Bioaccumulation of PCBs in liver tissue of dusky Carcharhinus obscurus, sandbar C. plumbeus and white Carcharodon carcharias sharks from south-eastern Australian waters.

Polychlorinated biphenyls (PCBs) are ubiquitous pollutants in the marine environment that are known to accumulate in apex predators such as sharks. Liver samples from dusky Carcharhinus obscurus, sandbar Carcharhinus plumbeus, and white Carcharodon carcharias sharks from south-eastern Australian waters were analysed for the seven indicator PCBs 28, 52, 101, 118, 138, 153 and 180. Median ∑PCBs were significantly higher in white than sandbar sharks (3.35 and 0.36 µg g(-1) lipid, respectively, p=0.05) but there were no significant differences between dusky sharks (1.31 µg g(-1) lipid) and the other two species. Congener concentrations were also significantly higher in white sharks. Significant differences in PCB concentrations between mature and immature dusky (3.78 and 0.76 µg g(-1) lipid, respectively) and sandbar (1.94 and 0.18 µg g(-1) lipid, respectively) sharks indicated that PCB concentrations in these species increased with age/growth. Higher-chlorinated congeners (hexa and heptachlorobiphenyls) dominated results, accounting for ~90% of ∑PCBs.

Metal and metalloid concentrations in the tissues of dusky Carcharhinus obscurus, sandbar C. plumbeus and white Carcharodon carcharias sharks from south-eastern Australian waters, and the implications for human consumption.

Shark fisheries have expanded due to increased demand for shark products. As long-lived apex predators, sharks are susceptible to bioaccumulation of metals and metalloids, and biomagnification of some such as Hg, primarily through diet. This may have negative health implications for human consumers. Concentrations of Hg, As, Cd, Cu, Fe, Se and Zn were analysed in muscle, liver and fin fibres (ceratotrichia) from dusky Carcharhinus obscurus, sandbar Carcharhinus plumbeus, and white Carcharodon carcharias sharks from south-eastern Australian waters. Concentrations of analytes were generally higher in liver than in muscle and lowest in fin fibres. Muscle tissue concentrations of Hg were significantly correlated with total length, and >50% of sampled individuals had concentrations above Food Standards Australia New Zealand's maximum limit (1 mg kg(-1) ww). Arsenic concentrations were also of concern, particularly in fins. Results warrant further investigation to accurately assess health risks for regular consumption of shark products.

Absorption of metals in mulloway (Argyrosomus japonicus) after ingesting nickel-plated carbon-steel hooks.

Previous research has alluded to the potential of metals being absorbed by fish after ingesting fishing hooks, which may have adverse effects on fish health and the organisms that consume them. Subsequently, this study aimed to quantify the potential of mulloway (Argyrosomus japonicus) to absorb metals during the decay of ingested nickel-plated carbon-steel hooks. Twenty-five treatment fish were allowed to ingest nickel-plated carbon-steel hooks during angling and then monitored with 25 controls (untreated fish) for up to 42 days for hook ejection and mortality. Blood, liver and muscle samples were collected from treatment, control and 14 wild-caught individuals to determine the concentrations of chromium, cobalt, copper, iron, manganese and nickel. The results showed that increased oxidation influenced hook ejection, and that hook-ingested fish had significantly elevated concentrations of nickel in their liver and blood, but not muscle. This research has shown that there is an avenue for metal absorption from ingested hooks.