Estandarización de la CPUE de la flota industrial de cerco del stock norte - centro de anchoveta peruana (Engraulis ringens Jenyns 1842) entre 1996 y el 2008

La pesquería de la anchoveta peruana (Engraulis ringens), considerada como la pesquería monoespecífica más grande del mundo, genera beneficios sociales y económicos de gran relevancia para el Perú. Por esto, es especialmente importante implementar un adecuado manejo de esta pesquería. En este sentido, es muy útil contar con indicadores de biomasa que permitan tener una idea del estado del stock. La CPUE (captura por unidad de esfuerzo), es considerada como un índice relativo de la biomasa en una unidad de tiempo porque la teoría asume que la CPUE y la biomasa son directamente proporcionales, sin embargo, en la práctica esta proporcionalidad casi nunca se cumple. Las razones que intentan explicar la no proporcionalidad van desde la influencia de factores relacionados a los pescadores (como las características de las embarcaciones), hasta factores relacionados a la distribución de los peces. Se asume que una manera de remover tales efectos es por medio de la estandarización. La metodología en el presente trabajo para estandarizar la CPUE se baso en la teoría de los Modelos Lineales Generalizados (GLM) con el cual se trata de reproducir los valores observados en función a una serie de variables explicativas; para este propósito también se utilizaron los Modelos Aditivos Generalizados (GAM) para observar el comportamiento de las variables. La medida a estandarizar fue la captura por duración de viaje, y las variables explicativas fueron el año, mes, capacidad de bodega, latitud, inercia espacial y distancia a la costa. La fuente de información para este proceso provino del Programa Bitácoras de Pesca (PBP) desarrollado en el IMARPE. El modelo obtenido explicó el 48.5% de la variabilidad del CPUE observado, lo cual es un resultado satisfactorio proviniendo de datos de la pesquería; siendo la variable con mayor influencia en el modelo la capacidad de bodega (49%), debido posiblemente a que la flota de anchoveta posee una capacidad elevada de captura y que los recursos pelágicos tienden a hiper-agregarse incluso cuando están siendo fuertemente explotados. A su vez las correlaciones obtenidas entre la CPUE estandarizada y datos de biomasa (0.55) nos indican que el GLM es un buen método para obtener series estandarizadas de CPUE.The Peruvian anchovy (Engraulis ringens) fishery, considered the biggest monospecific fishery in the world, produces very relevant social and economic benefits for Peru. Therefore, it is especially important to implement an adequate management of this fishery. In that sense, it is very useful to count with biomass indicators that provide an idea of the stock state. The CPUE (catch by unit effort) is considered a biomass relative index in a unit of time since theory assumes that the CPUE and the biomass are directly proportional; however, in the practice, this proportionality is hardly ever accomplished. The reasons that try to explain the no proportionality goes from the influence of the factors related to the fishermen (as the characteristics of the boats) to the influence of the factors related to fish distribution. It is assumed that one way to remove those effects is through the standardization. The methodology to standardize the CPUE used in the present study was based in the theory of the Generalized Linear Models (GLM) with reproduces the observed values in function of a series of explicative variables. For this purpose, the Generalized Linear Models (GLM) was also used to observe the performance of the variables. The measure to standardise was catch per journey length and the explicative variables were year, month, storage capacity, latitude, spatial inertia and distance to coastline. The information source for this process came from a Programme developed by the IMARPE: Programa Bitácoras de Pesca (PBP) (Programme of Fishery Logbooks). The obtained model explained the 48.5% of the observed CPUE variability, which is a satisfactory result since it came from fishery data; being the storage capacity the variable which influenced the most (49%) in the model, probably due to the elevated capture capacity of the anchovy fleet and the hyper - aggregation of the pelagic sources which occurs even when they are been highly exploited. Besides, the correlations obtained in the standardized CPUE and the biomass data (0.55) indicate that the GLM is a good method to obtain CPUE standardized series.Tesi

Oxygen Variability During ENSO in the Tropical South Eastern Pacific

The Oxygen Minimum Zone (OMZ) of the Tropical South Eastern Pacific (TSEP) is one of the most intensely deoxygenated water masses of the global ocean. It is strongly affected at interannual time scales by El Niño (EN) and La Niña (LN) due to its proximity to the equatorial Pacific. In this work, the physical and biogeochemical processes associated with the subsurface oxygen variability during EN and LN in the period 1958–2008 were studied using a regional coupled physical-biogeochemical model and in situ observations. The passage of intense remotely forced coastal trapped waves caused a strong deepening (shoaling) of the OMZ upper limit during EN (LN). A close correlation between the OMZ upper limit and thermocline depths was found close to the coast, highlighting the role of physical processes. The subsurface waters over the shelf and slope off central Peru had different origins depending on ENSO conditions. Offshore of the upwelling region (near 88°W), negative and positive oxygen subsurface anomalies were caused by Equatorial zonal circulation changes during LN and EN, respectively. The altered properties were then transported to the shelf and slope (above 200 m) by the Peru-Chile undercurrent. The source of nearshore oxygenated waters was located at 3°S−4°S during neutral periods, further north (1°S−1°N) during EN and further south (4°S−5°S) during LN. The offshore deeper (<200–300 m) OMZ was ventilated by waters originating from ~8°S during EN and LN. Enhanced mesoscale variability during EN also impacted OMZ ventilation through horizontal and vertical eddy fluxes. The vertical eddy flux decreased due to the reduced vertical gradient of oxygen in the surface layer, whereas horizontal eddy fluxes injected more oxygen into the OMZ through its meridional boundaries. In subsurface layers, remineralization of organic matter, the main biogeochemical sink of oxygen, was higher during EN than during LN due to oxygenation of the surface layer. Sensitivity experiments highlighted the larger impact of equatorial remote forcing with respect to local wind forcing during EN and LN

Toxicity of fipronil insecticide on the early life stages of Colossoma macropomum (gamitana)

The present study was aimed to determine the lethality of the insecticide fipronil on two early life stages, post-larvae, and fingerling, of Colossoma macropomum, by determining the lethal concentration 50 (LC50). Five nominal concentrations (0.12; 0.165; 0.21; 0.255 and 0.30 mg/L) and a control in 4 replicates per treatment for 48 hours of exposure were used for the post-larvae; and other nominal concentrations (0.22; 0.27; 0.34; 0.43 and 0.54 mg/L) and a control in 3 replicates per treatment for 96 hours of exposure were used for the fingerling stage. The LC50 value was calculated as 0.22 mg/L and 0.33 mg/L for the post-larvae and fingerling stages, respectively. In addition, the maximum concentration that causes no mortality (MCNM) and the minimum concentration that causes mortality (MCM) for the post-larvae stage were determined as 0.12 and 0.15 mg/L, respectively; and 0.16 and 0.22 mg/L for the fingerling stage, respectively. C. macropomum showed erratic swimming, spasms in the region of the peduncle, caudal fin, and accelerated opercular movement in both life stages. The LC50 values calculated in the present study are considered “highly toxic” for the early stages of life of this non-target organism, suggesting that C. macropomum may be a sensitive species to fipronil insecticide.Campus Lima Centr

Variabilité interannuelle et décadale de la productivité et de la zone de minimum d’oxygène dans le système d´upwelling du Pérou

The Peruvian upwelling system is one of the most productive regions of the world ocean and has a minimum oxygen zone (ZMO) in the sub-surface layers. This system is impacted by the El Niño (EN) and La Niña (LN) interannual climate events. We first study the impact of EN and LN events on primary productivity and dissolved oxygen, then the trends over the last decades. A coupled physics biogeochemical regional model, validated with observations, is used to study the hydrodynamic processes and biogeochemical cycles from 1958 to 2008. The model is able to realistically reproduce oceanic conditions during EN and LN phases, as well as trends observed in recent decades. During EN, chlorophyll decreases due to the deepening of the rich layers forced by the coastal waves and the limitation by the light in summer. The surface layer becomes more ventilated as the oxycline deepens. The source waters of the OMZ come from a more ventilated equatorial region. In recent decades, the productivity increase in summer and the progressive deoxygenation of subsurface waters are mainly due to equatorial variability, while local winds seem to play a minor role.Le système d’upwelling péruvien est l’une des régions les plus productives de l’océan mondial et présente une zone de minimum d'oxygène (ZMO) dans les couches sub-superficielles. Ce système est impacté par les phénomènes climatiques interannuels El Niño (EN) et La Niña (LN). Nous étudions d’abord l’impact des événements EN et LN sur la productivité primaire et l’oxygène dissous, puis les tendances au cours des dernières décennies. Un modèle régional couplé physique-biogéochimique, validé avec des observations, est utilisé pour étudier les processus hydrodynamique et les cycles biogéochimiques de 1958 à 2008. Le modèle est capable de reproduire avec réalisme les conditions océaniques pendant les phases EN et LN, ainsi que les tendances observées au cours des dernières décennies. Au cours de EN, la chlorophylle diminue en raison de l'approfondissement des couches riches forcé par les ondes côtières et de la limitation par la lumière en été. La couche de surface devient plus ventilée à mesure que l'oxycline s'approfondit. Les eaux sources de la ZMO proviennent d'une région équatoriale plus ventilée. Au cours des dernières décennies, l'augmentation de la biomasse phytoplanctonique en été et la progressive désoxygénation de subsurface sont principalement dues à la variabilité équatoriale, alors que les vents locaux semblent jouer un rôle mineur

Spatiotemporal variability and drivers of modeled primary production rates in the Northern Humboldt Current System

International audienc

Forcings and Evolution of the 2017 Coastal El Niño Off Northern Peru and Ecuador

International audienceEl Niño events, in particular the eastern Pacific type, have a tremendous impact on the marine ecosystem and climate conditions in the eastern South Pacific. During such events, the accumulation of anomalously warm waters along the coast favors intense rainfall. The upwelling of nutrient-replete waters is stopped and the marine ecosystem is strongly impacted. These events are generally associated with positive surface temperature anomalies in the central and eastern equatorial Pacific. During austral summer 2017, a strong surface temperature anomaly reaching ∼3-4 • C off Northern Peru and Ecuador led to intense coastal precipitations. However, neutral temperature anomalies were recorded in the equatorial Pacific. Using in situ measurements, satellite observations, and simulations from an eddy-resolving regional ocean circulation model, we investigated the physical processes triggering this peculiar 'coastal El Niño.' Its impact on the regional ocean circulation and heat budget off northern Peru and Ecuador was assessed. Using model sensitivity experiments, we investigated the respective roles of the equatorial Kelvin waves and local wind anomalies in driving the anomalously high nearshore sea surface temperature (SST). The atmospheric teleconnections which triggered the event were investigated using reanalysis data