Excess eating of shark in fish and chips and other meals is not just bad for the conservation of the species but may also damage human health, a new study shows.

Analysis of the tissue of 30 dusky, sandbar and great white sharks caught by long lines and in shark nets off the NSW coast found high levels of metals including mercury "that may have negative implications for human consumers", the study published in the Marine Pollution Bulletin found.

Male great white shark - one to avoid on the dinner table as well. Credit:Richard Vevers

According to the Food Standards Australia New Zealand website, fish is an excellent source of protein but the consumption of some species should be limited because of higher levels of mercury. These include limiting consumption of shark (flake), marlin and swordfish to no more than once a fortnight for pregnant women, while the general population should only eat flake and other fish species once per week, according to the FSANZ.

According to the shark study, in the two highest concentrations of mercury found, two 120-gram servings of either dusky or sandbar shark muscle tissue would be enough to exceed FSANZ's provisional tolerable weekly intake levels for mercury. Some 75 per cent of the dusky sharks and 58 per cent of the sandbar shark samples exceeded the FSANZ's maximum mercury limit, the report said.