Mercury and selenium levels in archive samples of wild Atlantic bluefin tuna from the Mediterranean Sea.

This study examined total mercury (THg) and selenium (Se) levels in archive samples (white and red muscles, liver, gills) of the wild Atlantic bluefin tuna (ABFT) (Thunnus thynnus) (n = 18) captured in the central Adriatic Sea. The influence of fish size, age, and tissue type on element distribution was examined. There were significant differences in THg and Se levels, and Se:THg molar ratios among tissues. THg levels were highest in liver and lowest in gills (liver > red muscle > white muscle > gills), while Se levels were also highest in liver but lowest in white muscle (liver > red muscle > gills > white muscle). Se:THg molar ratios were highest in gills (22-82), intermediate in liver (11-29) and red muscle (7-36), and lowest in white muscle (1.7-7.6). Concentrations of THg in all tissues and Se in liver and caudal muscle were positively correlated with tuna age and size, while the Se:THg molar ratio in gills and all white muscles was negatively correlated with tuna age and size, indicating that the protective role of Se against THg is reduced in older specimens. The selenium health benefit values (HBVSe) were above zero in all tissues, indicating a small excess of Se after Hg sequestration. However, since the obtained HBVSe for edible tissues were near zero (0.01-0.04), and more than 70% of white muscle samples and all red muscle samples exceeded the EU regulatory limit for THg in fish muscle, it would be advisable to limit their intake in adults to one meal per month.

Legacy persistent organic pollutants (POPs) in archive samples of wild Bluefin tuna from the Mediterranean Sea.

Polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) were quantified in archive samples of dorsal white muscle of the wild Bluefin tuna (BFT) (n = 9) collected in the central Adriatic. PCBs were the predominant organochlorine (OC) compounds (60.8-69.4% of the total OC load) found. The contribution of HCB and ΣHCHs was significantly lower, ranging from

Mercury and selenium in fish from the eastern part of the Adriatic Sea: A risk-benefit assessment in vulnerable population groups.

The study examines the levels of total mercury (Hg) and selenium (Se) in the muscle tissue of 12 commercially important fish species (n = 717) from 48 locations in the eastern Adriatic Sea, as a function of fish species, size and habitat. Risks and benefits of fish consumption regarding Hg and Se in children (7 years) and women of reproductive age (30 years) were also evaluated. All samples but one were compliant with the European regulatory limit for Hg in fish muscle. Concentrations (µg g-1 ww) of Hg (range: 0.014-1.37) and Se (range: 0.184-1.12) and Se:Hg molar ratios in fish were associated with habitat type. Demersal species had the highest Hg and the lowest Se concentrations, while pelagic species had the lowest Hg concentrations, highest Se concentrations and Se:Hg molar ratios. All species had Se:Hg molar ratios above 1 (range: 1.4-66.9) and a selenium health benefit value (HBVSe) above zero (range: 3.3-9.3), indicating Se excess after Hg sequestration. The intake of two meals per week of small pelagic-neritic and bento-pelagic fish is estimated to be a valuable source of essential Se, and does not pose a risk from toxic Hg exposure in children and women during the vulnerable reproductive period. Due to the low Hg and favorable Se:Hg molar ratio and HBVSe index, small pelagic species offer a good risk to benefit ratio of fish consumption and could be considered an optimal choice in these sensitive subpopulations.

Ecological role of bluefin tuna (Thunnus thynnus) fish farms for associated wild fish assemblages in the Mediterranean Sea.

The ecological effects of tuna fish farms are largely undocumented. This study confirmed their high capacity to attract surrounding wild fish. The aggregation effect persisted year round, without detectable seasonal differences. Farm impact was restricted to close proximity of the sea cages, and was more prominent over the bottom than in the water column strata. Tuna fish farms proved to be high energy trophic resources, as indicated by the enhanced fitness status of two focal species, bogue and seabream. Under abundant food supply, seabream appear to allocate the majority of energy reserves to gonad development. Farm associated bogue had greater parasite loads, with no detrimental effect on fitness status. Overall, tuna fish farms can be regarded as population sources for aggregated wild fish, and under the no fishing conditions within the leasehold areas, can serve as functional marine protected areas.

Biocomplexity in Populations of European Anchovy in the Adriatic Sea.

The sustained exploitation of marine populations requires an understanding of a species' adaptive seascape so that populations can track environmental changes from short- and long-term climate cycles and from human development. The analysis of the distributions of genetic markers among populations, together with correlates of life-history and environmental variability, can provide insights into the extent of adaptive variation. Here, we examined genetic variability among populations of mature European anchovies (n = 531) in the Adriatic (13 samples) and Tyrrhenian seas (2 samples) with neutral and putative non-neutral microsatellite loci. These genetic markers failed to confirm the occurrence of two anchovy species in the Adriatic Sea, as previously postulated. However, we found fine-scale population structure in the Adriatic, especially in northern areas, that was associated with four of the 13 environmental variables tested. Geographic gradients in sea temperature, salinity and dissolved oxygen appear to drive adaptive differences in spawning time and early larval development among populations. Resolving adaptive seascapes in Adriatic anchovies provides a means to understand mechanisms underpinning local adaptation and a basis for optimizing exploitation strategies for sustainable harvests.

Chlorinated compounds in the muscle tissue of fish from the Croatian Adriatic: preliminary data on contamination and the associated health risks.

Levels of 17 polychlorinated biphenyl congeners (PCBs) and seven organochlorine pesticides (OCPs) were measured in the muscle tissue of 18 commercially important fish species from the eastern Adriatic Sea. PCBs [