Mark Bethke (Ferreter) wrote,
>For those out there that say the numbers are not declining , whatever
happened to terebra taurinum which at one time was common throughout
florida, strombus gallus that was as common as alatus mitra florida , you
never see these anymore, or cymatium parthenopeum or cittarium pica both at
one time were as common as mud, futhermore not one of these species is
commercially havested , the numbers were whiped out by collectors who had
not restrictions .
 
That's quite an accusation, and I'd like to ask the old-timers some
questions about it. First, is the decline real? Second, are collectors
definitely the cause, or change of habitat as the area was developed? There
are a lot more people on Sanibel Island (Florida) now. Where does their
sewage go? How has the Sanibel environment changed in the last 30 years or
so?
 
It's hard to tell why a species declines in any given case. In some cases,
the decline is sudden and the species is slow to recover. This can be due
to unusually cold weather, storms, disease, introduction of a new predator
or parasite, oil spills, etc. ("mass mortality"). In others, the species
declines over a period of time, perhaps due to overfishing, overcollecting
the breeding adults, or to a gradual change in habitat (dredging, trawling,
lower influx of fresh water due to dams upstream, pollution, etc.).
 
The Pleistocene extinctions of large animals were probably due to
overhunting. By analogy, if only the largest and most attractive Sanibel
mollusks are in decline, then collecting may well be the cause of their
decline. Is this the case here?
 
Don't be quick to accuse. People have great confidence in themselves and
tend to think that they are responsible for changes in the ecosystem. This
is very often true, starting probably with the invention of fire and
weapons. But people sometimes blame themselves unfairly. Shallow-water
marine systems tend to have extreme, natural fluctuations in the
populations of plants and animals, even without people's interference.
Anecdotal data from collectors who settled on sparsely populated coasts
suggest this, and the paleontologic record proves it. It would be
remarkable if Sanibel molluscan populations were absolutely constant from
year to year.
 
Well, I've never visited Sanibel, so I don't have a clue. To those who have
the experience to answer a very complex question: How have Sanibel and its
mollusks changed over the years?
 
Andrew K. Rindsberg
Geological Survey of Alabama
Tuscaloosa, Alabama, USA
 
P.S. Of the species that Mark listed, Cittarium pica is eaten in the
Bahamas as a supposed aphrodisiac--as discussed in a previous thread. This
species is therefore one that may well have been overharvested by Man, but
not necessarily by horny shell collectors.
 
P.P.S. To North Americans: Have a pleasant, thoughtful, and thoroughly
enjoyable holiday this Thanksgiving.