Otolith microstructure reveals first sexual maturity as the main event in the formation of the first year ring in anchovy Engraulis encrasicolus in North Alboran Sea

• DOI: https://doi.org/10.22533/at.ed.813542510072

• Palavras-chave: Age determination; daily growth; small pelagics; sectioned otoliths; microstructure; validation

• Keywords: Age determination; daily growth; small pelagics; sectioned otoliths; microstructure; validation

• Abstract:

  Several studies have recently been published on measuring the age and growth of anchovy based on otolith microstructure, although the methodologies used were not analogous or easily reproducible. The three-dimensional complexity and heterogeneity of otoliths make establishing common interpretation criteria difficult. In the search for a simple and reproducible reading process, this study contrasts a different alternative, combining analysis of otolith frontal sections at two magnifications (×200 and ×400). The results of this study point to the frontal plane of the otolith at ×200 magnification as an improved method to determine the age of the anchovy through the microstructure, both in terms of reproducibility and precision. In addition, the readings of the daily growth increments (DGI) of the otolith sections indicated that in the first year of life the Alboran anchovy reaches 16.52 cm and that the seasonal ring defined by the otolith macrostructure of the first year corresponds to a winter ring that coincides with the first sexual maturation event. The DGI count has also been used to establish the most likely birth dates in July, coinciding with the anchovy spawning season in the area.