For some species, vertebra growth patterns are not discernible and thus alternative structures such as the neural arch (McFarlane et al., 2002) or dorsal fin spine (Clarke and Irvine, 2006) must be used.

Age estimation of billfishes (Kajikia spp.) using fin spine cross-sections: the need for an international code of practice.

Lengths of each fin spine, ray and dorsal fin height are taken from the base of each element.

Age studies using cross sections of the first dorsal fin spine (n = 1074 individuals), verified that vascularization in the inner portion of the spine does not interfere with age determination.

For example, Maraldo and MacCrimmon (15) found that dorsal fin spine and pectoral fin ray cross sections were unreliable for aging largemouth bass from northern waters.

Total length (TL): 145.0mm, standard length (SL): 111.0mm, head length (HL): 45.1mm, snout length (SL): 16.1mm, pre-dorsal length (PDL): 72.9mm, orbital diameter (OD): 15.7mm, post-orbital length (POL): 14.3mm, interorbital width (IW): 4.7mm, body depth (BD): 73.0mm, length of 1st dorsal fin spine (LDS): 28.6mm, caudal peduncle length (CPL): 19.8mm, pelvic length (PL): 33.2mm, pelvic width (PW): 8.9mm, 6 spines, 17 rays in dorsal fin, 12 rays in caudal fin, 14 rays in anal fin, 14 rays in pectoral fins, 1 spine, 1 ray in pelvic fins.

Catfish stridulation sounds are produced by microscopic bony ridges located on the distal end of the pectoral fin spine that are rubbed against the wall of the spinal fossa (3).

Their malevolent reputation is understandable if you've been stuck by a dorsal or pectoral fin spine. But, don't look at this versatile, easy to acquire, big-fish bait with disdain.

Origin of dorsal fin above second or third lateral line scale, predorsal length 3.3 (3.1-3.4) in SL; dorsal fin spines progressively longer, first 6.3 (6.9-7.8) in head length, and ninth 1.6 (1.9-2.2) in head length; longest (ninth) soft dorsal fin ray 3.6 (4.2-4.7) in SL; origin of anal fin below base of first soft dorsal fin ray, preanal length 1.9 (1.8) in SL; first anal fin spine 3.2 (3.3-4.3) in head length; second anal fin spine 2.9 (3.0-3.7) in head length; third anal fin spine 2.6 (2.6-3.3) in head length; longest (penultimate) soft anal fin ray 3.5 (3.8-4.1) in SL; caudal fin rounded, 1.3 (1.2-1.3) in head length; pectoral fin length 1.4 (1.3-1.4) in head length; pelvic fin length 1.6 (1.7-1.8) in head length.

First dorsal fin preceded by prominent, slightly curved dorsal spine attached to the first dorsal fin; dorsal fin spine long, 28.5% BDL, larger than first dorsal fin apex.

Part of a large chondrichthyan fin spine from Middle Pennsylvanian deposits of Illinois was described and named Xystracanthus mirabilis by St.