Difference between revisions of "Pollution and pelagic fish"

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<u>'''Heavy metals'''</u>
 
<u>'''Heavy metals'''</u>
  
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Methylmercury can biomagnify to high values in large carnivorous fish. These fish are also more active, causing them to need more oxygen. To extract more oxygen, they have to pump more water through their gills, causing them also to adsorb more contaminants. Unlike marine mammals and (possibly) sea birds, fish can't demethylate methylmercury, nor can they excrete it efficiently. Therefore old carnivorous fish often contain very large amounts of methylmercury, making them unfit for human consumption.<ref name="pub">Clark, R,B., 1999. Marine pollution. Oxford University press, Fourth edition, pp 161</ref>
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Heavy metals are thought to display a variety of sublethal effects on fishes.  
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Also, the presence of high concentrations of heavy metals forces the fishes to produce methalothionins. The energy they have to spend on the production of these detoxifying proteins can no longer be used on growth or reproduction.  
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<u>'''Organochlorine compounds'''</u>
 
<u>'''Organochlorine compounds'''</u>

Revision as of 08:48, 17 July 2009

Fish are through their gills continuously in direct contact with their environment. Unlike sea birds and marine mammals they can with these gills directly adsorb contaminants from their environment. Fish can therefore both be contaminated by eating and by direct uptake from the water. As they form the top of the food chain, large carnivorous fish will also experience problems from biomagnifying substances like methylmercury and organochlorine compounds.[1]

Heavy metals

Heavy metals are thought to display a variety of sublethal effects on fishes. Also, the presence of high concentrations of heavy metals forces the fishes to produce methalothionins. The energy they have to spend on the production of these detoxifying proteins can no longer be used on growth or reproduction.


Organochlorine compounds

Organochlorine pesticides in the 1960s very often caused acute toxic effects in fish. When sprayed on agricultural areas near the coast, they tended to ended up in large doses in nearby bays, resulting in massive local fish mortalities. This for instance caused fisheries in the Laguna Madre, a bay in Texas, to collapse. This was caused by pesticides sprayed on nearby . [2]


Case studies

Case study 1:Effects of xenoestogens in eels



References

  1. ↑ ↑ Kennish, M. J. (1996): Practical Handbook of Estuarine and Marine Pollution, CRC Press 524 pp
  2. ↑ Clark, R,B., 1999. Marine pollution. Oxford University press, Fourth edition, pp 161
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