Taxonomy of Finfish (1+2)

5.1.8 Morphometric Measurements for Cyprinids

Measurements made as in Hubbs and Lagler (1964), with additions and modifications based on Rainboth (1996) Numbers 1 to 32 are the original measurements and numbers 33 to 45 the additional truss measurements. 

1. Standard length extends from the anteriormost portion of the snout to the base of the middle caudal rays. It is referred to as “SL”.
2. Snout to urocentrum is similar to SL, but measures the length of the head and spinal column. extending from the snout tip to the posterior edge of the urocentrum. The urocentrum is found at the point where the last myoseptum intersects the horizontal septum and can be felt with the caliper points on small or soft specimens. 
3. Preanal length measures body length to the anteriormost base of the unbranched anal-fin rays (anal-fin origin). 
4. Predorsal length measures body length to the anteriormost base of the unbranched dorsal-fin rays (dorsal-fin origin). 
5. Prepelvic length measures from the anteriormost point of unbranched pelvic-fin rays (pelvic-fin (insertion) to the tip of the snout. 
6. Prepectoral length is the distance from snout tip to the point of pectoral-fin insertion. 
7. Preoccipital length measures to the posterior edge of the cranium at the dorsal midline. 
8. Snout to posterior margin of preopercle measures horizontal distance from the snout (not from possibly projecting lower or upper lips) to the posterior edge of the preopercle. 
9. Upper jaw length measures the distance from the anterior edge of the premaxilla to the posterior edge of the maxilla. 
10. Snout length measures from the anterior bony rim of the orbit to the tip of the snout, not including lips. 
11. Prenasal length extends from the center of the nasal valve to the tip of the snout, because the soft skin on the edges can contract with drying, but the valve does not move. 
12. Orbit width is taken on the widest horizontal plane from bone to bone.
13. Interorbital width is measured from the plane passing through the center of the pupil, because the supraorbitals vary in placement for different groups of barbels.
14. Internasal width can be taken from/to bony margin. It might also be referred to as width of ethmoid. This measurement is difficult to repeat with precision, because differing thicknesses of soft tissue can cause different lower caliper readings.
15. Head width can be taken with the caliper points placed at the nondilated preopercles.
16. Gape width is taken with the mouth shut and width compressed even if the mouth has been preserved in an expanded position. The caliper tips should be placed at the posterior edge of the furrow between the upper and lower lips at the angle of the jaws.
17. Lower jaw to isthmus extends from the anterior point of the mandibular symphysis to the hypohyal on specimens with closed pharynges, but is difficult to take when the pharynx is expanded.
18. Peduncle length is measured from termination of the anal-fin base to the caudal-fin base.
19. Dorsal origin to pelvic insertion is the body-depth measurement because it measures from point to point. This completes a snout to dorsal to pelvic triangle for use in shape analysis.
20. Dorsal spinous-ray length is measured from the basal articulation to the point where flexibility begins. Specimens with a weak or no spinous ray still have a basal region which is largely inflexible. Weakly-spined species usually show more incomplete articulations before the spine becomes flexible than heavily-spined species. Strongly- spined species usually have one or two partial articulations before the first fully flexible articulation.
21. Anal-fin height can be taken as the total length of the last anterior unbranched ray.
22. Head depth at nostril is measured as nearly vertical as possible at the nasal valve. This is a difficult measurement on which to achieve repeatable results, since it is not taken from landmark to landmark.
23. Head depth at pupil is measured along an imaginary vertical line passing through the center of the pupil. This is also a difficult measurement, especially on specimens with gaping mouths.
24. Head depth at occiput is taken from the posterior margin of the cranium at the dorsal midline on a vertical axis. The ventral position ends slightly posterior to the area where the gill membranes of each side fuse to the isthmus. This can be modified easily to end on the gill membrane-isthmus junction when calipers are used.
25. Peduncle depth can be taken at the region of least depth.
26. Caudal-fin length is measured from the urocentrum out the longest principal ray of either the upper or lower lobe, when spread to a natural position.
27. Dorsal-fin height can be is taken as the length of the last of the anterior unbranched rays.
28. Pectoral-fin length can be taken as the greatest extension of depressed fin from insertion, measured over the outer surface. The longer of the two fins is used. 
29. Pelvic-fin length taken in the same manner as the pectoral fin, with the longer of the two pelvic fins being used.
30. Pelvic axillary-scale length is taken from the point of pelvic insertion to the posterior tip of the axillary scale. In the species that have one scale at the base of the axillary papilla and another extending posteriorly, the posteriormost extension is measured. The longer measurement from either side can be used.
31. Maxillary barbel length measures the length of the barbel at the angle of the gape from the anterior edge of the often bulbous base to its full posterior extension. The greater measurement from either side can be used.
32. Rostral barbel length is the measure of the anterior barbel found at the junction of the lacrimal groove with the maxillary groove, at what is typically referred to as the most posterior point of the rostrum as bounded by the lacrimal groove on each side of the head. It is actually an anterior maxillary barbel and so is referred as the “rostral” barbel for the sake of brevity in the species accounts.
33. Occiput to dorsal origin is measured from the posterior margin of the cranium at dorsal midline to the base of the first unbranched dorsal ray in the erect fin.
34. Occiput to pectoral insertion can be taken from the posterior margin of the cranium at dorsal midline to the point of pectoral insertion at the anterior base of the fin.
35. Occiput to pelvic insertion is the distance from the same occipital point mentioned in the previous two measures to the point of pelvic-fin insertion at the base of the unbranched ray.
36. Dorsal insertion to pelvic insertion extends from the base of the posteriormost dorsal ray to the point of pelvic-fin insertion.
37. Dorsal origin to pectoral insertion is, as the name implies. from landmarks just described.
38. Dorsal origin to anal origin measures the distance from the base of the first unbranched ray in the erect dorsal fin to the base of the first unbranched ray in the erect anal fin.
39. Dorsal insertion to caudal base can be taken from the base of the posteriormost dorsal ray to the base of the caudal rays at the center of the peduncle, as in the conventional SL measurement.
40. Dorsal insertion to anal origin extends from the base of the posteriormost dorsal ray to the base of the first unbranched ray of the erect anal fin.
41. Dorsal insertion to anal insertion measures the distance between the bases of the posteriormost rays of the dorsal and anal fins.
42. Dorsal-fin base is measured from the base of the first unbranched ray to the base of the posteriormost ray in the erect fin.
43. Anal-fin base is measured in a manner similar to the dorsal-fin measure immediately preceding.
44. Pectoral insertion to pelvic insertion is the distance between the bases of the unbranched anterior rays of the pelvic and pectoral fins.
45. Pelvic insertion to anal origin is the distance between the bases of the anteriormost rays of the pelvic and anal fins.