Kamchatka Steelhead Project Science Report for the Utkholok River

Transcription

1 2017 Science Report for the Utkholok River Mara S. Zimmerman, Washington Department of Fish and Wildlife November 2017 This report summarizes the work completed on the Utkholok River in 2017 which was a continuation of the study initiated in 2016 as part of the under the terms of the WDFW-The Conservation Angler MOU. WDFW Science Report

2 Background Oncorhynchus mykiss exhibit notable life history diversity in the rivers of western Kamchatka. Individual life histories can be described by growth in the river, estuary, and ocean environments and at least five general life histories are defined by scale growth patterns (Kuzishchin et al. 1999). The life histories all begin with 2-5 years of freshwater growth and followed by an additional 1-4 years of growth either in the high seas, estuary, or river or some combination of these environments. Among rivers, different combinations of life histories are consistently observed and have been attributed to the physical complexity of the riverine environment (Pavlov et al. 2008; Kendall et al. 2015). Within rivers, Within rivers, O. mykiss with different life histories belong to single breeding populations but the relative numbers of each life history fluctuate over time (Savvaitova et al. 2002; Savvaitova et al. 2003). Genetic differentiation is observed among rivers but not among life histories (McPhee et al. 2007), and otolith microchemistry revealed that the life histories of O. mykiss offspring are not necessarily the same as their mothers (Zimmerman et al. 2003; K. Kuzishchin, personal communication). Different O. mykiss life histories observed in the rivers of western Kamchatka provide an opportunity to study steelhead diversity in an environment with minimal anthropogenic influence. The connection between energetic requirements and life history diversity is relevant to O. mykiss populations in Kamchatka as well as more broadly across the species range. Throughout their life cycle O. mykiss stores energy as lipids in white muscle tissue (Penney and Moffitt 2014), and the rate of storage is influenced by genetics, food availability, and the stream environment (i.e., temperature, gradient). Lipid storage in juvenile O. mykiss is one factor linked to whether the O. mykiss adopts a riverine (resident) or anadromous life history (McMillan et al. 2012; Sloat et al. 2014; Kendall et al. 2015). If food resources are too scarce or metabolic demands too high, this triggers a conditional response to move to a new environment for the next stage of their life history (Sloat et al. 2014). In some rivers, productivity of the freshwater environment is adequate for some or all of the population to forgo an ocean migration and the majority of the population adopts a riverine life history. In other rivers, O. mykiss must migrate to the highly productive but dangerous (high mortality risk) marine environment to locate adequate growth conditions. The link between energy storage and life history diversity of O. mykiss is better described for fish that are going to sea than those returning from sea. Anadromous O. mykiss returning from sea cease feeding in freshwater. In order to undergo upstream spawning migrations and long periods of fasting in freshwater, they use energy that was stored as lipids during their ocean feeding phase. Lipid depletion during migration and spawning of anadromous O. mykiss can be substantial, especially for populations that enter freshwater months prior to the actual spawning period. For example, the lipid content in white muscle tissue of summer steelhead (anadromous O. mykiss) returning to the Snake River (U.S.) declined by ~94% during upstream migration and spawning (Penney and Moffitt 2014). In comparison, riverine O. mykiss are believed to feed continuously in freshwater providing continuous energy inputs during their own migration and spawning activities. As a result of different feeding and metabolic requirements, one might expect that the different patterns of energy storage to be observed among the O. mykiss life histories. WDFW Science Report

3 The study conducted in the Utkholok River in 2016 and 2017 addresses the connection between energy storage and the life history diversity of O. mykiss. The anadromous O. mykiss return to this river in the months of September and October and overwinter for eight to nine months before spawning the following May and June (K. Kuzishchin, Moscow State University, personal communication). As a result, anadromous life histories are expected to store more lipids than the riverine life history in order to meet the energetic requirements of returning to overwinter and mature in freshwater. This assumes that during the period of time between freshwater entry of anadromous life history and spawning that the anadromous life histories cease feeding in freshwater, the riverine life history continues to feed, and the metabolic demands resulting from river temperatures and migration are substantial enough to deplete energy stored by individual fish. Females are expected to store more lipids than males in order to meet the energetic requirements of reproductive maturation (Hendry and Berg 1999). This assumes that females returning to Kamchatka rivers in the fall months adopt a stream-maturation strategy similar to that observed in summer-run steelhead in North America. This study will also use stable isotope techniques to validate the feeding environment interpreted from the scale growth patterns. This technique can distinguish feeding in different food webs based on the carbon and nitrogen source for that food web. Carbon-13 isotope ratios are used to differentiate feeding in coastal versus offshore food webs (Johnson and Schindler 2009) and nitrogen-15 isotope ratios are used to differentiate freshwater versus marine food webs (Kline et al. 1990) as well as trophic level within a food web (Vander Zanden and Rasmussen 2001; Post 2002). The δ 13 C and δ 15 N values in the fish tissue are expected to reflect the environment in which they undergo the most growth, i.e., after the smolt period. Previous studies have used this technique to compare ocean feeding of among species of Pacific salmon (Johnson and Schindler 2009) as well as differences among steelhead stocks from the same river (Quinn et al. 2012; Lamperth et al. 2017). At the adult life stage of O. mykiss in Kamchatka rivers, the anadromous life history is expected to have a lower δ 13 C than the estuarine life history, reflecting a more offshore basis for the anadromous feeding ecology and the riverine life history is expected to have a lower δ 15 N than the estuarine or anadromous life histories, reflecting a more terrestrial and freshwater basis for the riverine feeding ecology. Study Objectives Identify life histories of O. mykiss present in western Kamchatka rivers, Compare the adult body condition (somatic lipid content) and post-smolt feeding (stable isotopes) among life history types, and Compare these results to O. mykiss populations in the Pacific northwest. Study Site The Utkholok River flows 130 km from its headwaters to the Sea of Okhotsk. The river is low gradient (5 m/km) with base flows between 60 and 70 meter 3 /second (Pavlov et al. 2005). The Utkholok is a tundra-type river with a simple channel structure, tannic colored water, and river banks lined with willow trees. The river is primarily a meandering, single channel with combinations of riffles, pools, and long runs. The presence of off-channel sloughs, backwater areas, and tributaries increases in an WDFW Science Report

4 upstream direction. Several of the tributaries are known to be important spawning areas for O. mykiss; in the spring, tributary temperatures increase more rapidly than the main stem river and therefore tributary habitat provides the earliest stream conditions suitable for O. mykiss spawning (M. Gruzdeva, Moscow State University, personal communication). Figure 1. The Utkholok River in Kamchatka, Russia. Downstream reaches of the river (A) form a low gradient, meandering channel. Upstream reaches of the river (B) are confined by high bluffs. IN the headwaters (C), the river forms complex, braided channels that branch into small tributaries. Methods In 2017, field work was planned for 17 days between September 25 and October 11. Biological sampling included identifying gender, measuring length, girth, and fat content, and collecting scales and a fin clip. Gender was identified from external features including the jaw length (tip of jaw extends past the eye = male, tip of jaw not past the eye = female) and the presence of worn ventral edge of the caudal fin (prior redd digging = female). Length was the fork length measured from the tip of the snout to the fork in the caudal fin. Girth was the largest circumference of the body anterior to the dorsal fin. Twenty scales (10 each side) were collected from the area above the lateral line and posterior to the dorsal fin. Scales will be used to assign age and life history and for stable isotope and genetic analysis. Fat content of the dorsal muscle tissue was measured using a handheld microwave energy meter (Distell Fish Fatmeter, Model Number FM 692, Distell Inc., West Lothian, Scotland). This meter estimated water WDFW Science Report

5 content and converted this value to percent lipids using the strong inverse relationship between the two substances in fish tissue. The Trout-1 setting of the energy meter used in this study was calibrated to O. mykiss by the manufacturer. Eight readings were collected (four on each side) from the dorsal muscle tissue above the lateral line, consistent with the manufacturer s instructions and with the methods used in similar research (Crossin and Hinch 2005; Lamperth et al. 2017). Observations on fish condition (sea lice, lamprey wounds, seal or other predator scars) were recorded. Prior to release, each fish was tagged with a single numbered floy tag and photographed. Data was recorded on scale envelops in the field and transcribed to into electronic format each evening. Figure 2. Biological sampling of O. mykiss captured in the Utkholok River, fall Scientists, guides, and sponsors worked together in the sampling and data collection effort. MALE FEMALE Figure 3. Male and female O. mykiss captured in the Utkholok River were identified by snout shape, jaw length, overall body shape, and evidence of a worn caudal fin (that would indicate prior spawning activity of females). Tissue samples collected from each fish may be used to further validate gender using genetic techniques. WDFW Science Report

6 Results Sampling Effort Sampling occurred over 15 days between September 26 and October 10. Daily fishing effort was eight or nine hours with four to seven rods fished each day. The sampling team included four sponsors, three scientists, and two guides. Fishing effort was divided into two beats, each of which was fished daily by one of the two boats. One beat extended 10 river kilometers downstream from the field camp and the second beat extended 7 river kilometers upstream from the field camp. The field camp was located 40 river kilometers from the Sea of Okhotsk. Catch per unit effort averaged 2.7 to 7.2 O. mykiss per rod per day. A total of 428 O. mykiss were hooked and 281 were successfully landed (Figure 4). Of the landed fish, 269 were maiden captures and the remaining 12 were recaptures. All recaptured fish had been tagged in Maiden captures were visually assigned to one of two phenotypes steelhead or rainbow trout as described below. The steelhead phenotype represented 81% (n = 218) and the rainbow phenotype represented 19% (n = 51) of the maiden captures. Scale analysis will be used to further refine these phenotype assignments and described the complete life history of each fish according to their freshwater and ocean growth patterns. Figure 4. Number of O. mykiss caught in fishing effort on the Utkholok River, Life Histories Field Observations Similar to 2016, O. mykiss in 2017 were visually assigned to one of two different phenotypes that differed in size and coloration (Figure 5). Each of these visual categories actually represents multiple life WDFW Science Report

7 histories (i.e., freshwater and ocean growth patterns) that will be determined from scale analysis completed at Moscow State University after the field season. Phenotype 1 For the purpose of this report, individuals with this phenotype will be referred to as steelhead. Fork length ranged from 61 to 96.5 cm. Fish had an elongate body shape with purple-black and chrome coloration. Some fish were developing a freshwater coloration with black spots along the dorsal body surface and pink coloration on the cheek and along the lateral line. All fish lacked the chrome-olive hue observed in the smaller sized phenotype. Sea lice and gill parasites were observed. Many individuals had scrapes or open wounds consistent with seal, daggertooth (marine fish), and lamprey predation. None of the females were observed to have worn ventral edges to their caudal fins. Phenotype 2 For the purpose of this report, individuals with this phenotype will be referred to as rainbow trout. Fork length ranged from 27 to 68 cm. Fish had a football body shape. All fish had a freshwater coloration with pink coloration on the cheek and along the lateral line and a distinctive chrome-olive hue to their body. Black spotting patterns differed among individuals and were sometimes limited to the region above the lateral line and sometimes observed along the entire lateral side of the fish. No sea lice or gill parasites were observed. Minimal to no predator markings were observed on the body of individual fish. Several females had worn ventral edges to their caudal fin indicating prior spawn events. Figure 5. Diversity of O. mykiss observed during field sampling in the Utkholok River, Top panel is an 83 cm female steelhead (phenotype 1), and bottom panel is a 55 cm female rainbow trout (phenotype 2). WDFW Science Report

8 Biological Characteristics Of the 269 O. mykiss that were biologically sampled, gender was assigned to 245 individuals. Sampled steelhead were 64% female (n = 146) and 36% male (n = 81). Sampled rainbow trout were 47% female (n = 14) and 53% male (n = 16). Missing gender data were most common with rainbow trout less than 50 cm in fork length where the external features characterizing males and females were not pronounced. In order to finalize the analysis, additional genetic techniques will be needed to assign gender to these individuals as well as verify field calls for all individuals. Figure 6. Male and female O. mykiss captured in the Utkholok River, Graph shows the proportion of each gender by phenotype (steelhead, rainbow trout) based on field data collected for individual fish. WDFW Science Report

9 Fork length of all O. mykiss sampled averaged 72.9 cm and ranged between 27.0 to 96.5 cm. The distribution of lengths was bimodal with one mode around 45 cm and a second mode around 80 cm (Figure 7). Steelhead averaged 78.9 cm (range 61.0 to 96.5 cm). Rainbow trout averaged 48.1 cm (range 27.0 to 68 cm). Figure 7. Body size of O. mykiss captured in the Utkholok River, Graph shows the proportion of each phenotype (steelhead, rainbow trout) in each 5-cm length bin. Fat Content Fat content of the dorsal muscle of O. mykiss in the Utkholok River averaged 2.5% (range 0.7% to 4.9%). Contrary to our hypothesis, fat content of rainbow trout tissue was higher than that of steelhead (Figure 8). Within both phenotypes, females had higher fat content than males. Average fat content of female steelhead (average = 2.7%, range = 1.3 to 4.9%) was 1.3 times that of males (average = 2.1%, range = 1.0 to 4.5%). Average fat content of female rainbow trout (average = 2.9%, range = 1.9 to 4.1%) was 1.2 times that of males (average = 2.4%, range = 0.7 to 4.5%). This preliminary comparison will be updated once the life histories and gender assignments are finalized. WDFW Science Report

10 Figure 8. Fat content (%) of the dorsal muscle of O. mykiss from the Utkholok River, Fat content is summarized by field-assigned phenotypes 1: steelhead, 2: rainbow trout. Average and standard error for males and females are shown separately. Discussion and Recommendations Results from the 2016 and 2017 field seasons demonstrate that the Utkholok River is a good location for studying the ecological requirements of different life histories of O. mykiss. Steelhead and rainbow trout phenotypes were observed in all areas of the river that we fished, and, based on visual assignments, the rainbow trout phenotype represented 20% of the landed catch in both years. The majority of the river is accessible by jet boat during the fall months, with the exception of the extreme headwaters where the river depths become too shallow and the channel is filled with large volumes of wood debris that prevent easy navigation with a jet boat. In the spring, higher flows facilitate navigation to the headwater areas but a multiple day planned excursion is recommended for future exploration of this area of the river (M. Gruzdeva, Moscow State University, personal communication). Fat content of the O. mykiss caught in the Utkholok River was relatively low compared to known values from stream-maturing (i.e., summer run) North American populations (Penney and Moffitt 2014; Lamperth et al. 2017). Differences in energy storage among stream-maturing steelhead populations may reflect fine tuning to the metabolic requirements of their respective freshwater environments. In the Utkholok River (Kamchatka) the earliest returning steelhead are observed in the months of September and October, eight or nine months prior to spawning. They migrate relatively short distances (tens of kilometers) through a low gradient river and overwinter under relatively cold stream temperatures. In the Columbia River (U.S.), the earliest returning summer steelhead are observed in May or June, approximately nine months prior to spawning. They migrate relatively long distances (hundreds of kilometers) through high gradient stretches of river and over-summer and over-winter under relatively WDFW Science Report

11 warm stream temperatures. All of these factors distance of migration, strenuous conditions during migration, and stream temperature are likely to result in higher metabolic requirements for steelhead returning to the Columbia River populations than the Utkholok River. Consistent with these potential metabolic requirements, summer steelhead entering the Columbia River had an average of 5-6% fat content (Penney and Moffitt 2014; Lamperth et al. 2017) which is two times higher than the average of 2.5% lipid content observed for anadromous O. mykiss returning to the Utkholok River. The higher fat content observed in female than male O. mykiss was consistent with energetic requirements for reproductive maturation and spawning (Hendry and Berg 1999). Energy reserves are used by females to complete egg development and construct redds for spawning and by males to complete reproductive maturation and mate competition. The female-male difference in energy storage was observed in both the steelhead and rainbow trout phenotypes, suggesting that the energetic requirements of reproductive maturation may be at least partially robust to different feeding behaviors of the two life histories in the freshwater environment. The combination of 2016 and 2017 field seasons provided enough data to complete the planned analyses associated with energy storage of the multiple O. mykiss life histories in the Utkholok River. Preliminary analyses indicate that the fat storage of individuals adopting a rainbow trout (riverine) life history is higher than that of those with a steelhead (anadromous) life history, similar to energetic allocations observed at the juvenile life stage (McMillan et al. 2012; Sloat et al. 2014) and contrary to expectations based on energy requirements associated with the adult life stage. Next Steps to Complete the Planned Research Research conducted on the Utkholok River in 2016 and 2017 demonstrated good potential to further scientific understanding of O. mykiss diversity. Multiple life histories were clearly apparent in the catch and variation in fat content was observed among individuals. A comparison of Kamchatka and North American populations will provide important insight into the energetic requirements of anadromous steelhead in different ecosystems. Results from 2016 indicated that additional samples were needed to make the energetic comparisons; these additional samples were successfully obtained in the 2017 field season. The following steps are needed to complete the current study: Complete life history assignments from scale samples, Complete stable isotope analysis on a subset of available samples for each life history, Use genetic techniques to verify gender assignments made in the field, especially for the rainbow trout Finalize analysis that compares fat storage and feeding ecology (stable isotopes) among life histories In addition, future work to assign gender to individual O. mykiss in the field may benefit from existing ultrasound technology. Portable ultrasound devices have been successfully used to gather information on gonadal condition (male versus female, pre-spawn versus post-spawn) when external features are WDFW Science Report

12 not completely diagnostic (e.g., Evans et al. 2004; Macbeth et al. 2011). Data collection using the ultrasound technology involves scanning the dorsal-ventral surface of the fish; the process is nonlethal and adds minimal time to the sampling process. Use of this tool may be particularly useful for sampling of rainbow trout but would also help to validate gender of steelhead in cases where the assignment by samplers is uncertain. In the future, WDFW plans to explore use of this tool for evaluating maturation status (gonadal development) of O. mykiss; if successful, this may provide additional future opportunity to compare the energetics of Kamchatka and North American populations. Collaborative Science Model The is built on a model of collaborative science where scientists, guides, and anglers all participate in the data collection. Interactions on the river and at camp provide valuable opportunities for idea sharing and information exchange. In 2017, several of the participating anglers had previously fished the Utkholok River in some of the earliest years of the project (mid-1990s) which provided a rich perspective on the project past and present. In addition, scientists involved in the project made specific efforts to enrich these conversations and provide information that would help anglers to connect the fish that they were catching to scientific discovery. These interactive and instructional efforts included: Participation in data collection - During the process of biologically sampling fish in the field, anglers helped to record biological information that was gathered by scientists and guides who were sampling the fish. Reference guide - A high-level reference guide describing steelhead in Kamchatka was made available in the form of a laminated handout that remained in the dining cabin. The reference guide was a set of basic graphs and pictures that answered questions such as how old are the fish?, how big are the fish?, how many times does a steelhead return to the river? etc. Evening science presentation The science presentation described the history of the Kamchatka Steelhead Project. This presentation was prepared by scientists from Moscow State University and delivered by one of the scientists in each field camp. At the Utkholok River, the information was delivered in two evening presentations. The first presentation provided a spatial perspective to O. mykiss diversity and focused the diversity among rivers and the proposed connections between fish diversity and river complexity. The second presentation provided a temporal perspective on O. mykiss diversity and focused on the changes in age structure (freshwater, ocean) observed over four decades of Kamchatka steelhead research. Acknowledgements Angling effort in Session 1 was provided by Gary Ostenson, Kyle Ostenson, Otis Fugelso, and Brian Walker. Angling effort in Session 2 was provided by David Higman, John Higman, Daniel Higman, and Steve Pettit. Justin Miller and Dima Novrotski guided the fishing effort. Scientists participating in the project included Marina Gruzdeva (Moscow State University), Kirill Kuzishchin (Moscow State University), Matt Sloat (Wild Salmon Center), and Mara Zimmerman (Washington Department of Fish WDFW Science Report

13 and Wildlife). Tom Quinn (University of Washington) loaned a fat meter for the study and will collaborate on the stable isotope analysis. Participation of WDFW scientists in the Kamchatka Steelhead Project was possible due to financial support from The Conservation Angler. References Crossin, G. T., and S. G. Hinch A nonlethal, rapid method for assessing the somatic energy content of migrating adult Pacific salmon. Transactions of the American Fisheries Society 134: Evans, A. F., M. S. Fitzpatrick, and L. K. Siddens Use of ultrasound imaging and steroid concentrations to identify maturational status in adult steelhead. North American Journal of Fisheries Management 24(3): Hendry, A. P., and O. K. Berg Secondary sexual characters, energy use, senescence, and the cost of reproduction in sockeye salmon. Canadian Journal of Zoology 77: Johnson, S. P., and D. E. Schindler Trophic ecology of Pacific salmon (Oncorhynchus spp.) in the ocean: a synthesis of stable isotope research. Ecological Research 24(4): Kendall, N. W., J. R. McMillan, M. R. Sloat, T. W. Buehrens, T. P. Quinn, G. R. Pess, K. V. Kuzishchin, M. M. McClure, and R. W. Zabel Anadromy and residency in steelhead and rainbow trout (Oncorhynchus mykiss): a review of the processes and patterns. Canadian Journal of Fisheries and Aquatic Sciences 72: Kline, T. C. J., J. J. Goering, O. A. Mathisen, P. H. Poe, and P. L. Parker Recycling of elements transported upstream by runs of Pacific Salmon: 1. d15n and d13c evidence in Sashin Creek, southeastern Alaska. Canadian Journal of Fisheries and Aquatic Sciences 47: Kuzishchin, K. V., K. A. Savvaitova, and M. A. Gruzdeva Scale structure as criteria for the determination of local stocks of mikizha Parasalmo mykiss from western Kamchatkan and North American rivers. Journal of Ichthyology 39(6): Lamperth, J. S., T. P. Quinn, and M. S. Zimmerman Levels of stored energy but not marine foraging patterns differentiate seasonal ecotypes of wild and hatchery steelhead trout, Oncorhynchus mykiss, returning to the Kalama River, Washington. Canadian Journal of Fisheries and Aquatic Sciences 74(2): Macbeth, B. J., H. D. Frimer, J. R. Muscatello, and D. M. Janz Use of portable ultrasonography to determine ovary size and fecundity non-lethally in northern pike (Esox lucius) and white sucker (Catostomus commersoni). Water Quality Research Journal of Canada 46(1): McMillan, J. R., J. B. Dunham, G. H. Reeves, J. S. Mills, and C. E. Jordan Individual condition and stream temperature influence early maturation or rainbow and steelhead trout, Oncorhynchus mykiss. Environmental Biology of Fishes 93: McPhee, M., F. Utter, J. Stanford, K. Kuzishchin, K. Savvaitova, D. Pavlov, and F. Allendorf Population structure and partial anadromy in Oncorhynchus mykiss from Kamchatka: relevance for conservation strategies around the Pacific Rim. Ecology of Freshwater Fish 16(4): Pavlov, D., K. Kuzishchin, P. Kirillov, M. Gruzdeva, E. Maslova, A. Y. Mal tsev, D. Stanford, K. Savvaitova, and B. Ellis Downstream migration of juveniles of Kamchatka mykiss Parasalmo mykiss from tributaries of the Utkholok and Kol rivers (Western Kamchatka). Journal of Ichthyology 45(suppl 2): WDFW Science Report

14 Pavlov, D., K. Savvaitova, K. Kuzishchin, M. Gruzdeva, A. Y. Mal Tsev, and J. Stanford Diversity of life strategies and population structure of Kamchatka mykiss Parasalmo mykiss in the ecosystems of small salmon rivers of various types. Journal of Ichthyology 48(1): Penney, Z. L., and C. M. Moffitt Proximate composition and energy density of stream-maturing adult steelhead during upstream migration, sexual maturity, and kelt emigration. Transactions of the American Fisheries Society 143: Post, D. M Using stable isotopes to estimate trophic position: Models, methods, and assumptions. Ecology 83(3): Quinn, T. P., T. R. Seamons, and S. P. Johnson Stable isotopes of carbon and nitrogen indicate differences in marine ecology between wild and hatchery-produced steelhead. Transactions of the American Fisheries Society 141: Savvaitova, K., K. Kuzishchin, M. Gruzdeva, D. Pavlov, D. Stanford, and B. Ellis Long-term and short-term variation in the population structure of Kamchatka steelhead Parasalmo mykiss from rivers of western Kamchatka. Journal of Ichthyology 43(9): Savvaitova, K. A., M. A. Tutukov, K. V. Kuzishchin, and D. S. Pavlov Changes in the population structure of mikizha Parasalmo mykiss from the Utkholok River, Kamchatka, during the fluctuation in its abundance. Journal of Ichthyology 42: Sloat, M. R., D. J. Fraser, J. B. Dunham, J. A. Falke, C. E. Jordan, J. R. McMillan, and H. A. Ohms Ecological and evolutionary patterns of freshwater maturation in Pacific and Atlantic salmonines. Reviews in Fish Biology and Fisheries 24(3): Vander Zanden, M. J., and J. B. Rasmussen Variation in delta N-15 and delta C-13 trophic fractionation: Implications for aquatic food web studies. Limnology and Oceanography 46(8): Zimmerman, C., K. Kuzishchin, M. Gruzdeva, D. Pavlov, J. Stanford, and K. Savvaitova Experimental determination of the life history strategy of the Kamchatka mykizha Parassalmo mykiss (Walb.)(Salmonidae, Salmoniformes) on the basis of analysis of the Sr/Ca ratio in otoliths. Pages in Doklady Biological Sciences. Springer. WDFW Science Report