A Novel Procedure to Process Ocean Whitefish, Caulolatilus princeps, Otoliths in the Galapagos Marine Reserve

Abstract

Ocean Whitefish (Caulolatilus princeps) is an endemic species in the Galapagos Marine Reserve, Ecuador and is important economically in both the artisanal fishery and as a local food source. However, little is known about its life history in this region. To discern age structure information in the fishery for bony fish such as C. princeps, it is common to determine the count of annual growth rings on the species’ otoliths, or ear bones. The goals of this study were 1) to identify the most repeatable and accurate method for aging C. princeps from the examination of adult otoliths, and 2) to characterize the age structure of fish caught in the fishery, in the Galapagos. Sagittal otoliths were collected from fish caught in artisanal fishing locations around Santa Cruz Island, Ecuador and processed and analyzed at the Charles Darwin Research Station Marine Sciences Department laboratory. Fish selected for processing were drawn randomly from a large population and were similar in size and range across all subsamples. Samples (n=49) of otoliths each received one of five different otolith preparation procedures in order to visually count growth bands. Otoliths contain alternating clear and opaque bands of growth. Age was estimated by two readers independently counting bands (2x) without knowledge of the sex or size of the fish.