A Discussion on Age Determination Methods for Two Esquamate

Abstract:The annuli characteristics of four kinds of ageing materials (dorsal fin spines,operculums,vertebras and sagittae ) of Triplophysa (Triplophysa) teunis  and T. (Hedinichthys) yarkandensis were analyzed to assess their usage in age determination.176 T. (T.) teunis samples and 273 T. (H.) yarkandensis samples of different size were collected from Kezi River in southern Xinjiang in May 2008.The results showed that dorsal fin spines and operculums were unsuitable for ageing mostly because of the pseudoannuli and undistinguishing of annuli.The annuli characteristics on vertebras of T. (T.) teunis with a standard body length less than 6.0cm could not be seen easily, their interpretability and age agreement were 52.63% and 70% respectively.The interpretability and age agreement of vertebras of T. (H.) yarkandensis were 93.33% and 78.57% respectively,but there were some disturbances of fry checks and false rings on the vertebras of the fish under 5 years,which will decrease the accuracy of aging.Growth markers such as daily growth increments, checks ordiscontinuities and annuli can be seen on all sectioned sagittae.The annuli characteristics of the sectioned sagittae displayed a pattern of alternating zones of widely- and closely- spaced circuli,and the outer edges of the circuli were annuli.The ages of 171 samples can be identified from 174 T. (T.) teunis samples,their interpretability and age agreement were 98.28% and 94.74% respectively.The ages of 244 samples can be identified from 258 T. (H.) yarkandensis samples, their interpretability and age agreement were 94.57% and 93.44% respectively.Ages assigned to vertebras and sectioned sagittae from the same fish by the two independent readers, age agreement of T. (T.) teunis were 75.00% and 80.00%,age agreement of T. (H.) yarkandensis 73.81% and 83.33%,no significant difference between reader 1 and reader 2(P>0.05).The result indicated that sectioned sagittae were more suited to age determination for the two esquamate Triplophysa,vertebras can be as accessory ageing materials for older individuals.