title: Eight decades of sampling reveal a contemporary novel fish assemblage in coastal nursery habitats.
abstract: In order to adequately monitor biodiversity trends through time and their responses to natural or anthropogenic impacts, researchers require long time series that are often unavailable. This general lack of datasets that are several decades or longer makes establishing a background or baseline of diversity metrics difficult - especially when attempting to understand species composition changes against a backdrop of climate and ecological variability. Here, we present an analysis of a community of juvenile nearshore fishes based on nearly 8 decades of highly standardized Norwegian survey records. Using multivariate statistical techniques, we: (i) characterize the change in taxonomic community composition through time, (ii) determine whether there has been an increase in warm-water affinity species relative to their cold water affinity counterparts, and (iii) characterize the temporal change in the species' functional trait assemblage. Our results strongly indicate a shift toward a novel fish assemblage between the late 1990s and 2000s. The context of changes within the most recent two decades is in stark contrast to those during the 1960s and 1970s, but similar to those during the previous warm period during the 1930s and 1940s. This novel assemblage is tightly linked to the warming temperatures in the region portrayed by the increased presence of warm-water species and a higher incidence of pelagic, planktivorous species. The results indicate a clear influence of ocean temperature on the region's juvenile fish community that points to climate-mediated effects on the species assemblages of an important fish nursery area.
authors.affiliation: College of Earth, Ocean and Atmospheric Sciences, Oregon State University, Corvallis, OR, 97330, USA.
authors.forename: Caren
authors.initials: C
authors.lastname: Barceló
authors.affiliation: College of Earth, Ocean and Atmospheric Sciences, Oregon State University, Corvallis, OR, 97330, USA.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Ciannelli
authors.affiliation: Institute of Marine Research, Flødevigen, His, N-4817, Norway.|Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biology, University of Oslo, P.O. Box 1066 Blindern, Oslo, N-0316, Norway.|University of Agder, 4604 Kristiansand, Norway.
authors.forename: Esben M
authors.initials: EM
authors.lastname: Olsen
authors.affiliation: Institute of Marine Research, Flødevigen, His, N-4817, Norway.
authors.forename: Tore
authors.initials: T
authors.lastname: Johannessen
authors.affiliation: Institute of Marine Research, Flødevigen, His, N-4817, Norway.|Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biology, University of Oslo, P.O. Box 1066 Blindern, Oslo, N-0316, Norway.|University of Agder, 4604 Kristiansand, Norway.
authors.forename: Halvor
authors.initials: H
authors.lastname: Knutsen
mesh_terms: D000818:Animals; D044822:Biodiversity; D057231:Climate Change; D017753:Ecosystem; D005399:Fishes / Q000502:physiology*; D009664:Norway; D011157:Population Dynamics; D013997:Time Factors
keywords: Norwegian Skagerrak coast; climate change; community structure; juvenile fish; novel assemblage