Metal Contaminants in Fish: Blood as a Potential Non-lethal Monitoring Tool

The use of fish to monitor metal contamination is well established, but existing studies often focus on internal tissues that require the sacrifice of organisms. Developing non-lethal methods is thus a scientific challenge to enable large scale biomonitoring of wildlife health. We explored blood as a potential non-lethal monitoring tool for metal contamination in brown trout (Salmo trutta fario) as a model species. First, we investigated differences in metal contamination loads (i.e., Cr, Cu, Se, Zn, As, Cd, Pb and Sb) in different blood components (whole blood, red blood cells and plasma). Whole blood was reliable to measure most metals, implying that blood centrifugation is not necessary, thus minimizing sample preparation time. Second, we measured the within individual distribution of metals across tissues (whole blood, muscle, liver, bile, kidney and gonads) to test if blood could be a reliable monitoring tool compared to other tissues. Results show that the whole blood was reliable compared to muscle and bile to measure the levels of metals such as Cr, Cu, Se, Zn, Cd and Pb. This study opens the possibility for future ecotoxicological studies in fish to use blood instead of internal tissues to quantify some metals, thus reducing the negative impacts of biomonitoring on wildlife.

Bioaccumulation of mining derived metals in blood, liver, muscle and otoliths of two Arctic predatory fish species (Gadus ogac and Myoxocephalus scorpius)

Mining activities can cause adverse and long-lasting environmental impacts and detailed monitoring is therefore essential to assess the pollution status of mining impacted areas. Here we evaluated the efficacy of two predatory fish species (Gadus ogac i.e. Greenland cod and Myoxocephalus scorpius i.e. shorthorn sculpin) as biomonitors of mining derived metals (Pb, Zn, Cd and Hg) by measuring concentrations in blood, liver, muscle and otoliths along a distance gradient near the former Black Angel Pb-Zn mine (West Greenland). We detected metals in all tissues (except Cd and Hg in otoliths) and sculpin generally displayed higher concentrations than cod. For both species, concentrations were generally highest closest to the dominant pollution source(s) and gradually decreased away from the mine. The clearest gradient was observed for Pb in blood and liver (both species), and for Pb in otoliths (sculpin only). Similar to dissolved concentrations in seawater (but in contrast to bottom sediment), no significant decrease was found for Zn, Cd and Hg in any of the tissues. This demonstrates that by including tissues of blood (representing recent accumulation) and otolith (representing more long-term exposure signals) in the sampling collection, the temporal information on contaminant exposure and accumulation can be extended. We therefore conclude that both fish species are suitable as biomonitors near Arctic mine sites and, moreover, that blood and otoliths can serve as important supplementary monitoring tissues (in addition to liver and muscle traditionally sampled) as they provide extended temporal information on recent to long-term contaminant exposure.

Effects of graded levels of arachidonic acid on the reproductive physiology of Senegalese sole (Solea senegalensis): Fatty acid composition, prostaglandins and steroid levels in the blood of broodstock bred in captivity

Previous studies on Senegalese sole (Solea senegalensis) indicated that cultured broodstock (first generation, G1) have lower tissue levels of arachidonic acid (20:4n-6, ARA) than wild counterparts. ARA is metabolized to form prostaglandins (PGs) that are involved in steroid production and follicle maturation in fish. In the present study the effects of different dietary levels of ARA on blood lipid and fatty acid composition, prostaglandin (PGF2α, PGF3α, PGE2 and PGE3) levels and plasmatic steroid levels (11-ketotestosterone, 11-KT, testosterone, T and estradiol, E2) in G1 Senegalese sole were studied. For this purpose, 12 groups of ten fish (1:1 male and female), were fed six diets (each diets was fed to two groups) with different dietary ARA levels over nine months (diets A=0.7, B=1.6, C=2.3, D=3.2, E=5.0, F=6.0% ARA). ARA and CHOL levels in blood showed a significant increase in an ARA dose related manner (P<0.05) whereas EPA and EPA/ARA ratio were reduced. In males, steroid (11-KT and T) levels increased significantly with increasing dietary ARA in a dose dependent manner, whereas in females E2 did not show any change related to dietary ARA content. Plasma concentration of 3-series PGs (i.e., PGE3 and PGF3α) were reduced in parallel to increased ARA levels in blood (P<0.05) and levels of PGs 3-series were always higher than 2-series PGs (PGE2 and PGF2α). In conclusion there is an effect of dietary ARA on steroid production of Senegalese sole males, which might have important consequences in the reproduction of cultured fish.