ABSTRACT. The ingestion of invertebrates by herbivores on rocky intertidal shores is traditionally considered a casual phenomenon. However, a recent study of 29 species in northern Chile shows that animal consumption is widespread, consistent, and important, suggesting that some of these herbivores may actually be omnivores. Therefore, we examined the capability of three common Chilean herbivores (the key-hole limpets Fissurella limbata and Fissurella picta and the polyplacophoran Chiton granosus) to digest animal food. For each species, we conducted no-choice feeding experiments using artificial foods based on either algal or animal tissue from one of their frequent prey (Ulva rigida, Perumytilus purpuratus). After the feeding trials, we evaluated the total proteolytic activity (availability of free amino acids) in the digestive contents of the species studied and, as a reference, we evaluated this activity in animals obtained directly from the field. We found that all three species were able to eat animal food, and this consumption was not significantly different from that of algal food, suggesting that both foods were not only edible but at least similarly palatable. In addition, we detected comparable levels of proteolytic activity under the three feeding conditions for the three species. No statistical differences were found for C. granosus, but activity was significantly higher with animal food in F. limbata and with algal food in F. picta. Our data show the high digestive flexibility of these species, suggesting their ability for adaptive modulation and the possibility that they are true omnivorous consumers. We discuss the implications of these results for our current view of the structure of rocky intertidal food webs. Keywords: omnivorous, proteolytic, food web, key-hole limpet, polyplacophora, Chile.Consumo y digestión de alimento animal por herbívoros del intermareal rocoso: evaluación de flexibilidad digestiva y omnivoría en tres especies de pastoreadores RESUMEN. La ingestión de invertebrados por herbívoros de costas intermareales rocosas se considera tradicionalmente un fenómeno casual. Sin embargo, un estudio reciente en 29 especies del norte de Chile muestra que el consumo animal es generalizado, consistente e importante, sugiriendo que algunos de estos herbívoros pueden ser realmente omnívoros. Por tanto, se examinó la capacidad de tres herbívoros chilenos comunes para digerir alimento animal: las lapas Fissurella limbata y Fissurella picta, y el poliplacóforo Chiton granosus. Para cada especie, se efectuaron experimentos de alimentación sin elección usando alimentos artificiales basados en tejido animal o algal de algunas de sus presas frecuentes (Ulva rigida, Perumytilus purpuratus). Luego de los ensayos de alimentación se evaluó la actividad proteolítica total (disponibilidad de aminoácidos libres) en sus contenidos digestivos, y como referencia, se determinó la actividad en animales obtenidos directamente desde condiciones de terreno. Se encontró que las tres especies fueron capaces de come...

Edad de jurel -0,16(t+0,13) ] donde LH t es la longitud horquilla (cm) a tiempo t (años).PALABRAS CLAVE: anillos de incremento diario, Chile, edad, jurel, Trachurus murphyi.

We estimated the growth of Jack mackerel (Trachurus murphyi) using increments of daily growth, otolith weight and annual ring reading in sagittal otoliths. The daily micro-increments were used to fit ring density to the otolith radius (n = 4481) and then to estimate the age of the individual in days. The parameters of the von Bertalannfy growth equation were: maximum theoretical fork length, FL ∞ = 75 cm; individual growth coefficient, K = 0.16 year -1 ; theoretical age at which fish length is zero, t 0 = -0.19 years. The growth parameters of T. murphyi estimated using annual rings reading were: K = 0.10 year -1 , FL ∞ = 74.7 cm, t 0 = -0.50 years. The growth parameters estimated using otolith weight were: K = 0.15 year -1 , FL ∞ = 75.0 cm, t 0 = -0.48 years. The parameter K estimated with the daily micro-increments was similar to the K estimated using sagittal otolith weights. We constructed a size-age key for T. murphyi using otolith weight, OW (milligrams) as a variable was: OW= 0.0323*t-15.197 (r 2 = 0.68). We recommend using otolith weight to estimate age in T. murphyi due to this technique is statistically reliable, but also cheap and fast.