Successful collection and captive rearing of wild-spawned larval Klamath suckers

Shortnose Chasmistes brevirostris and Lost River Suckers Deltistes luxatus endemic to the Klamath River Basin on the California-Oregon border have experienced dramatic population declines in parallel with many other Catostomid species. Captive propagation has become a key element of many endangered fish recovery programs, although there is little evidence of their success in restoring or recovering fish populations. A novel rearing program for Klamath suckers was initiated in 2016 with the goal of developing a husbandry strategy that better balances the ecological, genetic, and demographic risks associated with captive propagation. We collected 4,306 wild-spawned Klamath sucker larvae from a major spawning tributary May-June 2016 and reared them at a geothermal facility established through a partnership with a local landowner and aquaculture expert. Mortality during collection was less than 1%. Larvae were reared in glass aquaria for 17-78 days until reaching approximately 30 mm total length, upon which they were moved to round fiberglass tanks for 14-46 days or until reaching approximately 60 mm total length. Overall survival of larvae to ponding for final growout was 71%. Larval tank rearing survival was 98% for 37 days until an isolated fish health incident affected three aquarium populations, reducing survival to transfer to 75%. Survival after transfer to round fiberglass tanks for 14-46 days was 94%. This study outlines the first successful collection and early life history husbandry of wild-spawned endangered Klamath suckers that we are aware of.

Electrofishing, Snorkel Spearing, and Piscicide Eradicate Brook Trout From a Small, Isolated Bull Trout Population

In 1992, a sampling crew from a multiagency group discovered a population of Bull Trout Salvelinus confluentus estimated at approximately 50 individuals in Threemile Creek, Oregon threatened with competition and hybridization with nonnative Brook Trout Salvelinus fontinalis. The group implemented Brook Trout and Bull Trout × Brook Trout hybrid removal using multiple techniques to conserve this population of Bull Trout in the Klamath River basin. From 1996 to 2000, backpack electrofishing and night snorkel spearing were used upstream of a culvert barrier to eradicate Brook Trout and hybrid trout from a 3.59-km section of Threemile Creek over 101 total days of effort (274 person-days of effort). Night snorkel spearing removed a lower percentage (7%) of target fish relative to electrofishing (93%), although this technique eliminated the risk of electrofishing injury to Bull Trout. Concurrent with the reduction and subsequent removal of Brook Trout, Bull Trout observations increased over 15-fold from 19 in 1996 to 299 in 2012 and Bull Trout distribution more than doubled, from 1.48 to 3.43 km during that same time. Immediately downstream in a separate 2.3-km section, the group eradicated Brook Trout using backpack electrofishing and rotenone application upstream of two man-made barriers from 2004 to 2010 over 43 total days of effort (150 person-days of effort). By 2016, Bull Trout had expanded their distribution throughout the upper 3.59-km section of Threemile Creek. Effort expended to eradicate Brook Trout was similar to successful eradication in other streams with comparable habitat characteristics and similar treatment length (< 3.0 km). However, similar removal attempts have not been successful in streams with comparable habitat characteristics that had longer treatment length (> 7.0 km). Application of piscicide may be more cost effective than manual techniques to remove Brook Trout when there is no risk to native fish of conservation concern, where target species are allopatric, and when piscicide use is publicly accepted. Brook Trout eradication proved valuable in providing Bull Trout the opportunity for range expansion and increased abundance necessary for recovery in the Klamath River basin.

Considerations for the Propagation and Conservation of Endangered Lake Suckers of the Western United States

Decades of persistent natural and anthropogenic threats coupled with competing water needs have compromised numerous species of freshwater fishes, many of which are now artificially propagated in hatcheries. Low survival upon release is common, particularly in systems with substantial nonnative predator populations. Extensive sampling for Shortnose (Chasmistes brevirostris) and Lost River Suckers (Deltistes luxatus) in the Klamath River Basin on the California–Oregon border have failed to detect any new adult recruitment for at least two decades, prompting an investigation into artificial propagation as an extinction prevention measure. A comprehensive assessment of strategies and successes associated with propagation for conservation restocking has not been performed for any Catostomid. Here, we review available literature for all western lake sucker species to inform propagation and recovery efforts for Klamath suckers and summarize the relevance of these considerations to other endangered fishes.