Analyzing Age, Reproduction, and Growth Patterns of Desert Sucker (C. clarkii) and Sonora Suckers (C. insignis)

Authors: Regan Doss, Scott Bonar

Year: 2024

Abstract

Understanding native Southwestern fish population dynamics is critical for management and conservation efforts amid drought and threats of habitat loss. Previously grouped into “rough fish”, the Sonora Sucker Catostomus insignis and Desert Sucker Catostomus clarkii are Species of Greatest Conservation Need in the state of Arizona. Age estimation, growth rates, and reproductive patterns of native desert catostomids (suckers) are essential for understanding aridland sucker population dynamics, but are poorly studied historically. This study provides a preliminary analysis of the gonadosomatic index (GSI), age structure, and growth patterns of Sonoran Sucker and Desert Sucker within two river systems in Arizona. The flow of the lower Salt River in central Arizona is controlled by a hydroelectric dam, with fish growth subject to the modified flow regime and temperatures of the reservoir’s hypolimnion. These flows differ from natural flow patterns and temperatures characteristic of Southwestern rivers, which mayaffect the growth and ageing patterns of the fish present. The undammed Blue River in eastern Arizona serves as a comparison to explore variations in reproductive and growth patterns under natural flow conditions. From May to August 2024, 104 individuals were sampled from both river systems. Each fish was measured for total length (mm) and weight (g), with a subset analyzed for pectoral fin ray and otolith extraction, as well as gonad volume (mL). Pectoral fin rays were used to estimate the age of both species, ranging from 0 to 7 years, through a double-blind survey, and growth rates were modeled using a VonBertalanffy growth curve. Length and age frequency distributions were developed for both river systems. While these results provide valuable insights, they are considered preliminary due to the limited sample size and temporal scope of the data collection.