Changes in mouth morphometries as related to the diet of Thyrsites atun (Euphrasen, 1791) from south-central Chile Cambios en la morfometría bucal y su relación con la dieta de Thyrsites atun (Euphrasen, 1791) en el centro-sur de Chile

In several species of carnivorous fishes, as they grow, body size and that of the mouth are related positively with prey size, however, the number and biomass of preys consumed by the fish don't present such a clear pattern. To verify these relationships in the fish Thyrsites atun, a total of 140 individuals were collected from industrial and semi-industrial landings in south-central Chile. The diet of T. atun was described by means of frequency, number and weight of preys, which were compared between sub-adult and adult fishes. We also measured mouth morphometry to compare them with the fish size and prey size. Mouth volume was also calculated to relate it with the number and weight of the ingested preys. Four prey species were found in their digestive tracts, Euphausia sp., Todarodes filippovae, Strangomera bentincki and Engraulis ringens, the latter being the most frequent prey (99.9 %). The mouth measures were dependent of predator body size. Equally, prey size turned out to be de