ABSTRACT The rough scad, Trachurus lathami Nichols, 1920, is a small pelagic species distributed along the West Atlantic coast. It is most abundant in the Southern Brazil (28°30’-34°S) and in the Southeastern Brazilian Bight (SEBB, 22°-28°30’S). The rough scad is fished by purse seines, which main target is the Brazilian sardine, Sardinella brasiliensis (Steindachner, 1879). Age and growth are vital to understand the life cycle of a species, to fishery management and ecosystem modeling. This study aimed to assess the age and growth of T. lathami, to identify its age structure in the SEBB, and to evaluate what causes the wide differences among Trachurus species in terms of body size and growth parameters. Data available on T. lathami was attained between 2008 and 2010 from surveys at SEBB. A total of 278 whole otoliths of T. lathami, total length between 27 mm and 208 mm, were analyzed and compared with the only other source of otolith data, from 1975. Three blind readings were performed and assessed using traditional methods to study fish age and growth. Zero up to eight rings were found, each ring corresponding to one year in the life of an individual of this species. The von Bertalanffy growth model parameters were L∞ = 211.90 mm and K = 0.319 year-1. The results of the analyses have shown similarities between 1975 and 2008-2010, indicating that the otolith development, the growth pattern and the age structure remained stable. T. lathami is the smallest species of Trachurus and it has the highest growth rates among them. This is probably related to the different temperatures where larvae/juvenile and adult grow, to the absence of a strong fishing pressure and to decadal population variability.

Este é o primeiro estudo detalhado sobre a idade e o crescimento da merluza Merluccius hubbsi no Brasil. Foram analisados 3.651 espécimes obtidos em cruzeiros de pesquisa e provenientes das frotas de arrasto e espinhel de fundo da região Sudeste-Sul do Brasil (21ºS a 34ºS) entre 1996 e 2001. Leituras de secções transversais de otólitos (corte, polimento e queima) foram realizadas para 686 indivíduos (397 fêmeas, 129 machos e 160 jovens com sexo não identificado), identificando-se zonas opacas e translúcidas. Foram calculados o incremento marginal e a porcentagem do tipo de borda, no tempo, para validação, resultando em um anel por ano, formado durante o verão-outono. Foram obtidos peixes com até oito anéis e seis anos de idade, sendo que os dois anéis depois do núcleo se formam durante o primeiro ano de vida. Foram aplicados métodos de retrocálculo aos dados de comprimento na idade e os parâmetros do modelo de von Bertalanffy foram estimados. O valor do comprimento máximo teórico variou entre 470,27 mm e 807,40 mm; a taxa de crescimento variou de 0,1657 a 0,3555 ano-1 e a idade teórica de comprimento zero entre -1,2846 e -0,4552 anos. O crescimento de fêmeas e machos difere significativamente. As técnicas aplicadas e os resultados obtidos foram discutidos, sendo comparados com estudos realizados no Uruguai e na Argentina e provendo informação importante para a gestão da espécie no Brasil, onde a merluza apresenta claros sinais de sobrepesca.

This is the first detailed study on the age and growth of the Argentine hake Merluccius hubbsi in Brazilian waters. A total of 3,651 specimens obtained from surveys and sampling landings using trawlers and long-lines in the South-Southeast Region (21ºS to 34ºS) between 1996 and 2001 were analyzed. Readings of sliced and burned otoliths were conducted on 686 individuals (397 females, 129 males and 160 young - sex not identified), identifying opaque and translucent zones. Marginal increment and edge type percentage methods were used for validation, resulting in one ring per year, formed during summer-autumn. Fish with no more than eight rings and six years of age were found, the two first rings after the core being formed during the first year. Back-calculation methods were applied to length/age data and the parameters of von Bertalanffy's growth model were fitted based on average length per ring. The value of maximum theoretical length varied between 470.27 mm and 807.40 mm; growth coefficient varied from 0.1657 to 0.3555 year-1 and the theoretical age at length zero between -1.2846 and -0.4552 years. Growth of females and males differed significantly. The techniques applied and the results obtained are discussed and compared with studies on hake conducted in Uruguay and Argentina, providing important information for the management of the species in Brazil, where it presents clear signs of overexploitation.

A merluza Merluccius hubbsi é uma espécie demerso-pelágica sobre a qual, apesar de sua importância nas pescarias da Região Sudeste-Sul do Brasil, poucos estudos foram realizados. Neste aspecto, destacam-se o Uruguai e a Argentina, países onde ela é o principal recurso pesqueiro e onde a existência de inúmeros estudos tem permitido o monitoramento da espécie. Neste estudo a maturação ovariana da merluza é analisada. Através do desenvolvimento ovocitário, apresenta-se uma escala de maturação e compara-se o emprego de escalas macro e microscópicas de maturação dos ovários. Constatou-se que os tipos de ovócitos e estruturas derivadas presentes nos ovários são semelhantes aos já descritos para a espécie e para teleósteos; o desenvolvimento dos ovócitos é sincrônico em grupos e a desova é parcelada. A identificação da maturação ovariana com base apenas em características morfológicas externas das gônadas apresenta muitos erros, principalmente na caracterização do estádio em maturação, sendo imprescindível a análise paralela do desenvolvimento ovocitário, realizada através de cortes histológicos dos ovários.

The Argentine hake Merluccius hubbsi is a demersal-pelagic species on which few studies have been undertaken, despite its importance for the fisheries of the South-Southeastern Brazilian region, . The species is the most important commercial fishery resource in Uruguay and Argentina, where several studies have permitted the proper monitoring of the species. The ovarian maturation of the Argentine hake is analysed in this study. A scale of maturation is presented in the light of the oocyte development and the use of macro and microscopic scales of ovarian maturation are compared. It was detected that the oocyte types and derived structures present in the ovaries are similar to those already described both for the species and for teleosts in general; group synchronous development and multiple spawning are typical. The identification of ovarian maturation based only on external morphological characteristics of the gonads presents many errors, mainly in the characterization of the stages of maturation, which makes imperative the parallel analysis of the oocyte development, undertaken through histological ovarian cross-sections.