The Humboldt Management Unit (HMU) encompasses eight, 8-digit USGS hydrologic units, including: North Fork (HUC 16040102), Upper (HUC 16040101), South Fork (HUC 16040103), Middle (HUC 16040105), Lower (HUC 16040108), and Little (HUC 16040109) Humboldt, and Rock (HUC 16040106) and Pine (HUC 16040104). The Humboldt River drainage is very large (>16,000 square miles), contains many large and interconnected fluvial systems, and represents the easternmost portion of LCT’s range. Some of the most climate-resilient fluvial habitats in Nevada are present in the HMU (i.e., Ruby Mountains). The Lower and Middle Humboldt, and Pine hydrologic units offer limited conservation potential due to mostly anthropogenic impacts (i.e., barriers, water diversions, reservoirs, higher water temperatures) and lack locally-adapted HMU LCT. North Fork, Upper, South Fork, and Little Humboldt, and Rock hydrologic units currently contain LCT populations, some of which are large interconnected systems that allow for the expression of migratory life-history characteristics and are quite resilient (e.g., Maggie Creek and Marys River). Each of these hydrologic units contain locally-adapted stream populations, thus it is important to achieve redundancy within each of the hydrologic units to ensure the genetic diversity within the HMU is conserved. Collectively, LCT within the HMU are genetically discrete from LCT found in other units.

The updated objectives for LCT in the HMU include:

Management Unit Wide:

HMU 1) Remove threats (i.e., competition, predation, hybridization) associated with non-native trout species to allow for the formation and/or maintenance of HMU LCT populations identified in HMU objectives 3–13; and

HMU 2) Ensure all habitats required to meet HMU objectives 3–13 function ecologically. In some cases, this may require restoration and/or management changes; and

HMU 3) Maintain existing, isolated populations that cannot individually meet the recovery population benchmarks provided in this document. Actively manage those populations based on guidance provided in the pending LCT Genetics Management Plan; and

Little Humboldt hydrologic unit:

HMU 4) Maintain the interconnected population (South Fork Little Humboldt River) and provide enough stream/river habitat to allow for the expression of migratory life-history characteristics in at least 1 additional recovery population (i.e., interconnected population); and

HMU 5) Establish at least 1 additional recovery population that is spatially separated from the interconnected populations required by HMU objective 4; and

North Fork Humboldt hydrologic unit:

HMU 6) Provide enough stream/river habitat to allow for the expression of migratory life-history characteristics in at least 1 recovery population (i.e., interconnected population); and

HMU 7) Maintain (or establish if necessary) at least 1 additional recovery population that is spatially separated from the interconnected population required by HMU objective 6; and

Rock hydrologic unit:

HMU 8) Maintain the interconnected population in the Willow Creek Complex; and

HMU 9) Maintain (or establish if necessary) at least 1 additional recovery population that is spatially separated from the interconnected population required by HMU objective 8; and

South Fork Humboldt hydrologic unit:

HMU 10) Provide enough stream/river habitat to allow for the expression of migratory life-history characteristics in at least 1 recovery population (i.e., interconnected population); and

HMU 11) Maintain (or establish if necessary) at least 2 additional recovery populations that are spatially separated from each other, and the interconnected population required by HMU objective 10; and

Upper Humboldt hydrologic unit:

HMU 12) Maintain the 2 existing interconnected populations (Maggie Creek and Marys River), and provide enough stream/river habitat to allow for the expression of migratory life-history characteristics in at least 1 additional recovery population (i.e., interconnected population); and

HMU 13) Maintain (or establish if necessary) at least 3 additional recovery populations that are spatially separated from each other, and the interconnected populations required by HMU objective 12.