Title: Assessing Estuarine Residence Time in Sockeye and Coho Salmon
1Assessing Estuarine Residence Time in Sockeye and
Coho Salmon
- Mary Anne Bishop,
- Sean P. Powers, And Gordon H. Reeves
2Salmonids
Sockeye
Silver
Pink
Chinook
NMFS
3PWS
Copper River
- 6th largest watershed in Alaska
- 2nd highest average discharge in Alaska
- 69 107 million tons suspended sediment
4(No Transcript)
5(No Transcript)
6(No Transcript)
7Objectives
- (1) determine the age of freshwater outmigration
and the length of residency in freshwater,
estuarine and marine habitats for a
representative sample of coho and sockeyes on the
Copper River Delta, Alaska - (2) document habitat use, prey items, and growth
of juvenile coho and sockeye during the estuarine
phase of migration and - (3) assess the predation risk of outmigrating
juveniles and returning adults in estuarine
habitats.
8Surface Salinity 2004
9Determining estuarine residence time
Traditional approach Field Sampling (May Oct,
2004 2005)
- Screw trap to document timing of outmigration by
life stage
- Fyke net and seine collection to examine upper
estuary sites.
- Mid-water trawls to document, mid and lower
estuarine occurrence
10Cordova.
Eyak R.
Scott R.
Sheridan R.
Eyak R.
Copper R.
Alaganik
Alaganik
Watershed
Fyke Net Seine Stations
Trawl station
Screwtrap
11Sockeye Migration Timing
Data are from the Eyak River Screwtrap in 2005
12Estuary
- Sockeye parr and smolt can be found throughout
the estuary from May to August - Peak abundance of sockeye smolt and parr occur
from late May until early July. - Based on CPUE over time, the max residence time
appears to be no more than 30-45 days for parr
and smolt.
Data from mid-water trawl samples
13Estuary
- Coho parr and smolt can be found through-out the
estuary in the summer - Peak abundance of coho smolt and parr occur from
mid-May until mid-June. - Based on CPUE over time, the max residence time
appears to be no more than 20-30 days for coho
parr and smolt.
Data from mid-water trawl samples
14Age of juvenile salmon collected in estuary
2005
2004
Coho
Sockeye
Coho
Sockeye
0
1
2
0
1
2
0
1
2
0
1
2
0
1
2
0
1
2
Upper
Mid
Upper
Mid
n 716 n 309 n 232 n 509
n 97
n 101
n 129
n 93
15Otolith Microchemistry
16Typical Adult Profiles
res time 40 days
17Validation of Sr Concentration as a proxy for
salinity
Salinity increase in experiment
18Validation of Sr Concentration as a proxy for
salinity
19Juveniles captured in the estuary
Estimated residence time 56 days
20Adult coho profile
Estimated residence time 19 days
21Summary
- Overall, there was general agreement between
results of the intensive field collections and
otolith chemical signatures with respect to
estuarine residence time. Both techniques
indicated a relatively brief period in estuarine
waters (10-45 day, average 30 days) for both
species. - Because estuarine habitats are critical for
osmoregulatory adjustment to marine waters and
offer rich foraging opportunities for smolt,
estuarine habitats represent essential habitat
for salmonid fisheries.
22Acknowledgments
Field Logistics Dan Bilderback, Sage
Charters Field Lab Assistance Brad Reynolds,
Ben Hermanns, Margarite Leeds, Sara
Ecolano, Signe Fritsch, Nate Geraldi, Monica
Powers, Kevan Gregalis
Funding sources
- North Pacific Research Board
- Prince William Sound Oil Spill Recovery
Institute