2.2 Prey sampling
Potential prey items to be collected for macronutrient and energetic
analyses were selected based on existing literature on sea otter diets
in Southeast Alaska . Five functional prey groups (crabs, clams, sea
cucumbers, snails, sea urchins) were identified that were composed of 13
target species for analysis. These five functional groups made up 95%
of sea otter diets (in terms of biomass) from visual foraging
observations. Five individuals of each target species were collected at
two sites (Fig. 1) in May 2018, August 2018, and February 2019. All
samples were collected in the intertidal zone. Two collection sites were
selected that encompassed the foraging observation sites and had
reliable access. Craig (Site 1) and Soda Bay (Site 2) represented
differences in sea otter occupation time (> 15 years for
Craig, and > 7 years for Soda Bay). Where there were more
sea otters present, there were less abundant invertebrate species for
collection. Additional samples were opportunistically collected around
POW if they were not present or in high enough abundance in the two
designated sites. Samples were held in seawater-filled buckets, cleaned
of sand and dirt, and then frozen at -18°C.
In the lab, samples were thawed, weighed, measured, and separated into
edible and inedible tissues. For bivalves, decapods, gastropods, and sea
urchins, all hard parts were removed and discarded, as they were
considered inedible as the sea otter excretes these contents . For sea
cucumbers, the entire organism was considered edible. Only crabs were
processed separately by sex. Remaining edible tissues were weighed and
homogenized in a Cuisinart Mini-prep food processor. A maximum of 4 g of
tissue was dried in a LECO Thermogravimetric Analyzer 701 (TGA) dryer at
135°C, or in a gravity convection oven (VWR Symphony 414004-552) at
70°C. Standards and duplicates were run with each dryer to confirm
consistent moisture values.