The Mystery of the Feeder Fish, or Who is Rosy Red?
Bob Muller
625 S. Altadena, Royal Oak, MI 48067
Michiganfish_at_aol.com
Last winter I ran into Jim Langhammer at the Aquarium Shop in Royal Oak,
Michigan. He asked if I knew what species rosy reds were and I replied that they
were fathead minnows. Jim responded that that's what most of the literature
says, but that he couldn't find a published account of the origin of the color
variety. Jim thought that because of their thin body shape they might be
bluntnose minnows instead. He commented that in Europe, all of the fishes in the
genus Pimephales are called "fatheads," and in fact, Pimephales means fathead.
Fathead minnows (P. promelas) and their close relatives the bluntnose (P.
notatus) and bullhead minnows (P. vigilax), are all raised as bait. All three
have ranges that have been extended due to stocking and bait bucket releases.
They are also known to hybridize. Who knows what's thrown into the breeding
ponds? The origin of today's commercial rosy reds are possibly hybrids.
Identifying the Rosy Reds
Rosy reds have two color varieties, red and natural, so I took a number of each
type home with me. As feeders they are sold as juveniles, so I intended to let
them grow. When they were big enough, I'd run them through the identification
keys in my books to see if I could find anything out of the ordinary. Jim also
took some home to see what he could come up with. As the fish grew and were
compared to the identification keys, we found no clear answers. Do we have
hybrids or just a pure version of one of the species? As might be expected with
fish that are found from New York to the Dakotas, and from Michigan to the Gulf,
you find considerable differences. Added to this, we were not helped in our task
by the fact that the bait industry ships fish all over the country, and hybrids
probably occur between bait releases and local fish. Jim and I looked through
every regional book we had. There were many differences and exceptions in their
keys. We also looked at every photo in those books and on the Internet, and in
most of the photos we found contradictions to the keys.
I did discover that in a spawn of only natural-color rosy reds, about 20% of
the fry have the red coloration. This is about the percentage expected from a
recessive gene carried by both parents in a population.
One area in which the identification keys we consulted remained reasonably
constant is that both the bluntnose and bullhead minnow have a complete lateral
line. (The fathead minnow's lateral line is incomplete and stops at the dorsal
fin.) One of the red-colored males had a complete lateral line; the
natural-colored male's lateral line stopped at his dorsal fin. Fathead males
usually get breeding tubercles on the nose and mandible, whereas bluntnose males
get them only on their nose. The natural-colored rosy red male had no tubercles
on his mandible. One natural-colored rosy red male developed both the pattern
and the short, deep-bodied shape of a breeding fathead. The male red-colored
rosy red had some of the patternšs form but the body shape didn't change. The
only conclusion Jim and I could reach was that we didn't have a pure species.
Jim started sending out e-mails to a number of people asking if they knew which
species the rosy red represented. Dr. Gerald R. Smith of the University of
Michigan responded that 15 years ago he keyed out rosy reds from a bait dealer
in Wisconsin as bullhead minnows (P. vigilax). He said that he would be happy to
look at our fish. Time for a road trip!
Jim, Leo Long, and I filled a styro with bags of fish and we were off to Ann
Arbor. Dr. Smith examined our fish and concurred with our observations on the
lateral lines. He also found that the male red-colored fish (with the complete
lateral line like a bullhead minnow) had a lateral scale count that matched that
of the fathead minnow. The only thing consistent with these fish was that they
didnšt fully match any Pimephales species. Perhaps 15 years ago rosy reds were a
color morph of bullhead minnows, but now they seem to be a hybrid swarm. Most
likely, the rosy reds from regional breeding facilities are a different mix of
the Pimephales clan depending on what has been in the breeding ponds.
Had it not been for Jim's question about rosy reds, I would have never
considered keeping this fish. Wild fatheads are so plain that whenever I
collected them they went right back into the creek. And I donšt think bluntnose
minnows look much better. As for the rosy red color bait minnows, I think that
they're so ugly that they should be fed to anything just to get rid of them. But
when the rosy reds prepared to spawn, I found that their behavior made them
worth keeping.
Spawning the Rosy Red
I kept my rosy reds in a 60-gallon tank in which the water temperature never
went below 60F. At the end of March, I noticed that the male chased several
darters from under a large, flat rock propped up to form a ledge. He started
guarding this site, and after about three weeks several hundred eggs appeared
stuck to the bottom of the rock. Every day more eggs were laid, sometimes by
several females at a time. The male and females would closely examine the eggs,
and only eggs that weren't attached to the rock would be eaten. When the male
was examining the eggs, he often rubbed his back against them. Pimephales have
spongy pads on their napes that contain mucus-secreting cells and taste organs.
The pad apparently allows males to mark their spawning sites and contains an
anti-fungal agent.
After about a week I could clearly see the eyes of the fry in the oldest eggs.
I removed the rock and placed it in a three-gallon tank with an air stone for
circulation. A few days later the bottom of the tank was covered with fry. I put
the rock back in the tank with the male. He immediately took up his guard
duties, cleaned off any fungused eggs (or ate some, or both), and started
spawning again. I have never seen eggs develop fungus when they were being
tended by a male. I added a lot of green water to the fry tank and after several
days began feeding APR (artificial plankton rotifer), microworms, and newly
hatched brine shrimp.
The adults have continuously spawned for almost three months. Thousands of
eggs have hatched, but since I have only occasionally seen fry I assumed that
the parents must be eating them. Despite adding about a dozen other Michigan
minnows to the tank, the male easily defends his eggs. After four weeks, I
removed the green water and started to feed the fry only flake food. There are
now over 100 fry in the three-gallon tank, but I must have fed over 500 of them
to my darters.
Rosy reds are the most prolific fish I have ever worked with. It's no wonder
that they're raised as a bait fish. I canšt think of any of the tropical minnows
kept in the hobby (barbs, rasboras, and danios) that guard--and clean!--their
eggs. These are extremely interesting behaviors to watch.
If you want to try something different at a dollar a dozen, rosy reds are the
best deal in town.
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