Diversity and Distribution of Mongolian Fish: Recent State, Trends and Studies

The studies in recent years (2000-2011) have allowed to make more precise the list and ranges of Mongolian fish. This is connected with new findings as well as the continuing process of invasion of alien species. Climate change and increase of human impact transformed ranges and local distribution of fish during last 30 years. Bias on ratio of ecological guilds, number of pathological findings are increasing, and declining of local diversity, rate of growth and fecundity of many species of fish are observed. In the course of long-term observation was confirmed periodically drying of waters of the Central Asian Lake Valley and temporal extinction of some populations of Altai osmans (genus Oreoleuciscus). The gold mining as a main anthropogenic factor in rivers of Arctic Ocean basin cause substantial silting of the grounds, increase of water turbidity, the lowering of flow velocity and heterogeneity of environment at separate sections led to a drastic fall in number of such species as taimen, lenok, grayling, minnows, burbot and to a growth of populations of the species adapting to new environments (golden carp, dace). Construction of hydraulic structures (dams in the basins of the Kobdo and Dzabkhan rivers), increase of pollutions, and intensification of fishery are new challenges for Mongolian fish populations

Diversity and Distribution of Mongolian Fish: Recent State, Trends and Studies

The studies in recent years (2000-2011) have allowed to make more precise the list and ranges of Mongolian fish. This is connected with new findings as well as the continuing process of invasion of alien species. Climate change and increase of human impact transformed ranges and local distribution of fish during last 30 years. Bias on ratio of ecological guilds, number of pathological findings are increasing, and declining of local diversity, rate of growth and fecundity of many species of fish are observed. In the course of long-term observation was confirmed periodically drying of waters of the Central Asian Lake Valley and temporal extinction of some populations of Altai osmans (genus Oreoleuciscus). The gold mining as a main anthropogenic factor in rivers of Arctic Ocean basin cause substantial silting of the grounds, increase of water turbidity, the lowering of flow velocity and heterogeneity of environment at separate sections led to a drastic fall in number of such species as taimen, lenok, grayling, minnows, burbot and to a growth of populations of the species adapting to new environments (golden carp, dace). Construction of hydraulic structures (dams in the basins of the Kobdo and Dzabkhan rivers), increase of pollutions, and intensification of fishery are new challenges for Mongolian fish populations

Diet analysis of the Khuvsgul grayling: (Thymallidae: Thymallus nigrescens)

Lake Khuvsgul has low fish diversity due to its ultra-oligotrophic conditions and contains only 10 fish species. In this study, we examined stomachs of the endemic species, Khuvsgul grayling (Thymallus nigrescens), and compared a diet variation among populations inhabiting littoral and pelagic zones. We collected fish samples from littoral and pelagic zones of the southwest, northwest, and east shores using gill nets, and preserved specimens and their stomachs in 4% formalin. In the laboratory, we weighed fish stomachs and identified organisms in the stomachs at mostly order levels. We then assessed the abundances of each taxonomic group and calculated percentages of their occurrences based on the number of fish specimens caught at each zone. In order to examine whether the diet of the Khuvsgul grayling differs by littoral and pelagic zones, we conducted non-metric multidimensional scaling (NMDS), Analysis of Dissimilarity (ANOSIM), and Similarity Percentage (SIMPER) analyses. All statistical analyses were performed using the vegan package in the R program. According to the results, we found 13 taxonomic groups in the fish stomachs. Among them, zooplankton was the most frequently occurring group in the diet of the pelagic populations, whereas larval dipteran was the most frequently occurring group in the diet of littoral populations. The diet difference between littoral and pelagic populations was statistically significant (ANOSIM: p<0.05) and the most difference was observed between zooplankton, dipterans, and gammarids (SIMPER: 45%, 63%, and 72%, respectively). Our findings revealed that the Khuvsgul grayling populations are dependent on food availability in their environment. Хөвсгөл хадран загасны идэш тэжээлийн анализ (thymallidae: thymallus nigrescens) ХУРААНГУЙ Хөвсгөл нуур ямдаг шимт (олиготрофик) учраас загасны зүйлийн бүрэлдэхүүний хувьд цөөн, 10 зүйлийн загас тархан амьдардаг. Энэхүү судалгааны ажилд бид эндемик загасны зүйл болох Хөвсгөл хадрангийн ходоодонд анализ хийж, гүн болон эргийн бүсийн популяцийн хооронд идэш тэжээлийн ялгаа бий эсэхийг харьцуулсан. Бид загасны дээжийг нуурын баруун урд, баруун хойд, зүүн эргийн гүн болон эрэг хэсгээс заламгайн тор ашиглан барьж, загас болон ходоодны дээжийг 4%-ийн формалинд фиксацлав. Лабораторийн нөхцөлд бид загасны ходоодыг жинлэж, идэш тэжээлийн бүрэлдэхүүнийг багийн түвшинд тодорхойлсон. Цаашлаад бид илэрсэн ангилал зүйн бүлгүүдийн арвийг тооцож, тэдгээрийн тохиолдлын хувийг эрэг, гүний бүсэд тархсан загасны бодгалийн тооноос хамааруулан бодож гаргав. Эргийн болон гүний бүсэд тархан амьдардаг Хөвсгөл хадран загас идэш тэжээлийн бүрэлдэхүүнээрээ хоорондоо ялгаатай эсэхийг бид non-metric multidimensional scaling (NMDS), Analysis of Dissimilarity (ANOSIM), болон Similarity Percentage (SIMPER) анализуудыг ашиглан шалгав. Эдгээр статистик анализыг R програм дээр vegan пакежийн тусламжтай гүйцэтгэв. Судалгааны дүнд бид загасны ходоодноос нийт 13 ангилал зүйн бүлгийг илрүүлсэн. Эдгээрийн дунд хөвмөл амьтад гүний бүсэд тархан амьдардаг популяцийн идэш тэжээлд, харин хос далавчтаны авгалдай эргийн бүсэд тархан амьдардаг популяцийн идэш тэжээлд тус тус өндөр давталттай илрэв. Эргийн болон гүний бүсийн популяцийн идэш тэжээлийн энэхүү ялгаа статистикийн хувьд ач холбогдолтой (ANOSIM: p<0.05) бөгөөд хамгийн их ялгааг хөвмөл амьтад, хос далавчтан, шаамий хавч (SIMPER: харгалзах хувь 45, 63, болон 72) үүсгэж байгаа болохыг тодорхойлов. Бидний судалгааны дүн Хөвсгөл хадрангийн популяци амьдрах орчинд тохиолдох идэш тэжээлээс хамааралтай болохыг харуулж байна. Түлхүүр үгс: Хөвсгөл хадран, Идэш тэжээл, Эргийн бүс, Гү

Geomorphology variables predict fish assemblages for forested and endorheic rivers of two continents

Stream fishes are restricted to specific environments with appropriate habitats for feeding and reproduction. Interactions between streams and surrounding landscapes influence the availability and type of fish habitat, nutrient concentrations, suspended solids, and substrate composition. Valley width and gradient are geomorphological variables that influence the frequency and intensity that a stream interacts with the surrounding landscape. For example, in constrained valleys, canyon walls are steeply sloped and valleys are narrow, limiting the movement of water into riparian zones. Wide valleys have long, flat floodplains that are inundated with high discharge. We tested for differences in fish assemblages with geomorphology variation among stream sites. We selected rivers in similar forested and endorheic ecoregion types of the United States and Mongolia. Sites where we collected were defined as geomorphologically unique river segments (i.e., functional process zones; FPZs) using an automated ArcGIS-based tool. This tool extracts geomorphic variables at the valley and catchment scales and uses them to cluster stream segments based on their similarity. We collected a representative fish sample from replicates of FPZs. Then, we used constrained ordinations to determine whether river geomorphology could predict fish assemblage variation. Our constrained ordination approach using geomorphology to predict fish assemblages resulted in significance using fish taxonomy and traits in several watersheds. The watersheds where constrained ordinations were not successful were next analyzed with unconstrained ordinations to examine patterns among fish taxonomy and traits with geomorphology variables. Common geomorphology variables as predictors for taxonomic fish assemblages were river gradient, valley width, and valley slope. Significant geomorphology predictors of functional traits were valley width-to-floor width ratio, elevation, gradient, and channel sinuosity. These results provide evidence that fish assemblages respond similarly and strongly to geomorphic variables on two continents

A Mixed-Method Approach for Quantifying Illegal Fishing and Its Impact on an Endangered Fish Species

<div><p>Illegal harvest is recognized as a widespread problem in natural resource management. The use of multiple methods for quantifying illegal harvest has been widely recommended yet infrequently applied. We used a mixed-method approach to evaluate the extent, character, and motivations of illegal gillnet fishing in Lake Hovsgol National Park, Mongolia and its impact on the lake’s fish populations, especially that of the endangered endemic Hovsgol grayling (<i>Thymallus nigrescens</i>). Surveys for derelict fishing gear indicate that gillnet fishing is widespread and increasing and that fishers generally use 3–4 cm mesh gillnet. Interviews with resident herders and park rangers suggest that many residents fish for subsistence during the spring grayling spawning migration and that some residents fish commercially year-round. Interviewed herders and rangers generally agree that fish population sizes are decreasing but are divided on the causes and solutions. Biological monitoring indicates that the gillnet mesh sizes used by fishers efficiently target Hovsgol grayling. Of the five species sampled in the monitoring program, only burbot (<i>Lota lota</i>) showed a significant decrease in population abundance from 2009–2013. However, grayling, burbot, and roach (<i>Rutilus rutilus</i>) all showed significant declines in average body size, suggesting a negative fishing impact. Data-poor stock assessment methods suggest that the fishing effort equivalent to each resident family fishing 50-m of gillnet 11–15 nights per year would be sufficient to overexploit the grayling population. Results from the derelict fishing gear survey and interviews suggest that this level of effort is not implausible. Overall, we demonstrate the ability for a mixed-method approach to effectively describe an illegal fishery and suggest that these methods be used to assess illegal fishing and its impacts in other protected areas.</p></div

Average density of derelict fishing gear by category (GN = gillnet material) and derelict gillnet fragments by mesh size in count and weight.

<p>Bars indicate average densities among the 2013 (dark grey, n_sites = 10, n_transects = 14) and 2014 shoreline transects (light grey, n_sites/n_transects = 7) weighted by transect length. Panels <b>A</b> and <b>B</b> indicate density in count (# km^-1) and Panels <b>C</b> and <b>D</b> indicate density in weight (g km^-1). Note variable y-axis scales.</p

Dietary overlap and selectivity among mountain steppe river fish in the United States and Mongolia

Abstract Lotic systems in mountain regions have historically provided secure habitat for native fish populations because of their relative isolation from human settlement and lack of upstream disturbances. However, rivers of mountain ecoregions are currently experiencing heightened levels of disturbance due to the introduction of nonnative species impacting endemic fishes in these areas. We compared the fish assemblages and diets of mountain steppe fishes of the stocked rivers in Wyoming with rivers in northern Mongolia where stocking is absent. Using gut content analysis, we quantified the selectivity and diets of fishes collected in these systems. Nonnative species had more generalist diets with lower levels of selectivity than most native species and native species had high levels of dietary specificity and selectivity. High abundances of nonnative species and high levels of dietary overlaps in our Wyoming sites is a cause of concern for native Cutthroat Trout and overall system stability. In contrast, fish assemblages characterizing Mongolia mountain steppe rivers were composed of only native species with diverse diets and higher selectivity values, suggesting low probability for interspecific competition

Location of shoreline surveys for derelict fishing gear, fish population monitoring sites, and interviews with park rangers and resident herders in Lake Hovsgol National Park (LHNP), Mongolia.

<p>Grey and black bars indicate the density (# km^-1) of derelict gillnet items observed in the 2013 (n = 10) and 2014 (n = 7) surveys, respectively (note different y-axis scale for Site 10). Black site numbers indicate the seven sites where fish population monitoring surveys were conducted in 2009 and 2011–13. Solid black lines indicate the park boundary and 17 ranger districts. Five rangers from five districts (dark grey; Hankh town limits represent one district) were interviewed. Herders were interviewed at Sites 3 (n = 3), 4 (n = 3), and 6 (n = 4). Small white triangles indicate tourist camps, large black circles indicate town centers, dotted black lines indicate primitive roads, and solid gray lines indicate rivers and seasonal steams.</p

Trends in the abundance of the five most abundant fish species in gillnet catches from 2009–2013.

<p>Points indicate the CPUE (kg net^-1 night^-1) of each 5-panel sequential mesh gillnet set (2 nets site^-1 x 7 sites yr^-1 = 14 sets yr^-1). Dark lines indicate linear mixed effects regressions fit to the catch data, gray shading indicates the confidence interval for each regression, and dashed lines indicate the prediction interval for the data. P-values are indicated in the upper right corner of each panel. Points are jittered around year for display. Note variable y-axis scales.</p