ± 4.76 pg cell-1). Phylogenetic analysis based on the LSU rRNA showed that the studied strains belonged to distinct molecular clades. The toxin profiles determined in this study provide further evidence of the taxonomic complexity of this species. © 2015 Elsevier Ltd. All rights reserved.

Tascheri R.,Institute Fomento Pesquero IFOP | Saavedra-Nievas J.C.,Seccion de Estadistica | Saavedra-Nievas J.C.,Diego Portales University | Roa-Ureta R.,University of Concepción
Fisheries Research | Year: 2010

Changing targeting behavior of fishing fleets and zero-catch records of the target species are two characteristics common to many multi-species trawl fisheries. These features complicate analyses intended to produce indices of relative abundance from commercial catch rate data. Trawl catch rates of Patagonian grenadier caught off Southern Chile were used to calculate indices of relative abundance for this species. To allow for targeting behavior and zero catches, we first defined a subset of relevant tows combining a logistic regression on the species catch composition and knowledge about the persistence of Patagonian grenadier in the catches from the area where historically it has been more abundant. A standardization analysis was then conducted on this subset of the data using a generalized linear model (GLM) framework. Analysis of deviance tables and standard residuals GLM diagnostic plots were used for selecting the statistical models that best described the data. The candidate models tested were the delta-lognormal, delta-gamma, quasi-Poisson and compound Poisson. The models that best supported the Patagonian grenadier catch rate data were the delta-lognormal and compound Poisson models. Standardization models were then extended to generalized linear mixed models to include the vessel main effect and the significant interactions with the year effect as random effects. Estimations of the annual series of relative abundance were then obtained from the coefficients of the year effects of these models, both of which showed higher abundance for the years 2001--2008 than in previous years of the series. © 2010 Elsevier B.V.

Quiroz J.C.,Institute Fomento Pesquero IFOP | Wiff R.,Institute Fomento Pesquero IFOP | Wiff R.,University of St. Andrews | Caneco B.,University of St. Andrews
Fisheries Research | Year: 2010

Methods to estimate annual mortality rate (M) are usually based on life history traits and their application provide a deterministic estimate for M. However, there are two sources of uncertainty coming from equations that describe these methods: (i) error in the life history traits estimates (hereafter 'trait-error') and (ii) variability of the equations coefficients (hereafter 'coefficient-error'). Thus, we use these two sources of uncertainty to incorporate error on M estimates for yellownose skate (Dipturus chilensis) and roughskin skate (Dipturus trachyderma) off the Chilean coast. Based on the quality of the life history parameters available for these species, five methods to estimate M were selected which required the analysis of lifespan a max, age at maturity a 50 %, and von Bertalanfy growth parameters (l ∞, t 0, and k). For Pauly's methods, the error on the habitat temperature was also assessed. Incorporating only uncertainty from trait errors produced estimates of median M for D. chilensis ranging from 0.12 to 0.15 year -1 for females and 0.14 to 0.18 year -1 for males. For D. trachyderma, this same estimate was 0.09-0.15 year -1 for both sexes combined. Incorporating all sources of uncertainty (trait and coefficient-error) increased the coefficients of variation (CV) of M nine-fold for D. chilensis (females) and seven-fold for D. trachyderma and increased estimates of M by up to 35% in comparison with median values. We think Pauly's method is the most appropriate for both analysed species in terms of trade-off between parameter needed and CV of M estimates incorporating all sources of uncertainty. Most of the empirical methods used herein were proposed, in principle, for teleost fishes within a deterministic framework. We discuss the applicability of these methods to elasmobranchs and how the incorporation of uncertainty may improve population modelling for these species. © 2010 Elsevier B.V. All rights reserved.

Rojas P.M.,Institute Fomento Pesquero IFOP | Landaeta M.F.,University of Valparaíso | Ulloa R.,Autonomous University of Nayarit
Revista de Biologia Marina y Oceanografia | Year: 2011

The impact of the El Niño event (1997-1998) on the spatial dynamics as well as on the changes in the aggregation patterns of anchoveta eggs and larvae due to the alteration in the thermal anomalies were analyzed. Six bio-oceanographic surveys were carried out in northern Chile from Arica (18°29′S, 70°19′W) to Antofagasta (23°38'S, 70°24′W) over different periods (before and during) of the 1997-1998 El Niño event. Changes in the vertical distribution and aggregation patterns of anchoveta in early life stages were registered as well as an increase in zooplankton biomass with the arrival of El Niño; moreover, the spatial distribution of anchoveta was altered due to the gradually poleward displacement of spawning areas as a result of the arrival of subtropical warm waters from the north. The increase in zooplankton biomass linked to a change in the species composition suggests a negative impact on the anchoveta larval feeding. Our results suggest that abrupt changes in the environment would have immediate consequences on the spatial distribution of anchoveta in early life stages, causing a potential impact on the recruitment of this small pelagic fish in the Humboldt Current System off northern Chile.

San Martin M.A.,Institute Fomento Pesquero IFOP | Wiff R.,Institute Fomento Pesquero IFOP | Saavedra-Nievas J.C.,Institute Fomento Pesquero IFOP | Cubillos L.A.,University of Concepción | Lillo S.,Institute Fomento Pesquero IFOP
Fisheries Research | Year: 2013

The Chilean hake (Merluccius gayi gayi) is one of the most important demersal resources fished in Chile since the early 1940s. Since 1993, an acoustic survey program was established to assess the abundance of this resource. A sudden decrease in abundance was observed after 2002, along with changes in the species demography and spatial distribution. These changes represent a spatial re-distribution of the stock (latitude, longitude, and depth) which was associated with concomitant changes in environmental conditions (temperature, salinity, and dissolved oxygen). The main aim of this paper is to determine habitat preferences in Chilean hake and associated changes in its abundance with environmental conditions. Estimates of Chilean hake abundance were based on acoustic survey conducted between 1993 and 2006 from Coquimbo (29°30'S) to Chiloé Island (41°28.6'S). Chilean hake abundance was modelled using generalised additive models with environmental variables and location as covariates. In the interannually analysis, location and temperature were the most important explanatory covariates of Chilean hake abundance. Analyses of the data across years revealed that time, Chilean hake aggregation depth, and temperature were the most important covariates. The changes observed in spatial distribution can be divided into two periods. During the first period (1993-2001) high values of Chilean hake abundance were found in salinities between 34 and 34.4. psu, temperatures of 8 and 11. °C, and depths between 125 and 400. m. During the second period (2002-2006) the stock increased in the southernmost area closer to the coast and were associated with low salinities (<34. psu). In this paper we discuss the spatial and temporal changes in Chilean hake abundance, their habitat preferences, and how the association between abundance and environmental variables changes during these periods of high and low abundance. © 2013 Elsevier B.V.

Quiroz J.C.,Institute Fomento Pesquero IFOP | Wiff R.,Institute Fomento Pesquero IFOP | Cubillos L.A.,University of Concepción | Barrientos M.A.,Pontifical Catholic University of Valparaíso
Fisheries Research | Year: 2011

The yellownose skate (Dipturus chilensis) is one of the most important component of the commercial elasmobranch fishery off Chile with an extensive distribution range from 36°44'S-55°13'S. Nevertheless, fishery management for this species does not extend beyond the central zone off Chile (36°44'-41°28'S), leaving the southern zone (41°28'S-55°13'S) without a proper fishing effort regulation. As a result, fishing pressure has increased dramatically in the southern zone, with unknown potential consequences for this elasmobranch population. In the absence of rigorous fishery-biological data, we used a matrix population model to assess yellownose skate demographic traits under different fishing mortality levels. A Leslie matrix model was implemented, where changes in age classes are defined in terms of of life history parameters. Uncertainty was incorporated by applying a Monte Carlo method to survival, age at maturity, and fecundity. Three scenarios were evaluated based on different assumptions about survival, fishing mortality rates, and age at 50% of vulnerability. These scenarios showed a slow growth rate for population abundance (3-15% per year) with no fishing exploitation. The population reaches equilibrium at low mortality levels (0.31yr-1), which is consistent with estimates reported for other rajidae skates. The elasticity analysis indicates that juvenile survival contributes the most to variations in the population growth rate. The sustainable mortality rate has a positive, non-linear relationship with age at 50% of vulnerability. Projections using different selectivity patterns showed that the population abundance is stable only when age-dependent fishing mortality removes individuals of older ages. We concluded that yellownose skate is extremely vulnerable to fishing exploitation and it is remarkably sensitive to juvenile and early life stages survival, implying that management actions are needed to ensure a sustainable exploitation. © 2011 Elsevier B.V.

Cerna F.,Institute Fomento Pesquero IFOP | Plaza G.,Pontifical Catholic University of Valparaíso
Bulletin of Marine Science | Year: 2014

Age, growth, maturity, and natural mortality estimates were made for chub mackerel (Scomber japonicus Houttuyn, 1782) captured off the Chilean Pacific coast. The von Bertalanffy growth parameters for combined sexes from north and central-south areas were L∞ = 36.9 cm, k = 0.22 yr -1, and t0 = -1.35 yrs, and L∞ = 40.0 cm, k = 0.23 yr-1, and t0 = -1.34 yrs, respectively. The spawning period in the northern area ranged from November to February of each year; it was restricted to January and February in the central-south area. The size at maturity (Lm50%) estimated for the north and central south areas, respectively, were 25.1 and 29.6 cm fork length (FL) in males, and 25.9 and 28.1 cm FL in females. Natural mortality was similar in the two areas: 0.45 yr-1 in the north and 0.46 yr-1 in the central-south region. Results support the existence of two stocks off Chile's southeastern coast. © 2011 Rosenstiel School of Marine and Atmospheric Science of the University of Miami.

The role of daily vertical migration (DVM) of ichthyoplanktonic associations off Punta Angamos, in northern Chile, was examined. In September 1998 and January 1999, two oceanographic surveys were conducted during coastal upwelling events. Fish larvae were collected during the day/night in three depth strata (0-20, 20-80 and 80-200 m) and inside/outside of upwelling filaments. The study area was dominated by a southward flow along 200 m depth; meanwhile, the Ekman layer did not exceed 20 m depth. The greatest accumulation of larvae was found in the middle layer (20-80 m), where the current velocity was low and did not interact with the circulation associated with upwelling the filament formation. Most fish larvae were found in non-upwelling waters in the middle stratum. Independent of the origin of water (upwelling/non-upwelling), larvae of Dioge-nichthys laternatus (Myctophidae), Engraulis ringens (Engraulidae) and Bathylagus nigrigenys (Bathylagidae) showed a deeper vertical distribution during the day, suggesting a daily vertical migration. This behavior can potentially increase retention of larvae near the coast in productive areas through vertical evasion of the Ekman layer during upwelling events.

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