There was also the one spawning method you described in the Susquehanna
where the fish were coaxed to spawn naturally. That's why I asked if those
adults were released post-spawning. It would also be useful to know the
details of the hand spawning, and how they select male-female crosses, sperm
mixing and egg mixing, etc. These are all important considerations for a
good spawning protocol.
> what of the limited gene pool that is being
> created through the use of hatchery fish? No one seems to have thoroughly
> addressed this issue. For example: 4000 adults are sacrificed to
> produce 20
> million stocked larvae annually into a river. The escapement 5
> years down the
> line indicate that 70% of the returns are of hatchery origin. Do
> this for 15 years. Is genetic diversity being limited, and in what way?
> Consider the comparison to a small wild run of 4,000 fish being allowed to
> repeat spawn over the same time period. Life history
> characteristics among these 4,000 can be very different.
> Genetically how different would these two populations (one-time spawning
> hatchery shad vs. repeat spawning wild shad) be?
That's why I first asked the question about multiple spawning rates. More
important than whether they CAN spawn multiple times is whether they DO.
For example, steelhead are repeat spawners but their repeat rate is less
than 15%. I imagine the repeat rate of an individual shad is less than that
because of their ecological significance as marine forage fish (the odds of
surviving to spawn a second and third time are probably not great). I'm not
basing that on anything I read. I just have a feeling that the majority of
spawners are young fish. What are needed are studies on population
structures of pre-spawning fish in the river (e.g., do they represent a
range of age-classes? Do age structures of the hatchery fish and wild fish
populations differ, etc.?)
> American shad from various runs do school together while they
> mature in the ocean, and when they overwinter.
What do you mean by "overwinter"?
> No one knows these answers, and very few are looking for them (as
> far as I can
> tell). Right now the emphasis is on simply trying to bring the
> shad back through
> whatever means possible -- including hatcheries, strict fishing
> closures, fish
> lifts and passages around dams, etc. Granted, the genetics of the
> whole process
> may prevent the shad population from returning to the millions
> that can once
> again sustain a commercial fishery. But at least the fish won't
> be extinct. At
> the very least, future generations of East Coast residents will
> be able to watch
> the shad return in the spring (a rite of spring celebrated by various shad
> festivals in Maryland and elsewhere).
Do these festivals celebrate shad or shad fishing? Shad as a resource or as
an ecologically significant species? And how about the suckers and other
unforgotten species the dams impacted? I don't mean to belittle their
efforts or the importance of shad on Atlantic coastal communities, but the
states and agencies and power companies involved in this really should have
done the research you say they haven't. The power companies that want their
dams relicensed aren't going to acknowledge they are operating on a river
with a stock facing potential extinction. Just being content with having
fish swimming once again isn't enough, especially now that we have the
technology to distinguish between evolutionarily distinct population groups.
-- Jay DeLong Olympia, WA
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