Science Questions

I recently heard a statistic quoted on a TV program which concerned me, but I haven’t been able to confirm it’s accuracy. They said that 90% of all big fish in the sea have disappeared in the last 40 years. This could be reversed if fish stocks are left to recover, provided certain fish have not become extinct. Is this simply down to over fishing, or is there a different explanation , such as global warming? Tad, Cambridge

We have had declines up to 90% of some fish, and overfishing seems to be the main culprit.  Whether or not fish stocks can recover is a different matter, we may have altered the marine ecosystem so much that recovery might not be possible.  
You may have heard that there’s not much cod left in the sea, especially around Canada.  A crash in cod numbers shut down many canadian fisheries in the 1980s, but the numbers of cod have not recovered despite much lower fishing.

A caller also pointed out that although trawlermen must throw back any juvinile fish, those below a certain size, often the nets damage or kill the small fish anyway, and so the damage is already done.  A better way would be to establish protected areas, but they may be prone to poaching.  We currently only have about 1% of the Earth’s ocean protected.

August 2007