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Percent Stomach Emptiness in Fish Collections: Sources of Variation and Study Design Implications
VINSON, M. R. AND T. R. ANGRADI. Percent Stomach Emptiness in Fish Collections: Sources of Variation and Study Design Implications. REVIEWS IN FISHERIES SCIENCE. CRC Press LLC, Boca Raton, FL, 19(2):63-73, (2011).
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We summarized fish stomach content data from 369,000 fish from 402 species in 1,096 collections made between 1925 and 2009 and report on the percentage of individuals with empty stomachs (PES). The mean PES among all species, locations, habitats, dates, and collection methods was 26.4%. Mean PES varied significantly among collection methods, orders, trophic groups, foraging behaviors, habitats, and with the length of the species at maturity. Most of the variation in PES was explained by species length, collection gear type, and two autecological factors: trophic group (piscivore PES>non-piscivore PES) and foraging location (water column forager PES>benthic forager PES). After accounting for variation with fish length, PES did not vary with stomach removal collection method (dissection v. gastric lavage), feeding time, or time of collection. There was some evidence that collecting fish at times when they are inactive (e.g., collecting diurnal fish at night) increases sample PES. PES was similar between fresh and saltwater fish, but differed within finer habitat classifications in these two ecosystems. Among habitats, PES appeared to follow a general prey availability or productivity gradient: PES of open ocean collections>estuary collections, lentic>lotic, and pelagic>littoral. Gear type (active or passive) was the most influential factor affecting the occurrence of empty stomachs that can be readily controlled by researchers.