Starting from 2004 the razor clam Ensis minor disappeared in the Gulf of Trieste (Italy) to reappear in 2008 when a similar species, Solen marginatus, crashed. E. minor peaked in 2011, when at least three successive recruitment events occurred. The species is difficult to rear and no restocking seem feasible. The density in 2012 was quite high in spite of a really bad February’ sea, and the fishery obtained good economic income. Scarce recruitment was observed in 2013 and no settlement was found up to the end of 2014. Presently E. minor is going low but S. marginatus is growing in densities again. These observations are difficult to explain: it could be a natural cycle perhaps based on competition between species. But the decrease in population density in beach restoration site (where E. minor disappeared, as survey results showed in September, 2014) could be a proxy for some tentative explanation: even if the cycles could be natural events it’s interesting to underline that both species did not recover after beach restoration. So the possibility that beach restoration can be at least in part responsible for the simultaneous absence of Ensis and Solen should be taken in account.
Sometimes they come back and disappear again
DEL PIERO, DONATELLA
2014-01-01
Abstract
Starting from 2004 the razor clam Ensis minor disappeared in the Gulf of Trieste (Italy) to reappear in 2008 when a similar species, Solen marginatus, crashed. E. minor peaked in 2011, when at least three successive recruitment events occurred. The species is difficult to rear and no restocking seem feasible. The density in 2012 was quite high in spite of a really bad February’ sea, and the fishery obtained good economic income. Scarce recruitment was observed in 2013 and no settlement was found up to the end of 2014. Presently E. minor is going low but S. marginatus is growing in densities again. These observations are difficult to explain: it could be a natural cycle perhaps based on competition between species. But the decrease in population density in beach restoration site (where E. minor disappeared, as survey results showed in September, 2014) could be a proxy for some tentative explanation: even if the cycles could be natural events it’s interesting to underline that both species did not recover after beach restoration. So the possibility that beach restoration can be at least in part responsible for the simultaneous absence of Ensis and Solen should be taken in account.Pubblicazioni consigliate
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