DOI: 10.5061/dryad.66t1g1k76
title: Steller sea lion pup plasma metabolites

description: Geographic differences in population growth trends are well-documented in
 Steller sea lions (Eumetopias jubatus), a species of North Pacific
 pinniped listed under the U.S. Endangered Species Act in 1990 following a
 marked decline in population abundance that began during the 1970s. As
 population growth is intrinsically linked to pup production and survival,
 examining factors related to pup physiological condition provides useful
 information to management authorities regarding potential drivers of
 regional differences.  During dam foraging trips, pups
 predictably transition among three fasting phases, distinguished by the
 changes in the predominant metabolic byproduct. We used standardized
 ranges of two plasma metabolites (blood urea nitrogen and
 β–hydroxybutyrate) to assign pups to fasting categories (n=1528,
 1990–2016, 12 subpopulations): Recently Fed–Phase I
 (digestion/assimilation–expected hepatic/muscle glycogen usage), Phase II
 (expected lipid utilization), transitioning between Phases II–III
 (expected lipid utilization with increased protein reliance), or Phase III
 (expected protein catabolism). As anticipated, the majority of pups were
 classified as Recently Fed–Phase I (overall mean proportion=0.72)
 and a few pups as Phase III (overall mean proportion=0.04). By
 further comparing pups in Short (Recently Fed–Phase II) and Long
 (all other pups) duration fasts, we identified three subpopulations with
 significantly (p&lt;0.03) greater proportions of pups dependent upon
 endogenous sources of energy for extended periods, during a life stage of
 somatic growth and development: the 1) central (0.27 ± 0.09) and 2)
 western (0.36 ± 0.13) Aleutian Island (declining population trend) and 3)
 southern Southeast Alaska (0.32 ± 0.06; increasing population trend)
 subpopulations had greater Long fast proportions than the eastern Aleutian
 Islands (0.10 ± 0.05; stabilized population).  Due to contrasting
 population growth trends among these highlighted subpopulations over the
 past 50+ years, both density-independent and density-dependent factors
 likely influence the dam foraging trip duration, contributing to longer
 fasting durations for pups at some rookeries.
description: Steller sea lion pups were captured live on their
 natal rookeries. They were restrained physically or chemically. Blood
 samples were drawn from the vein of the caudal gluteal plexus into blood
 tubes with anticoagulants (ethylenediaminetetraacetic acid or sodium
 heparin). During field physical examinations, morphometrics (mass,
 standard length, axillary girth) and sex were recorded for most pups, as
 well as any observed external abnormalities. Blood samples were kept
 chilled in the field until centrifuging (3000–3500 rpm for ten minutes),
 typically within four hours of collection. Plasma aliquots were stored at
 -20°C during the remainder of the field research trips (3–10 days) and at
 -80°C thereafter (months to years, maximal interval of 8 years) following
 return to the laboratory. Plasma-derived [BUN] and
 [β-HBA] were measured via spectrophotometer (SpectraMax 340PC384,
 Molecular Devices, San Jose, CA) using commercially-available endpoint
 assay kits: [BUN] via StanBio Kit #2050 and Sigma Aldrich Kit #66-20 and
 #MAK006; [β-HBA] via StanBio Kit #2440 and Sigma Aldrich Kits #310 and
 #MAK001 (StanBio, EKF Diagnostics USA, Boerne, TX; Sigma Aldrich, now
 Millipore Sigma, St. Louis, MO). Plasma samples with moderate to severe
 hemolysis were not included.  Technical replicates were ≤10% coefficient
 of variation. Calculations of metabolite concentrations were made using
 Softmax Pro (v. 4.8) software or the open-access interface MyAssays.com,
 applying a four-parameter logistic curve. A point-of-care ketometer
 (Precision Xtra™, Abbott Laboratories, Abbott Park, IL, ketometer
 precision=0.1 mmol/L [β-HBA]) was also used. Samples measuring between
 0.2–0.4 mmol/L via ketometer were further analyzed via the biochemical
 assay to improve precision around that threshold important to fasting
 category assignment (threshold=0.3mmol/L; assay precision≈0.01 mmol/L
 [β-HBA]). The means of the technical replicates are reported in mmol/L for
 each metabolite.
description: # Steller sea lion pup plasma metabolites
 [https://doi.org/10.5061/dryad.66t1g1k76](https://doi.org/10.5061/dryad.66t1g1k76) **The data are organized into 10 columns:**   PupID                         a unique identifier for each Steller sea lion pup   CaptDate                  date of capture and sampling: month/day/year   BroadRegion            one of four geographic regions in which the pup was born:  Russia, Aleutian Islands, Gulf of Alaska, Southeast Alaska   Subpopulation         one of 12 subpopulations where the pup was born:  4 within Russia (Sea of Okhotsk, Kuril Islands, Kamchatka Peninsula, Commander Islands); the Aleutian Islands (3) and Gulf of Alaska (3) are each divided into western, central, and eastern sections; and Southeast Alaska is separated into southern (historical rookeries) and northern (relatively newly-established rookeries) sections   Sex                              sex of the pup:  male, female   Mass\_kg                    mass of the pup recorded at time of capture in kilograms   DSL\_cm                     dorsal standard length of pup recorded at time of capture in centimeters   GirthAx\_cm               axillary girth of the pup recorded at time of capture in centimeters   B-HBA                        plasma beta hydroxybutyrate concentration in mmol/L; value reported is the mean of the technical replicates   BUN                            blood (plasma) urea nitrogen concentration in mmol/L; value reported is the mean of the technical replicates   **Missing Data** Missing data are represented as “NA”.  This applies to the fields Sex, Mass\_kg, DSL\_cm, and GirthAx\_cm.