Can salmonids (Oncorhynchus spp.) be identified to species using vertebral morphometrics?

Remains of anadromous Pacific salmon and trout (genus Oncorhynchus) are common in archaeological sites from California to Alaska; however, morphological similarity generally precludes species identification, limiting the range of questions that salmonid remains can address in relation to past human use and ongoing efforts in conservation biology. We developed a relatively simple, rapid, and non-destructive way to classify salmon and trout vertebrae from archaeological contexts to species using length, height and the ratio of length to height. Modern reference material was obtained from all seven anadromous Oncorhynchus species native to the west coast of North America. A minimum of ten adult Chinook (Oncorhynchus tshawytscha), chum (Oncorhynchus keta), coho (Oncorhynchus kisutch), pink (Oncorhynchus gorbuscha), and sockeye salmon (Oncorhynchus nerka) and cutthroat (Oncorhynchus clarki clarki) and steelhead trout (Oncorhynchus mykiss) were skeletonized and vertebra length and height were measured. Morphometric analyses compared species classification success based on Linear Discriminant Analysis (LDA), Classification and Regression Trees (CART), and randomForest, with CART performing the best. Classification analyses used all seven species individually, but because of considerable overlap among several species we also conducted analyses on four species groupings. We assigned Chinook salmon and cutthroat to their own groups based on their dissimilarities from each other and the other species. The remaining species were divided into two group complexes (a) chum, coho, and steelhead; and (b) pink and sockeye. When we grouped species according to similar morphology, CART overall success rates increased, ranging from 92 to 100%. Individual species with the highest successful classification rates using CART were Chinook salmon and cutthroat, from 92 to 100%, respectively. We applied our classification to an assemblage of ancient (1000–3000 year old) salmonid vertebrae from the Swiftwater Rockshelters excavations on the upper Wenatchee River in Washington State, U.S.A.     

Local labour markets and socio-economic change: evidence from Danish towns, 2008–2013

The recent financial and economic crisis had substantial but spatially differentiated impacts on growth. However, there is still a lot left to be understood about the local aspects of the crisis. One of these aspects is its socio-economic consequences. This paper investigates local socio-economic change to Danish towns from 2008 to 2013, with a focus on the impact of local labour market (LLM) structures on change. Socio-economic change in towns is measured both directly as mean income and employment growth, and indirectly as population and human capital growth. The paper relies on micro-data and uses robust regression to generate results. Several findings are presented, but the two main conclusions are: first, the LLM structures of towns still influence local socio-economic development; and, second, towns experience better socio-economic development if they are in close proximity to a larger labour market and/or have a large ratio of commuters in the working population.