Vertebral abnormalities in free-living Chinook salmon (Oncorhynchus tshawytscha, Walbaum) in New Zealand

Figures & data

Table 1. Prevalence of abnormality phenotypes by region in 101 free-living New Zealand Chinook salmon.

Deformity phenotype	LKS				Fusion				Compression and/or reduced intervertebral space				Vertical shift
Prevalence of deformity phenotype in fish	83.2%				10.9%				18.8%				19.8%
Number of instances of each deformity phenotype by region (R)	R^†1	R2	R3	R4	R1	R2	R3	R4	R1	R2	R3	R4	R1	R2	R3	R4
	15 (0)	71 (0)	51 (0)	27 (1)	3 (0)	4 (0)	4 (1)	0 (0)	6 (0)	10 (3)	5 (1)	1 (0)	10 (0)	4 (0)	9 (5)	0 (0)

Note: Mild abnormalities (severity 1) are included. Numbers of moderate and severe abnormalities (severity 2 and 3) for each type and region are given in parentheses. Note that some fish had more than one deformity.

^†Region.

Figure 1. Examples of deformities found in free-living female Chinook salmon captured during spawning migrations up the Rangitata (A,B) and Waimakriri Rivers (C,D,E), in Canterbury, New Zealand. Types refer to the classification system of Witten et al. (2009). A, A salmon with multiple deformities. Compressions of four vertebrae, numbers 26–29, and reduction of intervertebral spaces. Some loss of internal radiologic structure (left inset, Types 3,4). Vertical shifts (Type 17) of vertebrae numbers 39–43 (right inset). B, Kyphosis (Type 15) in the ural region without radiological changes in vertebral morphology. More caudal vertebrae normally show reduced length towards the tail fin. C and C’, Radiograph (C) of part of postcranial and abdominal regions showing dorsal vertical shifts (Type 17) of vertebrae 7–10 and in bone preparations (C’), showing uneven spacing between vertebrae. D and D’, Radiograph (D) and bone preparations (D’) showing lordosis (Type 14) at the level of vertebrae 10–12 and dorsal compression of vertebra 11. Vertebra 11 was 15.1% shorter dorsally than ventrally. E and E’, Radiograph (E) and bone preparations (E’) of multiple vertical shifts (Type 17) of vertebrae 40–46. Alternating compression dorsally and ventrally (see vertebrae 40,42,44) is more easily identified in articulated bones than in radiographs. Dorsal lengths of vertebrae 40,42,44 were significantly longer by 4.8% than ventral lengths (paired t-test, P = .017, d.f. = 2).

Table 2. Mineral content of vertebrae 30 and 31 from 8 free-living reproductively active and 10 immature freshwater farmed female Chinook salmon.

	Dry matter (%)	Ash (%)	Ca (mg/g)	Phos (mg/g)
Free-living (N = 8)	83.43*	44.15*	142.93*	80.03*
±SE	0.27	0.40	2.39	1.04
FW farmed (N = 10)	85.29	48.74	165.32	88.76
±SE	0.38	0.27	1.08	0.70

*Indicates significantly different P < .0001 t-Test.

Witten PE, Gil-Martens L, Huysseune A, Takle H, Hjelde K. 2009. Towards a classification and an understanding of developmental relationships of vertebral body malformations in Atlantic salmon (Salmo salar L.). Aquaculture. 295(1–2):6–14. English. doi: 10.1016/j.aquaculture.2009.06.037

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