1. Effects of variable and size- selective gill-net fishing on life- history evolution in grayling Thrond O Haugen & Leif Asbjørn Vøllestad

2. What to expect from size-selective fishing?  LL Size-selective fishing GrowthAdult survival —— — ? + — Growth + — ?  In other words: An open question!  When considered trait by trait

3. What to expect from size- selective fishing—a reaction norm perspective  Theoretical studies show that variation in growth-dependent survival affects the shape and posision of maturation reaction norms (e.g. Stearns & Koella 1986)  For any combination of mortality responses to growth, rapid growers are predicted to mature earlier than slow growers  Expect a smaller age-size maturation space with increasing mortality

4. Age at maturity Size at maturity 0.1 0.9 0.5 a b |slope|= |-a/b| width = c c Increasing mortality Maturation reaction norms and survival

5. The study species

6. Egg Swim-up larvae Fry Larvae Juvenile Mature Lake/river Tributary Gravel 130-140 °D 2–3 weeks During September 3-8 years Max age: 28 years

7. The study system Les Aur Ht Os ØM Lesjaskogsvatnet Aursjøen Hårrtjønn Osbumagasinet Øvre Mærrabottvatn 10 km N 1954 1920 1910 1880 Norway Lake Mesh size (mm) Effort a Fishery since Les30 b 200–250e.p. c ØM29>>2501970s Ht290–1001950s Aur3580–100e.p. Os30120–150e.p. a Number of gill nets per km 2 per year b The present mesh-size. It has changed during the 1900s c e.p. = entire period

8. Characteristics of the lakes and the grayling populations Microsatellite F ST = 0.05–0.21 Juvenile trait Q ST = 0.00–0.92 Koskinen, Haugen & Primmer (2002), Nature

9. Lesjaskogsvatnet 1903–2000 28 mm 30 mm 30 + 22 mm 28 + 22 mm 32 mm 30 + 22 mm 190020001950 Monofilament nylon nets Multiple mesh-size survey Relaxed size-selective fishery SIntensive size-selective fishery

10. The Objectives  Do grayling (and co-occuring trout) decrease age and size at maturity in systems with intensive size-selective fisheries?  Among-lake level (synchronic data)  Within-lake level (allochronic data)  If so, is this solely due to growth-rate changes/differences resulting from changed/differential fishing pressure?

11. Methods  Multiple mesh-size gill-nets  12–52 mm for the synchronic data  6–10 surveys in the 1995–1999 period per lake  19–52 mm for the allochronic data  7 surveys  Ageing and back calculation of growth using otoliths  Maturation pattern estimated from multiple logistic regression  Life-table simulations

12. The synchronic data

13. Differential maturation pattern 0.10.9 0.1 0.5 0.9 0.1 0.9 0.5 0.1 0.5 0.9 0.1 0.5 0.9

14. Life-history evolution in response to differential survival Haugen (2000), Oikos; Haugen & Vøllestad (2001), Genetica

15. Convergent evolution Haugen (2002), Submitted

16. Responses to differential fishing intensities LL Survival Age at maturity Number of gill nets per km 2 per year Standardized trait value (sd unit) 0 -2 1 2 0 100300200 G3G2 G1 2.8 Fecundity GSIEgg size Haugen (2002), Submitted

17. Also affects maturation reaction norms Age at maturity Size at maturity a b |slope|= |a/b| width = Haugen (2000), Oikos

18. Life-table simulations

19. Predictions for Lesjaskogsvatnet Haugen & Vøllestad (2001), Genetica

20. Responses to changed fishing regime 1992: 30+22 mm 1975: 28+22 mm 32 mm 1982: 30+22 mm 1985: 30 mm 1927: 28 mm 28/30+22 mm 32 mm 30 mm 28 mm Haugen & Vøllestad (2001), Genetica

21. Has growth changed during the 1900s?  Yes, but not as expected according to changes in density  Selection for lowered growth under high fishing pressure Back calculated length (mm) Haugen & Vøllestad (2001), Genetica

22. Conclusions  All three data sets supported that the maturation pattern evolved in response to size-selective fisheries  In an adaptive manner  The response was not due to changed or differential growth pattern  Not a plasticity response  In Lesjaskogsvatnet growth changed directly in response to gill-net selection and not indirectly due to density effects

23. That’s all folks!