Rapid high-quality imaging of fishes using a flat-bed scanner

Abstract

Photography has played an increasingly important role infish taxonomy, systematic studies, aquarium literature, fieldguides, and fisheries literature. Images are a particularlyimportant aid in taxonomy for recording pigmentationpatterns as well as meristic and morphometric character-istics. Photographs have also been used for estimating fishweights and lengths (Baugh 1982).Several techniques have been developed for photo-graphing preserved fish specimens (Randall 1961; Emeryand Winterbottom 1980; Flescher 1983; Holm 1989). Themost popular technique (Emery and Winterbottom 1980)involves the use of an inclined glass plate inside anaquarium to stabilize the specimen and artificial lighting.This setup has two disadvantages; the imaging of speci-mens is slow, and small fish specimens are sometimesdifficult to position between the inclined plate and theaquarium glass.The value of digital images, termed ‘‘e-Vouchers’’(Monk and Baker 2001), in documenting both specimensthat are too large to retain, and in providing broader accessto smaller specimens, is becoming an important data layerin modern natural history collections. However, thegrowing scale of biological inventories means that strate-gies are needed to gather high-quality images rapidly andcost-effectively. There is also an increasing trend formodern genetic resource collections to maintain onlinecatalogs, the most elaborate of which host digital imagesillustrating various aspects of organismal morphology. Forexample, the international Fish Barcode of Life campaign(http://www.fishbol.org) aims to establish a comprehensivereference library of DNA barcodes for all fish specieswithin the next 5 years, a task that will require the sequenceanalysis and imaging of some 500,000 specimens.Here we report a simple, inexpensive technique forimaging small- to medium-sized fishes by using a standardflat-bed photo scanner (HP Scan Jet 4850), clear transpar-ency film for copiers, a ruler, and a color bar (total costapproximately 200 US$). Figure 1 shows the workplaceused for imaging frozen fish specimens up to 25 cm inlength.The transparency film was first placed on the scannersurface, followed by one to five specimens. We employedtransparency film to protect the scanner surface fromexposure to water, preservation liquid, and secretions fromthe fish skin. Its use also avoids cross-contamination ofsamples, which might pose a problem for subsequentgenetic analysis.By convention, lateral photographs of the left side aremost useful for taxonomic purposes. Because size andcoloration are often important for identification, a color barand ruler were included in every scan. To ensure optimalillumination, a brushed glass plate was placed above thefishes. To avoid reflections, most of the water or preser-vation liquid was removed from the fish skin beforeimaging.Scans were taken with different resolutions rangingfrom 300 to 1,800 dpi. The resulting images were pro-cessed with Adobe Photoshop 6.0. Single-specimenimages were cut (4