NOTE Sekiguchi and Best. In vitro digestibility of some prey species of dolphin 
389 
Table 2 
The generalized sequence of digestion for fish and squid in the artificial digestion experiments. 
Weight 
remaining (%) 
Squid 
Fish 
95-85 
Begins to lose skin and viscera 
Abdomen breaks up; begins to lose skin and viscera 
85-60 
Loses fins; muscle reduced 
Most of skin and viscera are gone; loses eyes and tail; 
head begins to be digested 
60—40 
Tentacles featureless; mantle splits, 
exposing the pen 
Head is gone; muscle reduced; releases otoliths 
40-30 
Flesh reduced further 
Muscle disintegrates; backbone exposed 
30-10 
Beaks, eyes, and pen released 
Muscle reduced further 
<10 
Beaks, eyes, part of pen, 
and a little flesh remain 
Pieces of muscle and skin, and some vertebrae remain 
and goby were also digested quickly 
and reduced to less than 10% of their 
original weight within 15 hours. Most 
species, however, took longer for com- 
plete digestion (about 20 h); maas- 
banker took as long as 27 hours to be 
reduced to less than 10% of its origi- 
nal weight. 
Table 3 lists the T 20 values for each 
sample species. The T. 1() values var- 
ied between species sampled (from 
5.68 h to 21.35 h), but for most spe- 
cies, the T 20 value was roughly 13 h. 
Among the 12 species and size groups 
sampled, maasbanker had the slow- 
est rate of digestion and lanternfish 
the highest, being digested about 3.8 
times faster than maasbanker. Red 
squid was digested faster than most 
fish species except lanternfish, 
whereas the digestion rate of chokka 
squid was slower than that of large 
round herring, hake, goby, red squid, 
and lanternfish. 
There appeared to be differences 
between digestion rates of different 
sizes of the same species (Table 3). 
Smaller anchovy and pilchard were 
digested about 1.2 times faster than 
larger ones, but round herrings 
showed the opposite pattern. How- 
ever, for anchovy and round herring, 
the T 20 values for large and small fish 
were not significantly different 
(£=1.65, df=8,P=0.1381, for large fish; 
£=1.05, df=8, P=0.3256, for small 
fish). The two size groups of pilchard 
had significantly different T 20 values 
