Executive Summary

This mission provided a reconnaissance of the Langeri River and some of its tributaries and drainage area, to determine the effects placer gold mining on the aquatic habitat in the river and aimed to provide potential restoration strategies and additional assessment opportunities. The Langeri River supports several species of salmon important for commercial ocean fisheries and also supports populations of the critically endangered Sakhalin taimen (Parahucho perryi).

Recent historic placer mining activities within the Langeri River Watershed have simplified aquatic habitats through the reconfiguration of valley shape and associated stream channel, removal of riparian vegetation and change in sediment composition and would likely take many decades to recover aquatic and riparian habitats similar to pre‐mined conditions, if at all.  Current mining operations are creating episodic high turbidity events, which result in significant clay sediment deposition over spawning gravels.

The following recommendations were offered to increase understanding of the current conditions and to foster the recovery of riparian and aquatic habitats:

Assessment of Past Mining Areas: Conduct a more detailed assessment of the tributaries to the Langeri River that have had been placer mined over the past several decades to:

1. determine if the reclaimed areas meet regulatory requirements for reclamation

2. determine if reclaimed areas provide adequate habitat for commercial salmon stocks,  Sakhalin taimen and other native species, and

3. develop a long‐term, feasible, monitoring strategy, to determine if the reclaimed areas are on a trajectory towards improved aquatic and riparian habitat or whether additional active restoration work is needed.

Assessment of the Effects of Ongoing Mining: A study of stream channels and aquatic habitat below the active mining area would provide information on changes to channel substrate conditions, available spawning habitat, aquatic (including macroinvertebrate) species composition, and distribution, and water quality.

The assessment should also develop a long term, affordable monitoring program that would document any changes and/or trends in the river conditions.

Restoration of the Moyga River: The recently mined area along the Moyga River could provide an ideal pilot project area to restore the stream channel and riparian areas to evaluate improvements to riparian and aquatic habitats. Restoration of this reach would also protect the quality of the water supply for the Village of Pervomayskoye.

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