Landscape, colonization, and life history: their effects on genetic diversity in four sympatric species inhabiting a dendritic system

To what degree are patterns of genetic structure in fragmented systems the result of contemporary landscape versus history? We examined the distribution of genetic diversity as a function of colonization history and contemporary landscape in four fish species inhabiting a hierarchically fragmented, unaltered system, the Kogaluk drainage (Labrador): lake trout (Salvelinus namaycush), longnose sucker (Catostomus catostomus), round whitefish (Prosopium cylindraceum), and lake chub (Couesius plumbeus). The footprint of colonization history was still observable in the three species where this issue was examined regardless of the generations since their arrival. Approximate Bayesian computation (ABC) analyses suggest colonization took place from the southwest. The species exhibit similar diversity patterns despite different [Formula: see text] values and generation intervals. Contemporary gene flow was largely negligible except for gene flow from a centrally located lake. These results suggest landscape has driven colonization history, which still has influence on genetic structuring. The species are widespread. Understanding how they behave in the pristine Kogaluk provides a baseline against which to evaluate how other anthropogenically perturbed systems are performing. Improved understanding of historical and contemporary processes is required to fully explain diversity patterns in complex metapopulations.

Use of Stable Carbon and Nitrogen Isotopes to Trace Natural and Anthropogenic Inputs into Riverine Systems in the Athabasca Oil Sands Region

Stable isotopes of carbon and nitrogen in fish were examined as a potential tracer of exposure to oil sands constituents in naturally eroded environments and in areas of anthropogenic activity (municipal and industrial effluent discharges; oil sands surface mining) within the Athabasca River drainage basin of northern Alberta, Canada. Longnose sucker (Catostomus catostomus), trout-perch (Percopsis omiscomaycus), and slimy sculpin (Cottus cognatus) showed changes in δ13C values with the river gradient. Site-specific differences in the δ13C values of fish were more pronounced for the small-bodied fish species in the lower reaches of a tributary (slimy sculpin) and immediately downstream of tributary inputs along the Athabasca River (trout-perch), where potential exposure to the oil sands constituents is elevated. There were also species and site-specific trends for δ15N values. Site-specific trends attributed to municipal or industrial effluent discharge or tributary inputs may prove to be a useful tool for defining residency on the oil sands deposit. This study has provided baseline data of isotope values for fish species which are currently used (longnose sucker) or may be used in future environmental effects monitoring programs. Defining residency and exposure to the oil sands deposit is critical to establishing exposure-response relationships, particularly since there are new expansions to oil sands mining operations.

Anadromous Sturgeons: Habitats, Threats, and Management

<em>Abstract.</em>—In 1999 and 2000, gill-net sampling was used to determine the effect of sediment deposition (sand) on the relative abundance (catch per unit effort [CPUE]) of Atlantic sturgeon <em>Acipenser oxyrinchus</em> and lake sturgeon <em>A. fulvescens</em> frequenting the Île Madame open-water disposal site using a before–after and control–impact sampling design. A total of 1,108 fish of 11 different species were captured in the vicinity of the sediment disposal site. Sauger <em>Sander canadensis</em>, longnose sucker <em>Catostomus catostomus</em>, Atlantic sturgeon and lake sturgeon were the four most abundant species. Atlantic sturgeon CPUE was significantly higher in 1999 than in 2000, while lake sturgeon CPUE was similar in both years. After sediment disposal operations, we observed a significant decrease (3–7 times lower) in the Atlantic sturgeon CPUE at the impacted station compared to the control stations: CPUE dropped from 5.8 to 0.8 fish/ station-day in 1999 and from 1.8 to 0.5 fish/station-day in 2000. A significant reduction in CPUE values was also noted in the sediment dispersal area downstream from the disposal site after dumping. For both years, lake sturgeon CPUE at the impacted station was not significantly different from control stations after sediment disposal. These results suggest site avoidance and a negative impact of sediment disposal operations for Atlantic sturgeon but not for lake sturgeon. Management implications of these results are discussed in relation to sediment disposal operations in the St. Lawrence estuarine transition zone, an important habitat for both sturgeon species.

Application of Multi-stable Isotope (13C, 15N, 34S, 37Cl) Assays to Assess Spatial Separation of Fish (Longnose Sucker Catostomus catostomus) in an Area Receiving Complex Effluents

Incorporation of stable isotope analysis (SIA) into routine environmental effects monitoring programs of receiving waters may enable determination of the spatial extent of biotic exposure and discrimination among sources of complex effluents. To evaluate this hypothesis, longnose sucker (Catostomus catostomus) were collected from four sites along the Athabasca River, Alberta (upstream reference site, two sites downstream of effluents from two pulp and paper mills, and a site downstream of effluent from a municipal sewage treatment plant). Stable isotopes of carbon, nitrogen, sulfur and chlorine were analyzed in bone, gonad, liver and white muscle tissues of the fish. In general, most sites and tissues differed according to δ13C, δ15N and δ34S values. Also, an interaction between site and tissue was observed for δ15N values. A better insight into the usefulness of stable isotopes was obtained through the use of multivariate discriminant function analysis. δ15N and δ34S signatures of gonad and liver tissues of males were most effective at classifying fish according to site (~70% for both tissues). For all tissues except bone, fish from the upstream reference site were most separable from all others, especially females. δ37Cl values for female gonads and male livers were related to sites downstream of the pulp and paper mills. Future research should routinely include SIA of fish tissues, but also of effluents, receiving waters and food web components to better resolve links between specific effluents and fish exposure.