Sopochnaya River Reproductive Effort and Life History Diversity of O. mykiss in Kamchatka

What Is Life History? An Individual and a Population Phenomenon A suite of individual traits involving growth and reproduction that govern the time of occurrence of key events (principally reproduction) during the lifetime of an individual. The distribution of these traits among individuals within a population determines (in large part) the distribution (proportions) of life history phenotypes within the population.

Life History Polyphenism: the occurrence of multiple life histories within a common spatial and temporal environment

Why Does Polyphenism Occur? Some candidate explanations are: Niche-filling:diversification in order to occupy a stable array of niches; Bet-hedging: diversification in order to cope (persist) in the face of a variable and largely unpredictable environment; Random variation in survival & growth produces phenotypes with differing optimal life histories.

Pacific Salmon Reserve System - Reference Rivers

Kamchatka Salmonid Biodiversity Project Research Sites 1.Voyampolka 2.Sadanka (Tigil) 3.Snatolvayam 4.Kvachina 5.Utkholok 6.Sopochnaya 7.Saichek 8.Oblukovina 9.Krutogorova 10.Kol 11.Utka 12.Bolshaya 13.Zhupanova Tributaries of Kamchatka River

Kamchatka Mykiss Populations: Relevant Features 5 – 6 Phenotypes (Life History Variants) Reproductive Interactions among Anadromous and Non- Anadromous Types are Common. Strongly Skewed Sex Ratios between Phenotypes: Anadromous are ~70 % female; Non-Anadromous are similarly male-biased. Age-at-Maturity is Relatively Old: (5 – 8). For Steelhead, this is Related to Older Average Smolt Ages (2- 4). For Non-Anadromous, this is Related to Slower Specific Growth Rates (the average 17 in. rb is 7 years old). Fecundity and Frequency of Repeat Spawning is High Among Steelhead. Up to 40% of annual returns are 2nd- time spawners; up to 23% are 3rd-time; up to 10% are 4th- time repeat spawners.

The Environmental Context of Mykiss Diversity in Kamchatka 1) Geomorhpic complexity is high: rivers flow through long coastal plains (> 100 k) and have complex, well-developed, and dynamic floodplains. 2) Many of these same rivers have extensive, complex estuaries. 3) Tundra influence produces brownwater mainstems and/or tributaries that appear to be particualry important to anadromous mykiss. 4) Rivers have abundant annual runs of 6 species of Pacific salmon (including cherry salmon, and riverine sockeye) providing a huge marine nutrient subsidy for the aquatic and riparian food web. 5) The annual thermal regime is restricted. Mainstem river temperatures are near zero for 6 months (Nov. – May).

UTKHOLOK RIVER

Hourly Temperature Profile Utkholok River October 13, 2001 to October 20, 2002 Y-axis scale: 5 degrees C. Bottom Line: 0 C, Top Line: 20C.

Key issues from life history theory concerning reproductive effort and fitness For iteroparous animals there are three features to the relationship between reproductive effort and individual lifetime fitness, defined as the number of offspring that survive to reproductive age: 1) Reproductive Investment: Indexed by GSI. 2) Trade-Offs between Number of Offspring and Size of Offspring. 3) Trade-Offs Between Current Reproduction and Survival to Reproduce in the Future. There May Also be Developmental Constraints Limiting Either Offspring Size or Number of Offspring (or both)

Summary of Log-Log Scaling Relationships for Kamchatka Steelhead

Summary of Key Features of Kamchatka Mykiss Data Temperature and egg development: degree-days during summer and fall are limited. There is likely a significant trade-off between provisioning eggs to insure survival-to-emergence, egg development time, and time for post-emergence fry growth before the onset of winter. Despite high fecundity, GSI is relatively low compared to Atlantic and Pacific salmon. Consequently, egg size is relatively small.

Fitness Implications Total investment in reproductive tissue increases with size faster than would be expected on the basis of increase in body cavity volume or net weight. The rate of increase in egg mass is not matched by an equivalent (1:1) rate of increase in the individuation of egg mass. However, the implied tendency for egg size (egg weight) to increase with egg mass and body size is not strong. Hence, GSI reveals no strong trend with body size. This suggests that egg size is constrained to lie within a narrow range so as to achieve an increase in egg number with body size over the range of body size in the data set (680 to 900 mm FL; 3 to 8.1 kg net wt.). Low to modest GSI suggests Kamchatka SH are constrained in total investment in egg mass they can make prior to fall river entry, and are additionally constrained to trade egg size for egg number to optimize individual fitness.

A Puzzle Regarding Fecundity and Sex Ratio Differences Between Mikizha Phenotypes The fecundity and sex ratio differences between resident and anadromous mikizha suggest strong reproductive interactions between phenotypes: If populations of resident and anadromous mikizha are of equal size and are both in equilibrium and if the fecundity of anadromous females is 3x the fecundity of resident females, anadromous mortality must be 3x greater than resident mortality. Such mortality would not select for anadromy!

Implications for Life History Polyphenism of Kamchatka mykiss Steelhead likely subsidize male-biased life history types (resident, riverine-estuarine, estuarine) However, age-structured population modeling suggests that reciprocal subsidization is likely to occur as well, wherein females of male-biased life history types produce a small but regular proportion of anadromous progeny. Such a contribution may be required in order to maintain a (dynamic) equilibrium in total population size and in the proportion of life history phenotypes that compose the total population -- at least at multi-generational time scales. Consequently, long-term persistence of the population complex composed of all the life histories (including anadromous ones) may be dependent upon such reciprocal reproductive contributions!

Proximate Issues to be Addressed What is the relationship between phenotypes and genetic populations within each river? Is there one panmictic population or several more or less disjunct populations? If there are several, are populations identified with particular life history types? Are there significant differences in basic life history traits among phenotypes?

Acknowledgements and Thank You’s Kurt Beardslee: Executive Director, Washington Trout. Guido Rahr: Executive Director, Wild Salmon Center. Professor Jack Stanford: Director, Flathead Lake Biological Station, University of Montana. Academician Dmitri Pavlov: Department of Ichthyology,Moscow State University. Professor Oksana Savvaitova: Dept. of Ichthyology, Moscow State Univeristy Assistant Professor Kiril Kuzishchin: Dept. of Ichthyology, Moscow State University. The Wild Salmon Center. The Trust for Mutual Understanding. The Gordon and Betty Moore Foundation.

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