Phyllis and Jim wrote:
Oldest koi is around 25 years old, but pond is now 29 years old and
we also put 40 tiny baby Golden Orfe in several batches over the
first two years and we still have about a dozen of them (they are
huge and it's not worth putting any more koi in whilst they are
there since the koi respond to the adult orfe pheromones and now
don't grow!!)


We have not added orfes. How did you learn about the pheromone
influence of orfes on koi?

Phyllis
Phylliss

Sorry for late reply.

The issue of pheromones is well documented (I've seen many references since
I started to keep fish and I was also into marines - seahorses, in
particular - for a long time). I was a member of British Koi Keepers and
British Marine Aquarists, read all the magazines available over here, in the
UK, and also tried to get as much as possible from the USA. I also attended
the UK trade association for a couple of years as a representative of the
Seahorse group I set up.

Koi not generating pheromones when they reach adulthood was common knowledge
(and is why koi kept in a koi only system only stop growing when they reach
their natural limit or the size dictated by the conditions, e.g. pond size
or, more exactly, depth), but all (or most) other fish do (used for sex
changes in some marine fish). It was "common knowledge" (in other words - I
can't remember the exact source, but there many!) in the 1970s/1980s that
although koi did not generate pheromones they react to other fish
(particularly goldfish since these are from the same family of fish) and
there were several references to orfe, as well. My own experience supports
this.

Peter
--
Peter & Elizabeth Corser
Leighton Buzzard, UK