Modoc sucker - U.S. Fish and Wildlife Service

VI. RECOMMENDATIONS FOR ACTIONS OVER THE NEXT 5 YEARS
Implementation of these recommendations over the next 5 years would provide information that
would allow us to consider delisting of the Modoc sucker in our next 5-year review:
Predation by Non-native Fishes
Predation by non-native fishes in the Turner (largemouth bass) and Rush Creek (brown trout)
drainages is recognized as a potential threat to Modoc sucker populations if it is not monitored
and active management carried out. Amelioration of this threat could be crucial to ensuring the
long-term viability of self-sustaining Modoc sucker populations in the Turner and Rush Creek
drainages. Recommended actions (some already initiated) include:
1) Suppression of existing non-native populations through monitoring and active removal in
the Turner and Rush Creek (Johnson Creek, in particular) drainages. [ongoing]
2) Screening the outflows of Beeler Reservoir and Reservoir J in the upper Turner Creek
watersheds of the Modoc National Forest to prevent largemouth bass from dispersing
downstream into Modoc sucker habitat. Loveness Reservoir outlet was screened by the
Forest in 2006 and that effort appears successful.
3) Assessment of existing constructed barriers in lower Turner and Johnson Creeks to
determine their role in preventing upstream invasion of non-natives and balancing this
with the constraints they may put on connectivity between Modoc sucker populations and
upstream spawning migrations. Necessary repairs to the barriers should be made if
warranted.
4) Development of a long-term management plan the is highly likely to be implemented to
assure the continued monitoring and management of non-native fish as well as
monitoring and management to maintain the effectiveness of the fish barriers.
Genetics
The ongoing Modoc sucker genetics program has helped resolve the relationships of Pit River
suckers, as well as the occurrence and distribution of introgression between Modoc and
Sacramento sucker populations. Future projects should address questions of genetic diversity,
effective population size, and population bottlenecking, as well as better resolving the degree of
introgression within local populations and monitoring changes over time. The Abernathy FTC is
continuing to explore the genetic diversity within populations and possible species-specific
markers for studying introgression using nuclear microsatellites (expected conclusion 2009).
Recovery Planning
The 1984 recovery action plan for the Modoc sucker is outdated. One of the threats that guided
many of the original recovery goals and actions (i.e., hybridization) has been reassessed, and the
threat of non-native fishes needs to be more actively addressed. Therefore, if appropriate, the
Service should consider development of a revised recovery plan.
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