Early male maturity in O. mykiss: influences of condition

and temperature

John McMillan

NOAA/NWFSC

J. Dunham, M. Fitzpatrick

G. Reeves, C. Jordan

• Females– Reproductive fitness closely tied to size

• Males– Size less important because of mating tactics

Anadromous- large males (fighters, mimics, sneakers)

Resident- small males (sneakers, group)

Life History and Sex

Male Life History Expression

• Genetics– H2 for growth to age-1 = 0 – 0.3

• Reviewed by Hendry and Stearns 2004

• Environment– Temperature (e.g., extent of growing

season)

• Individual condition– Growth and lipids

• Early maturity lipid, growth

• O. mykiss– Anadromous- resident

males– Distributed across varying

environments

• Science– Mating behavior– Reproductive

contributions– Life history expression?

Age-1+ resident male maturity

1. Is probability of maturity positively associated with size and lipids?

2. Do size and lipids differ between streams w/contrasting growing seasons?

Age-1+ resident male maturity

1. Is probability of maturity positively associated with size and lipids?

2. Do size and lipids differ between streams w/contrasting growing seasons?

John Day River• O. mykiss

– Observations of small resident males

• Diverse landscape

• Survey sites and sampling– 30 Sites: ~ 100 m in length, ODFW-EMAP – July – September 2007 – 3 – 12 fish/site in age-1+ size range

Methods• Sex/maturity

– Dissection & microscopy

• Age– Otoliths and scales

• Condition– Growth rate: Fork length (mm) at age-1+

– Whole body lipid content: chemical lipid extraction

• Temperature– Thermographs: Sept. 11,2007 – August 11, 2008

FL: p-value = < 0.0001

Lipid: p-value = 0.0036

n = 88

FL: p-value = < 0.0001

Lipid: p-value = 0.0036

n = 88

0.0

5.0

10.0

15.0

20.0

Mea

n T

empe

ratu

re (

Cº)

Warm Streams

Cool Streams

Males & Femalesn = 88n = 80

- Wilcoxon Rank-Sum

- p-value = 0.37

•No difference in length

•No difference in lipids- Wilcoxon Rank-Sum

- p-value = 0.54

Fork Length (mm)

Lipid Content

110

0%

5%

F M

10%

90

130

150

Warmer = longer FL Age 1+

Wilcoxon Rank-Sum: p-value = 0.03

COLD WARM

80

100

120

140

Fo

rk L

en

gth

(m

m)

n = 68n = 55

Cooler = higher lipids (%)

Wilcoxon Rank-Sum: p-value = < 0.001

COLD WARM0.00

0.02

0.04

0.06

0.08

Wh

ole

Bo

dy

Lip

id (

%)

Conclusions

• Increased size, lipid = more likely mature– Consistent with most research on fish in captivity

and wild– Lipids and length did not covary!

• Differs: brook charr and brown trout• Greater length = anadromy

• Those studies did not measure lipid content

Temperature

• Longer in warmer streams– Supported by Tattam (2006)– Other explanations

• Maternal effect• Emergence timing and prior residence

• Higher lipids in cooler streams– Consistent with other species of fish

• John Day similarities (Feldhaus 2006)

– Suggests a general pattern

Implications

• Evolution– Proximate influences

– Ultimate consequences

• Ecology– Evolution x environment

• Management– Varying sex ratios in smolts?

• Jason DunhamJason Dunham - USGS, - USGS, Gordie ReevesGordie Reeves - USFS, - USFS, Marty Marty FitzpatrickFitzpatrick - USGS, - USGS, Chris JordanChris Jordan – NOAA – NOAA

• OSU OSU – Justin Mills, Mark Terwilliger, Matt Sloat– Justin Mills, Mark Terwilliger, Matt Sloat

• ODFWODFW – Tim Unterwegner, Jeff Neal, Jim Ruzycki, Chris – Tim Unterwegner, Jeff Neal, Jim Ruzycki, Chris James, Shelly Miller, Lisa Borgersen, Ryan Couture, James, Shelly Miller, Lisa Borgersen, Ryan Couture, Joseph O'NeilJoseph O'Neil

• FIELD WORKFIELD WORK – Nick Weber, Jeremiah Leslie, Ian – Nick Weber, Jeremiah Leslie, Ian Tattam, Bill McMillanTattam, Bill McMillan

• FUNDINGFUNDING – NOAA, USGS, North Fork Umpqua – NOAA, USGS, North Fork Umpqua Foundation, Oregon Fly Fishers Club, Delson Bridge to Foundation, Oregon Fly Fishers Club, Delson Bridge to the Future Fund, Washington County Flyfishers, the Future Fund, Washington County Flyfishers, McLoughlin Northwest SteelheadersMcLoughlin Northwest Steelheaders

QUESTIONS?