Age estimation of juvenile European hake Merluccius merluccius based on otolith microstructure analysis: a slow or fast growth pattern?

Abstract

The main goal of this study was to examine otolith microstructure and to estimate the age and growth of European hake Merluccius merluccius from the eastern Mediterranean Sea. One hundred and twenty-nine specimens ranging from 102 to 438 mm in total length (LT ) were used. Age estimations were based on the study of the otolith microstructure, which was revealed after grinding both frontal sides of otoliths. The enumerations of the daily growth increments (DGI) as well as their width (WDGI ) measurements were made on calibrated digital images. The number of DGI in otoliths ranged between 163 and 717. Four phases in the WDGI evolution were distinguished: (1) larval-juvenile pelagic phase, with an increasing trend in WDGI up to the 60th DGI, (2) settlement phase, with a short-term deceleration in WDGI between the 61st and 150th DGI, (3) juvenile demersal phase, characterized by a stabilization of WDGI from 151st to 400th DGI and (4) adult phase, with a decreasing trend in WDGI after the 400th DGI. Age, sex and month of formation were found to affect the WDGI in all phases, with the exception of age at the juvenile demersal phase. The power curve with intercept model described best the relationship of M. merluccius LT with age (TDGI ), according to Akaike criteria, revealing differences in growth between females [LT = 65 · 36(TDGI )(0 · 40) - 388 · 55] and males [LT = 69 · 32(TDGI )(0 · 37) - 352 · 88] for the sizes examined. The mean daily growth rates were 0·61 mm day(-1) for females and 0·52 mm day(-1) for males, resulting in an LT of 283 and 265 mm at the end of their first year of life. In comparison with previous studies on the Mediterranean Sea, the results of this study showed a greater growth rate, similar to results from tagging experiments and otolith microstructure analyses for M. merluccius in other geographic areas.

Spatial distribution pattern of European hake, <em>Merluccius merluccius</em> (Pisces: Merlucciidae), in the Mediterranean Sea

“…El análisis de longitud muestra valores medios inferiores a 200 mm TL de la mayoría de las áreas investigadas. duction (Al-Absawy 2010), age and growth (Ligas et al 2015, Pattoura et al 2015, feeding (Carpentieri et al 2005, Mellon-Duval et al 2017, and exploitation and fishery management (Russo et al 2017, Tsagarakis et al 2017. These studies on the Mediterranean Sea are regional but most contributions have a local focus.…”

Multiscale analysis on otolith structural features reveals differences in ontogenesis and sex in Merluccius merluccius in the western Adriatic Sea

“…The relationships between otolith parameters (length, OL; width, OW; perimeter, OP; area, OA; circularity, OC; aspect ratio, OAR; roundness, OR; solidity, OS; volume, OV; weight, Oweight; micro-density, Omicro; bulk density, Obulk; porosity, Oporo; organic matrix, OM%) and TL were determined for undifferentiated, females, males and for all the individuals combined [ 39 ]. The best fits with the data to describe the relationships between otolith variables and fish somatic growth were first evaluated by curve estimation regression for three different curve models (linear, power and exponential, electronic supplementary material, table S3).…”