STATUS OF SIBERIAN WHITEFISH COREGONUS LAVARETUS PIDSCHIAN (GMELIN, 1788) IN THE SYSTEM THE TANJU RIVER - LAKE VARCHATO (THE VOIKAR RIVER BASIN)

The Voikar river is a spawning tributary of the lower Ob. Spawning grounds of Siberian whitefish are located both on the river Voikar and on the river Tanju (a tributary of the Voikar), which flows into lake Varchato. The Varchatovis canal flows out of lake Varchato and merges with the river Voikar. Studies have shown that in the system the Tanju river - lake Varchato live Siberian whitefish different from those of other Ural spawning tributaries of the Ob river and of the Ob itself by their age structure, presence of only re-maturing species with a high rate of growth and fecundity. It was found that after breeding on the spawning ground in the Tanju river some individuals of Siberian whitefish do not flow to the Ob river, but remain in system the Tanju river - Varchato lake. In two or three years it matures and goes back to spawn in the Tanju river, merging with the spawning stock which goes up the Ob river. There are no individuals that are constantly living in lake Varchato, as all juveniles, when still being larvae, flow down to the Ob river. That gives grounds for including Siberian whitefish of Varchato lake into the Ob population of semi-passing Siberian whitefish. The presence of re-maturing species in the system of the Tanju river - lake Varchato creates reproductive reserve of breeders that increase heterogeneity and population size. However, in the last decade as a result of total poaching of Siberian whitefish in lake Varchato during feeding and wintering its numbers declined sharply.

Experimental and field evaluation of otolith strontium as a marker to discriminate between river-spawning populations of walleye in Lake Erie

Otolith microchemistry is a commonly used tool for stock discrimination in fisheries management. Two key questions remain with respect to its effectiveness in discriminating among river-spawning populations. First, do larvae remain in their natal river long enough for their otoliths to pick up that system’s characteristic chemical signature? Second, are larval otolith microchemical differences between natal rivers sufficiently large to overcome spatiotemporal variation in water chemistry? We quantified how larval age, the ratio of ambient strontium to calcium concentrations (Sr:Ca), and water temperature influence otolith Sr in both lab-reared and wild-collected Lake Erie walleye (Sander vitreus). Otolith microchemistry shows promise as a spawning stock discrimination tool, given that otolith Sr in larval walleye (i) is more strongly influenced by ambient Sr:Ca than by temperature; (ii) reflects Sr:Ca levels in the natal environment, even in larvae as young as 2 days old; and (iii) can effectively discriminate between larvae captured in two key Lake Erie spawning tributaries, even in the face of short larval river residence times and within-year and across-year variation in ambient Sr:Ca.

Use of genetic markers to aid in re-establishing migratory connectivity in a fragmented metapopulation of bull trout (Salvelinus confluentus)

Dams and other barriers fragment important migratory corridors for bull trout ( Salvelinus confluentus ) across the species range. Three dams constructed without fish passage facilities prevented migratory bull trout in the Lake Pend Oreille and Clark Fork River system in Idaho and Montana, USA, from returning to their natal spawning tributaries for nearly 100 years. We genotyped bull trout from 39 spawning tributaries to assemble a baseline data set that we used to develop a real-time genotyping and analysis protocol to assist with upstream fish transport decisions. Self-assignment tests and analysis of blind samples indicated that unknown individuals could be assigned to their region of origin with a high degree of confidence. From 2004 to 2010, genetic assignments were conducted for 259 adult bull trout collected below mainstem dams. Based on genetic assignments, 203 fish were transported upstream above one or more dams. This protocol has helped re-establish connectivity in a fragmented system, providing increased numbers of spawning adults for numerically depressed populations above the dams. We discuss the utility of genetic data for assisting with upstream passage decisions.

Identifying Tributaries to Jackson Lake Important for Snake River Cutthroat Trout Recruitment

Across their range, native salmonid species are imperiled due to habitat loss, alteration, and competition with non-native salmonids. New challenges, such as the effects of climate change on stream flow and water temperature create new problems for these species and highlight the importance of understanding their juvenile and adult life histories. Specifically, identifying life history movement patterns as it relates to spawning sites and juvenile rearing streams. We measured strontium isotope values of 13 tributaries and mainstem waters of the lower Snake River and Jackson Lake as well as otoliths collected from resident/juvenile cutthroat trout to determine if we could find unique isotopic signatures throughout the watershed. Strontium isotope values were similar for otoliths and water samples collected at the same location. Strontium isotope yielded unique isotope values across the watershed and between tributaries and the Snake River and Jackson Lake. Only three tributaries were undifferentiated using strontium stable isotopes. These were Pilgrim, Dime, and Sheffield Creeks. Due to their close proximity geographically and their geologic similarities it is not surprising we were unable to differentiate these three tributaries from each other. Future work using trace element analysis might provide further differentiation between these three creeks. Using this new information, we can now begin to look at adult cutthroat from Jackson Lake and the Snake River and determine their natal origins and fidelity to spawning tributaries. Using this information, managers can guide conservation efforts for cutthroat trout in the Jackson Lake watershed.

Statolith microchemistry as a technique for discriminating among Great Lakes sea lamprey (Petromyzon marinus) spawning tributaries

Laurentian Great Lakes fishery management agencies are seeking ways to identify natal origins of parasitic- and spawning-phase sea lamprey ( Petromyzon marinus ) so that efforts to control this invasive species can be prioritized. We developed laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) as a technique to quantify elemental concentrations in larval sea lamprey statoliths and explored the use of statolith microchemistry as a tool to discriminate among larval sea lamprey production streams. Our analyses demonstrate that (i) traversing across the statolith with the laser is preferable to drilling down through its apex, (ii) preserving specimens in 95% ethanol versus freezing them has minimal effects on elemental concentrations, (iii) a minimum of 15 individuals per stream should accurately depict stream-specific statolith elemental signatures, and (iv) LA-ICP-MS is preferable to particle-induced X-ray emission (PIXE) for statolith analysis, based on higher precision, lower cost, reduced sampling-time requirements, and wider availability. Using LA-ICP-MS, we could discriminate among larvae from 13 streams located in Lakes Michigan, Huron, and Superior with 82% classification accuracy, indicating that this tool holds promise for determining natal origins of sea lamprey in the Great Lakes.

Dose-Related Toxicity of Copper and Cadmium in Striped Bass Larvae from the Chesapeake Bay: Field Considerations

Copper and cadmium monitoring in Chesapeake Bay sediments indicates that metal contamination exists in nursery areas for striped bass (Moronesaxatilis), which has been in serious decline over the last 17 years. Whole water metal concentrations in one spawning river were within an order of magnitude of published acutely toxic concentrations. Larval striped bass were exposed in the laboratory to copper and cadmium concentrations which were acutely toxic over a 96h period (24 and 19 µg L−1, respectively), and to sub-lethal concentrations of these metals over a three week period. Larvae from acutely toxic metal treatments, sub-lethal metal concentrations and control tanks were analyzed for cadmium and copper and the frequency distribution of metal body burdens was compared with field data. The distribution of copper concentrations in laboratory-exposed larvae was completely within the range of field specimens, and there was considerable overlap in cadmium frequency distributions from laboratory and field larvae. These results together with other published data suggest that environmental metal concentrations in some spawning tributaries of the Chesapeake Bay may pose a threat to striped bass, and the suggestion is made that greater efforts should be made to link laboratory and field toxicological data.

Evidence for Size-Selective Mortality of Juvenile Sockeye Salmon (Oncorhynchus nerka) in Babine Lake, British Columbia

Otolith – body length relations and back-calculation procedures were used to test the hypothesis that mortality of juvenile sockeye salmon (Oncorhynchus nerka) in Babine Lake, British Columbia, is size selective. Samples of the 1978 brood of sockeye were collected as fry from spawning tributaries as juveniles in the main basin, and as smolts at the outlet. Total otolith length was chosen as the most useful otolith dimension for back-calculation of fork length at emergence. Sockeye from the various tributaries show different fork length – otolith length relationships necessitating a weighting procedure for comparisons involving samples of mixed stocks from the lake. Instantaneous daily growth rate and In fork length during the early lake-rearing period were significantly correlated. Smaller juveniles grew more slowly than larger individuals in mid-july, and a hierarchy of sizes was maintained. The distributions of total otolith length at emergence for fry, surviving juveniles, and smolts indicate selective mortality of fish with smaller otoliths, hence of small size at emergence. Survivals from the lower and upper halves of the initial total otolith length distribution were 8.9 and 63.6%, respectively. Comparable estimates for back-calculated fork lengths at emergence were 27.2 and 43.4%. Size-selective mortality is most intense in the late summer and early autumn, and may be associated with predation and parasitism.

Homing of Brook Trout (Salvelinus fontinalis) in Matamek Lake, Quebec

Brook trout (Salvelinus fontinalis) showed both in-season and repeat homing to spawning tributaries of Matamek Lake, Quebec. Of 283 trout clipped from Gallienne Creek and Kaikhosru Creek during August and September, 1971, 31.1% returned to the homestreams to spawn in 1972. During July and August, 1972, 450 trout were tagged and displaced from these two streams and released at three points (0.20–4.50 km) in the lake. Of these fish, 44.0% homed, 0.2% strayed to the opposite stream and the remainder were unaccounted for. Percentage returns from the deepwater release point was much lower than returns from the two inshore release points, and average return time was proportional to the distance from the homestream.