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I have often wondered about this myself. I have seen lesions caused by
parasites behind the first dorsal fin of several shark species, most notably
blacktip sharks (Carcharhinus limbatus). Could it be that these fin
extensions, usually seen at the base of fins, serve to break up laminar flow
over the body and thus decrease the size of the boundary layer? If this is
true then it is possible that the extensions would make it more difficult for
parasitic organisms to attach to the body of their host. Just a thought.
Trey Driggers
Quoting Jon Shenker <[log in to unmask]>:
> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><>
> If you reply to this message, it will go to the whole list.
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>
> Hi Randy.
>
> Interesting. I've got 6 juveniles in my tank now, and I'm going to
> spend
> some time watching.....
>
> We're looking for juv. tarpon nursery marshes around the entire state of
> FL.
> Do you by any chance know any
> juv. habitats on the west coast, or have some colleagues who might have
> seen
> juvenile tarpon in some of the marshes/impoundments and other stagnant
> habitats?
>
> Thanks!
>
> Jon
>
> ----- Original Message -----
> From: "Randy E Edwards" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Thursday, October 10, 2002 1:50 PM
> Subject: Re: dorsal filaments?
>
>
> > ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><>
> > If you reply to this message, it will go to the whole list.
> > ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><>
> >
> > Jon,
> >
> > Here is an off-the-wall-hypothesis for you: Several species with
> dorsal
> > filaments (tarpon, threadfin herring, threadfin shad) exhibit similar
> > "rolling" behaviors, in which the fish come to the surface and some of
> the
> > fish's dorsal surface is momentarily out of the water. Could it be
> that
> > filaments on the dorsal fin provide some control during such "rolls"
> ?
> >
> > Randy E. Edwards, Ph.D.
> > Research Fish Ecologist
> >
> > USGS-BRD-FCSC
> > Center For Coastal & Regional Marine Studies
> > 600 Fourth Street South
> > St. Petersburg, FL 33701-4846
> > Phone: 727/803-8747 (x3069)
> > FAX: 727/803-2031
> > [log in to unmask]
> >
> > Do not tell fish stories where the people know you; but particularly,
> don't
> > tell them where they know the fish. [Mark Twain]
> >
> >
> >
> > Jon Shenker
> > <[log in to unmask] To:
> [log in to unmask]
> > > cc:
> > Sent by: Subject: dorsal
> filaments?
> > Scientific forum
> > on fish and
> > fisheries
> > <FISH-SCI@SEGATE
> > .SUNET.SE>
> >
> >
> > 10/08/02 04:02
> > PM
> > Please respond
> > to Scientific
> > forum on fish
> > and fisheries
> >
> >
> >
> >
> >
> > ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><>
> > If you reply to this message, it will go to the whole list.
> > ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><>
> >
> > An off-the-wall question:
> >
> > Does anyone have any good hypotheses about the function of the
> elongated
> > dorsal filaments that are found in some fish species?
> >
> > In the lower teleosts:
> > Tarpon have very long filaments, ladyfish don't.
> > Shafted bonefish (Albula nemoptera) has the dorsal filament, bonefish
> (A.
> > vulpes) don't.
> > Three or four North American clupeids have filaments, the rest don't.
> >
> > In the elasmobranchs, many species have some sort of elongation of
> the
> > dorsal fin beyond the fin base, but the fin seems elongated into
> distinct
> > filaments in hammerhead, bonnetheads and others.
> >
> > A hydrodynamic function? Maybe in elasmos, who have larger, stiffer
> > filaments, but in the slender , flexible filaments of teleosts?
> > Why would some closely-related species have them, and others not?
> >
> > Would removing a portion of the dorsal filament of a tarpon (for DNA
> > analysis) have an impact on the fish?
> >
> > Any information or speculation would be welcome.
> >
> > On another note: My old copy of Reuben Lasker's (ed.) Marine Fish
> Larvae
> > has finally been shredded beyond repair before I found time to
> photocopy
> > it.
> > It's an oldie but a goodie for helping students get started in the
> larval
> > fish field. I haven't had any luck finding a copy for sale in the
> used
> > book
> > web sites. If anyone sees a copy for sale, please let me know.
> >
> > Thanks.
> >
> > Jon Shenker, Ph.D.
> > Associate Professor of Marine Biology and Aquaculture
> > Department of Biological Sciences
> > Florida Institute of Technology
> > 150 West University Boulevard
> > Melbourne, FL 32901
> > 321-674-8145
> > FAX 321-674-7238
> > [log in to unmask]
> >
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************************************************************
William B. Driggers III, Ph.D.
Research Associate
University of South Carolina
Department of Biological Sciences
Columbia, SC, USA 29208
Phone: 803.777.7988
Fax : 803.777.4002
************************************************************
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