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Subject: Re: Fish swimming direction
From: Charles Gowan <[log in to unmask]>
Reply-To:Academic forum on fisheries ecology and related topics <[log in to unmask]>
Date:Tue, 20 May 1997 14:51:44 -0400

text/plain (36 lines)

Darran Crabtree wrote:
>I am interested in determining whether the Irondequoit
>wetland contributes young fish biomass (age 0+ and 1+) to the adjacent
>Irondequoit bay.  To do this I must quantify the movements through the
>mouth of the Irondequoit creek (the only connection between the wetland
>and the bay).  I envision (I realize envisioning can get me in trouble)
>setting a portion of a gillnet (small mesh) perpendicular to the flow of
>the creek.  I will set it for only a short duration of time, anywhere from
>0.25-1.0 hr.  What are your opinions of my assumption that the orientation
>of the fish in the gillnet (head stuck in the net pointed downstream or
>upstream) is indicative of the direction that that young fish is going
>(out of the wetland or into the wetland).

I would recommend a two-way weir rather than a gillnet.  Compared to the
gillnet the weir will 1) not kill fish, 2) can be run 24-h a day so that if
diel pulses do occur you will not miss them, 3) there will be no ambiguity
about the direction fish were moving when caught, 4) the chance of fish
escaping past the sampling location without being detected is probably
lower.  By a stroke of coincidence :), I have used two-way weirs to monitor
fish movement (see Gowan and Fausch, Can. J. Fish. Aq. Sci. 53:1370-1381 for
a description of how to construct the weirs out of materials available at
any hardware store).  Please contact me directly if you would like more details.


Charles Gowan
Department of Biology and Environmental Studies Program
Randolph-Macon College
Ashland, VA 23005
FAX: 804-752-4724
email: [log in to unmask]

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