Using microchemistry to determine natal origin of Razorback Sucker in the San Juan River

Authors: Stephani L. * Clark Barkalow, Steven P. Platania, Jennifer L. Kennedy

Year: 2015 (xlvii)

Abstract

Although Razorback Sucker, Xyrauchen texanus, reproduce in the San Juan River, there is no evidence of recruitment of naturally produced fish to the adult population. Untagged Razorback Sucker are detected annually in the San Juan River; however, it is unknown whether they originated in the river or are hatchery produced fish that lack PIT tags. A non-lethal method for determining natal origin is necessary to assess recruitment of Razorback Sucker in the San Juan River. Elemental (Sr/Ca and Ba/Ca) and isotopic (87Sr/86Sr) microchemical analyses of fin rays and otoliths were used to determine if recruitment is occurring in wild Razorback Sucker populations in the San Juan River and to ascertain natal origin of untagged fish. Isotopic and elemental analyses revealed significant differences between hatcheries and the San Juan River allowing determination of natal origin for untagged Razorback Sucker. An important finding of this study was the identification of a naturally produced Razorback Sucker (224 mm TL) which represents recruitment to a larger size class than had been previously been documented in the San Juan River. Comparison of isotopic signatures of otoliths, fin rays, and water from the same source revealed that fin ray isotopic signatures were better correlated with water than were otolith isotopic signatures. Analysis of fin ray microchemistry is a useful, non-lethal tool for assessment of recruitment of Razorback Sucker in the San Juan River, and has applications for management and conservation of other endangered species.