Improved estimates of digestion correction factors and passage rates for harbor seal (Phoca vitulina) prey in the northeast Atlantic
Abstract
Diet composition in pinnipeds is widely estimated using hard prey remains recovered from feces. To estimate the size and number of prey represented in fecal samples accurately, digestion correction factors (DCFs) must be applied to measurements and counts of fish otoliths and cephalopod beaks. In this study, 101 whole prey feeding trials were conducted with six harbor seals (Phoca vitulina) and 18 prey species. We derived species- and grade-specific estimates of digestion coefficients (DCs) and species-specific recovery rates (RRs) to account for partial and complete digestion, respectively. Greater than 98% of otoliths were passed within three days of consumption. RRs were smallest for Atlantic salmon smolts (RR = 0.306, SE = 0.031) and increasingly larger for sandeels (RR = 0.494, SE = 0.017), flatfish (RR = 0.789, SE = 0.033), and large gadoids (RR = 0.944, SE = 0.034). Species-specific otolith width DCs were smallest for Trisopterus species (DC = 1.14, SE = 0.015) and increasingly larger for flatfish (DC = 1.27, SE = 0.045), large gadoids (DC = 1.32, SE = 0.067) and sandeels (DC = 1.57, SE = 0.035). RRs were similar to those from gray seals (Halichoerus grypus), but harbor seal species- and grade-specific DCs were generally smaller. Differences in partial and complete digestion rates among prey species and between seal species highlight the importance of applying DCFs when reconstructing diet.
Citation
Wilson , L J , Grellier , K & Hammond , P S 2017 , ' Improved estimates of digestion correction factors and passage rates for harbor seal ( Phoca vitulina ) prey in the northeast Atlantic ' , Marine Mammal Science , vol. 33 , no. 4 , pp. 1149-1169 . https://doi.org/10.1111/mms.12436
Publication
Marine Mammal Science
Status
Peer reviewed
ISSN
1748-7692Type
Journal article
Rights
© 2017 Society for Marine Mammalogy. This work has been made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at https://doi.org/10.1111/mms.12436
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