RE: NANFA-- darter larvae

Hoover, Jan J ERDC-EL-MS (
Tue, 5 Jun 2001 16:57:50 -0500

>>>Matthews (1998) mentions some studies in which flood events kill almost
all larval
fishes present, even before the peak of the hydrograph, but I'd be willing
to bet that the observed mortality was caused by impingement into the drift
nets at high velocity.<<<

I think that's very possible. A spate of water going through a fine mesh
drift net would be pretty rough on a larval fish. By contrast, larval fish
allowed to swim freely or to drift passively can survive a surprising range
of hydraulic forces. Paddlefish larvae, for example, can survive frequent,
low turbulence and entrainment at velocities up to 3 m/s (immediate
mortality at greater forces resulting from detached yolk sac, twisted spine,
or indeterminate [internal?] damage).

>>>I'm coming up with dispersal rates on
the order of about 25 km/yr in a downstream direction, and 15 km/yr
upstream....I was hoping to be able to ascribe dispersal to larval drift,
but I don't
think that will be the case, unless flood events played a role.<<<

This makes sense to me. One small study we did indicated that the more
littoral species are more likely to swim downstream or drift. Darters seems
like they ought to do this.

Dave, you have probably already thought of this, but can you correlate
hydrographic peaks with first downstream record? I assume stage data are
available. Are collections pretty extensive?

/"Unless stated otherwise, comments made on this list do not necessarily
/ reflect the beliefs or goals of the North American Native Fishes
/ Association"
/ This is the discussion list of the North American Native Fishes Association
/ To subscribe, unsubscribe, or get help, send the word
/ subscribe, unsubscribe, or help in the body (not subject) of an email to
/ For a digest version, send the command to
/ instead.
/ For more information about NANFA, visit our web page,