Hábitos alimentarios del besugo Epigonus crassicaudus combinando contenido estomacal e isótopos estables

El besugo, Epigonus crassicaudus, es una especie de importancia económica para la actividad pesquera que opera en el centro-sur de Chile. A pesar de ello, poco es lo que se conoce respecto a su biología. En este sentido, este trabajo estudió los hábitos alimentarios combinando análisis estomacales y de estabilidad isotópica. Los resultados del análisis dan cuenta de la importancia de los peces mesopelágicos (Myctophidae, Stomiidae) en la dieta con un aporte del 80%, seguido por crustáceos (Sergestes arcticus) alcanzando un 10%. No se detectaron diferencias en la dieta en peces con distinto grado de madurez sexual. En tanto, los valores de los isótopos de nitrógeno y carbono mostraron valores de promedio de 17,12 ± 1,1 δ 15N y de -17,51 ± 0,7 δ 13C, respectivamente. La constitución de valores de δ 13C fue proporcional al tamaño corporal de los besugos: individuos de mayor tamaño habitan en ambientes más demersales que ejemplares de menor tamaño. De acuerdo a estos resultados, el besugo  se sitúa como consumidor secundario

Métricas alimentarias de dos condrictios meso-bentónicos en aguas de Chile central: Food metrics of two meso-benthic chondrichthyans in waters of central Chile

Little has been studied of the food metrics of most chondrichthyans, which provide baseline information for the assessment of fishing status to guide the development of ecosystem-based management plans. Therefore, the main goal of this study was to approach the isotopic niche of Dipturus chilensis and Callorhinchus callorynchus in Valparaíso (central Chile). The main findings showed that C. callorynchus presented a narrow ellipse (E= 0.79; RC= 4.14; θ= 1.39), meanwhile D. chilensis, presented an ellipse with greater extension (E= 0.95; RC= 8,23; θ= -0.11), therefore a wide isotopic niche

A global perspective on the trophic geography of sharks

Sharks are a diverse group of mobile predators that forage across varied spatial scales and have the potential to influence food web dynamics. The ecological consequences of recent declines in shark biomass may extend across broader geographic ranges if shark taxa display common behavioural traits. By tracking the original site of photosynthetic fixation of carbon atoms that were ultimately assimilated into muscle tissues of 5,394 sharks from 114 species, we identify globally consistent biogeographic traits in trophic interactions between sharks found in different habitats. We show that populations of shelf-dwelling sharks derive a substantial proportion of their carbon from regional pelagic sources, but contain individuals that forage within additional isotopically diverse local food webs, such as those supported by terrestrial plant sources, benthic production and macrophytes. In contrast, oceanic sharks seem to use carbon derived from between 30° and 50° of latitude. Global-scale compilations of stable isotope data combined with biogeochemical modelling generate hypotheses regarding animal behaviours that can be tested with other methodological approaches.This research was conducted as part of C.S.B.’s Ph.D dissertation, which was funded by the University of Southampton and NERC (NE/L50161X/1), and through a NERC Grant-in-Kind from the Life Sciences Mass Spectrometry Facility (LSMSF; EK267-03/16). We thank A. Bates, D. Sims, F. Neat, R. McGill and J. Newton for their analytical contributions and comments on the manuscripts.Peer reviewe

Stomach Contents and Stable Isotope Analysis Reveal Ontogenetic Shifts and Spatial Variability in Brama Australis Diet

Many marine fisheries rely on production and energy flow in the pelagic zone, thus sustainable management of exploited pelagic fishes benefits from insight into temporal, spatial and ontogenetic variability in the trophic ecology of these species. Here we analyze stomach contents and stable isotopes to reveal spatial variability (focusing on two fishing grounds, north and south of an oceanographic barrier in the Pacific Ocean) and ontogenetic changes (contrasting immature and mature) in Southern Ray’s Bream (Brama australis) diet composition in Chilean waters. Stomach contents analysis indicated that euphausiids were predominant components of the diet in both fishing grounds and ontogenetic stages. Patterns of prey long-term assimilation, revealed in Bayesian mixing models of predator and prey isotopic values of δ15N and δ13C, differed from diet as indicated in stomach contents. Shrimps and crustacean larvae were more important than euphausiids in the northern and southern fishing ground, respectively. In both fishing grounds, diet shifted after maturity towards increased use of shrimps. Combining methods of stomach contents analysis and stable isotopes analysis is a powerful approach to determining predator-prey relationships and energy flow in pelagic fishes

Stomach Contents and Stable Isotope Analysis Reveal Ontogenetic Shifts and Spatial Variability in Brama Australis Diet

Many marine fisheries rely on production and energy flow in the pelagic zone, thus sustainable management of exploited pelagic fishes benefits from insight into temporal, spatial and ontogenetic variability in the trophic ecology of these species. Here we analyze stomach contents and stable isotopes to reveal spatial variability (focusing on two fishing grounds, north and south of an oceanographic barrier in the Pacific Ocean) and ontogenetic changes (contrasting immature and mature) in Southern Ray’s Bream (Brama australis) diet composition in Chilean waters. Stomach contents analysis indicated that euphausiids were predominant components of the diet in both fishing grounds and ontogenetic stages. Patterns of prey long-term assimilation, revealed in Bayesian mixing models of predator and prey isotopic values of δ15N and δ13C, differed from diet as indicated in stomach contents. Shrimps and crustacean larvae were more important than euphausiids in the northern and southern fishing ground, respectively. In both fishing grounds, diet shifted after maturity towards increased use of shrimps. Combining methods of stomach contents analysis and stable isotopes analysis is a powerful approach to determining predator-prey relationships and energy flow in pelagic fishes

Evaluating the relationship between the growth of fish and energy component of their prey

Fish growth analysis is a fundamental part of research in fisheries biology, aquaculture, and physiology. However, there is the question of whether the addition of mass and length depends on the amount of energy a prey can deliver. This study tested the hypothesis that there is an effect on the length/weight ratio of the predator, under the premise that fish that ingest prey with a greater amount of energy will have greater mass growth, in contrast to those that ingest food with lesser energy. The fish in this experiment was under controlled laboratory conditions under two types of food treatment and one control (low energy vs high energy amount). The energy-rich treatment had a significant effect on the mass increase (GLM; F = 2.72; P = 0.031), and the length/weight ratio was greater in the fish under the energy-rich treatment (ANCOVA; F = 3.59; P = 0.043). However, the IGR showed that fish presented low rates of intrinsic size growth (ANOVA; F = 0.189; P = 0.828)

New insights on the trophic ecology of blue (<i>Prionace glauca</i>) and shortfin mako sharks (<i>Isurus oxyrinchus</i>) from the oceanic eastern South Pacific

<p>The blue shark (<i>Prionace glauca</i>) and the shortfin mako shark (<i>Isurus oxyrinchus</i>) are two large and highly migratory sharks distributed in most oceans. Although they are often caught in the south Pacific Ocean long-line fisheries, their trophic ecology is poorly understood. Stable isotopes with Bayesian mixing and dependence concentration models were performed to determine the diet and trophic differences between the two species in the South-eastern Pacific Ocean. According to the mixing models, fishes are the most important prey of these sharks. Dolphin calves and remains were found in the stomachs of both species, which represents a novel finding in trophic ecology of South Pacific sharks. Intra-specific differences were found in <i>P. glauca</i>, but not in specimens of <i>I. oxyrinchus</i>. The two sharks showed a high degree of diet overlap (73%), primarily over mackerel and dolphin carcasses. Our results indicate that blue and shortfin mako sharks have a generalist feeding strategy in the eastern Pacific Ocean, with a strong preference for teleost fishes and also for dolphin carcasses. Therefore, trophic studies are useful to understand energy flow through the food web, and the trophic position of key species.</p

A global perspective on the trophic geography of sharks

Sharks are a diverse group of mobile predators that forage across varied spatial scales and have the potential to influence food web dynamics. The ecological consequences of recent declines in shark biomass may extend across broader geographic ranges if shark taxa display common behavioural traits. By tracking the original site of photosynthetic fixation of carbon atoms that were ultimately assimilated into muscle tissues of 5,394 sharks from 114 species, we identify globally consistent biogeographic traits in trophic interactions between sharks found in different habitats. We show that populations of shelf-dwelling sharks derive a substantial proportion of their carbon from regional pelagic sources, but contain individuals that forage within additional isotopically diverse local food webs, such as those supported by terrestrial plant sources, benthic production and macrophytes. In contrast, oceanic sharks seem to use carbon derived from between 30° and 50° of latitude. Global-scale compilations of stable isotope data combined with biogeochemical modelling generate hypotheses regarding animal behaviours that can be tested with other methodological approaches