88 The Queensland Naturalist 
March 1948 
FISH AT SOMERSET DAM — STANLEY RIVER 
DOROTHEA F. SANDARS 
Immediately below the wall of Somerset Dam, on 
the doAvn stream side, is a confined area known as the 
spillway, and below this again is another confined area 
known as the dissipator. During the year, and especially 
after rainy periods, abundance of fish cf several types 
may be observed in these two areas. These fish have 
undoubtedly been attracted upstream by the taste of the 
“fresh." When the water overflows the dam wall, 
quantities of planktonic life, which forms the food of 
many fish. is carried downstream, and it is this 
phenomenon which is commonly referred to as a “fresh.” 
One of the commonest fish seen in the dissipator 
of Somerset Dam during many months of the year is 
the Bony Bream — Nnnalolosa come. This fish is usually 
seen in large shoals and the fish themselves may range 
from approximately H inches to 12 inches in length. 
On occasions, the typical “silvery" appearance of these 
fish appears to be marred, and on close observation this 
will be seen to be due to the presence of freshwater 
fungus. At least one type has been identified- -Isoachlya 
unisporu (kindly identified by Associate-Professor D. A. 
Herbert) ; but it is thought possible that other genera 
may be present in this locality. 
It is interesting to note that a great percentage of 
the fish caught is usually injured, frequently on their 
sides towards the caudal (or tail) fin. These wounds are 
acquired during the attempt by the fish to scale the 
concrete wall separating the dissipator from the spillway. 
These wounds, no doubt, are the scat for infection by 
the fungus. 
These Bony Bream, in common with most other fish, 
harbour eeto parasitic flatworms (Trematoda-Monogena) 
on their gills. These flatworms are attached by efficient 
adhesive structures, which take the form of special 
suckers on the posterior end of the body. By this means 
of attachment the worms cling to the gill-filaments of 
the fish host. The body of these gill-worms is usually 
very similar in shape to that of the gill-filaments them- 
selves, and so. lying parallel to the latter, they are usually 
difficult to determine. The gill-worms present on 
Nematolosa come range in length between two and three 
mas, 
