| Summary: | Tese de mestrado, Ecologia Marinha, 2023, Universidade de Lisboa, Faculdade de Ciências Data on age and growth of fish is crucial for understanding vital traits of species and their populations. Boarfish is a pelagic fish with a wide distribution in the Northeast Atlantic and is one of the most commonly discarded non-commercial species on the Portuguese coast. Due to its potential valorisation as a new fishery in the Northeast Atlantic, boarfish has become object of interest of several published studies, contributing to the growing knowledge on this species’ age and growth. However, since no standard protocol has been implemented for boarfish, studies have used a variety of different otolith preparation techniques to estimate age, leading to contradicting and discrepant age conclusions. Thus, this dissertation aimed to gather important biological information on boarfish age and growth for the Portuguese west coast, while accomplishing 4 main objectives: 1) define a standard protocol for age estimates, 2) validate assigned ages, 3) determine the best growth model and 4) serve as benchmark study for the species growth parameters, before boarfish commercial exploitation initiates in this area. By comparing three different otolith ageing methodologies, whole otoliths are suggested as the best method to estimate boarfish age, with maximum age reaching 15 years. In relation to boarfish growth, this species revealed a biphasic growth pattern, starting with a much faster growth in the first years of life, that slows down at 2.44 years of age, when individuals start to allocate energy for sexual maturation. This finding was corroborated through the implementation of a maturity ogive and analysis of fish size and otolith length relationship. Growth modelling of this species was possible with the Bayesian inference approach that allowed for the improvement of results, which came to be a crucial tool in estimating realistic growth parameters, when only biased and imperfect data is available.
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