Study of the growth pattern of juvenile European hake (Merluccius merluccius L.) using whole otoliths and length frequency distributions from commercial catches and groundfish surveys

A review of length distributions of commercial landings from bottom trawls, small gillnetters and groundfish surveys in Galicia has led to a new hypothesis about the individual growth of young hake from the Southern Stock (ICES Divisions VIlle and IXa). According to this new hypothesis, hake grow to about 20 cm in the first year of life and up to 35-40 cm during the second. This is in contrast with the more widespread belief that hake grow to about 15 em and 24 during the first and second years of life respectively. Consequences of the new hypothesis are that landings of hake from trawls and small gillnetters would be mainly composed of 1 year old hake and that they would reach first maturity at age 3. An interpretation of the pattern of otolith rings consistent with this hypothesis is that 6 months after birth a first hyaline ring is formed, probably associated with the change from pelagic to demersal life and that another hyaline zone with opaque rings evbedded in it is formed during the first winter. Although this study refers to hake from the Southern stock, it is possible that these conclusions are applicable also to hake from the Northern stock (ICES Divisions VIIIa,b, Sub-areas VI,VII and IV )

Sardine (Sardina pilchardus Walb.) stock differential distribution by age class in Divisions Vlllc and IXa

A migration pattern of sardine juveniles and spawners is suggested as an explanation of the similarities observed between the stock differential distributions from catch in numbers (1979-1985) and from acoustic estimation (1983-1986), both by age group, in Divisions Vlllc and IXa

Primeros datos sobre la dinámica del «stock» de merluza europea (Merluccius merluccius L.) frente al litoral gallego

Durante la campaña «Merluza NW 74", realizada en aguas gallegas, se extrajeron los otolitos de 272 merluzas, que hicieron posible conseguir una primera aproximación a la clave talla-edad, y al relacionarlos con las capturas de merluza obtenidas durante la campaña, una estimación de la mortalidad total. Los resultados muestran que el parámetro K de la ecuación de V. Bertalanffy estaría comprendido entre 0,069 y 0,O83, Y L∞ entre 143 y 124 cm. La mortalidad de las clases 1+ a II+ sería 0,94, y de la clase III+ en adelante, de 0,6. La alta cifra de mortalidad entre las clases II+ y JII+, y el sesgo a la izquierda de la talla media de la clase II+, demostrarían una emigración hacia fuera de la costa de la merluza mayor de esta clase de edad y de clases posteriores.During "Merluza NW 74" survey, undertaken off Galicia shores in August 1974, otoliths of 272 hakes were collected, that made possible to obtain a first approach to the length-age key ; and, relating these data with hake catches during the survey, a first estímate of total mortality was obtained. Results show that the K value from V. Bertalanffy equation would be between 0,069 and 0,083, and L∞ between 143 and 124 cm. Total rnortality between age classes I+ and II+ would be 0,94, and for classes III+ and older, 0,6. The high mortality figure between I+ and III+ classes, and the skewness to the left in the mean length of this class, woulcl show an emigration offshore for the bigger hake of this age-class and older.Versión del editor

Estudios de cartografía, selectividad y marcado de merluza europea, Merluccius merluccius L., frente al litoral gallego

Versión del editor0,000

An analysis of the historical catches of hake, 1936-1977, in subareas IV, VI, VII and VIII

Changes in the catch level of hake since 1936 to 1977 corresponding to subareas IV, VI, VII and VIII -area of distribution of the northern stock of hake, plus division VIIIc- are described and analysed. Four periods can be defined in relation to the catch level: 1) The wars period, 1936-1944, with catches reduced for the course of the spanish civil war, and the second big war; 2) Post-war period, 1945-47, when the effort recovered suddenly at least the prewar level, with very high catches consisting of a portion of the big standing stock accummulated during the wars period plus the surplus.; 3) 1953-1964, with catches stabilized at a level between 70 and 85000 tons; and 4) 1964-77, with catches between 60 and 70000 tons. The document shows how most of the reduction of the catch happened in divisions lVa+Vla, and atributes this decrease in the catch of hake to the strong increaee in trawl effort on the Northern divisions

Some correlations between CPUE series of hake (Northern Stock)

This document describes results of computing correlations between different CPUE series of hake (Northern Stock). Results show that significant correlations between some series appeared when same lag was allowed between series. Lesconil artisans CPUE (fishing in division VIlla) in year t seems to be correlated to CPUE La Rochelle "artlsans" on the same year, to La Coruña trawlers fishing in subarea VII on year (t+1) and to La Rochelle "hauturiers" fishing in subarea VII on year (t+3) ; these "hauturiers" CPUE is correlated with Lorient trawlers CPUE fishing in divisions IVa + VIa two years later. These correlations allow to become more confident on these CPUE series. However, it is difficult to believe that plots like the one in fig. 7 can prove that there is a direct cause to affect relationship between hake CPUE from "artisans" in subareas VII and VIII and hake CPUE from "hauturiers" fishing in divisions IVa + VIa two years later

Systematic Mapping of the Spanish Continental Margin.

Publicado

Cenozoic Tectonics on the Galicia Margin, Northwest Spain.

Publicado

A check of traditional parameters based on fishing effort in the surface fishery of juvenile albacore in the Northern Atlantic

In this paper, the authors try to check if there exists a relationship between catchability and stock size in the juvenile albacore surface fishery in the North Atlantic stock. The conclusions are that this relationship does not seem to take place; fishing effort reflects very well F, and CPUE changes reflect abundance changes in the stock in the period analyzed. The authors call readers' attention to the possibility that a "significant" correlation between q and N does not mean a cause to effect relationship between these two variables.Les auteurs du présent document ont tent de vérifier s'il existe une relation entre la capturabilité et la taille du stock dans la pêcherie de surface de germon juvénile du stock de l'Atlantique nord. Les conclusions sont que cette relation ne semble pas se présenter; l'effort de pêche reflète tres bien F et les changements de la CPUE illustrent ceux de l'abondance du stock pour la période analysée. Les auteurs attirent l'attention du lecteur sur la possibilité de ce qu'une corrélation "significative" entre q et N puisse ne pas signifier qu'il existe une relation de cause à effet entre ces deux variables.Este documento intenta comprobar si existe una relación entre la capturabilidad y el tamaño del stock de atún blanco juvenil en la pesquería de superficie del Atlántico Norte. La conclusión es que no existe tal relación; el esfuerzo pesquero refleja bien la F y los cambios en la CPUE reflejan cambios en la abundancia del stock durante el periodo analizado. Los autores señalan que existe una posibilidad de que una correlación "significativa" entre q y N no supone una relación causa-efecto entre estas dos variables