Thursday 4 February 2016

Zebra Fish-crossing

There has been an invasion from the East; but it's not more about Syrians washing up of the beaches of Europe, we're talking about more distant  inhabitants [not human] washing up in the coastal waters of Syria and other countries in the Near East. There have been significant changes to the marine ecology since the opening of the Suez Canal - called Lessepsian migrations after the supervising engineer . Mostly these have occurred on the Mediterranean side because the sea level is slightly lower than in the Red Sea so water has been streaming into the Med for the last 150 years. For several years after the canal was opened, the hypersaline Great Bitter Lakes, which form part of the canal track, killed off most things which attempted to explore North&Eastwards. The salinity fell by dilution and so more and more species are making the transit. The Red Sea is more salty and less nutrient-rich than the Med, so its inhabitants are well 'ard and compete successfully against the fat effete Mediterraneans.  When Egypt built the Aswan Dam to tame and control the flooding of the Nile - and generate some electricity for a developing nation - that reduced the inflow of fresh water to the Eastern Med; which brought up the salinity; which made it less traumatic for the invaders.

Fish passing in the Night
Some 300 species - of fish, molluscs and crustaceans - have been recorded in the Mediterranean. There is some evidence that the rate of novel introductions is increasing and if you're properly trained in marine taxonomy you can find previously undocumented invasive species wherever you look - six new species of fish near the island of Rhodes for example.  I can't find anyone screaming about habitat destruction or the demise of native species, so it's not something we should lose sleep about . . . yet.  When another Red Sea native the scorpionfish Pterois volitans was dumped into the sea off Florida, that was a disaster.  And it might be another story now that the Egyptian government has widened the canal to double the revenue [to $13bn] and reduce passage time. Certainly the Guardian was predicting the end of the world as we know it in 2014.

The number of species travelling upstream to the less hospitable Red Sea, are about 100x less: seemingly limited to two species of goby Gobius paganellus, and Gobius cobitis, and a large carnivorous seabass Argyrosomus regius.

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