Trends in size-at-age, sex ratios, and age-at-return in hatchery and wild Chinook salmon across BC

Annual change in mean age, age composition, mean size, size-at-age and female composition were estimated within each Chonook salmon population using linear regressions and age-specific patterns across populations and geographical regions.

The clearest trends observed were in mean size and size-at-age. Both showed declines across most populations with statistical significance. Declines varied in magnitude across populations and age classes. Mean age showed variable, yet statistically significant declines across most stocks, and appeared to be driven by reductions in the relative proportion of the oldest (ocean-4) and increases in the youngest age classes (ocean-2). Low-enhancement stocks (stocks with mean pHOS < 10%) showed mixed trends in mean age and age composition.

The proportion of females showed variable declines across populations, of which only a small proportion were significant. There was no consistent pattern for the few wild and low-enhancement populations. Our study shows that the size and age of BC Chinook salmon have declined since the 1970s. Declines such as these may be caused by fishing, predation, competition and hatchery enhancement, however in this review we did not explore quantitative models that incorporate these factors. Simple analyses show some evidence for the effect of hatchery enhancement on declining mean size and size-at-age, with some populations showing increases in size for the youngest age class but declines for the oldest.

Date (Publication): 2023-03

Code: 10.48689/ce6a455b-ed5b-4cea-83d3-9fa3c5e56d73

Cited responsible party

Organisation name	Individual name	Electronic mail address	Role
UBC Institute for Resources, Environment and Sustainability	Ravi Maharaj	info@ires.ubc info@ires.ubc.ca	Principal investigator
Lake Babine Nation	Andrew Rosenberger	salmon@psf.ca	Principal investigator
Pacific Salmon Foundation	Samantha (Sam) James, MSc, RPBio	sjames@psf.ca	Principal investigator

Purpose: Since 1977, the Salmonid Enhancement Program (SEP) “aims to rebuild vulnerable salmon stocks, provide

harvest opportunities, work with Indigenous and coastal communities in economic development, and

improve fish habitat to sustain salmon populations”1. However, hatcheries may also pose important risks

to wild salmon that may undermine these objectives.

Status: Completed

Point of contact

Organisation name	Individual name	Electronic mail address	Role
Pacific Salmon Foundation	Samantha (Sam) James, MSc, RPBio	sjames@psf.ca	Point of contact
UBC Institute for Resources, Environment and Sustainability	Ravi Maharaj	info@ires.ubc info@ires.ubc.ca	Point of contact
Lake Babine Nation	Andrew Rosenberger	salmon@psf.ca	Point of contact

Government of Canada Core Subject Thesaurus

Nature and Environment > Fisheries resources

Global Change Master Directory (GCMD) Science Keywords, Version 15.9

Earth Science > Biological Classification > Animals/Vertebrates > Fish > Ray-finned Fishes > Salmons/Trouts

Language: English

Topic category

Biota

Distribution format

Name	Version
PDF	1.4

Distributor contact

Organisation name	Individual name	Electronic mail address	Role
Pacific Salmon Foundation		salmon@psf.ca	Distributor

OnLine resource

Protocol	Linkage	Name
WWW:DOWNLOAD	https://soggy2.zoology.ubc.ca/geonetwork/srv/api/records/ce6a455b-ed5b-4cea-83d3-9fa3c5e56d73/attachments/HatcheryReview-BioTrends-Screen.pdf	HatcheryReview-BioTrends-Screen.pdf

OnLine resource

Protocol	Linkage	Name
DOI	https://doi.org/10.48689/ce6a455b-ed5b-4cea-83d3-9fa3c5e56d73	Digital Object Identifier (DOI)

Metadata

File identifier: ce6a455b-ed5b-4cea-83d3-9fa3c5e56d73 XML

Metadata language: eng; CAN

Character set: UTF8

Hierarchy level: Non geographic dataset

Hierarchy level name: report

Date stamp: 2023-06-07T02:53:05.397Z

Metadata standard name: North American Profile of ISO 19115:2003 - Geographic information - Metadata

Metadata standard version: NAP - CAN/CGSB-171.100-2009

Metadata author

Organisation name	Individual name	Electronic mail address	Role
Pacific Salmon Foundation	Terry Curran	terry.curran@shaw.ca	Author

Overviews

biotrends in hatchery and wild salmon

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