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Muddy pens can negatively affect welfare and performance of feedlot beef cattle. In some regions with temperate weather, plastic greenhouse covers, above the entire pens are used to fatten cattle in a clean and dry environment. The objective of this research was to investigate effects of greenhouse roofed pens on beef cattle feedlot performance in temperate weather. Data were collected from a feedlot located in Central Mexico between 2016 and 2019. The study included 1,062 closeouts of pens with 68,305 crossbred bulls fed in pens with or without a greenhouse roof. Feeding ranged from 82 to 210 d, depending on the initial weight of cattle, which ranged from 255 to 511 kg. For each pen, average daily dry matter intake (DMI; kg of DMI·animal−1·d−1), average daily gain (ADG, kg·animal−1·d−1), and feed efficiency (G:F, ADG/DMI) were measured. Factorial analyses were performed to test the interaction and main effects of initial weight grouping (light, medium, and heavy), roof, and season as fixed effects, and year as a random effect. None of the three-way interactions were significant (P > 0.51). There was no initial weight grouping × roof interactions for DMI and ADG (P > 0.31). There was (P = 0.03) an initial weight grouping × roof interaction for G:F, as pens of all initial weight groups had greater (P < 0.01) G:F in pens with greenhouse roof than its counterpart in pens without greenhouse roof, but the advantage was greater for pens with light cattle (0.178 vs. 0.166; P < 0.01). There was no initial weight grouping × season interactions for all variables (P > 0.39). There was no roof × season interaction for DMI (P = 0.47), but there were interactions for ADG and G:F (P < 0.01). The ADG was not different (P > 0.13) during summer and autumn based on the roofing system, but pens with greenhouse roofs had greater ADG during spring (1.70 vs. 1.61) and winter (1.68 vs. 1.64; P ≤ 0.01). The G:F was greater (P < 0.01) in all seasons for pens with a greenhouse roof, with the most prominent advantage during spring (0.173 vs. 0.160). There were main effects for cattle initial weight grouping and roof for all variables (P < 0.01). Season affected DMI and G:F (P < 0.01). Pens with greenhouse roofs had decreased DMI (9.70 vs. 9.86), greater ADG (1.67 vs. 1.63), and increased G:F (0.173 vs. 0.166) compared to pens without greenhouse roofs (P < 0.01). Pens with greenhouse roofs in feedlots located in temperate regions positively affect beef cattle performance.

Se analizó el nivel hídrico (1914-2016) y las precipitaciones (1981-2016) en el Lago Titicaca para determinar patrones de variabilidad interanual, decenal y multidecenal. A las variables de nivel del lago y de precipitación, se les aplicó análisis estadísticos y la técnica de ondeletas (wavelets), encontrándose que la precipitación tiene una periodicidad anual y que el nivel del lago obedece, principalmente, a períodos decenales. El tiempo que demora (retardo) el lago para mostrar variación del nivel hídrico, por efecto de las precipitaciones, es de 2 a 3 meses. Así mismo, la data fue correlacionada con el Índice de Oscilación del Sur (IOS), la Oscilación Decenal del Pacífico (ODP) y el Índice Multivariado ENSO (EMI), determinándose que la evolución tiempo-frecuencia de los datos de nivel hídrico del lago y precipitación respecto del Índice Multivariado ENOS, muestran una asociación de fase alternada o de signo opuesto entre sí.

Se analizó la variabilidad espacio-temporal de la dieta de jurel Trachurus murphyi frente a Perú de 1977 a 2011. Un total de 21058 estómagos fueron analizados utilizando métodos bivariados y el Modelo de Árbol de Regresión Multivariado (ARM). Se utilizó como variable respuesta la composición gravimétrica de la dieta, con respecto a diferentes variables predictivas como años, profundidad de la isoterma de 15 °C, Índice de Oscilación del Sur (IOS), Índice de Oscilación Decadal del Pacífico (PDO), anomalía de la temperatura superficial del mar, zona (norte, centro y sur) y distancia de la costa. Nuestros resultados nos permitieron identificar dos escenarios diferentes, uno desde el año 1977 al 2000, donde la dieta del jurel T. murphyi estuvo fuertemente dominada por Euphausiidae, y otro escenario después del 2000, donde el jurel T. murphyi consumió mayor diversidad de presas, principalmente Euphausiidae, camaroncito rojo Pleuroncodes monodon y Zoeas. Se destaca que el primer escenario corresponde a condiciones cálidas y el segundo a condiciones frías, ambas coincidentes con los periodos multidecadales. A diferencia de estudios anteriores que muestran que la anchoveta Engraulis ringenses una presa abundante, en este estudio no fue significativamente importante. Espacialmente, los Euphausiidae dominaron la dieta en el norte-centro de Perú, mientras que al sur, la composición de las presas fue más diversa. La dieta también varió significativamente según la distancia a la costa, con mayor proporción de P. monodoncerca a la costa y con respecto a su etapas de desarrollo ontogenético., We analyzed the spatiotemporal variability of Jack mackerel Trachurus murphyi diet off Peru from 1977 to 2011. A total of 21058 stomachs were analyzed using bivariate methods and the Multivariate Regression Tree Model (MRT). The gravimetric composition of the diet was used as response variable with respect to different predictor variables such as years, depth of the 15°C isotherm, Southern Oscillation Index (SOI), Index of the Pacific Decadal Oscillation (PDO), sea surface temperature anomaly, zone (north, center and south) and distance to the coast. Our results allowed us to identify two different scenarios. From 1977 to 2000 the Jack mackerel T. murphy diet was strongly dominated by Euphausiidae, and since 2000 when T. murphyi consumed a greater diversity of prey, mainly Euphausiidae, squat lobster Pleuroncodes monodon and Zoea. It is noted that the first scenario corresponds to warm conditions and the second to cold conditions, both coincident with observed multidecadal periods. In contrast to previous studies showing that the anchovy Engraulis ringens is an abundant prey, in this study anchovy was not significantly important. Spatially, the Euphausiidae dominated the diet in central-northernPeru, while further south the prey composition was more diverse. The diet also varied significantly according to the distance from the coast (higher proportion of P. monodoncloser to the coast) and the ontogenic stages.

Coastal shellfish are being threatened by several drivers acting at multiple temporal and spatial scales, including fishing, climate, and globalization of markets. We evaluated large- scale and long-term combined effects of fishing, climate, and economic variables on 2 congeneric clams that inhabit sandy beaches of the Pacific (Mesodesma donacium) and the Atlantic (M. mac- troides) in South America. Bioeconomic and climatic variables, such as coastal sea surface temper- ature anomalies (SSTA) and broad-scale climatic indices (Pacific Decadal Oscillation and Atlantic Multidecadal Oscillation), were related to variations in clam populations in a differential way according to latitude and oceanographic features. For M. donacium, the nature and sign of the relationships between landings and explanatory predictors markedly differed between biocli- matic units. El Nino Southern Oscillation events negatively affected landings in Peru and northern Chile, whereas landings increased in southern Chile and showed a positive correlation with increasing SSTA, suggesting a positive effect at the southernmost edge of the species distribution. Long-term trends in the abundance of M. mactroides were related to fishing intensity and SSTA. As anticipated by basic economic theory, deficit of supply relative to demand, exacerbated by very low harvesting costs, pushed the price up and has driven these clam species to levels close to extinction (anthropogenic Allee effect). The lack of response of the stocks to long-term closures suggests that these systems exceeded critical thresholds (tipping points). Information on early warnings of tipping points is needed to help manage coastal shellfisheries that are increasingly threatened by long-lasting and large-scale stressors.

Jack mackerel Trachurus murphyi (JM) and chub mackerel Scomber japonicus (CM) are medium size pelagic fish predators and highly exploited resources. Here we investigated the spatiotemporal patterns of JM and CM diet composition using a large dataset of stomach samples collected from 1973 to 2013 along the Peruvian coast. In total 47,535 stomachs (18,377 CM and 29,158 JM) were analysed, of which 23,570 (12,476 CM and 11,094 JM) were non-empty. Results show that both species are opportunistic and present a trophic overlap. However, despite their smaller maximal size, CM consumed more fish than JM. Both diets presented high spatiotemporal variability. Spatially, the shelf break appears as a strong biogeographical barrier affecting prey species distribution and thus CM and JM diet. Opportunistic foragers are often considered as actual indicators of ecosystem changes; we show here that diet composition of CM and JM reveal ecosystem changes but is not always a good indicator of changes in prey biomass as prey accessibility and energy content can also play an important role. In addition we found that El Nino events have a surprisingly weak effect on stomach fullness and diet. Finally our results show that the classic paradigm of positive correlation between diversity and temperature is unlikely to occur in the Humboldt Current system where productivity seems to be the main driver. We show how energy content of forage species and the strength of the oxygen minimum zone most likely play an important role prey diversity and accessibility, and thus in fish foraging behaviour.

Se describen los escenarios ambientales y los patrones de variabilidad observados en el mar peruano a partir del análisis de información obtenida por el Instituto del Mar del Perú entre los años 1960 – 2011. Se examinan datos de cruceros de investigación oceanográfica, de evaluación de recursos pesqueros y bío-oceanográficos, además de información de diversas publicaciones sobre el mar peruano y sus recursos. Los datos de temperatura, salinidad y contenido de oxígeno, fueron interpolados para obtener promedios mensuales y construir series espaciales y temporales. En la superficie, las Aguas Costeras Frías (ACF) y Aguas Subtropicales Superficiales (ASS) crean condiciones ambientales diferentes a las de la parte subsuperficial donde predomina la intromisión de las aguas ecuatoriales a través de la Corriente Subsuperficial Perú-Chile (CSPC). En el norte, durante el verano y otoño, predominan en la capa superficial aguas cálidas de origen ecuatorial. En el centro, aguas de origen ecuatorial interactúan con las ACF del afloramiento costero. El sur está influenciado por las ASS y el afloramiento costero con mayor intensidad, indicando una mayor actividad en el Sistema de la Corriente del Perú (SCP)., Environmental scenarios and variability patterns observed in the Peruvian waters are described based on the analysis of information obtained by the Instituto del Mar del Peru between 1960 and 2011. This information includes data from oceanographic, stock assessment and bio-oceanographic scientific research surveys, published information was also used to complete this study. Sea temperature, salinity and oxygen content data was interpolated to obtain monthly averages and build temporal and spatial series. Surface Cold Coastal Waters (ACF) and Subtropical Surface Water (SSW) create environmental conditions that are different from those in the subsurface, where the intrusion of equatorial waters dominates through the Peru-Chile Subsurface Current (CSPC). In the north, during the summer and fall, there is predominance in the surface layer of waters from the equatorial system. In the central zone the equatorial waters interact with ACF from coastal upwelling. The south is more strongly influenced by the coastal upwelling and the ASS, which is an indicator of increased activity in the Current System of Peru (SCP).

Se analiza información de diversas variables ambientales de macroescala disponibles desde 1876 para el Pacífico Sudoriental y datos más recientes de desembarques y biomasas de jurel Trachurus murphyi Nichols 1920 en el mar peruano en relación con áreas probables de masas de agua equivalentes a Aguas Costeras Frías (ACF) y Aguas Subtropicales Superficiales (ASS). Se concluye que el Índice de Oscilación Decadal del Pacífico (PDO) presenta expresiones de variabilidad coherentes con las encontradas para el Índice de Oscilación del Sur (SOI) y que los cambios observados en las biomasas de T. murphyien el mar peruano reflejan cambios en la disponibilidad del recurso asociado a patrones de variabilidad seculares (SOI) y decadales (PDO). Tales fluctuaciones en la disponibilidad del recurso afectan las pesquerías de Ecuador, Perú y norte de Chile, las que muestran variaciones importantes en sus desembarques y habrían dado una imagen sesgada de la abundancia conduciendo a diagnósticos errados de la real situación del recurso. Estos patrones de variabilidad afectarían también las manifestaciones de El Niño, haciendo que se inicien en otoños o primaveras australes dependiendo de si el PDO imperante es negativo o positivo. Por otro lado, en función a la distancia euclidiana de las varianzas del SOI se identifican periodos de alta (1876 – 1925 y 1976 – 2012) y baja (1926 – 1975) variabilidad; y con el PDO se diferencian periodos cálidos (1925 – 1944 y 1975 – 1994), frio (1945 – 1974) y templados o interfaces (1895 – 1924 y 1995 – 2012), siendo estos últimos producto de la interacción con los momentos de alta variabilidad., This paper analyses information on various macro environmental variables available since 1876 for the Southeast Pacific and more recent data on Jack mackerel Trachurus murphyi (Nichols, 1920) landings and biomass in the Peruvian sea, relating them to probable areas of water masses equivalent to Cold Coastal Waters (CCW) and Subtropical Surface Waters (SSW). It is concluded that the index of the Pacific Decadal Oscillation (PDO) presents expressions of variability that are consistent with those found for the Southern Oscillation Index (SOI) and that the detected changes in biomass of Jack mackerel T. murphyiin the Peruvian sea reflect changes in the availability of the fish stock associated with secular (SOI) and decadal (PDO) variability patterns. These fluctuations in stock availability impact fisheries in Ecuador, Peru and northern Chile, which show significant variations in their landings and would have given a biased picture of the state of abundance, leading to wrong diagnoses of the real situation of the exploited stocks. These patterns of variability would also affect the appearance of El Niño, making them start in the southern hemisphere autumn or spring depending on whether the current PDO is positive or negative. Periods of high (1876 – 1925 and 1976 – 2012) and low (1926 – 1975) variability are also identified in relation to the Euclidean distance of the variances of the SOI; and in relation to the PDO a distinction is made between warm (1925 – 1944 and 1975 – 1994), cold (1945 – 1974) and tempered or interface periods (1895 – 1924 and 1995 – 2012), the latter being explained by the interaction between periods of high variability.

El Pacifico suroriental es una de las areas mas productivas del planeta debido a su intensa dinamica de circulacion oceanica cuya manifestacion mas importante, desde el punto de vista oceanografico y biologico, la constituye los afloramientos costeros que generan una elevada produccion primaria y secundaria que sustentan importantes poblaciones de peces que son la base de la economia pesquera de la region. Sin embargo, en esta region la normalidad es la variabilidad, que responde a patrones reguladores de macroescala como los estacionales, interanuales, periodicos y seculares, como procesos de corto, mediano, largo y muy largo plazo. En estos escenarios ambientales aparecen como factores o manifestaciones de variabilidad el ENOS (El Nino Oscilacion del Sur), la ODP (Oscilacion Decadal del Pacifico) y la VSP (Variabilidad Secular del Pacifico) como los mas conspicuos. Tanto la temporalidad como los factores de variabilidad afectan el ecosistema y, dentro de este a los recursos y sus pesquerias. Estos cambios estan referidos al tiempo, espacio, poblaciones y pesquerias. Es decir, los procesos de dinamica poblacional de los recursos, como reclutamiento, crecimiento y mortalidad natural y por pesca, estan siendo afectados permanentemente, a intensidades y frecuencias escalares diferentes. Esta situacion estaria induciendo respuestas dinamicas de las poblaciones que a su vez generan estados poblacionales frente a cada uno de los momentos o escenarios ambientales imperantes. El trabajo presenta un analisis de los patrones normativos y factores de variabilidad usando variables ambientales, biologicas y pesqueras y se identifican escenarios que explicarian los cambios de las poblaciones y sus pesquerias facilitando la adopcion de medidas de gestion aplicables a cada estado ambiental. Esto permitira la planificacion de las pesquerias para prevenir colapsos socioeconomicos y financieros, asi como obtener los maximos beneficios en los diferentes momentos ambientales.

Se presenta una reseña de los efectos del fenómeno "El Niño 1997-98" en los recursos pesqueros del ecosistema de afloramiento peruano, dando especial énfasis a los cambios en los patrones de distribución y abundancia de los recursos anchoveta, sardina y merluza; ya los cambios en la autoecología de los mismos recursos. Finalmente, se comenta sobre las similitudes y diferencias de los efectos de este fenómeno con otros eventos de la misma naturaleza., It is presented a review of "El Niño 1997-98" effects on fishery resources of Peruvian upwelling ecosystem, given emphasis to the changes in distribution and abundance patterns of anchovy, sardine, and Peruvian hake; and autecology changes of the same resources. Finally, it is analyzed similarities and differences of this phenomenon effect with other events of the same nature.

The Humboldt Current ecosystem off western South America is a typical eastern boundary current upwelling system which is characterized by high levels of organic production. It is dominated by four pelagic schooling fish species: anchovy (Engraulis ringens), sardine (Sardinops sagax sagax), horse mackerel (Trachurus murphyi) and mackerel (Scomber japonicus peruanus). The Peruvian anchovy fishery has been analysed from an ecosystem perspective in two books (Pauly and Tsukayama, 1987; Pauly et ah, 1989). Effects of physical and biological changes on the biomass yield of pelagic fish in the Humboldt Current were described by Alheit and Bernal (1993). A characteristic feature of the Humboldt Current ecosystem is the drastic short-term perturbations caused by the ‘El Nino-Southern Oscillation’ (ENSO). The nature and consequences of ENSO events have been described in numerous articles (for key references see Arntz and Tarazona, 1989).