lon (160-L) mixed population aquarium. Tankmates
living in the tank at the time were a pair each of
Amphiprion ocellaris (Darwin variant), Pajama Cardinalfish, Sphaeramia nematoptera, and Goldtail Demoiselles,
Chrysiptera parasema.
Right from the start the fishes exhibited confrontational behavior and indulged in mild skirmishes. One
individual grew more rapidly and dominated the other,
weaker specimen. From this I subsequently assumed that
I had two individuals of the same sex and that the desired pairwise maintenance wasn’t to be a reality. I therefore hoped that my aquarium had sufficient cover and
was large enough for the two fishes to keep out of each
other’s way. In autumn 2007 I had to move for career
the Blue assessor (Assessor macneilli) is closely related to the
Yellow assessor (A. flavissimus).
reasons. The tank was temporarily set up at my parents’
home and was housed there for the following year and
a half.
During my only occasional observations I noticed
that the smaller fish often disappeared for weeks, leading
me to assume several times that it was no longer alive.
When it then reappeared, I was greatly relieved. Because
the larger assessor often also exhibited bite marks, missing scales, or torn fins, I assumed that its smaller conspecific was more seriously injured and in hiding, healing
its wounds.
In March 2009 I moved again. The tank was in-
creased to 53 gallons (200 L) and I finally had time for
extensive observation again. Purely by chance I discov-
ered a crevice in the aquarium decor, into which the
smaller fish frequently retreated. At first glance I could
see only part of its caudal fin and was pleased when sig-
nificant movement demonstrated that the assessor was
still alive. Then in April I observed something that really
couldn’t be true as it was known for a fact that A. flavis-
simus was a mouthbrooder: the fish was now sitting in
the crevice in such a position that I could see it head-on,
and the pectoral fins were fanning a gelatinous mass!
Before long there was no doubt left in my mind: the fish
was “juggling” a ball of eggs, but it didn’t take them into
its mouth!
Breeding Assessor flAvissimus
My interest in the breeding of the Yellow Assessor was
awakened after I discovered that my assessors didn’t exhibit the mouthbrooding behavior described in the literature, but instead a ball of eggs was guarded in a cave by
the male. The same observation was made independently
and published almost simultaneously by Wolfgang Mai
