> Von: ichthos_at_comcast.net
> Antworten an: nanfa_at_aquaria.net
> Datum: Tue, 23 Sep 2003 15:00:09 +0000
> An: nanfa_at_aquaria.net
> Betreff: RE: NANFA-- Bluenose Shiners & Pond Update
>
>> Does anyone know if Pt.hypselopterus and Pt.welaka will cross.
>> I believe they are found in some of the same locations, at least in
>> the FL panhandle. If I were to put both species in my pond and the
>> sailfins would spawn maybe it would stimulate the bluenose to also.
>> Anyone got other ideas?
>
> It's conceivable that they may, since many intergeneric hybrids occur in the
> wild among nest associates. I would keep them separate. (FYI, hubbsi &
> welaka will likely be placed in a separate genus from the rest of
> Pteronotropis; they form their own monophyletic group.)
>
> Also, it's not the nest per se that help induce facultate & obligate nest
> associates to spawn, but likely pheromones from the spawning hosts.
> (CFI has induced Phoxinus cumberlandensis to spawn in captivity by
> adding stoneroller milt to the tank.) Therefore, keeping associates and
> host in separate parts of the pond *may* be okay, depending on the size
> of the pond and water circulation.
>
> Regarding the benefits of nest association to host and associate --
>
> At least 35 minnow species borrow the nests, and sometimes also the
> parental duties, of larger fishes. Most of these associates are
> broadcasters that spawn over the nests of nest builders like
> Campostoma, Semotilus, Exoglossum, and Nocomis, while others have
> the gumption to spawn in the nests of fishes that would otherwise eat
> them, including bowfins, sunfishes, and basses. The benefits to the
> associates are clear. Why expend the energy to move all those rocks and
> dig those pits when you can get a bigger fish to do it for you instead? And
> why worry about protecting your young when a bigger, meaner fish will
> happily, if not unknowingly, "adopt" your eggs and babies?
>
> But the benefits of nest associations are not one-sided. Both hosts and
> associates benefit by the fact that the more eggs or fry there are in the
> nest, the risk of losing them to other predators is spread out between the
> two species.
>
> Heres a simplified example:
>
> Lets say an eel enters a chub nest and eats half of the chubs 1000 eggs
> before it gets full or is chased away. Only 500 chub eggs survive. If that
> nest contained an equal number of shiner eggs, then, statistically
> speaking, only one in two of the chubs eggs will be eaten. By letting a
> shiner spawn in its nest, the chub has increased its egg survivability from
> 500 to 750 eggs.
>
> Chris Scharpf
> Baltimore
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