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April-June 2006
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Marine Salmon Interactions Program

Protected Species Research on Steelhead at Little Port Walter Marine Station

While there are no Endangered Species Act (ESA) listings of salmonids in Alaska, ongoing research on Sashin Creek drainage anadromous steelhead and rainbow trout at Little Port Walter (LPW) is providing much useful and important data to help in recovery programs of many listed salmon and steelhead populations in the Pacific Northwest. Rainbow trout in these studies, originating from steelhead parents, were planted in Sashin Lake above high waterfalls and have been isolated there as a self-sustaining population for 70 years. This situation provides unique opportunities for a variety of genetic and life history studies relevant to protected species recovery efforts. Some of the current studies under way include: basic life history research for appropriate ESA listing determinations; comparisons of genetic variation between anadromous and resident populations; effects of small founder populations on genetic variability; effects of 70 years of freshwater sequestration on residual anadromous characteristics; and developing and evaluating cross types between these populations through breeding studies.

Aspects of several of these studies were the focus of research activities in spring 2006 involving several collaborators and agencies. Auke Bay Laboratory researchers Adrian Celewycz, Pat Malecha, and Frank Thrower were assisted by Drs. Krista Nichols and Michael Zanis from Purdue University, who spent 2 weeks at LPW to collect data for quantitative trait loci (QTL) analysis for identifying genomic regions associated with smoltification and the evolution of anadromy.

Four scientists from the Northwest Fisheries Science Center, Orlay Johnson, Melissa Byrd, Jason Miller, and Jim Myers each spent a week at LPW in June 2006 collecting data for bilateral asymmetry analysis, QTL analysis, and final data on the freshwater growth phase for approximately 9,400 steelhead tagged with passive integrated transponder (PIT) tags.

This data collection period represented the endpoint of the freshwater rearing phase of the 2004 brood of juvenile steelhead just prior to their transition phase to seawater (smolting). Approximately 9,500 juveniles were tagged in April and June of 2005 from 69 families representing eight lines of fish of pure anadromous (steelhead) and pure resident (rainbow) types plus hybrid and inbred lines. Approximately 9,300 fish with functioning tags were weighed and measured and subsamples were taken for DNA, blood sodium, and seawater challenges, and over 1,000 digital photographs of fish representing each life history phase (smolt, mature, resident) in all families were taken for truss and bilateral asymmetry analysis.

Heritability estimates of smolting, maturation, and growth will be made to compare estimates made on parents (F1), which have already been published (Thrower et al. 2004), with estimates made for their offspring (F2). QTL analysis will be conducted, pending funding, to specifically determine the loci responsible for smolting and early maturation so that the genetic underpinnings of these important traits can be fully understood. This information is vital in determining the genetic and demographic importance of resident rainbow trout populations in maintaining and restoring anadromous steelhead populations throughout the western United States where the majority of the anadromous steelhead populations are listed on the Endangered Species List.

In addition to the work on hatchery juveniles, the adult steelhead weir was installed on 2 April 2006 to collect wild- and hatchery-produced steelhead returning to Sashin Creek from several research projects including research on Inbreeding and Outbreeding depression. A total of 75 wild adults were collected, which is the second highest recorded escapement for 18 years of escapement data and over 630 coded wire tagged experimental fish; this is also the largest return ever recorded. One of the most significant findings of the inbreeding research to date is the dramatic difference between survival in low versus high selection environments. A low selection environment is characteristic of hatchery operations where fish are protected from predators, provided abundant food, and in general maintain high survivals. After released from the hatchery into the wild, however, all manner of selection pressures come to bear on the anadromous smolts. In this case, inbred steelhead smolts survived well in the hatchery but their marine survival was poor.

Very little research has been done on the effects of inbreeding on populations in a wild environment ,and virtually nothing has been done with anadromous fish. The results of earlier research (by other researchers) in captive environments have been variable with modest reductions in fitness proportional with inbreeding coefficient in some studies. These results were not dissimilar to those observed at LPW during the low selection, freshwater phase; however, survival in a high selection environment while at liberty in the North Pacific Ocean has indicated a severe disadvantage for the inbred individuals. These results have serious implications for the persistence of small populations and should provide incentive for managers to maintain population levels above those at which inbreeding depression effects might occur.

By Frank Thrower
 

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