The spawning period for mackerel in the North Sea

The intensity and duration of the spawning of mackerel (Scomber scombrus L.) was studied by daily plankton sampling from late May to early July 1976 at a single locality in the central part of the spawning area in the North Sea. The main spawning, as indicated by the presence of newly spawned eggs, started in early June and probably ended in early July. Slight maxima in egg numbers were recorded in early and late June. On an average, about 25 newly spawned eggs per m^2 were found. The incubation time was estimated to 9 - 10 days. Newly hatched larvae occured from mid June, with a maximum number in early July

Age and growth of hake Merluccius merluccius Linnaeus, 1758 from the Northeast Atlantic (ICES division IXa)

El objetivo de este estudio fue estimar los parámetros de edad y crecimiento de la merluza europea Merluccius merluccius Linnaeus, 1758 del nordeste atlántico (división IXa del CIEM, aguas continentales portuguesas), mediante el análisis de otolitos. Se observaron en total 951 cortes de otolitos, cubriendo un rango de longitud de peces de 10 a 80 cm, capturados en campañas realizadas entre octubre de 1996 y julio de 1997. La interpretación de los anillos anuales siguió los últimos criterios adoptados sobre atribución de edades, particularmente para los primeros grupos de edad. Se obtuvieron las claves trimestrales de edadlongitud considerando los sexos conjuntamente, así como la longitud media observada por edad. Se ha realizado una validación indirecta de los resultados basada en el análisis de las frecuencias de tallas utilizando el método de Bhattacharya. Los parámetros de crecimiento de la ecuación de Von Bertalanffy fueron L∞ = 110,6 cm, k = 0,08 años-1 y t0 = -0,97 años, valores similares a los estimados por otros autores para esta especie.The present study estimates age and growth parameters of the European hake Merluccius merluccius Linnaeus, 1758 from the Northeast Atlantic (ICES division IXa, Portuguese continental waters), based on otolith analysis. A total of 951 otoliths sections were examined, covering a length range of 10-80 cm, from fish taken during surveys carried out between October 1996 and July 1997. The annual ring interpretation followed the recently established standard ageing criteria, particularly for the first age groups. Quarterly age-length keys, for combined sexes, and the respective mean length at age were obtained. An indirect validation based on length-frequency analysis was performed using the Bhattacharya method. The estimated Von Bertalanffy growth parameters were L∞ = 110.6 cm, k = 0.08 year-1 and t0 = -0.97 year. These values are similar to those reported by other authors for the same species.Instituto Español de Oceanografí