Palatability of Marine Invertebrates — Russell 
453 
water. Particles were seized before they reached 
the bottom. 
A known amount of food was introduced, 
and the amount remaining uneaten after 2 hr 
was removed and weighed after excess water 
was removed. This gave a rough measure of 
the amount of food to be fed each day. Table 
1 gives food consumption in gm/gm fish/week. 
Testing Methods 
Feeding trials were made each day before 
normal feeding. During tests less normal food 
(prawn) was given to allow for other food 
eaten. Only two or three unpalatable materials 
could be tested in one series of tests, i.e. within 
1 hr. If more were tested, the fish ignored even 
normally palatable material for 3-4 hr. 
Comparisons of palatability were made by 
dropping simultaneously two equal-sized frag- 
ments on the water’s surface as distant from 
the fish as possible. As soon as the particles hit 
the water, the fish swam towards them. Usually 
both particles were falling through the water by 
the time the fish reached them. The reaction of 
the fish to each fragment was observed, and an 
estimate made of which was preferred. The 
size of pieces used was that most suitable for the 
species (see Experiment I). Tests were repeated 
twice where possible, with an interval of at least 
one day between tests. 
whenever a person approached an aquarium. 
This was particularly so with Gamhusia and 
Carassius. It was considered that this response 
would not affect the results: while the initial 
attraction was visual, final acceptance depended 
on other factors. 
EXPERIMENT I 
GENERAL REACTIONS TO INTRODUCED 
MATERIAL 
The reactions of each species to one palatable 
material (Metap emeus') , and to one "neutral,” 
inedible material (plastic tubing) was tested. 
The significance of different particle size for 
later tests of palatability was noted. 
Results 
Gamhusia reacted to a large piece of Meta- 
penaeus by clustering densely round it and 
biting at it vigourously for up to 30 minutes. 
Fragments less than 4 mm across were eaten too 
rapidly by one or two fish to allow proper 
classification of palatability. 
Gamhusia investigated briefly anything 
dropped into the water. They swam up to a 
piece of plastic tubing, bit at it a few times, 
and then let it fall to the bottom where it was 
ignored. 
Carassius swallowed immediately small frag- 
Anticipatory 
responses 
were soon evident ments 
TABLE 1 
Details of Test Animals 
(less than 4 mm 
Employed 
across) of any material. 
AQUARIUM DENSITY: 
AMOUNT OF FOOD 
SIZE OF FISH 
NO. OF FISH 
NORMALLY 
SPECIES 
(cm) 
DIETARY TYPE 
PER TANK 
GIVEN/WEEK 
Gamhusia 
2. 5-3. 5 
omnivorous 
20-30 
0.03 gm/gm 
Carassius 
5-6 
omnivorous 
(Suyehiro, 1942) 
4-6 
0.035 gm/gm 
delates 
6-9 
no published data; 
omnivorous in 
aquaria. 
4-6 
0.2 gm/gm 
Torquigener 
6-9 
no published 
record; omnivorous 
in aquaria. 
Suyehiro (1942) 
records two related 
spp. as omnivorous. 
4-6 
0.2 gm/gm 
