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

Caracterización del ámbito de hogar y dieta en juveniles de la tortuga Carey, eretmochelys imbricata (Linnaeus, 1766), durante una temporada no reproductiva, en Punta Coyote, Península Nicoya, Costa Rica

Tesis (Magíster en Biología Marina)Comprender como es el uso espacial por parte de los animales marinos es crucial para el desarrollo de estrategias de manejo de los ecosistemas marinos, tanto para amenazas indirectas como el cambio climático, así como más directas de origen antrópico; cobrando relevancia el conocimiento de los factores que inducen el patrón de uso del hábitat y la obtención del alimento. En las tortugas marinas hacen falta datos clave sobre la biología, ecología y situación poblacional, así como su interacción con los humanos y las amenazas, en especial los hábitat de alimentación y aguas neríticas, los cuales son imperativos obtener para mejorar los esfuerzos de conservación, monitoreo y manejo de poblaciones de juveniles de una manera más local. En el caso de la tortuga Carey Eretmochelys imbricata (Linnaeus, 1766), son escasos estos estudios debido a su baja densidad poblacional. Esta es una especie clave dentro del ecosistema marino y actualmente en peligro crítico de extinción, con una pérdida del 75.5% de sus poblaciones del Océano Pacífico, por lo que se les considera como una de las poblaciones más amenazas a nivel mundial. Punta Coyote corresponde a un área de alimentación, reclutamiento y desarrollo de juveniles, pero con fuerte presencia de actividades y artes de pesca que pueden perjudicar a las tortugas marinas ahí presentes, lo cual motiva a la comunidad para promover el cuidado de esta especie. Considerando que el uso diferencial del espacio, para muchas especies, está definido por la disponibilidad de los recursos necesarios para su desarrollo biológico adecuado, además teniendo en mente la Teoría Óptima de Forrajeo la hipótesis planteada es, "El uso espacial de Eretmochelys imbricata en Punta Coyote, se verá determinado por la disposición del sustrato roso, así como por la presencia del alimento preferencial para la especie". Se establece como Objetivo General, "Caracterizar el Ámbito de Hogar y la dieta de E.imbricata en función de factores ambientales". Para ello, las tortugas fueron capturadas, marcadas, medidas, pesadas, seobtuvo su contenido gastroesofágico y se les adosó un trasmisor acústico y en uno de los caso un transmisor satelital, lo cual permitió reconocer su ubicación y así se determinó su Ámbito de Hogar y Centro de Actividad. En total fueron capturadas 7 tortugas, todas correspondientes a juveniles. De estos animales, 1 no fue rastreada, 5 fueron rastreadas acústicamente y 1 rastreada con un transmisor satélite. De los animales capturados, 2 fueron recapturas de hace dos años. Se determinó que su dieta preferencial es Codium isabelae y Rhopalaea birkelandi. Tanto el Ámbito de Hogar como el Centro de Actividad, se encuentra asociado principalmente al sustrato rocoso, distancia a la desembocadura y a la abundancia de R.birkelandi. Tanto las recapturas y el rastreo satelital, permiten supones que se trata de animales residentes de su hábitat de alimentación. Adicionalmente, de todos los puntos registrados solo uno fue al interior de la Reserva Nacional de Vida Silvestre Caletas Ario (RNVSCA), lo cual reafirma que Punta Coyote es un área de importancia para la conservación y protección de la especie. Los resultados obtenidos en este estudio permitirá esclarecer de mejor manera la distribución de esta especie en Punta Coyote, apoyando el establecimiento de una mejor AMP, conjuntamente con entregar mayor información ecológica y conductual de esta especie en una región en donde los estudios son escasos. A pesar del bajo número de ejemplares utilizado en esta investigación, éste es mayor que el implementado en otros estudios del mismo tipo para esta especie.Understanding how is the space use by marine animals is crucial for the development of management strategies for marine ecosystéms, both indirect threats such as climate change, as well as more direct anthropogenic; gaining relevant knowledge of the factors that induce the pattern of habitat use and obtaining food. In sea turtles key data are needed on the biology, ecology and population status and their interaction with humans and threats, especially food habitat and neritic waters, which are imperative to get improve conservation efforts, monitoring and management of young animal in a more local form. In the case of the hawksbill turtle Eretmochelys imbricata (Linnaeus, 1766), few such studies due to its low population density. This is a key specie inside marine ecosystem and currently critically endangered with a loss 75.5% their populations Pacific Ocean so them considered a populations more threats worldwide. Punta Coyote corresponds to a feeding area, recruitrnent and development of youth, but with a strong presence of fishing gear and activities that may harm sea turtles there present, which motivates the community to promote the care of this species. Whereas the differential use of space for many species, is defmed by the availability of resources necessary for their proper biological development also in rnind Optimal Foraging Theory the hypothesis is, "The Space Use of Eretmochelys imbricata in Punta Coyote, will be determined by the arrangement of the rocky substrate, and by the presence of food preference for the species". General Target is set to, "Characterizing the Home Range and diet of E.imbricata according environmental factors ." To this end, the turtles were captured, marked, measured, weighed, gastroesophageal content was obtained and were attaching a sound transrnitter and a case of a satellite transrnitter, which allowed us to recognize its location and thus determine the scope of Home Range and Activity Centre. A total of 7 turtles were captured, all corresponding to juveniles. Of these animals, 1 was not traced, 5 were tracked acoustically and 1 tracked with a satellite transrnitter. Of trapped animals, 2 were recaptures two years ago. W as deterrnined the diet preferential Codium isabelae and Rhopalaea birkelandi. Both the Home Range as the Activity Center, is mainly associated with rocky substrate, distance to the mouth and the abundance of R.birkelandi. Both recapture and satellite tracking, suggest that animals are residents in feeding habitat. Additionally, all registered points was only one within the National Wildlife Reserve Caletas Ario (RNVSCA), which reaffirms that Punta Coyote is an area of importance for the conservation and protection of the species. The results this study will clarify better the distribution this species Punta Coyote, supporting establishing better AMP jointly with deliver greater ecological information and behavioral this species in a region where studies scarce. Despite the low number of specimens used in this research, it is larger than the one implemented in other studies of the same type for this species

Potencial de Tegula atra (mollusca : Gastropoda) como biorregulador del crecimiento de algas en estanques de cultivo de lenguado Paralichthys adspersus

One of the main problems in aquaculture lies in the stress to which the species in cultivation can be subjected, therefore the development of alternative techniques such a mixed culture are beneficial to minimize stress and improve the industry. Tegula atra is a gastropod that lives in subtidal and intertidal, with local economic importance and due its herbivorous behavior, we hypothesized that T. atra may be valuable in controlling macroalgae growth in culture tanks by mixed culture. Grazing percentage, respiratory behavior and excretion of nitrogen wastes, were measured in three size classes of T. atra, which were maintained in mixed culture together with the economically relevant Chilean flounder. While the largest specimens of T. atra (Class 3) were the most efficient in terms of algae consumption, the other classes were less effective and did not show significant differences in each other within a 24-hour period. Smaller and larger size classes organisms (Class 1 and Class 3), consumed the greatest amount of oxygen within a period of 120 min. Finally, smallest organisms (Class 1) emitted the greatest nitrogen wastes, in a period of 120 min. As the grazing ability was higher in larger specimens (Class 3), they could be the ideal candidates for polyculture. However, medium-sized specimens (Class 2) may be the most suitable, due its low O2 consumption and lower excretion of NH3, producing less negative effect on water quality. Future studies should evaluate the potential negative impacts of T. atra on the physiology of its cohabitants

Potencial de Tegula atra (Mollusca: Gastropoda) como biorregulador del crecimiento de algas en estanques de cultivo de lenguado Paralichthys adspersus

Abstract: One of the main problems in aquaculture lies in the stress to which the species in cultivation can be subjected, therefore the development of alternative techniques such a mixed culture are beneficial to minimize stress and improve the industry. Tegula atra is a gastropod that lives in subtidal and intertidal, with local economic importance and due its herbivorous behavior, we hypothesized that T. atra may be valuable in controlling macroalgae growth in culture tanks by mixed culture. Grazing percentage, respiratory behavior and excretion of nitrogen wastes, were measured in three size classes of T. atra, which were maintained in mixed culture together with the economically relevant Chilean flounder. While the largest specimens of T. atra (Class 3) were the most efficient in terms of algae consumption, the other classes were less effective and did not show significant differences in each other within a 24-hour period. Smaller and larger size classes organisms (Class 1 and Class 3), consumed the greatest amount of oxygen within a period of 120 min. Finally, smallest organisms (Class 1) emitted the greatest nitrogen wastes, in a period of 120 min. As the grazing ability was higher in larger specimens (Class 3), they could be the ideal candidates for polyculture. However, medium-sized specimens (Class 2) may be the most suitable, due its low O₂ consumption and lower excretion of NH3, producing less negative effect on water quality. Future studies should evaluate the potential negative impacts of T. atra on the physiology of its cohabitants.Resumen: Uno de los principales problemas en la acuicultura es el estrés al que se pueden ver sometidas las especies en cultivo, por esto el desarrollo de técnicas alternativas para minimizar el estrés son de gran ayuda. Tegula atra es un gastrópodo que habita en el submareal e intermareal, con importancia económica local y debido a su conducta herbívora, se planteó la hipótesis que esta especie puede ser útil en el control del crecimiento de macroalgas en los estanques, mediante cultivo mixto. En el presente estudio, se midió el porcentaje de ramoneo, la conducta respiratoria y excreción de desechos nitrogenados de tres clases de talla de T. atra, las cuales se mantuvieron en estanques con Paralichthys adspersus. Los ejemplares de mayor talla de T. atra (Clase 3) fueron los más eficientes en términos de consumo de algas, dentro de un período de 24 horas. Los organismos pertenecientes a las clases de tallas pequeñas y grandes (Clase 1 y Clase 3), consumieron mayor cantidad de oxígeno dentro de un periodo de 120 min. Finalmente, los organismos de menor talla (Clase 1) fueron los que emitieron la mayor cantidad de desechos nitrogenados, en un período de 120 min. Dado que, la capacidad ramoneadora fue mayor en los ejemplares de talla superior (Clase 3), éstos podrían ser los candidatos ideales para el policultivo, sin embargo, al considerar la respirometría, los animales de talla media (Clase 2), serían óptimos, por su bajo consumo de O₂ y menor excreción de NH3, generando un menor impacto negativo en la calidad del agua. Futuros estudios debieran evaluar los posibles impactos negativos a nivel fisiológico que pueda tener la presencia de T. atra, sobre sus cohabitantes

Potencial de Tegula atra (Mollusca: Gastropoda) como biorregulador del crecimiento de algas en estanques de cultivo de lenguado Paralichthys adspersus

Uno de los principales problemas en la acuicultura es el estrés al que se pueden ver sometidas las especies en cultivo, por esto el desarrollo de técnicas alternativas para minimizar el estrés son de gran ayuda. Tegula atra es un gastrópodo que habita en el submareal e intermareal, con importancia económica local y debido a su conducta herbívora, se planteó la hipótesis que esta especie puede ser útil en el control del crecimiento de macroalgas en los estanques, mediante cultivo mixto. En el presente estudio, se midió el porcentaje de ramoneo, la conducta respiratoria y excreción de desechos nitrogenados de tres clases de talla de T. atra, las cuales se mantuvieron en estanques con Paralichthys adspersus. Los ejemplares de mayor talla de T. atra (Clase 3) fueron los más eficientes en términos de consumo de algas, dentro de un período de 24 horas. Los organismos pertenecientes a las clases de tallas pequeñas y grandes (Clase 1 y Clase 3), consumieron mayor cantidad de oxígeno dentro de un periodo de 120 min. Finalmente, los organismos de menor talla (Clase 1) fueron los que emitieron la mayor cantidad de desechos nitrogenados, en un período de 120 min. Dado que, la capacidad ramoneadora fue mayor en los ejemplares de talla superior (Clase 3), éstos podrían ser los candidatos ideales para el policultivo, sin embargo, al considerar la respirometría, los animales de talla media (Clase 2), serían óptimos, por su bajo consumo de O₂ y menor excreción de NH3, generando un menor impacto negativo en la calidad del agua. Futuros estudios debieran evaluar los posibles impactos negativos a nivel fisiológico que pueda tener la presencia de T. atra, sobre sus cohabitantes

Ecología trófica de dos peces de la familia Gempylidae en aguas oceánicas del Pacífico Sur Oriental

The feeding of the escolar fishes Ruvettus pretiosus and Lepidocybium flavobrunneum has not been reported yet for southeastern Pacific waters. The main goal of this work was to study the trophic relationships using stomach contents and stable isotopes, δ15N and δ13C, based on mixing models. Results showed that both fish had differences in the importance of the prey, feeding strategy and habitat use. Also, they presented similar values of δ15N (~20‰) and δ13C (~-16‰), but a low probability of niche overlapping

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

Evaluating Food Metrics of Lanternfishes in Waters of the Southeastern Pacific Ocean

Using carbon and nitrogen stable isotope values, we analyzed the trophic position (TP) and the isotopic niche width of lanternfishes from three different areas in the Southern Pacific Ocean. Fishes from Perú had slightly higher δ13C values compared with fish from Chilean areas. In contrast, δ15N values increased with latitude (North to South). Myctophids TP differed between the three study areas (highest in Central Chile, lowest in Peru). Peruvian fishes had a smaller isotopic niche than the lanternfishes of those from Chile

Evaluating Food Metrics of Lanternfishes in Waters of the Southeastern Pacific Ocean

Using carbon and nitrogen stable isotope values, we analyzed the trophic position (TP) and the isotopic niche width of lanternfishes from three different areas in the Southern Pacific Ocean. Fishes from Perú had slightly higher δ13C values compared with fish from Chilean areas. In contrast, δ15N values increased with latitude (North to South). Myctophids TP differed between the three study areas (highest in Central Chile, lowest in Peru). Peruvian fishes had a smaller isotopic niche than the lanternfishes of those from Chile