Detailed Research Information

Detailed project information for
Study Plan Number 09046

Branch : Conte Anadromous Fish Laboratory

Study Plan Number : 09046

Study Title : Dam removal: a review of biological, physical and socioeconomic impacts

Starting Date : 01/01/1999

Completion Date : 09/30/2003

Principal Investigator(s) : Letcher, Ben

Primary PI : Letcher, Ben

Telephone Number : (413) 863-3803

Email Address : bletcher@usgs.gov

SIS Number : 5003570

Primary Program Element : Fisheries and Aquatic Resources

Second Program Element : Fish and Aquatic Habitats

Status : Completed

Abstract : BACKGROUND
Early attempts to reintroduce Atlantic salmon to southern New England rivers in the 1960s resulted in initial success. In the Connecticut River, for example, approximately 200 to 500 adult salmon have returned annually since the inception of the program. However, the increased effort of smolt and fry stocking in the 1980s and 1990s has not resulted in increased adult returns, indicating decreases in return rates of hatchery and stream-reared smolts.

The reason(s) for these low returns are unclear. Currently, fry and parr survival and production of smolts in headwater rearing habitats appear to be high. There are some indications of losses of smolts during downstream migration due to delays caused by dam impoundments, turbine mortality, or predation, yet these losses have not been quantified and summarized on a cumulative, basin-wide level. Several recent attempts to estimate these losses have included trapping, tracking of smolts via radio telemetry through the Connecticut River mainstem (U.S. Fish and Wildlife Service, unpublished data), estimation of numbers of smolts passing dams via mark-recapture methods (Northeast Utilities, unpublished data), and conventional turbine mortality and passage studies (Harza Engineering/RMC Environmental Services, 1991 et seq.). However, these studies have produced ambiguous results or outmigration estimates limited to only a portion of the basin or specific dam.

There have been no studies to investigate the entry of Connecticut River smolts into the estuary or marine environment. Emigrant smolts leaving the river are believed to move eastward from the river mouth through Long Island Sound, but there are no data to verify this assumption or characterize specific migration routes. Transition from the freshwater to the marine environment is a critical phase in smolt migration. Physiological studies indicate that salmon smolts migrating at the end of the migratory period (late May and early June) lose the capacity for rapid seawater entry (McCormick et al. 1997). Late migrants, especially those delayed by obstructions, may have poor survival upon arrival at the estuary.

There is presently an urgent need to estimate losses of emigrant smolts from headwater habitats (or at least from Holyoke Dam (river km 138), the last significant obstruction within the mainstem) to the mouth of the Connecticut River. Although it is extremely difficult to quantify total outmigration of smolts from the entire river system, some estimate of the level of smolt outmigration in the lower river would be useful in determining whether or not low adult returns are due to smolt mortality during downstream migration, and in identifying factors within the freshwater, estuarine, and marine environments that affect smolt survival.
OBJECTIVES
1) Estimate overall mortality of emigrant smolts between Holyoke Dam and the mouth of the Connecticut River (primary objective).

2) Characterize behaviors and movement patterns in response to entry into the marine environment at the mouth of the Connecticut River and adjacent areas of Long Island Sound.

3) Document and quantify possible delays and mortality at mainstem hydroelectric dams.
HYPOTHESES TO BE TESTED
1) Outmigration and survival of Atlantic salmon smolts in the Connecticut River is quantifiable.

2) Survival of smolts from Holyoke to the estuary averages > 30%

3) Rate of downstream migration is related to physical factors and smolt physiological status

4) Transition of smolts to the marine environment is a complex process related to salinity and temperature tolerance

For More Information :

° Home

U.S. Department of the Interior || U.S. Geological Survey
11700 Leetown Road, Kearneysville, WV 25430, USA
URL: http://www.lsc.usgs.gov
Maintainer: lsc_webmaster@usgs.gov
Last Modified: October 21, 2002 dwn
Privacy Policy and Disclaimers || FOIA || Accessibility

Branch :	Conte Anadromous Fish Laboratory
Study Plan Number :	09046
Study Title :	Dam removal: a review of biological, physical and socioeconomic impacts
Starting Date :	01/01/1999
Completion Date :	09/30/2003
Principal Investigator(s) :	Letcher, Ben
Primary PI :	Letcher, Ben
Telephone Number :	(413) 863-3803
Email Address :	bletcher@usgs.gov
SIS Number :	5003570
Primary Program Element :	Fisheries and Aquatic Resources
Second Program Element :	Fish and Aquatic Habitats
Status :	Completed
Abstract :	BACKGROUND Early attempts to reintroduce Atlantic salmon to southern New England rivers in the 1960s resulted in initial success. In the Connecticut River, for example, approximately 200 to 500 adult salmon have returned annually since the inception of the program. However, the increased effort of smolt and fry stocking in the 1980s and 1990s has not resulted in increased adult returns, indicating decreases in return rates of hatchery and stream-reared smolts. The reason(s) for these low returns are unclear. Currently, fry and parr survival and production of smolts in headwater rearing habitats appear to be high. There are some indications of losses of smolts during downstream migration due to delays caused by dam impoundments, turbine mortality, or predation, yet these losses have not been quantified and summarized on a cumulative, basin-wide level. Several recent attempts to estimate these losses have included trapping, tracking of smolts via radio telemetry through the Connecticut River mainstem (U.S. Fish and Wildlife Service, unpublished data), estimation of numbers of smolts passing dams via mark-recapture methods (Northeast Utilities, unpublished data), and conventional turbine mortality and passage studies (Harza Engineering/RMC Environmental Services, 1991 et seq.). However, these studies have produced ambiguous results or outmigration estimates limited to only a portion of the basin or specific dam. There have been no studies to investigate the entry of Connecticut River smolts into the estuary or marine environment. Emigrant smolts leaving the river are believed to move eastward from the river mouth through Long Island Sound, but there are no data to verify this assumption or characterize specific migration routes. Transition from the freshwater to the marine environment is a critical phase in smolt migration. Physiological studies indicate that salmon smolts migrating at the end of the migratory period (late May and early June) lose the capacity for rapid seawater entry (McCormick et al. 1997). Late migrants, especially those delayed by obstructions, may have poor survival upon arrival at the estuary. There is presently an urgent need to estimate losses of emigrant smolts from headwater habitats (or at least from Holyoke Dam (river km 138), the last significant obstruction within the mainstem) to the mouth of the Connecticut River. Although it is extremely difficult to quantify total outmigration of smolts from the entire river system, some estimate of the level of smolt outmigration in the lower river would be useful in determining whether or not low adult returns are due to smolt mortality during downstream migration, and in identifying factors within the freshwater, estuarine, and marine environments that affect smolt survival. OBJECTIVES 1) Estimate overall mortality of emigrant smolts between Holyoke Dam and the mouth of the Connecticut River (primary objective). 2) Characterize behaviors and movement patterns in response to entry into the marine environment at the mouth of the Connecticut River and adjacent areas of Long Island Sound. 3) Document and quantify possible delays and mortality at mainstem hydroelectric dams. HYPOTHESES TO BE TESTED 1) Outmigration and survival of Atlantic salmon smolts in the Connecticut River is quantifiable. 2) Survival of smolts from Holyoke to the estuary averages > 30% 3) Rate of downstream migration is related to physical factors and smolt physiological status 4) Transition of smolts to the marine environment is a complex process related to salinity and temperature tolerance
For More Information :
° Home


U.S. Department of the Interior \|\| U.S. Geological Survey 11700 Leetown Road, Kearneysville, WV 25430, USA URL: http://www.lsc.usgs.gov Maintainer: lsc_webmaster@usgs.gov Last Modified: October 21, 2002 dwn Privacy Policy and Disclaimers \|\| FOIA \|\| Accessibility