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Costa, A. M. 2009. Macroscopic vs. microscopic identification of the maturity stages of female horse mackerel. – ICES Journal of Marine Science, 66: 509–516.The consequences to fisheries management of erroneous macroscopic identification of maturity stages are evaluated. The percentage error in macroscopic identification of maturity stages of female horse mackerel (Trachurus trachurus) from the Portuguese coast was determined and analysed by maturity stage, between the periods January–June and July–December, between research surveys and commercial landings, and between per year and month and by length class, to assess its implications in determination of spawning season, maturity ogives, and spawning-stock biomass. The highest percentage errors in macroscopic identification were between late ripening and partly spent stages, in fish >30 cm, and for all fish collected in 1998 and 2005. Late ripening was generally macroscopically underestimated, and the partly spent stage overestimated. The implications for the information provided to the ICES assessment working group are analysed. [ABSTRACT FROM PUBLISHER]

Garrido, S., Murta, A. G., Moreira, A., Ferreira, M. J., and Angélico, M. M. 2008. Horse mackerel (Trachurus trachurus) stomach fullness off Portugal: index calibration and spatio-temporal variations in feeding intensity. – ICES Journal of Marine Science, 65: 1662–1669.An index for stomach fullness used in the routine biological sampling of horse mackerel from Portuguese waters was calibrated about the correspondent stomach mass. The fullness scale comprises four levels (1, empty; 2, <50% filled; 3, >50% filled; 4, bursting) that are easily attributed to whole stomachs during the sampling process. Significant differences were found among the four levels of the fullness scale in their relative stomach masses, indicating that the index can be used for the semi-quantitative analysis of feeding intensity in this species. The fullness index was applied to study spatio-temporal variations in horse mackerel feeding off the Portuguese coast, using data collected from 1985 to 2006 on commercial vessels and research cruises. There was no significant difference in feeding intensity between sexes. Smaller horse mackerel and those in the resting stage of reproduction fed more intensively than larger and spawning fish. Feeding intensities of fish from the southern and northwest coasts of Portugal were greater than for those captured along the southwest coast. Horse mackerel feeding intensity was greater at dawn and varied seasonally, being higher during spring and autumn and lower during winter. Interannual variation in feeding intensity of horse mackerel captured along the west coast of Portugal revealed a significant but slight decrease in recent years. [ABSTRACT FROM PUBLISHER]

This paper reports the results for the surveillance of nine organochlorine pesticides (HCH isomers (a, ß, e, ?), p , p '-DDD, p , p '-DDT, p , p '-DDE, p , p '-DDD, HCB and aldrin) in muscle of three fish species, European pilchard ( Sardina pilchardus ), Atlantic horse mackerel ( Trachurus trachurus ) and Atlantic mackerel ( Scomber scombrus ). Analytical methodology included n -hexane extraction, clean-up with 2% deactivated Florisil, and quantification with gas chromatography-electron capture detection (GC-ECD). The highest mean concentrations were found for p , p '-DDT in sardine and mackerel at levels of 30.1 and 109.9?µg?kg -1 , respectively, and for p , p '-DDD in horse mackerel at 51.9?µg?kg -1 . Three species had higher levels for S-DDT than S-HCH. The estimated daily intake of organochlorine pesticides in the three species showed that in sardine, the highest EDIs were found for aldrin, at 1.8?ng?kg -1 bw day -1 , which represents 1.8% of the acceptable daily intake (ADI), and for ß-HCH, at 4.0?ng?kg -1 bw day -1 , representing 0.4% of ADI. Lowest values were found for Atlantic mackerel. Statistical analysis to determine the differences in mean concentrations of pesticides between species, and any correlation between groups of residues related with each one of the species, was undertaken. [ABSTRACT FROM AUTHOR]

The results of preliminary investigations on the possible relationships between coastal upwelling variability observed with satellite remote sensing, and sardine and horse mackerel recruitment dynamics in the west coast of Portugal are presented. The analysis of a sardine-recruitment time-series for the period 1976–1998 shows that there has been a decreasing trend since 1983 (with the exceptions of 1991 and 1992), the years from 1993–1995 representing the lowest values in that time series. Horse mackerel exhibited a decrease from 1986 until 1990, and from 1992–1995, the latter representing the lowest value for the period 1986–1998. Sea surface temperature (SST) derived from satellite data were used to compute monthly SST upwelling indices along the Portuguese west coast over a period from 1987–1997. The analysis focused on seasonal and annual upwelling variability off Portugal, and its possible effects on sardine and horse mackerel recruitment to the fishery. An increasing trend in SST upwelling indices during the winter (January–March), especially between 1992 and 1995 was found. The upwelling events observed off Portugal during winter months, which correspond to the spawning season for sardine and horse mackerel, had a negative impact on the recruitment of these fish species. This effect on recruitment could be due to an increase in conditions favourable to the offshore transport of larvae and consequently an increase in their mortality. Prior to 1992, when no upwelling events occurred during winter, recruitment dynamics was closely linked with the spring–summer seasonal upwelling variability off the Portuguese west coast. [ABSTRACT FROM PUBLISHER]