112 



ergy Regulatory Commission (FERC) Judge who rejected smolt transportation in 

 favor of spill and in-river migration (FERC 1992: FERC 1994). This decision regard- 

 ing two mid-Columbia River dams followed lengtny technical study and debate. 



The scientific, legal and ecological basis for spillway smolt passage does not pre- 

 clude the need for rigorous monitoring and evaluation to fine time this management 

 tool. 



Adaptive management requires continued critical analysis of the spill program in 

 order to maximize benefits and minimize risks. The NMFS spill policy embraces this 

 need effectively. This approach allows managers to learn as they go in order to con- 

 tinually improve the effectiveness and efficiency of recovery efforts. These efforts 

 allow managed spill levels to be modified on a real time basis to address specific 

 concerns such as gas supersaturation or adult passage. 



3. Are there risks to migrating smolts and returning adults associated with high 

 levels of dissolved nitrogen resulting from spill? 



Gas Dubble trauma (GBT) in fish associated with operation of hydroelectric dams 

 is a risk taken very seriously by the Federal and state fish management agencies 

 and tribes. IDFG agrees with every other anadromous fish management agency and 

 tribe in the Colunibia River Basin that benefits associated wiOi a carelully con- 

 trolled spill program, coupled with extensive monitoring and evaluation, far out- 

 weigh potential risks associated with GBT. 



Dissolved gas levels in rivers can be elevated by the operation of hydroelectric 

 dams, particularly when spill occurs. Under such "supersaturated" conditions, gases 

 tend to come out of solution, potentially affecting fish and other aquatic orgamsms. 

 Gas bubbles or emboli can develop in circulatory systems and tissues. This occur- 

 rence is referred to as gas bubble trauma (GBT) because it is a physical, not patho- 

 lorical, response to an environmental condition (Jensen et al. 1986). 



To reduce risk of GBT in migrating salmon, IDFG supports a controlled dissolved 

 gas management program designed to keep gas concentrations in the 120-125 per- 

 cent range. This range will allow for enough spill to reap the benefits of this recov- 

 ery tool, yet maintain risk of GBT within acceptable umits. Gas supersaturation 

 standards in most states typically call for no more than 110 percent saturation to 

 avoid GBT in fish. This is a general standard and does not account for the ability 

 of fish to effectively avoid GBT. All Snake and Columbia River dams have adequate 

 water depth in their tailrace for GBT avoidance. 



The spill policy implemented by NMFS includes adequate provisions to adaptively 

 manage spill and minimize risk of GBT through monitoring, evaluation and re- 

 search. State and Federal agencies and tribes worked collectively to develop the spill 

 monitoring program. Implementation of the biological monitoring component of tnis 

 program has run smoothly this year, and has maintained the flexibihty to respond 

 to in-season concerns and modifications. 



The managed spill program implemented in 1995 has had virtually no detectable 

 adverse impact on migrating juvenile and adult salmon and steel head. Extensive 

 monitoring has consistently revealed that less than 1 percent of migrating juveniles 

 sampled have symptoms of GBT. The symptoms that were found in a few fish were 

 at very low levels and were unlikely to cause mortality. Adult salmon that have 

 been sampled have not shown any symptoms of GBT. It is important to note that 

 the monitoring program was able to respond quickly and effectively to sampUng con- 

 cerns voiced by scientists representing tne power utilities (e.g., internal sampling for 

 GBT symptoms, and examinations of fish collected prior to entering the bypass sys- 

 tem). 



Tliis result is not surprising, and is the result of carefiil risk assessment by the 

 agencies and tribes prior to implementation of the spill program this year. It is re- 

 grettable that the flul benefits of spill have not been realiz^ this year. NMFS and 

 the Army Corps of Engineers had the opportunity to achieve 80 percent fish passage 

 efficiency at tne dams this spring, yet tell short because of excessive emphasis on 

 transportotion and lack of confident adherence to the spill program and its biologi- 

 C£d monitoring program. IDFG is concerned that this timid approach to spill has re- 

 duced surviv^ from what could have been realized. 



4. Have there been investigations of the effect of supersaturated water on resident 

 fish? Have the results of these studies been incorporated into current policy? 



IDFG monitored resident fish in the North Fork and mainstem Clearwater rivers 

 below Dworshak Dam during and after spill events this past spring. The Corps of 

 Engineers total dissolved gas monitoring sites indicate that dissolved gas levels in 

 the river ranged up to 120 percent saturation during spill. No mortality of resident 

 fish has been detected as a result of spill. Less than 1 percent of the 453 resident 

 riverine fish sampled fi*om April 24, 1995 through May 26, 1995, had external symp- 

 toms of GBT, and these symptoms were very low level (i.e., only one or two bubbles 

 observed per fish). 



