Assessing upstream invasion risk in alien freshwater fishes based on intrinsic variations in swimming speed performance

Managing the spread and impact of invasive species requires an understanding of what limits their dispersal into new areas. Here, we investigated an intrinsic component of invasive species dispersal, via assessments of the swimming speed performance of four species of alien freshwater fish at risk of invading the upper reaches of a montane river system in south‐east Australia. Using water flow measurements taken from a range of potential barriers to their upstream dispersal (fishways, culverts, natural riffle habitats), we assessed the likelihood of alien species passage based on intrinsic differences in swimming speed performance. With the four alien fish species displaying a wide range of sprint swimming speed (U_sprint) capabilities, our logistic regression analysis identified pipe culverts as being a challenge to dispersal by all but the largest individuals of one species (Rainbow trout, Oncorhynchus mykiss). Notably, fishway installations facilitating passage of the sympatric threatened species, Macquarie perch (Macquaria australasica), could allow upstream dispersal of a key threatening species (European perch, Perca fluviatilis). Our study highlights the utility of locomotor capabilities for assessing the likelihood of upstream dispersal by species following human‐assisted introductions to the lower parts of a catchment.     

Transhumance as Antidote for Modern Sedentary Stock Raising

Few grazing themes so endure yet are so difficult for outsiders to document with certainty as historical and current-day livestock grazing routes: stock driveways. Excursions from one biome, ecotone, or landscape to another—in general, undertaken to seasonal cues — allow livestock owners and their hired herders to exploit different environments that offer notable advantages in terms of freeing livestock from unvarying diet, overtaxed grazing grounds, common diseases, and cycles of drought or drenching rain. Movement at whatever scale permits herders or shepherds an escape from monotony when they shift grazing grounds to montane-woodlands or back to lowland environments in travel that benefits both jaded humans and husbanded animals. Significant economic and ecological advantages accrue from the shifts of seasonal silvopastoralism, but the terrain, and in particular the routes animals travel, often stretch across varied land ownerships, and sifting out rights of passage is an ethnographic adventure requiring longstanding observation and consistent fieldwork. Formal scholarship about the road between is less established than literature of “the trail,” which is a staple feature of folklore, film, and fiction. As concern grows about the energy costs of using highways or railroads to move livestock, attention returns to traditional practices and legal accommodations that make possible trailing livestock under their own power. Across Europe are 4 million ha of land associated with livestock driveways, once widespread in the United States as an item of Spanish-Mexican heritage. This synthesis focuses on livestock driveway establishment in two landscapes: Spain and, secondarily, the western United States of America, with an overarching theme of how stock driveways can connect ecosystems and, by sustaining customary use, knit together silvopastoral society.