Impact on Growth and Feed Availability from Including Jack Mackerel (Trachurus japonicas) Meal in Rockfish (Sebastes schlegeli) Feeds Which Otherwise Replace Fish Meal with Chicken By-Product Meal.

This study was conducted to elucidate the impact on the growth and feed availability of rockfish (Sebastes schlegeli) from including jack mackerel meal (JMM) in feeds which otherwise substitute 20% fish meal (FM) with chicken by-product meal (CBM). Six formulated feeds were designed to be isonitrogenous and isolipidic. Specifically, 55% FM was included in the control (Con) diet. In the Con diet, 20% FM was substituted by CBM, and then the graded levels (0, 20, 40, 60, and 80%) of JMM were included instead of FM, named as the C20J0, C20J20, C20J40, C20J60, and C20J80 diets, respectively. Five hundred and forty juvenile rockfish (initial weight of 11.2 g) were assigned to 18 tanks. All experimental feeds were fed to triplicate groups of rockfish twice daily for 8 weeks. Superior weight gain, specific growth rate (SGR), and feed intake of rockfish fed the C20J60 and C20J80 diets compared to rockfish fed the Con and C20J0 diets were observed. However, the feed utilization, biological indices, proximate composition, amino acid profiles, and blood chemistry of the rockfish were not affected by the dietary treatments. The slightly but not significantly higher economic profit index and growth performance were obtained in the C20J60 diet compared to the C20J80 diet. In conclusion, the C20J60 diet was the most recommendable treatment based on the improvement in growth performance (weight gain and SGR) and feed intake of rockfish, and the highest economic return to farmers.

Effects of Dietary Inclusion of a Crude Protein Source Exhibiting the Strongest Attractiveness to Red Sea Bream (Pagrus major) on Growth, Feed Availability, and Economic Efficiency.

Dietary incorporation of an attractive feed protein source is a practical method of enhancing feed intake and consequently improving the growth of fish. The attractiveness of 18 crude protein sources to juvenile red sea bream (Pagrus major) and the effects of the dietary inclusion of the crude protein source that exhibited the strongest attractiveness on growth, feed availability, and economic efficiency were determined. Jack mackerel meal (JMM) showed the strongest attractiveness to red sea bream among 18 crude protein ingredients. In an 8-week feeding trial, 810 juveniles were randomly distributed into 27 tanks (30 fish/tank). Nine experimental diets were prepared. The control (Con) diet included 60% fish meal (FM). Various levels (1, 3, 5, 10, 20, 40, 60, and 100%) of JMM were included at the expense of FM in the Con diet, and the resulting diets were named the JMM1, JMM3, JMM5, JMM10, JMM20, JMM40, JMM60, and JMM100 diets, respectively. Fish were hand-fed to apparent satiation twice daily for 8 weeks. The weight gain, specific growth rate, and feed consumption of red sea bream that were fed the JMM40, JMM60, and JMM100 diets were significantly (p < 0.0001 for all) higher than those of the fish fed all other diets. However, dietary JMM inclusion had no remarkable impacts on the feed utilization, biological indices, and chemical composition of the whole body of red sea bream. In terms of the economic view of the study, the economic profit index of red sea bream fed the JMM40, JMM60, and JMM100 diets was significantly (p < 0.0001) greater than that of the fish fed all other diets. In conclusion, the strongest attractiveness to red sea bream among 18 crude protein sources was observed in JMM. The inclusion of more than 40% JMM at the expense of FM in the diet of red sea bream is highly recommended for practical feed formulations to induce remarkable improvement in the growth performance of fish and the economic returns for farmers.

A mixed-species shoal including fewer heterospecifics is preferred by jack mackerel Trachurus japonicus juveniles.

Mixed-species shoals of fishes were reported from various environments such as coral reefs and temperate lakes. The driving mechanism of forming mixed-species shoal can be either haphazard or a preferential choice by an individual. Here, we tested if jack mackerel Trachurus japonicus, a temperate marine pelagic fish, could choose a shoal composition using vision based on a choice experiment. Shoal preference of jack mackerel juveniles was evaluated by presenting shoals comprising one to four heterospecifics (half-lined cardinal Ostorhinchus semilineatus) out of four shoal members to the focal fish. When both conspecific and heterospecific shoals were presented to a single jack mackerel, the focal fish showed a preference for the conspecific rather than heterospecific shoal, indicating that they can choose a conspecific shoal based on the visual information. However, when a focal fish encountered both conspecific and mixed-species shoals including fewer heterospecifics (one out of four individuals), the latter was preferred. The result implies that jack mackerel can judge a preferable composition of shoal using visual information. The inclusion of fewer heterospecifics may be exploiting oddity effects, whereby minority species are exposed to relatively high vulnerability to predators, as well as resulting in reduced competition for food while maintaining predator vigilance in a shoal.

Analysis of the Persistence and Particle Size Distributional Shift of Sperm-Derived Environmental DNA to Monitor Jack Mackerel Spawning Activity.

Environmental DNA (eDNA) analysis holds great promise as an efficient and noninvasive method to monitor not only the distribution of organisms but also their spawning activity. In eDNA analysis-based monitoring of spawning activity, the detection of sperm-derived eDNA is a key point; however, its characteristics and dynamics are completely unknown. The present study focuses on the persistence and particle size distribution (PSD) of eDNA derived from the sperm of Japanese jack mackerel. First, we investigated the time-dependent degradation and the PSD of sperm-derived eDNA by artificially adding sperm to seawater. Next, we kept fish in tanks and examined the changes in eDNA concentration and PSD before and after spawning. The results of two experiments showed that the degradation of sperm-derived eDNA proceeded rapidly, with PSD shifting to a smaller size regardless of the DNA region (Cyt b or ITS1). Additionally, it was shown that the nuclei and mitochondria released from sperm through degradation had a size distribution that was not simply dependent on each organelle size. These results will contribute to elucidating the characteristics and dynamics of eDNA specifically during the spawning season and to further developing eDNA analysis as a powerful tool for the monitoring of spawning activity.

Fish allergy tolerance 16 months after diagnosis.

Fish allergy is generally thought to be persistent, and approximately 80% of patients with fish allergies do not develop tolerance even 10 years after diagnosis. There have been no reports of rapid tolerance development in patients with severe fish allergies. We report the development of tolerance 16 months after the diagnosis of fish allergies. A 13-month-old boy was diagnosed with rosefish allergy (Sebastes matsubarae) and Japanese jack mackerel allergy (Trachurus japonicus). To find out which species of fish he could consume safely, he underwent several oral food challenge (OFC) tests. It was determined that he could consume tuna, salmon, cod, sardine, chub mackerel (Scomber japonicus), and Japanese amberjack (Seriola quinqueradiata) without eliciting signs of allergy. He continued to eat the fish that did not produce allergic reactions three to four times a week. The titer of serum allergen-specific immunoglobulin E (IgE) to fish had decreased in a subsequent ImmunoCAP®-specific IgE blood test performed 16 months after the diagnosis of the rosefish allergy. Following this test result, he underwent OFCs with rosefish and Japanese jack mackerel, both of which turned out to be negative, and it was determined that he had developed tolerance to fish. In this case, the repeated OFCs were useful in identifying fish species that were safe for consumption. In addition, the decrease in allergen-specific IgE was useful in predicting the development of tolerance. We hypothesize that proactive consumption of available fish species may lead to this rapid induction of tolerance to fish allergens.

Fish allergy tolerance 16 months after diagnosis

Fish allergy is generally thought to be persistent, and approximately 80% of patients with fish allergies do not develop tolerance even 10 years after diagnosis. There have been no reports of rapid tolerance development in patients with severe fish allergies. We report the development of tolerance 16 months after the diagnosis of fish allergies. A 13-month-old boy was diagnosed with rosefish allergy (Sebastes matsubarae) and Japanese jack mackerel allergy (Trachurus japonicus). To find out which species of fish he could consume safely, he underwent several oral food challenge (OFC) tests. It was determined that he could consume tuna, salmon, cod, sardine, chub mackerel (Scomber japonicus), and Japanese amberjack (Seriola quinqueradiata) without eliciting signs of allergy. He continued to eat the fish that did not produce allergic reactions three to four times a week. The titer of serum allergen-specific immunoglobulin E (IgE) to fish had decreased in a subsequent ImmunoCAP®-specific IgE blood test performed 16 months after the diagnosis of the rosefish allergy. Following this test result, he underwent OFCs with rosefish and Japanese jack mackerel, both of which turned out to be negative, and it was determined that he had developed tolerance to fish. In this case, the repeated OFCs were useful in identifying fish species that were safe for consumption. In addition, the decrease in allergen-specific IgE was useful in predicting the development of tolerance. We hypothesize that proactive consumption of available fish species may lead to this rapid induction of tolerance to fish allergens (AU)

The growth and age structure of Chilean jack mackerel (Trachurus murphyi) following its influx to New Zealand waters.

The Chilean jack mackerel (Trachurus murphyi) is a predominantly Southeast Pacific Ocean species. It is relatively difficult to determine its age, and multiple studies of its growth off South America have produced markedly different sets of von Bertalanffy parameters. T. murphyi was first identified from New Zealand waters in the mid-1980s and has comprised part of the commercial landings of Trachurus species (along with Trachurus declivis and Trachurus novaezelandiae) since then. Results from 13 years of age determination of New Zealand samples using sectioned otoliths indicate that a partially validated age determination method has been developed, with a precision level (average percentage error) of 4.6%. The best available von Bertalanffy growth parameters for the New Zealand population (sexes combined) are as follows: L∞ , 51.9 cm fork length; K, 0.223 per year; t0 , -0.5 year. Analyses by sex showed that males have a significantly larger L∞ than females. Estimated annual catch-at-length and catch-at-age distributions from the fishery are presented for 2007-2019. There have been at least two episodes of immigration of T. murphyi from international waters, but little evidence of spawning success to maintain the New Zealand population.

Estimating fish population abundance by integrating quantitative data on environmental DNA and hydrodynamic modelling.

Molecular analysis of DNA left in the environment, known as environmental DNA (eDNA), has proven to be a powerful and cost-effective approach to infer occurrence of species. Nonetheless, relating measurements of eDNA concentration to population abundance remains difficult because detailed knowledge on the processes that govern spatial and temporal distribution of eDNA should be integrated to reconstruct the underlying distribution and abundance of a target species. In this study, we propose a general framework of abundance estimation for aquatic systems on the basis of spatially replicated measurements of eDNA. The proposed method explicitly accounts for production, transport and degradation of eDNA by utilizing numerical hydrodynamic models that can simulate the distribution of eDNA concentrations within an aquatic area. It turns out that, under certain assumptions, population abundance can be estimated via a Bayesian inference of a generalized linear model. Application to a Japanese jack mackerel (Trachurus japonicus) population in Maizuru Bay revealed that the proposed method gives an estimate of population abundance comparable to that of a quantitative echo sounder method. Furthermore, the method successfully identified a source of exogenous input of eDNA (a fish market), which may render a quantitative application of eDNA difficult to interpret unless its effect is taken into account. These findings indicate the ability of eDNA to reliably reflect population abundance of aquatic macroorganisms; when the "ecology of eDNA" is adequately accounted for, population abundance can be quantified on the basis of measurements of eDNA concentration.

Selective collection of long fragments of environmental DNA using larger pore size filter.

Environmental DNA (eDNA) can exist in water with various sizes and states. Among them, relative to extra-cellular DNA, intra-cellular DNA such as cell and tissue fragments can mainly be detected at larger size fractions, and may be protected from enzymatic DNA degradation processes. Here, we verified the hypothesis that the selective collection of such large-sized eDNA enhances the efficiency of capturing less-degraded eDNA, based on a tank experiment using Japanese Jack Mackerel (Trachurus japonicus) as a model species. We concentrated different volumes of rearing water using the filters with different pore sizes (0.7 µm and 2.7 µm), and quantified the copy number of short and long mitochondrial and short nuclear DNA fragments of target species in water samples. As a result, the ratio of long to short eDNA concentrations was higher in the larger pore size filter, which would support our stated hypothesis. In addition, the ratio of nuclear to mitochondrial eDNA was lower in the larger pore size filter. These results imply a difference in the persistence of nuclear and mitochondrial DNA between intra- and extra-cellular environments. Moreover, larger filter pore size did not necessarily decrease the yields of eDNA, and there was little difference in yields in smaller filtration volumes. The findings of this study indicate the potential to select information from eDNA signals by focusing on eDNA of specific size and state, which may contribute to efficient utilization of the information on species taxonomy and physiology in water samples.

Ontogenic and seasonal variations of metal content in a small pelagic fish (Trachurus picturatus) in northwestern African waters.

Marine organisms are exposed to great changes induced by human beings due, among others, to discharges into the oceans, increasing marine pollution. For this study, 294 specimens of Trachurus picturatus from the Canary Islands were analyzed during a period of 2 years. The concentration of 11 anthropic metals and trace elements was determined in each individual using the Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) technique. Statistical analyses were carried out considering the following factors: oceanographic season, maturity of the gonads, size of the specimens, season. Immature specimens had higher concentration in more metals than the mature specimens. This fact may be due to the fact that these specimens require a much higher metabolic rate due to their growth and do not detoxify like mature specimens.

Effect of water temperature and fish biomass on environmental DNA shedding, degradation, and size distribution.

Environmental DNA (eDNA) analysis has successfully detected organisms in various aquatic environments. However, there is little basic information on eDNA, including the eDNA shedding and degradation processes. This study focused on water temperature and fish biomass and showed that eDNA shedding, degradation, and size distribution varied depending on water temperature and fish biomass. The tank experiments consisted of four temperature levels and three fish biomass levels. The total eDNA and size-fractioned eDNA from Japanese Jack Mackerels (Trachurus japonicus) were quantified before and after removing the fish. The results showed that the eDNA shedding rate increased at higher water temperature and larger fish biomass, and the eDNA decay rate also increased at higher temperature and fish biomass. In addition, the small-sized eDNA fractions were proportionally larger at higher temperatures, and these proportions varied among fish biomass. After removing the fish from the tanks, the percentage of eDNA temporally decreased when the eDNA size fraction was >10 µm, while the smaller size fractions increased. These results have the potential to make the use of eDNA analysis more widespread in the future.

Rapid degradation of longer DNA fragments enables the improved estimation of distribution and biomass using environmental DNA.

The advent of environmental DNA (eDNA) analysis methods has enabled rapid and wide-range ecological monitoring in aquatic ecosystems, but there is a dearth of information on eDNA degradation. The results of previous studies suggest that the decay rate of eDNA varies depending on the length of DNA fragments. To examine this hypothesis, we compared temporal change in copy number of long eDNA fragments (719 bp) with that of short eDNA fragments (127 bp). First, we isolated rearing water from a target fish species, Japanese Jack Mackerel (Trachurus japonicus), and then quantified the copy number of the long and short eDNA fragments in 1 L water samples after isolating the water from the fish. Long DNA fragments showed a higher decay rate than short fragments. Next, we measured the eDNA copy numbers of long and short DNA fragments using field samples, and compared them with fish biomass as measured by echo intensity. Although a previous study suggested that short eDNA fragments could be overestimated because of nontarget eDNA from a nearby fish market and carcasses, the eDNA concentrations of long fragments were correlated with echo intensity. This suggests that the concentration of longer eDNA fragments reflects fish biomass more accurately than the previous study by removing the effects of the fish market and carcasses. The length-related differences in eDNA have a substantial potential to improve estimation of species biomass.

El jurel Trachurus murphyi y las variables ambientales de macroescala

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. murphyi en 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. murphyi in 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

Aspectos reproductivos del jurel Trachurus murphyi

Se analiza y discute la serie temporal del Índice Gonadosomático (IGS) y la talla de primera madurez del jurel Trachurus murphyi Nichols 1920 en el Perú calculada mensualmente entre los años 1967 - 2012. Sobre la base de estos análisis se determinó la variación anual e interanual del ciclo reproductivo, además se demostró que frente a la costa del Perú T. murphyi tiene un solo periodo de desove relativamente amplio y que ocurre con un máximo en el mes de noviembre de cada año. Asimismo, se evidenció que durante más de cuatro décadas T. murphyi ha desovado regularmente cada año en el mar peruano. La actividad reproductiva del T. murphyi tiene una mayo variabilidad en el Perú y el periodo de desove tiene picos de menor magnitud pero de mayor amplitud con respecto al desove que ocurre frente a la costa de Chile. El análisis de las tallas de primera madurez no presentó cambios significativos a lo largo de toda la serie en el mar peruano.

The time series of monthly gonadosomatic index (GSI) and biannual size at first maturity of Jack mackerel Trachurus murphyi Nichols 1920 in Peru between 1967 and 2012 is analyzed and discussed. The annual and interannual variation of the reproductive cycle was determined. It is shown that in Peru T. murphyi has a single relatively extended spawning period with a maximum in November each year. It is also shown that for more than four decades T. murphyi has spawned regularly every year in Peruvian waters. The reproductive activity of T. murphyi has a greater variability off Peru and the spawning period has peaks of lesser magnitude but extend longer than observed in the spawning occurring off Chile. The analyses of the sizes at first maturity of Jack mackerel in Peruvian waters did not show significant changes throughout the entire period observed.

Escala de madurez gonadal del jurel Trachurus murphyi Nichols 1920

El presente trabajo describe la escala de madurez gonadal macroscópica del jurel Trachurus murphyi Nichols 1920, validada con estudios microscópicos y en uso en Perú. La escala consta de seis estadios de maduración para hembras y machos, que van desde el estadio 0 (virginal) al estadio V (recuperación en hembras, posexpulsante en machos). Para el estudio, se contó con 350 ejemplares provenientes del plan de seguimiento de la pesquería pelágica y de cruceros de evaluación de recursos pelágicos; dichos ejemplares fueron colectados desde el 2006 al 2009. La escala cataloga a los individuos virginales en el denominado estadio 0, lo cual permite la separación práctica entre juveniles (estadio 0) y adultos (estadios I a V). Se discute las bondades de la escala validada para el jurel T. murphyi, la cual se compara con otras escalas de madurez propuestas para especies de la misma familia. El análisis de las características microscópicas de los ovarios confirman la tipificación de desove parcial ya descrita por otros autores.

This paper describes the macroscopic scale of gonad maturity stages of Jack mackerel Trachurus murphy Nichols 1920, validated by microscopic studies, and being used in Peru,. A scale of six maturity stages are identified for females and males, ranging from stage 0 (virgin) to stage V (recovery in females, post-spermiation in males). The gonads of 350 specimens were analyzed. These specimens were collected as part of a pelagic fishery monitoring programme and during pelagic stock assessment surveys between 2006 and 2009. Virgin individuals are classified as stage 0 (virgin), which draws the distinction between (non-reproductive) juveniles and (reproductive) adults in stages I to V. The advantages of using the validated stages of gonad development of Jack mackerel T. murphyi are discussed and are compared to other scales of maturity stages proposed for other species in the same family. The analysis of the microscopic characteristics of the ovaries confirms that Jack mackerel is a batch spawner, which has already been described by other authors.

Edad y crecimiento del jurel Trachurus murphyi en el Perú

Se determinó la edad y se estimó el crecimiento del jurel Trachurus murphyi Nichols 1920, mediante la lectura y medición de anillos anuales de crecimiento en 977 pares de otolitos de especímenes entre 3 y 71 cm de longitud total colectados dentro del dominio marítimo peruano durante el año 1978 y parte de 1977 y 1979. Se comprobó la validez de las marcas anuales en 50 otolitos con 5 marcas o zonas anuales, y también con el análisis del incremento marginal mensual en 240 otolitos de especímenes entre 35 y 39 cm obtenidos entre julio 1977 y junio 1979. A partir de las medidas de los anillos anuales y sus respectivas tallas retrocalculadas se estimaron los parámetros de crecimiento en longitud y peso de la ecuación de von Bertalanffy: longitud infinita (L∞) =80.77 cm, peso infinito (W∞) = 3744.10 g, coeficiente de crecimiento (k) = 0.155 y edad teórica a la longitud 0 (t0) = -0.356. Se discuten las diferencias y semejanzas con las curvas y parámetros de crecimiento calculados por otros autores, haciendo énfasis en aquéllos cuyos resultados contribuyen a validar los estimados en el presente trabajo. Según los parámetros estimados, el T. murphyi peruano tendría una velocidad de crecimiento mayor que el T. murphyi de más al sur

The age and growth of Jack mackerel Trachurus murphyi Nichols 1920 was determined by the reading and measuring annual growth rings from 977 pairs of otoliths from specimens between 3 and 71 cm total length collected within the Peruvian maritime domain during 1978 and part of 1977 and 1979. The validity of the annual marks was confirmed with 50 otolith with 5 marks or annual zones, and also with the analysis of the monthly marginal increment in 240 otoliths of specimens between 35 and 39 cm obtained from July 1977 to June 1979. From the annual rings measurements and their respective retroestimated sizes, the following parameters of the von Bertalanfy ecuation for growth in length and weight were estimated: infinite length (L∞) = 80.77 cm, infinite weight (W∞) = 3744.10 g, growth coefficient (k) = 0.155, and theoretical age at length 0 (t0) = -0.356. The estimated parameters suggest that the Peruvian T. murphyi has a faster growth rate than the more southern T. murphyi

Estimación del crecimiento del jurel Trachurus murphyi capturado en el Perú, a partir del análisis de las frecuencias por tallas

Se presentan las estimaciones de los parámetros de crecimiento del modelo de von Bertalanffy para el jurel Trachurus murphyi Nichols 1920 capturado en el mar peruano entre 1972 y 2012, a partir de análisis de frecuencias por tallas. La L∞ fue estimada a partir de la máxima talla observada a lo largo de la historia de su pesquería y se le mantuvo como parámetro fijo en la estimación del parámetro de crecimiento k a partir del ajuste directo de una curva de crecimiento sobre la progresión mensual de modas. Los valores estimados fueron: L∞ = 81.6 cm y k = 0.167 año-1. Se destaca que este valor de k es similar al estimado por otros autores y con otros métodos para el Perú, y es a su vez más alto que el estimado para el T. murphyi capturado frente a las costas de Chile. Estos resultados sugieren que el T. murphyi en el Perú tiene una velocidad de crecimiento más alta que el T. murphyi de Chile

This paper presents estimates of the von Bertalanffy growth parameters for Jack mackerel T. murphyi caught in Peruvian waters from 1972 to 2012, based on length frequency analysis. L∞ was estimated from the maximum length observed throughout the history of the fishery, and was kept as a fixed parameter in the estimation of k obtained by fitting a growth curve to the monthly progression of modes. The estimated values were: L∞ = 81.6 cm and k = 0.167y-1. It is highlighted that this k values is similar to those estimated by other authors for Peru, and is higher than those estimated for the T. murphyi caught off in Chile. These results suggest that T. murphyi caught in Peru has a faster growth rate than the T. murphyi from Chile

Patrones de distribución y abundancia del jurel Trachurus murphyi en el Perú

Se analiza información de cruceros bio-oceanográficos del IMARPE con estaciones hasta 100 mn de la costa y entre 0 y 180 m de profundidad entre 1961 y 2011; información de observadores científicos a bordo de buques arrastrero-factoría de media agua nacionales, soviéticos y cubanos que operaron entre 1983 y 1998; y series de tiempo de anomalías de temperatura superficial del mar, profundidad de la isoterma de 15 °C y salinidad de 1950 a la fecha. Se identifican y describen tres patrones de distribución vertical y profundidad de las capturas de jurel Trachurus murphyi en relación a cambios en condiciones ambientales: (1) cuando ocurren fenómenos El Niño (EN) fuertes los cardúmenes se distribuyen entre 100 y 200 m de profundidad, las capturas son altas y varían poco entre día y noche; (2) cuando hay fuertes afloramientos los cardúmenes se distribuyen entre 0 y 75 m de profundidad, la pesca es más oceánica y superficial y (3) cuando se refuerza la Extensión Sur de la Corriente de Cromwell (ESCC), los cardúmenes están entre 0 y 300 m de profundidad, la pesca es más costera, a mayor profundidad de día y más superficial de noche. T. murphyi es menos abundante en períodos fríos, cuando dominan Aguas Costeras Frías (ACF) y se alejan de la costa las Aguas Subtropicales Superficiales (ASS), y más abundante en periodos cálidos, asociados a eventos EN y dominancia de la ESCC. Se observa segregación latitudinal por tamaños en relación a la Oscilación Decadal del Pacífico

This paper analyzes information from IMARPE bio-oceanographic surveys conducted between 1961 and 2011 covering an area from 0 to 100 nm from the coast with observations at depths from 0 to 180 m; information from scientific observers on board Peruvian, Soviet and Cuban factory trawlers operating between 1983 - 1998; as well as time series of sea surface temperature anomalies, depth of the 15 °C isotherm and sea surface salinity from 1950 to date. Three patterns in the vertical distribution and depth of catches of Jack mackerel Trachurus murphyi are identified and described in relation to changing environmental conditions: (1) During strong El Niño (EN) events shoals are at depths between 100 - 200 m, catches are higher and dont change much between day and night; (2) During strong upwellings shoals are shallower, at depths between 0 - 75 m and catches are more oceanic (offshore) and closer to the surface; and, (3) When there is a strengthen Southern Extension of the Cromwell Current (SECC) shoals are at depths between 0 and 300 m, fishing takes place closer to the coast being deeper during the day and shallower during the night. During cold periods there is lower abundance of T. murphyi due to the prevalence of Cold Coastal Waters (CCW) and the offshore shift of the Subtropical Surface Waters (SSW), while abundance is higher during warmer periods associated with EN events and the strengthening of the SECC. A certain latitudinal segregation by sizes in relation to the Pacific Decadal Oscillation is also observed

Ecología trófica del jurel Trachurus murphyi en el Perú entre 1977 - 2011

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 pre dictivas 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 ringens es 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. monodon cerca 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-northern Peru, 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. monodon closer to the coast) and the ontogenic stages.