Chlorinated Hydrocarbons in Livers of American Mink (Mustela vison) and River Otter (Lutra canadensis) from the Columbia and Fraser River Basins, 1990–1992

We investigated chlorinated hydrocarbon contaminants in aquatic mustelid species on the Fraser and Columbia Rivers of northwestern North America. Carcasses of river otter (Lutra canadensis) (N=24) and mink (Mustela vison) (N=34) were obtained from commercial trappers during the winters of 1990–91 and 1991–92. Pooled liver samples were analyzed for organochlorine pesticides, polychlorinated biphenyls (PCBs), including non-ortho congeners, polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs). Most samples contained detectable concentrations of DDE, PCBs, although there was substantial variability in patterns and trends among neighboring samples. Concentrations of DDE were in some mink and several otter samples from the lower Columbia River elevated (to 4700 g/kg wet weight); excluding one mink sample from the Wenatchee area, mean DDE levels generally decreased between 1978–79 and 1990–92. PCBs were present in all samples. PCB concentrations in otter livers collected from the lower Columbia were ten-fold lower than measured a decade previously; nevertheless, a sample taken near Portland had a mean concentration of 1500 g/kg, within a range of concentrations associated with reproductive effects in captive mink. Concentrations of 2,3,7,8-TCDD and TCDF were generally below detection limits, except for one otter collected near a pulp mill at Castlegar, on the upper Columbia, with 11 ng TCDD/kg in liver. Elevated concentrations of higher chlorinated PCDD/Fs, probably resulting from use of chlorophenolic wood preservatives, were found in both species; one otter sample from the lower Columbia had 2200 ng OCDD/kg. International TCDD toxic equivalent levels in mink (31 ng/kg) and otter (93 ng/kg) from the lower Columbia River approached toxicity thresholds for effects on reproduction in ranch mink.     

Temporal and Spatial Trends in Chlorinated Hydrocarbon Concentrations of Mink in Canadian Lakes Erie and St. Clair

Mink (Mustela vison) carcasses were collected from local commercial trappers from fall 1998 to spring 2003 from tributaries and marshes within 4.8km from the shores of Lakes Erie and St. Clair, including the Wheatley Harbour and St. Clair River Areas of Concern (AOCs), as well as from inland sites (8 to 40km from shore). Liver concentrations, on a lipid weight basis, of chlorinated hydrocarbons were measured and compared among sites and to tissue concentrations of mink from two previous collections from similar sites over the past 25 years. Mink from the western Lake Erie sites, which included the Wheatley Harbour AOC, had significantly higher concentrations of sum PCBs and PCB Aroclors than those from the St. Clair corridor or inland sites, with concentrations from the rest of Lake Erie being intermediate. Dieldrin concentrations were also significantly higher in western Lake Erie than many other sites, and those of oxychlordane and mirex also tended to be higher (0.05 < p < 0.1). There were no differences in contaminant concentrations between the St. Clair River AOC and the downstream non-AOC Lake St. Clair site, with the exception of slightly higher levels of octachlorostyrene (OCS). Concentrations of PCBs and other chlorinated hydrocarbons in mink showed a general decrease over the past two decades. In contrast, PCBs and some organochlorine pesticides tended to increase, significantly so with oxychlordane, in western Lake Erie mink over the same time period. DDE declined at all sites. Currently, mink liver PCB concentrations are within the range associated with reproductive impairment, as determined from captive mink studies, in 11.7% of all animals collected from the Lakes Erie and St. Clair basin overall, but in almost 40% of individuals from western Lake Erie.     

去势对育成期雄水貂生长发育及毛皮质量的影响

对不同d龄（55、85、115、145）去势雄水貂的生长发育及毛皮质量的研究结果表明：55d龄去势的雄水貂在打皮时（205d龄）体重和体长均极显著低于未去势者（P＜0．01）；毛皮质量有所提高，但55d龄去势的雄水貂皮张长度明显降低（P＜0．05）；说明水貂去势不宜早于85d龄．组织学研究结果表明：去势雄性水貂骺板P区软骨细胞数目较多，D区较窄，细胞肥大过程延迟,钙化及骨化速度降低；骺板宽度变化的测定表明：雄性水貂骺板融合时间在145d龄左右，55、85d龄去势雄性水貂骺板融合延迟40d以上．骺板融合的延迟虽然使55d龄去势雄性水貂挠骨长度相对于体长增加，55、85d龄去势雄性水貂挠骨长度相对于体重增加，但是并没有使骨骼绝对长度增加．115d龄以后去势对雄性水貂骺板融合没有影响．对不同日龄去势雄水貂血清睾酮水平亦进行了测定分析．     

Landscape connectivity: A conservation application of graph theory

We use focal-species analysis to apply a graph-theoretic approach to landscape connectivity in the Coastal Plain of North Carolina. In doing so we demonstrate the utility of a mathematical graph as an ecological construct with respect to habitat connectivity. Graph theory is a well established mainstay of information technology and is concerned with highly efficient network flow. It employs fast algorithms and compact data structures that are easily adapted to landscape-level focal species analysis. American mink (Mustela vison) and prothonotary warblers (Protonotaria citrea) share the same habitat but have different dispersal capabilities, and therefore provide interesting comparisons on connections in the landscape. We built graphs using GIS coverages to define habitat patches and determined the functional distance between the patches with least-cost path modeling. Using graph operations concerned with edge and node removal we found that the landscape is fundamentally connected for mink and fundamentally unconnected for prothonotary warblers. The advantage of a graph-theoretic approach over other modeling techniques is that it is a heuristic framework which can be applied with very little data and improved from the initial results. We demonstrate the use of graph theory in a metapopulation context, and suggest that graph theory as applied to conservation biology can provide leverage on applications concerned with landscape connectivity.