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Subject: Re: Control of Odonata in fish culture
From: "A. Matsuo" <[log in to unmask]>
Reply-To:Academic forum on fisheries ecology and related topics <[log in to unmask]>
Date:Mon, 16 Sep 1996 21:08:36 -0400
Content-Type:text/plain
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Dear Mr. Dough,

        There's some comments I want to do about your reply as Control of
Odonata in fish culture:

        The tropical region is known by the high temperatures, and also to
the fast development of organisms. The fish I'm trying to rear is the
tambaqui, an Amazonian fish of high commercial importance value, specially
in the North region of Brazil. It's a Characiform, the species is Colossoma
macropomum. The larvae reach the exogenous feeding at 7-8mm long, 2 or 3
days after the eclosion. Their first food consists mainly of cladocerans and
copepods (0,3-0,4mm), in spite of high densities of rotifers at the tanks.
They exhibit high selectivite in preys, but when it is scarce, they accept
the rotifers as an alternative food and also dry diet early in the life. As
you can see, this preys are smaller than the larvae and there's no problem
concerned to the predation by this crustaceans in the pond rearing. The
dragonfly that usually put their eggs in the tanks, which I suspect to be a
species of Anisoptera, have big nymphs which in a space of time about 2
weeks of development, reach 2-3cm in lenght, and become a potential predator
of the larvae, which at this time have a lenght smaller than the nymphs. The
nymph, is therefore, at the highest level of the trophic chain in the tank
ecosystem.
        The problem of inseticides used on ponds is that it kills the
cladocerans and copepods, which are the first food of this larvae. I also
heard about Dipterex, but it has the same problems of other biocides tested
here in Brazil. Maybe it would be successful if used when the larvae begin
to feed on dry diets, replacing the live food of larvae. There's some
controversials about the acceptation of dry diets for the tambaqui larvae.
Some authors say something about the day 8 of exogenous feeding, but other
said that the dry food intake begin just after day 20. Personally, I still
have not chance to check it, but I hope do it soon. The food is changed when
the larvae becomes higher, preying on Chironomidae larvae.

        Thank you for your time. I really enjoyed your comments and I'm
looking forward to meet yoy virtually.

        With regards,

                Aline Matsuo.
_______________________
Aline Matsuo.
National Institute for the Amazonian Research
Alameda Cosme Ferreira, 1756
CEP 69083-000
Manaus - AM - Brazil

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