Northeast Atlantic Mackerel Research Articles

Growth variability of mackerel (Scomber scombrus) off north and northwest Spain and a comparative review of the growth patterns in the northeast Atlantic

Abstract This paper studies the age, male and female growth patterns and the interannual growth variability during the 1990–2000 period of the northeast Atlantic mackerel (Scomber scombrus Linnaeus, 1758) off north and northwest Spain (ICES Divisions VIIIc and IXa north). Age was determined by interpreting and counting growth rings on the otoliths (sagitta) of 7732 individuals caught during the spawning seasons by the commercial fleet and during fisheries research surveys. The parameters of the von Bertalanffy growth curve were estimated for sex combined for the whole period studied (L∞=42.7 cm, k=0.268 per year, t0=−2.17 years) and for each year; for males (L∞=42.1 cm, k=0.276 per year, t0=−2.15 year) and females (L∞=43.0 cm, k=0.264 per year, t0=−2.21 year) for the whole period studied. The values of L∞ and k of the growth curves in males and females exhibited significant differences (likelihood ratio test, P

Behaviour of mackerel schools during summer feeding migration in the Norwegian Sea, as observed from fishing vessel sonars

AbstractIn July 2002, two commercial vessels were used to study the distribution of Northeast Atlantic mackerel (Scomber scombrus L.) during their feeding migration in the eastern part of the Norwegian Sea between 62°N and 70°N. Pelagic trawling and school tracking with SIMRAD 24–36 kHz sonar demonstrated that the stock was distributed throughout the study area. Information about time, geographic position, size, depth, speed, and direction was stored for each school during tracking. This study reports analyses of data from 63 schools that were tracked for 30 s or longer. All schools were recorded at depths of less than 100 m, and the majority (65%) were found between the surface and 40 m. The direction of migration (north 0° ± 22.5°, northeast 45° ± 22.5°, etc.) was non-random, with east and west as dominant swimming directions. School size and migration speed varied from 1 to 7000 tonnes and 0 to 6 m s−1, respectively. Methodological improvements are discussed.

Scope for Efficient Multinational Exploitation of North-East Atlantic Mackerel

The three major harvesters of North-East Atlantic mackerel are modelled as exercising alternative coalitional strategies. Incentives for coalition formation are analysed by finding the maximum rents that harvesters can obtain under all possible coalition arrangements. The main result is that for a wide range of parameter values, the all-player coalition is unstable if joint rents cannot be redistributed amongst the players. Without transfers, the outcome is the type of non-cooperative fishing currently observed. However, if transfers are possible, side payments can be found for the mackerel fishery to sustain the efficiency gains of joint maximization. It is shown how they can be set to enhance the likelihood of their being accepted by players operating under a regional fisheries management organisation, or to be self-enforcing and protect against defection by sub-coalitions.

Environmental factors and recruitment of mackerel, Scomber scombrus L. 1758, along the north-east Atlantic coasts of Europe

Increasingly, scientific publications refer to some of the environmental factors affecting the recruitment in fish species. However, presently, there is little information available concerning the influence of the environment on the recruitment of Scomber scombrus, the North-east Atlantic mackerel (NEAM). In this contribution, North Atlantic Oscillation (NAO), upwelling and turbulent mixing (or `turbulence') series were compared with recruitment estimates, at age-0. The results show that the southern prespawning migration pattern of the Atlantic mackerel is directed towards areas with low turbulent mixing at spawning time, providing a `stable environment' for egg and larval survival. In the southern areas, where the spawning starts, the turbulence conditions of prespawning and spawning periods have the largest influence on the success of recruitment; this is related, possibly, to the more `stable' weather in the subsequent months and for the remainder of the year. In contrast, in the northern areas, the role of turbulence over the entire year becomes increasingly more relevant; this is related, possibly, to the high levels of turbulence during autumn and winter, which may become limiting to the survival of juveniles. About 50% of the variability in the Atlantic mackerel recruitment may be explained by means of environmental variables, such as turbulence. Other variables, such as upwelling and NAO, are only slightly, or not, statistically significant.

Ectoparasites on northeast Atlantic mackerel (Scomber scombrusL.) from western and north sea stocks

Mackerel caught in the North Sea (130), Skagerrak (148) and southwest of Ireland (176) were examined for ectoparasites. The most common parasites were Kuhnia scombri and K. sprostonae (Monogenea), ...

Prevalence and development of intraleucocytic haemogregarines from Northwest and Northeast Atlantic mackerel, Scomber scombrus L.

Abstract. Scomber scombrus on both sides of the North Atlantic were infected with similar intraleucocytic haemogregarines. Detection of parasites in blood smears alone was found to be an unreliable indicator of prevalence. In the Northwest Atlantic, prevalence of blood infections varied annually and seasonally, with an average of 18.4%, whereas tissue imprints showed up to 98.3% prevalence. Northeast Atlantic fish had a 4.0% prevalence in blood smears and 100% in spleen imprints. Age 1 mackerel were the principal hosts of haemogregarines in the Northwest Atlantic. Scanty infections of single and paired parasites were observed primarily in lymphocytes and neutrophils of peripheral blood and tissue imprints. Also present in the blood and tissues of Northwest Atlantic mackerel were intracellular schizonts with up to 20 merozoites, and fish from the same region showed haemogregarines within histological lesions in kidney and spleen. Ultrastructural studies on Northeast Atlantic mackerel indicated the parasite is apicomplexan and morphologically dissimilar to Haematractidium scombri. Its relationship with Goussia clupearum was not determined.