Supplementary File Northeastern Naturalist

Online Supplementary File 1 to: McCosker, C., K. Ono, M. Dufault, d. Mellone, and Z. Olson. 2020. Metabarcoding fecal DNA reveals extent of Halichoerus grypus (Gray Seal) foraging on invertebrates and incidence of parasite exposure. Northeastern Naturalist 27:681–700.

Note: the content of supplementary files is not subject to proof editing by the journal staff. Thus, the responsibility for the accuracy of all information and correctness of its presentation in this file lies solely with the author(s).

Supplementary Table 1. Digestion coefficients (DC) and number correction factors (NCF) for prey species recovered from Grey Seal scat samples. Under DCs, the numbers 1-3 refer to a level of erosion for each otolith, with 1 indicating the otolith was pristine, 2 indicating the otolith was moderately eroded, and 3 indicating the otolith was heavily eroded.

Species DC Source NCF Source

Alosa pseudoharengus Wilson (Alewife) * *

Ammodytes spp. (Sand Lance) 1.25 (1, 2) 1.58 (3) 3 3.6 2

Clupea harengus Linnaeus (Atlantic Herring) 1.04 (1) 1.11 (2) 1.32 (3) 3 3.0 2

Gadidae (unknown gadid) 1.08 (1, 2) 1.55 (3) 3 1.07 3

Glyptocephalus cynoglossus Linnaeus (Witch Flounder) 1.0 (1, 2) 1.18 (3) 3 1.24 3

Hippoglossina oblonga Mitchill (Fourspot Flounder) 1.1 (1, 2) 1.32 (3) 3 1.24 3

Hippoglossoides platessoides Fabricius (American Plaice) 1.05 (1, 2) 1.36 (3) 3 2.2 2

Limanda ferruginea Storer (Yellowtail Flounder) 1.1 (1, 2) 1.32 (3) 3 2.2 2

Merluccius bilinearis Mitchill (Silver Hake) 1.73 (1, 2, 3) 3 1.4 2

Pleuronectidae (unknown flatfish) 1.1 (1, 2) 1.32 (3) 3 1.24 3

Pseudopleuronectes americanus Walbaum (Winter Flounder) 1.1 (1, 2) 1.32 (3) 3 1.6 2

Sebastes spp. (Redfish)** 1.12 (1, 2, 3) 3 N/A N/A

Urophycis regia Walbaum (Spotted Hake) *** ***

Urophycis spp. (Red/White Hake) 1.08 (1, 2) 1.4 (3) 3 2.1 1

*used DC and NCF for Atlantic Herring, **used DC for Myoxocephalus sp., ***used DC and NCF for Silver Hake. Sources: (1) Ampela 2009 (2) Bowen 2000 (3) Grellier and Hammond 2006.

Supplementary Table 2. Prey length and wet weight equations from the literature used to estimate original prey length and

Species Length Equation Source Wet Weight Equation Source

Alosa pseudoharengus Wilson (Alewife) FL,mm:OL = 78.94 6 FL:W = 3.6716 7

Ammodytes spp. (Sand Lance) FL = -4.377 + 9.024(OL) 1 W = 0.1248(FL)1.75 1 log(W) = 0.03 + Clupea harengus Linnaeus (Atlantic Herring) FL = 6.341(OL) - 2.057 2 2 3.28log(OL) FL,mm = -100.65 + Glyptocephalus cynoglossus Linnaeus (Witch Flounder) 4 W = 0.077(OL)4.633 4 78.29(OL) ln(W) = -12.3202 + Hippoglossina oblonga Mitchill (Fourspot Flounder) * 7 3.1463ln(FL) ln(FL) = 4.0339 + Hippoglossoides platessoides Fabricius (American Plaice) 5 W = 0.0023(FL)3.36 1 1.2425ln(OL,cm) Limanda ferruginea Storer (Yellowtail Flounder) FL = -6.979 + 6.709(OL) 1 W = 0.0023(FL)3.36 1 ln(FL) = 3.0111 + Merluccius bilinearis Mitchill (Silver Hake) 5 W = 0.0059(FL)3.05 2 1.0276ln(OL,cm) Pseudopleuronectes americanus Walbaum (Winter Flounder) FL = -8.559 + 8.389(OL) 2 W = 0.0079(FL)3.12 2 ln(FL) = 3.1273 + Sebastes spp. (Redfish) 5 W = 0.013(FL)3.06 2 1.1437ln(OL,cm) Urophycis regia Walbaum (Spotted Hake) ** **

Urophycis spp. (Red/White Hake) FL = 1.525(OL)1.1456 3 W = 0.003998(FL)3.1718 3 biomass from corrected otolith length.

*used Winter Flounder equation, **used Silver Hake equation Sources: (1): Bowen and Harrison 1994, (2): Bowen and Harrison 1996, (3): Clay and Clay 1991, (4): Härkönen 1986, (5): Hunt 1992, (6): Rojo 2015, (7): Wigley et al. 2003.

Supplementary References Ampela, K. 2009. The diet and foraging ecology of Gray Seals (Halichoerus grypus) in United States waters. Ph.D. Dissertation. The City University of New York, New York City, New York. 188 pp. Bowen, W.D. 2000. Reconstruction of pinniped diets: Accounting for complete digestion of otoliths and cephalopod beaks. Canadian Journal of Fisheries and Aquatic Science 57(5):898–905. Bowen, W.D., and G.D. Harrison. 1994. Offshore diet of Grey Seals Halichoerus grypus near Sable Island, Canada. Marine Ecology Progress Series 112:1–11. Bowen, W.D., and G.D. Harrison. 1996. Comparison of Harbor Seal diets in two inshore habitats of Atlantic Canada. Canadian Journal of Zoology 74:125–135. Clay, D., and H. Clay. 1991. Determination of age growth of White Hake (Urophycis tenuis Mitchell) from the southern Gulf of St. Lawrence, Canada (including techniques for commercial sampling). Canadian Technical Report of Fisheries and Aquatic Sciences. Marine and Anadromous Fish Division, Moncton, New Brunswick, Canada. 29 pp. Grellier, K., and P.S. Hammond. 2006. Robust digestion and passage rate estimates for hard parts of Grey Seal (Halichoerus grypus) prey. Canadian Journal of Fisheries and Aquatic Sciences 63(9):1982–1998. Härkönen, T. 1986. Guide to the otoliths of the bony fishes of the Northeast Atlantic. Danbiu ApS. Biological Consultants, Hellerup, Denmark. 256 pp. Hunt, J.J. 1992. Morphological characteristics of otoliths for selected fish in the northwest Atlantic. Journal of Northwest Atlantic Fishery Science 13:63–67. Rojo, A.L. 2015. Report in the fish otolith collection at the Nova Scotia Museum of Natural History. Curatorial Report. Nova Scotia Museum, Halifax, Nova Scotia, Canada. 176 pp. Wigley, S.E., H.M. McBride, and N.J. McHugh. 2003. Length-weight relationships for 74 fish species collected during NEFSC research vessel bottom trawl surveys, 1992-99. NOAA Technical Memorandum. Northeast Fisheries Science Center, Woods Hole, MA. 26 pp.