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We used seabird surveys and concurrent oceanographic observations in the Northern Gulf of Alaska during spring 1998-2019 to evaluate how seabirds responded to temperature variability, including a protracted marine heatwave, in a highly heterogeneous ecosystem. We examined temporally changing distributions of seabirds along the Seward Line, a 220 km transect across the shelf and slope, and evaluated relationships between water-mass properties and seabird abundance. Environmental factors associated with abundance include depth, water-column temperature and salinity, and surface-current velocities. Environmental responses of alcids and gulls contrasted with those of procellariiform (tubenose) seabirds, and their trajectories suggest a possible shift in community composition under future climate warming. Changes in seabird distribution and abundance associated with a shift from cold to warm conditions were especially pronounced over the middle- and outer-shelf domains, which are transitional between coastal and oceanic water masses. The abundance of tubenoses increased during and after the heatwave, whereas alcids and gulls shifted inshore, exhibited reproductive failures, and experienced mass mortalities due to starvation. Tubenoses appear well-adapted to periods of lower productivity during warming events because of their flight efficiency, allowing them to search widely to locate prey patches. In contrast, alcids, which forage by diving and have energetically expensive flight, appear sensitive to such conditions. 

Abstract Hyperspectral data encode information from electromagnetic radiation (i.e., color) of any object in the form of a spectral signature; these data can then be used to distinguish among materials or even map whole landscapes. Although hyperspectral data have been mostly used to study landscape ecology, floral diversity and many other applications in the natural sciences, we propose that spectral signatures can be used for rapid assessment of faunal biodiversity, akin to DNA barcoding and metabarcoding. We demonstrate that spectral signatures of individual, live fish specimens can accurately capture species and clade-level differences in fish coloration, specifically among piranhas and pacus (Family Serrasalmidae), fishes with a long history of taxonomic confusion. We analyzed 47 serrasalmid species and could distinguish spectra among different species and clades, with the method sensitive enough to document changes in fish coloration over ontogeny. Herbivorous pacu spectra were more like one another than they were to piranhas; however, our method also documented interspecific variation in pacus that corresponds to cryptic lineages. While spectra do not serve as an alternative to the collection of curated specimens, hyperspectral data of fishes in the field should help clarify which specimens might be unique or undescribed, complementing existing molecular and morphological techniques.