Why is there a difference in sex ratio between hatchery and wild steelhead? Neil Thompson1, Kassi Cole2, Laura McMahon1, Melanie Marine1, Lyle Curtis and Mike Blouin1 1 Department of Zoology, Oregon State University 2 Department of Zoology, University of Hawaii

Hood River steelhead

Hood River Sex Ratio 1.07 Average sex ratio over all run years Wild Wild sex ratio Hatchery Hatchery sex ratio Run Year # Male # Female (Females per male) 1991 290 434 1.50   182 111 0.61 1992 159 260 1.64 99 133 1.34 1993 132 264 2.00 85 0.86 1994 100 104 1.04 56 57 1.02 1995 112 167 1.49 172 106 0.62 1996 118 175 1.48 334 301 0.90 1997 88 137 1.56 220 1.28 1998 188 1.68 156 166 1.06 1999 355 567 1.60 151 150 0.99 2000 372 645 1.73 533 415 0.78 2001 406 648 670 527 0.79 2002 485 1.87 231 366 1.58 2003 245 386 506 497 0.98 2004 160 208 1.30 238 297 1.25 2005 300 1.44 461 396 2006 186 313 267 2007 116 235 2.03 72 122 1.69 2008 81 140 202 190 0.94 2009 255 411 1.61 772 1076 1.39 Average sex ratio over all run years 1.07 Wild population always female biased Hatchery population 50:50 ratio , 9 years female biased, 10 years male biased

Hood River Sex Ratio Wild population: ALL 19 years female biased Average ratio - 61:39 Hatchery population: 9 years female biased Average ratio - 51:49 Wild population always female biased Hatchery population 50:50 ratio , 9 years female biased, 10 years male biased Question: Why is there a difference in sex ratio between wild and hatchery populations?

Potential explanations Lower rates of residency in male hatchery fish Selection against hatchery females, in the hatchery or at sea Sex reversal of chromosomally XX females into phenotypic males

Potential explanations Lower rates of residency in male hatchery fish Selection against hatchery females, in the hatchery or at sea Sex reversal of chromosomally XX females into phenotypic males

Sex determination in steelhead Y chromosome = male No Y chromosome = female

Mechanism of Sex Reversal Aromatase enzyme Converts testosterone to estrogen High temperature inhibits aromatase

Mechanism of Sex Reversal Aromatase enzyme Converts testosterone to estrogen High temperature inhibits aromatase Expect chromosomal females develop testes

Why Aromatase? Spawned in Parkdale, Oregon Reared at Oak Springs on Deschutes R. Deschutes warmer than Hood River

Research question Does the chromosomal gender match the phenotypic gender in Hood River steelhead? If not, what % is non-matching? What direction is mismatch?

Research question Does the chromosomal gender match the phenotypic gender in Hood River steelhead? If not, what % is non-matching? What direction is mismatch? Does the sex ratio in the hatchery population change from juvenile release to adult return?

Methods - Adults Adults sampled at Powerdale dam (1991-2009) Gender, origin, fin clip taken by ODFW Random 96 individuals per run type & sex Total 384 adult samples Wild and Hatchery origin

Methods - Juveniles Juveniles produced following Hood River Production Program protocols Sampled at 1 year of age Fin clip & floy tagged Bodies preserved in formalin Gonad inspected by stereomicroscopy Fish type, family, spawn date

Chromosomal gender OmyY1 marker - gender marker 4% non-concordance rate Male band Positive reaction band

Phenotypic gender Adults: ODFW staff visually sexed fish @ powerdale

Phenotypic gender Adults: 1 year olds: ODFW staff visually sexed fish @ powerdale 1 year olds: Visually sexed gonads Male, female or unknown

Research question Does the chromosomal gender match the phenotypic gender in Hood River steelhead? If not, what % is non-matching? Mismatch = sex reversal Test for non 50:50 sex ratio Chi-square test

Results - Adults 341 successful reactions 7 fish mismatched (2.1 % non-concordance) Male-to-female and female-to-male mismatch Chromosomal Run Gender % Non-concordance Winter Male 2.27 Female 1.15 Summer 1.28 3.41

Results - Juveniles 173 successful reactions 6 fish mismatched (3.5 % non-concordance) Male-to-female and female-to-male mismatch Juvenile ID Spawn Date Family ID Fish Type 2 4/20/2010 2821x2796 HH 3 5/24/2010 382x477 WW 29 5/10/2010 2764x2783 44 2812x2761 62 5/17/2010 458x2804 WH 223 2774x383 HW

Overall Results Adults No evidence for sex reversal Mismatches in both directions Rate not above published non-concordance rate ODFW staff VERY good at visually identifying gender – both run types

Overall Results Adults Juveniles No evidence for sex reversal Mismatches in both directions Non-concordance rate below published rate Mismatches from 6 different families, 4 spawn dates and 4 fish types

Potential explanations Lower rates of residency in male hatchery fish Selection against hatchery females, in the hatchery or at sea Sex reversal of chromosomally XX females into phenotypic males

Juvenile sex ratio at release # Male # Female Chromosomal 85 88 Phenotypic 87 86 *Not different from 50:50 ratio* Chi-square p-values of 0.82 & 0.94

Juvenile sex ratio at release # Male # Female Chromosomal 85 88 Phenotypic 87 86 *Not different from 50:50 ratio* Chi-square p-values of 0.82 & 0.94 50:50 at release and at return to the dam No selection against females in hatchery or at sea!

Potential explanations Lower rates of residency in male hatchery fish Selection against hatchery females, in the hatchery or at sea Sex reversal of chromosomally XX females into phenotypic males

Potential explanations Lower rates of residency in male hatchery fish Christie et al. 2011 Molecular Ecology

Thank You! Jim Gidley & Albert Santos Lyle Curtis & staff Blouin lab Parkdale fish facility Lyle Curtis & staff Oak Springs hatchery Blouin lab