Are plants making fish happy???
Dallas E. Weaver, Ph.D.
deweaver at gte.net
Mon Mar 30 12:01:53 EST 1998
Terry Hawk doesn't seem to like the idea of holding the vet who started
this whole question responsible for his irresponsible actions.
Remember he was "<bold>the head of the local veterinarian
authority</bold>" doing an <bold>inspection</bold>, this is not a staff
member or hired local vet whose advice, free or otherwise, can be taken
for what it's worth. He is abusing his authority with undocumented
and irresponsible demands operating from a position of ignorance.
I have had several customers (I also sell to zebras, embryos, etc. to
researchers) who tell me that their animal welfare people say how many
fish they can stock in a tank. What is interesting is that the size,
type and capacity of the water treatment system is never questioned
even though this is the controlling variable determining the tank
capacity and the volume of the tank is usually irrelevant. Zebras will
grow, breed and give good food conversions at 40 kg/M3 (about 100/l of
young adult fish) which means that you really only need a few liters of
tank volume for 100 pr of breeders, it you have enough filtration and
mass transfer (Oxygen and CO2) capability. Note: If you stress a fish,
the food conversion and growth rate both drop and they won't breed.
Dr. Hawk seemed to imply that we must prove the authority's demands
"may be detrimental to raising a particular species of fish" with
publications or evidence. Most of the questions we are talking about
are below the "Least Publishable Unit" for peer reviewed journals and
is considered proprietary in the private sector. Other that what has
been in this e-mail exchange, I have never published or presented any
of my work on structure, tank color, light levels, water SS, densities,
etc. relevant to zebra danio production.
I contend that all individuals who have authority to demand other
conform must limit those demands to those areas that they can provide
evidence and know what they are talking about. The burden of proof
should be on the authority. The "just doing their job" argument
doesn't hold when the demands are not technically sound and it will add
I have to deal with "authorities" in many fields and every time an
inspector comes in the door, you can figure it will cost at least a
thousand dollars in time and money. I have no problems with demands
which will improve safety and are solidly based in reality, but I have
very major problems with items which decrease safety or are based upon
unrealistic assumptions or simply are stupid (like the pluming
inspector that demanded that I use all copper pipe, valves and fittings
in the systems because that is what the pluming code says must be used
inside a building). This whole plant in the tank issue is equally
stupid, but at least it won't kill the fish like copper pipe would.
If you are really interested in minimizing the stress on the animals,
there are many other factors that are much more relevant. We can start
with larval nutrition and go all the way to tank color, outside
movment, automatic feeding (no movment), red lights (switch day and
night) so the fish can't see the operator and proceed on to water
quality and trace element chemistry.
Dallas E. Weaver, Ph.D. Scientific Hatcheries
deweaver at gte.net 5542 Engineer Dr.
714-890-0138 Huntington Beach, CA
Fax 714-890-3778 92649
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