![Thumbnail: [Volume 63, 1934 page 502]](/journals/rsnz/images/rsnz_63/thumbnails/rsnz_63_04_0629_0502_ac_02.gif)
Longitudinal Diameter of the Scales.
The longitudinal diameter corresponds to the anterior-posterior axis of the fish. In the tables that follow the scale measurements are given in actual micrometer divisions, eighteen of which equal one millimeter.
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| Anterior | A | B | C | D | E | F | Aver. | Posterior | |
| 1 | 42.3 | 48.3 | 49.5 | 55.5 | 54.0 | 49.5 | 49.8 | ||
| 2 | 49.0 | 48.5 | 50.0 | 56.5 | 54.5 | 53.2 | 51.9 | ||
| 3 | 54.0 | 57.0 | 60.0 | 59.2 | 59.0 | 56.5 | 57.6 | ||
| Lateral Line. | |||||||||
| 4 | 46.0 | 48.5 | 60.2 | 52.7 | 61.0 | 51.0 | 53.3 | ||
| 5 | 40.0 | 42.5 | 47.0 | 49.5 | 54.5 | 61.5 | 49.2 | ||
| 6 | 31.0 | 42.0 | 53.0 | 66.0 | 59.0 | 55.5 | 51.1 | ||
| Aver. | 43.8 | 47.8 | 53.2 | 56.6 | 57.0 | 54.5 |
It is seen from the above that the scales from different regions of the body vary considerably in total length. The anterior scales are generally shorter than those posteriorly situated. Anteriorly,
![Thumbnail: [Volume 63, 1934 page 503]](/journals/rsnz/images/rsnz_63/thumbnails/rsnz_63_04_0630_0503_ac_02.gif)
the scales above the lateral line are larger than the corresponding ventral scales. The most satisfactory scales for age and growth determinations are those situated in the following areas:—C. 1, 2, and 3, D. 1, 2, and 3, and E. 1, 2, and 3. The following reasons are given for this statement:—
| (1) |
The scales in this region (save those actually on the lateral line) are the first formed in the young fish. |
| (2) |
The circuli, and consequently the winter bands, are of a more definite character in the scales from this region than in the scales from other parts of the body. |
It should be remembered that the above statement holds only for fish in general, for the character of the scales from this area exhibits only relative differences from the scales from other parts of the body. Further, scales from the same area of the body, in two individual fish of exactly the same size (length and weight), may differ more than scales taken from different parts of the body of the same fish.
Certain regions of the body are covered with scales which are without exception characteristic in shape and form of circuli. For instance, those situated at the base of the gill-covers, or at the base of the caudal fin, or again those on the belly may be cited. It has been found frequently that such scales may not show the first winter band. The lateral line scales are, of course, characteristic; they are with few exceptions useless for age determination. The abdominal scales, although varying considerably in form, are relatively broad compared with their length. In area they are the largest scales on the body, especially is this apparent in large fish.