of the Fishery Board for Scotland. 
161 
and nothing more ; but, strictly, the use of the term { immature' should 
be confined to the condition of the reproductive organ — the milt or roe — 
since no individual of a species can be considered ' mature ' until it is 
able to reproduce its kind. There is another sense in which the word 
1 immature ' is used in the case of fish, namely, to indicate the condition 
of the reproductive organ at a period remote from the time of spawning. 
Thus, for example, a haddock examined in October will be found to have 
the reproductive organ small and ill-developed, quite irrespective of the 
size of the fish, and in one sense such a specimen might be called 
immature, although it had spawned in the previous March. I am aware 
that other factors besides the biological one, such, for instance, as the 
economic one relating to saleable and unsaleable fish, have been associated 
with the question of immature fish. I shall refer to these in the sequel. 
I propose to restrict the term 'immature' to young fish which have 
never developed ripe milt or roe — which have not yet become adult ; and 
this must be kept carefully in view. It will be found that in this sense 
the maximum size of immature individuals of different species of fish (or, 
what is the same thing, the minimum size of mature individuals) varies 
immensely. An immature fish may be a large lish, and a mature fish 
may be very small. 
The limit of size which divides an immature from an adult specimen of 
any fish has not previously been determined, or indeed attempted. No 
doubt this is owing to the fact that the investigation is more difficult, 
and involves more labour than one might anticipate. As a rule, fish 
spawn for a comparativsly brief period each year, and it is not always 
easy to obtain ripe specimens in sufficient numbers. 
In order to determine this fundamental point, I have had nearly 13,000 
food fishes, belonging to all the important species examined at all times of 
the year, each fish being carefully measured, and the condition of the 
reproductive organ registered.* Of this number 756 were found ripe, 
and 1426 nearly ripe, and I have taken the minimum length of these 
specimens as mainly indicating the limit of size between maturity and im- 
maturity. The results in regard to the ripe fish are set forth in Table I.; 
those regarding the ' nearly ripe ' in Table II. 
Table I. — The Maximum and Minimum Lengths (in inches) of Ripe Fish, f 
Difference 
Name of Fish. 
Largest. 
Smallest. 
between 
Largest and 
Average 
Size. 
Number 
Ripe. 
Number 
Examined. 
Smallest. 
Plaice, 
28 
13 
15 
207 
157 
2212 
Lemon sole, 
18 
8* 
w 
84 
14*9 
56 
863 
Common dab, . 
14 
. 54 
8-5 
108 
2061 
Long rough dab, 
Flounder, 
35i 
64 
9 
91 
115 
1488 
16* 
7 
94 
10-1 
82 
217 
Witch sole, 
194 
14 
54 
17-3 
14 
223 
Little sole, 
*i 
81 
a 
4 
4-0 
5 
38 
Turbot, . 
28 
23 
5 
25-2 
4 
68 
Haddock, 
23 
11 
16-1 
20 
1375 
Whiting, . 
17£ 
s 
84 
12'6 
54 
1318 
Cod, 
39 
26 
13 
32-6 
8 
957 
Gurnard, . 
18 
84 
94 
12-4 
124 
1299 
Cat-fish, . 
42 
27 
15 
34-8 
9 
59 
* This has been maiuly done by Mr Thomas Scott, F.L.S., one of the naturalists 
of the Fishery Board, and partly by Mr Peter Jamioson, assistant naturalist. 
t In all cases the extreme length is given, from the tip of the snout to the tip of 
the tail. 
I 
