Wednesday, 25 February 2015

Koraalduivel

Pterois volitans, the lionfish or scorpionfish [L] is, in an aquarium, a beautiful, exotic and restful creature to watch - far more entertaining than television. I first met them when I was working in the fish department of Blijdorp Zoo in Rotterdam.  I had a near-death experience with a stone fish and weekly encounters with piranhas, but nothing unhappy happened in my dealings with the koraalduivel (coral-devil), as we called them back there, then. They live in the warm-tropics from the Red Sea through the Indian Ocean to the Pacific, and are voracious feeders on smaller fish. They don't swim fast with all their finery dragging them back, but they pounce very quickly. The stripes are partly camouflage but mainly a don't-mess-with-me advertisement fashioned by millennia of evolution to go with their toxicity. They produce a poison in their feathery spines that will make you feel really sick if it doesn't kill you.  The toxin is 70% identical to that of Synanceia verrucosa, with whom I had my NDE.  If you can by-pass the spines, they are good to eat.

Now here's a story that some F*@&!ng idiot dumped a gravid female into the warm water off Fort Lauderdale Florida in 1985 (rather than eating her and have done with it) and her offspring have since spread over 4 million sq.km across the Caribbean and down the coast of South America. It has been a lot worse than flushing a Christmas-gift crocodile down the toilet into the NYC sewers [Snopes: not true!] because lionfish eat a lot and grow fast and there are no natural predators on that side of the Atlantic. There seems, however, to be a solution akin to weeding your rose-garden. The things you like (roses, native fish and crustacea) may be in danger of being swamped to oblivion, but can be given a competitive edge by some selective culling. You know that no amount of pulling nettles Urtica dioica and scutch Elymus repens from your roses is going to eliminate the weeds but a little work on that front will let you see the flowers. There have been a number of ventures and competitions to encourage scuba divers and snorklers to take out lionfish because they taste so good but mainly because a prize or bounty has been offered.  A controlled experiment in the Netherlands Antillies showed that a culling scheme in Bonaire reduced the biomass of these predators to a quarter of that seen in nearby Curaçao.

It works, at least partly, because Pterois have gone the aposematic route and so are clearly visible against the reefs.  A similar scheme on land offering bounties for bringing Burmese python Python bivittatus corpses to the Florida Fish and Wildlife Service has so far shelled out 68 times, not even denting the estimated population of 50,000 of these well camouflaged and invasive snakes.  What is emphasised in Hannah Hoag's essay in Nature is that, having established some baseline for belief that culling lionfish helps the local ecosystem, the next step is to do some basic research. Is it better to kill the biggest lionfish? Are they the most fertile? What is the minimum nmber to cull to make a difference? How quickly do diminishing returns kick in as the kill-quota increases? Is there a best time of year, or a better place to target? Will killing the easiest lionfish to kill increase the fitness of the population?

The 2002-2003 Victorian Fox Bounty Trial [PDF] is cited as a cunning plan that was expensive and did not work. $A10 was paid out for each fox-tail that was submitted to a score of centres across the State of Victoria in Australia. 150,000 tails were turned in for cash and there was no significant impact on the density or depredations of the foxes Vulpes vulpes (one of several European mammals introduced to Australia in the 19thC. There are even suggestions that the cull increased the number of foxes by disrupting the local social structure or encouraging the influx of foxes from outside the culling area.  There is certainly anecdotal evidence that fox-tails were shipped in from outside the State by enterprising bounty-hunters with cousins up-country.  Despite the evidence that bounty-hunting in 2002-2003 was useless, the scheme was allocated another $4 million in 2011 for a repeat performance that is still current. Agronomists in these WEA islands are convinced that killing badgers Meles meles is an effective way of preventing tuberculosis in cattle, but this is really more of an article of faith than strongly backed by scientific evidence. There is evidence with badgers that culling in one area will encourage influx of fertile badgers from the surrounding area.

Hello?  Research?  Evidence?

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