Aquaculture

Silver (Ag) ions are among the most toxic metallic ions to aquatic biota. In southern Argentina, fish from Patagonian lakes have liver Ag concentrations [Ag] among the highest ever reported globally. Silver concentration in phytoplankton from Lake Moreno (1.82 ± 3.00 lg g À1 dry weight, DW) was found to be significantly higher than [Ag] in zooplankton (0.25 ± 0.13 lg g À1 ). Values in snails and decapods (0.60 ± 0.28 lg g À1 and 0.47 ± 0.03 lg g À1 respectively), were higher than in insect larvae (0.28 ± 0.39 lg g À1 for Trichoptera). We examined trophic transfer of Ag in the biota using stable nitrogen and carbon isotopes ratios (d 15 N and d 13 C respectively). Silver concentrations in the biota of Lake Moreno were not associated with any particular C source, as assessed by d 13 C. Hepatic [Ag] significantly increased with trophic position, as measured by d 15 N, within the brook trout sample set. Biodilution of Ag was observed between primary producers and small forage fish when whole body [Ag] was analyzed. Nevertheless, when considering whole food web biomagnification and hepatic [Ag] of top predator fish, a significant positive regression was found between [Ag] and trophic position, as measured by d 15 N. The importance of species-specific and tissue-specific considerations to obtain more information on Ag trophodynamics than that usually presented in the literature is shown. To the best of our knowledge, this is the first study in assessing Ag trophodynamics and tissue-specific biomagnification in a whole freshwater food web.

The present study was conducted to determine if parasite induced mortality existed in a "puyen" population in Moreno Lake, southern Argentina. Data on both parasite abundance and degree of aggregation of parasite frequency distribution showed the absence of fish mortality induced by A. apophalliformis.

The Northern Patagonian Andean range shared by Chile and Argentina has numerous glacial oligotrophic lakes protected in a series of National Parks. Recent baseline surveys indicated that concentrations in muscle and liver tissues from various fish species from across Nahuel Huapi and Los Alerces National Parks in Argentina were comparable or higher than similar fish species from other parts of the world. As a result, Lake Moreno, in Nahuel Huapi National Park, was chosen to investigate multiple element sinks, trends, and transfer in a representative Patagonia aquatic food web. The metals and metalloids Ag, As, Ba, Br, Cs, Co, Cr, Fe, Hg, K, Na, Rb, Se, and Zn were analyzed in three size plankton fractions, submerged macrophytes, biofilm, insect larvae, amphipods, decapods, gastropods (snails), annelids (earthworms), and forage fish. Except for nanoplankton (10-53 μm; small-celled algae, rotifers) and microplankton (53-200 μm; larger algae, ciliates, zooplankton nauplii), which share elemental compositional similarities, each taxon category had its own distinctive compositional pattern, revealed by principal component analysis. Nano-and microplankton tend to be relatively elevated in some metals, including As, Co, Cr, Fe, Hg, Zn, and Rb, followed by biofilm. Shredder-scrapper Trichoptera (caddisflies) have higher concentration of most of the studied elements than other insect larvae taxa, especially carnivorous Odonata (Anisoptera, dragonflies), which were associated with lower elemental contents. Those trends point to an overall tendency for biodiminishing element concentrations with trophic level in the benthos of Lake Moreno.

Se estudiaron la trofodinámica y algunos aspectos vinculados al riesgo toxicológico para la biota y los seres humanos, de cinco elementos químicos potencialmente tóxicos en comunidades de tres lagos pertenecientes a los Parques Nacionales Nahuel Huapi y Los Alerces (PNNH y PNLA respectivamente) en la Patagonia Norte, Argentina. Los elementos son: cromo (Cr), cobalto (Co), plata (Ag) (único elemento no esencial), arsénico (As) y selenio (Se). En estudios previos, el Cr, el Co y la Ag fueron asociados a contaminación antrópica en el área de estudio, y en el caso de este último metal, con niveles de concentración en hígados de peces situados entre los más altos informados a nivel global.

La Salmonicultura representa una industria de considerable importancia económica en Latinoamérica y diversos países del mundo, sin embargo, su desarrollo en Argentina es aún incipiente y limitado a la producción semiartesanal de trucha arco iris en la Norpatagonia. No obstante, dado el potencial mucho mayor de la actividad en el País- tanto en ambientes dulceacuícolas como marinos - en este apunte se brinda un pantallazo sobre tecnologías de producción avanzadas que podrían implementarse en la Argentina en el futuro, sin descuidar las técnicas semiartesanales. Mas allá del tipo de tecnología, se enfatizan los principios generales para la cría de los salmónidos en general, aunque con ejemplos y mayor cantidad de información referidos a truchas arco iris- la especie regional- y salmón del Altántico, la especie de mayor
gravitación económica a nivel internacional.

La bibliografía sobre Salmonicultura no abunda en español y se encuentra dispersa, este apunte pretende contribuir a solucionar este inconveniente. Es el resultado de varios años de recopilación bibliográfica y de elaboraciones propias. Las fructíferas charlas/discusiones con los estudiantes, que agradezco profundamente, me permitieron enriquecer la primera edición publicada en 2018.

El presente trabajo se propone subrayar los aspectos aplicados propios de una disciplina zootécnica, sin descuidar el rigor teórico. Así, sus destinatarios son tanto estudiantes de pre-grado de la Tecnicatura en Acuicultura, como de grado de las carreras de Licenciatura en Biología y Profesorado en Biología, todas de la Universidad del Comahue-Bariloche. Mientras los primeros, encontrarán un manual con los contenidos principales incluidos en el programa, los segundos
podrán utilizar el apunte como punto de partida para una mayor profundización teórica.

El criterio adoptado en cuanto a las citas bibliográficas en el texto, es el de incluirlas sólo cuando los temas tratados se mantienen con cierto grado de controversia.

El presente apunte está organizado en diez unidades de contenido muy diverso, que incluyen desde tópicos biológicos y ambientales hasta económicos. Esta diversidad refleja el carácter multidisciplinar de la Salmonicultura y se propone estimular la reflexión interdisciplinar. En la unidad uno, se ofrecen datos estadísticos de producción y una semblanza de la actividad en distintos países junto con aspectos de la biología de los salmónidos; la unidad dos introduce el agua, enfocada como medio que ofrece las condiciones de cultivo y también como ambiente receptor de los desechos. La producción de “semilla” y el “engorde” son materia de las unidades tres y cuatro respectivamente, en ellas se priorizan los aspectos conceptuales y análisis cuantitativos antes que las descripciones de equipamientos e instalaciones. La unidad cinco, por su parte, presenta los sistemas de recirculación incluida la acuaponía; las unidades seis y siete proponen una forma de análisis cuantitativo para diagramar la producción mediante el uso de una hoja de cálculo. Los conceptos y métodos básicos sobre mejoras genéticas en producción de salmónidos son tratados en la unidad ocho. Un vistazo a algunas técnicas simples de elaboración del producto, que incluye nociones de inocuidad alimentaria, se presenta en la unidad nueve. Finalmente, en la unidad diez se incluyen conceptos y técnicas económicas, especialmente las técnicas de medición de rentabilidad.

This study was conducted to analyze at histopathological level, lesions produced by Acanthostomoides apophalliformis in the native fish Galaxias maculatus, and relate them to quantitative results on parasite-induced fish mortality, in Lake Moreno, Southern, Argentina. Absence in most lesions of inflammatory reaction, unaltered hepatic parenchyma at a short distance from the foci of the lesions and viable appearance of parasites, all suggest a good reciprocal adaptation.. This hypothesis is reinforced by data showing the absence of A. apophalliformisinduced mortality in the fish population.

This study was conducted to analyze at histopathological level, lesions produced by Acanthostomoides apophalliformis in the native fish Galaxias maculatus, and relate them to quantitative results on parasite- induced fish mortality, in Lake Moreno, Southern, Argentina. Absence in most lesions of inflammatory reaction, unaltered hepatic parenchyma at a short distance from the foci of the lesions and viable appearance of parasites, all suggest a good reciprocal adaptation.. This hypothesis is reinforced by data showing the absence of A. apophalliformisinduced mortality in the fish population. Key-words: Galaxias maculates. Acanthostomoides apophalliformis. Histopathology. Parasite - induced host mortality.

Selenium (Se) is a global contaminant of potential concern. It has been found in the liver of rainbow trout in Lake Moreno, a mountain lake in Patagonia, Argentina, at concentrations of 96.48 µg g-1dry weight (DW), which is up to six times higher than the toxic threshold (15 µg g-1) estimated for several fish species. Se concentration in muscle of brook trout in the same lake (1.36 µg g-1, DW) and in nearby Lake Futalaufquen (1.75 µg g-1, DW) could pose a health risk for humans. By using stable isotopes of carbon and nitrogen, I analyze the process leading to these hazardous concentrations, at the same time referring to the heterogeneity in conceptual models and some faults in experimental design that frequently appear in the literature. A reevaluation of experimental design using regression analysis in Lake Moreno showed the importance of experimental replication to discover the influence of diet on [Se] in fish. Reconsideration of the underlying conceptual model showed that the main pathway of Se to fish livers does not present the highest trophic magnification factor. Moreover, results from the nearby lakes Nahuel Huapi and Futalaufquen showed possible effects of experimental confounding. The analyses in this study are potentially useful for other trace elements and locations.

Mussels, Diplon chilensis, from Lake Moreno, a double-basined mountain lake in southern Argentina, is known to have elevated concentrations of chromium (Cr, 425 mg g À 1 dry weight DW) and arsenic (As, 35 mg g À 1 DW), attributed to untreated sewage. To further understand the trophodynamics of Cr, As and cobalt (Co), we investigated concentrations and transfer throughout the food web in each basin of Lake Moreno. Each basin differs in morphology in that the gently-sloping Lake Moreno West has more littoral habitat than deeper Lake Moreno East with its higher proportion of pelagic habitat. Despite the morphological differences, both basins share similar water quality parameters and species assemblages. As a result, Lake Moreno provides an exceptional opportunity to compare trophodynamics of elements that enable us to hypothesize pelagic-littoral habitat coupling in response to lake morphology as the underlying factor influencing both Cr pathway and Co and As trophodynamic modeling. Using stable isotopes of nitrogen (d 15 N) and carbon (d 13 C) to characterize metals trophodynamics in each basin, biodilution of As, Cr and Co were indicated by negative regressions. This is confirmed by elevated As, Co and Cr concentrations in phytoplankton (11.3 7 5.7, 7.4 7 4.9, 44.5 740.7 mg g À 1 DW respectively), while zooplankton and biofilm had the next elevated concentrations. Those elevated concentrations are in contrast with lower concentrations in sport fish such as rainbow trout (0.5 7 0.5, 0.2 7 0.3, 1.8 7 1.2 mg g À 1 DW). Higher concentrations of Cr in fish were associated with higher proportion of benthic/littoral prey items in western basin, and were confirmed by significant correlation with d 13 C values. Arsenic, Co and Cr concentrations in fish, while elevated, do not post health risks to human or wildlife consumers.

This study was conducted to analyze at histopathological level, lesions produced by Acanthostomoides apophalliformis in the native fish Galaxias maculatus, and relate them to quantitative results on parasite-induced fish mortality, in Lake Moreno, Southern, Argentina. Absence in most lesions of inflammatory reaction, unaltered hepatic parenchyma at a short distance from the foci of the lesions and viable appearance of parasites, all suggest a good reciprocal adaptation.. This hypothesis is reinforced by data showing the absence of A. apophalliformisinduced mortality in the fish population.