Recuperación, erosión y retención de otolitos en bolos de Guanay: ¿Son los bolos realmente buenos indicadores de la dieta?

Jaime Jahncke; Cecilia Rivas

Authors

Jaime Jahncke Instituto del Mar del Perú
Cecilia Rivas Instituto del Mar del Perú

Keywords:

Leucocarbo bougainvillii, otoliths, diet, Guanay Cormorants, erosion

Abstract

Otoliths recovery ratio, erosion in otoliths size and maximum retention of ingested otoliths were assessed in 13 captive Guanay Cormorants. Birds were fed with fresh fish previously measured and marked. Birds produced pellets in 55,05% of the days that the experiment lasted. Pellets containing otoliths were produced in 37,81% of the cases (n=2.134). Pellets contained 14,79% of ingested otoliths and 26,61% of ingested eye crystals, recovery percentages changed with fish species. Differences were found between ingested fish size and otoliths estimation of fish size for main prey species. From 80% to 100% of retained otoliths were expulsed during the first three days. Larger otoliths may remain up to 9 days. Proposed methodology allowed a better estimation of diet and higher precision when estimating prey consumption. It is possible to estimate amount of ingested food if recovery percentage of each species is known. Results show that pellet information is valuable because allows to estimate accurately proportions of each ingested prey in the diet. However, does not permit to estimate ingested prey sizes and further research in this subject is still needed.

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