Exploring Life History Characteristics of Naturalized Versus Stocked Chinook

Grant: # 1198

Grant Amount: $256,107.00

Board Decision Year: 2011

U.S. Geological Survey - Lake Erie Biological Station (Sandusky)

Lake Erie Biological Station

Rogers, Mark (mwrogers@usgs.gov) 734-214-9324

GLFT - Ecosystem Health and Sustainable Fish Populations-D - Ecological and biological fisheries research to inform management

Project Details

This project conducted historical data analysis and field data collection to evaluate divergence in life-history characteristics (age- and size-at-maturity, spawning run time, and fecundity) of naturally-reproduced and hatchery-stocked Chinook and coho salmon in Lake Michigan with implications for fisheries and fisheries management.

The project team found weak evidence of changes in life-history demographics through time and that environmental effects may be more influential than population-specific characteristics. Maturity at age did not change, size-at-maturity varied through time with a weak declining trend in weight through time but a trend was not detected for adult total length though time. The researchers identify a decrease in the male:female ratio through time. Mean annual weights of adult females exhibited an asymptotic relationship with prey biomass and a positive linear relationship with annual Chinook Salmon stocking rates.

Age- and size- at maturity revealed no differences among spawning populations. The researchers found no differences in mean fecundity between spawning populations, however they did find that the largest and heaviest eggs were from the mixed population, smallest from the naturalized population, and intermediate sized from the hatchery-stocked population.

Egg thiamine concentrations differed between naturalized and mixed population females in 2012. In 2013, the researchers again found those differences, but results from hatchery-stocked fish indicated they did not differ from either naturalized or the mixed population. On average, Chinook salmon egg thiamine concentrations were above the ED50 (concentrations below the ED50 are associated with 50% larval mortality). Coho salmon samples from the Platte River were, on average, below the ED50 and significantly lower than Chinook salmon levels.

In general, the results did not indicate significant life -history divergence between naturalized and hatchery-stocked Chinook salmon populations in Lake Michigan. The researchers found weak evidence of changes in spawner demographics in a historical analysis and few significant differences from a field study that sampled naturalized, mixed, and hatchery-stocked populations. The team did find significant differences in egg thiamine concentrations between mixed and naturalized Chinook salmon spawning populations, but the hatchery-stocked population did not differ from the other types.

Documents

2011.1198 Final Report
View - Rogers_chinook_final_report_v2.pdf