steve trumble | Baylor University (original) (raw)

Papers by steve trumble

Marine Mammal Science, Nov 7, 2020

Carbon (δ 13 C) and nitrogen (δ 15 N) stable isotope analysis is a valuable ecological tool for a... more Carbon (δ 13 C) and nitrogen (δ 15 N) stable isotope analysis is a valuable ecological tool for acquiring information regarding foraging behavior, isoscapes, and trophic position (

The FASEB Journal, Apr 1, 2013

The FASEB Journal, Apr 1, 2011

Frontiers in Marine Science, Aug 24, 2022

Northern elephant seals (Mirounga angustirostris), like many marine mammals, rely on internal lip... more Northern elephant seals (Mirounga angustirostris), like many marine mammals, rely on internal lipid stores, specifically fatty acids (FAs) stored in the blubber layer, to meet metabolic needs. The energetic demands of northern elephant seals vary with ontogeny, as each life-history stage experiences different metabolic requirements due to development, growth, and breeding. To date, no comprehensive study has reported on changes in blubber FA profiles across northern elephant seal age groups or sex. Therefore, our objective was to determine how blubber FAs differ across ontogeny and sex in northern elephant seals. As a sexually dimorphic mammal, northern elephant seals go through sex-specific ontogenetic changes in morphology and physiology; we hypothesized that these changes would be reflected in their FAs profiles. To determine this, FAs profiles were compared from full blubber cores collected from 79 northern elephant seals across four age groups. We provide the first evidence of blubber fatty acids differing across ontogeny as NES transition from young, developing seals to mature fully developed adults. However, we did not find differences in blubber FAs profiles between the sexes. Monounsaturated fatty acids (MUFAs) are found in the highest proportions across all NES age classes and sexes, followed by SFAs and PUFAs; this highlights the important role MUFAs play in maintaining fluidity of the blubber layer and in thermoregulation. The individual FAs with the highest concentrations (C16:1, C18:1n9 and C16:0) in northern elephant seal blubber are similar to those in other marine mammals. Weaned pup FAs profiles were significantly different from all other age classes; adults and juveniles also showed age-specific differences. Specifically, weaned pups had the highest proportions of SFAs and the lowest proportions of PUFA, suggesting use of PUFAs to aid development. Each life history stage of NES is interconnected to previous and future stages, making FA accumulation, mobilization, and storage an important process throughout an individual's life. Further, any changes to this Frontiers in Marine Science frontiersin.org 01

The FASEB Journal, Apr 1, 2007

Frontiers in Physiology, 2012

Diving mammals, are under extreme pressure to conserve oxygen as well as produce adequate energy ... more Diving mammals, are under extreme pressure to conserve oxygen as well as produce adequate energy through aerobic pathways during breath-hold diving. Typically a major source of energy, lipids participate in structural and regulatory roles and have an important influence on the physiological functions of an organism. At the stoichiometric level, the metabolism of polyunsaturated fatty acids (PUFAs) utilizes less oxygen than metabolizing either monounsaturated fatty acids or saturated fatty acids (SFAs) and yields fewer ATP per same length fatty acid. However, there is evidence that indicates the cellular metabolic rate is directly correlated to the lipid composition of the membranes such that the greater the PUFA concentration in the membranes the greater the metabolic rate. These findings appear to be incompatible with diving mammals that ingest and metabolize high levels of unsaturated fatty acids while relying on stored oxygen. Growing evidence from birds to mammals including recent evidence in Weddell seals also indicates that at the whole animal level the utilization of PUFAs to fuel their metabolism actually conserves oxygen. In this paper, we make an initial attempt to ascertain the beneficial adaptations or limitations of lipids constituents and potential trade-offs in diving mammals. We discuss how changes in Antarctic climate are predicted to have numerous different environmental effects; such potential shifts in the availability of certain prey species or even changes in the lipid composition (increased SFA) of numerous fish species with increasing water temperatures and how this may impact the diving ability of Weddell seals.

Physiological and Biochemical Zoology, Nov 1, 2008

Mammals balance heat dissipation with heat production to maintain core body temperatures independ... more Mammals balance heat dissipation with heat production to maintain core body temperatures independent of their environment. Thermal balance is undoubtedly most challenging for mammals born in polar regions because small body size theoretically results in high surface-area-to-volume ratios (SA:V), which facilitate heat loss (HL). Thus, we examined the ontogeny of thermoregulatory characteristics of an ice-breeding seal (Weddell seal Leptonychotes weddelli). Morphology, blubber thickness, rectal temperature (T(r)), muscle temperature (T(m)), and skin temperatures on the trunk (T(s)) and flipper (T(f)) in 3-5-wk-old pups, yearlings, and adults were measured. Adults maintained the thickest blubber layers, while yearlings had the thinnest; T(r) and T(m) fell within a narrow range, yet T(r) and T(m) decreased significantly with body length. All seals maintained skin temperatures lower than T(r), our index of core body temperature. The T(s)'s were positively correlated with environmental temperatures; conversely, T(f)'s were not. Although pups had the greatest proportion of blubber, their greater SA:V and limited ability to minimize body-to-environment temperature gradients led to the greatest calculated mass-specific HL. This implies that pups relied on elevated metabolic heat production to counter HL. Heat production in pups and yearlings may have been aided by nonshivering thermogenesis in the skeletal muscle via the enhanced muscle mitochondrial densities that have been observed in these segments of this population.

The Journal of Experimental Biology, 2013

In 1940, Scholander suggested that stiffened upper airways remained open and received air from hi... more In 1940, Scholander suggested that stiffened upper airways remained open and received air from highly compressible alveoli during marine mammal diving. There are few data available on the structural and functional adaptations of the marine mammal respiratory system. The aim of this research was to investigate the anatomical (gross) and structural (compliance) characteristics of excised marine mammal tracheas. Here, we defined different types of tracheal structures, categorizing pinniped tracheas by varying degrees of continuity of cartilage (categories 1-4) and cetacean tracheas by varying compliance values (categories 5A and 5B). Some tracheas fell into more than one category along their length; for example, the harbor seal (Phoca vitulina) demonstrated complete rings cranially, and as the trachea progressed caudally, tracheal rings changed morphology. Dolphins and porpoises had less stiff, more compliant spiraling rings while beaked whales had very stiff, less compliant spiraling rings. The pressure-volume (P-V) relationships of isolated tracheas from different species were measured to assess structural differences between species. These findings lend evidence for pressure-induced collapse and re-inflation of lungs, perhaps influencing variability in dive depth or ventilation rates of the species investigated.

Polar Biology, Mar 17, 1998

The diet of adult and juvenile Weddell seals (Leptonychotes weddellii) in McMurdo Sound, Antarcti... more The diet of adult and juvenile Weddell seals (Leptonychotes weddellii) in McMurdo Sound, Antarctica, was determined from both scat and stable isotope analyses, to ascertain if foraging behavior varied with age, season, or diving pattern. Scats were collected over 6 years and recovered hard parts identi®ed. Stable carbon and nitrogen isotope values were determined for seal blood samples and potential prey items and used to identify primary prey species and assess trophic interactions. Pleuragramma antarcticum remains were recovered from between 70 and 100% of the scats, and there was little evidence for inter-annual or age-speci®c variation in foraging behavior. However, stable isotope and dive data analyses indicated that while most seals foraged predominantly on pelagic ®sh and squid, some juveniles concentrated on shallow benthic Trematomus spp. Combining these three methods permitted ®rm conclusions about diet and foraging behavior to be drawn.

The FASEB Journal, Mar 1, 2008

Polar Biology, May 1, 2004

The diets and trophic interactions among Weddell, crabeater, Ross, and leopard seals in the easte... more The diets and trophic interactions among Weddell, crabeater, Ross, and leopard seals in the eastern Ross Sea, Antarctica, were investigated by the use of stable isotope techniques during the 1999-2000 summer seasons. The d 13 C and d 15 N values in seal serum clearly distinguished the three Antarctic pack-ice seal species at different trophic positions (Weddell>Ross>crabeater). These patterns appeared to reflect a close linkage to their known foraging ecology and diving behaviors, and agreed well with their presumed dietary diversity. The more enriched d 13 C and d 15 N values in male Weddell seals than those in females suggested differences in foraging preferences between them. Significant differences in d 15 N were also found among different age groups of Weddell seals. A strong correlation between the C:N ratios and serum cholesterol was probably due to extremely high cholesterol levels in phocids. Comparisons of isotope data with harbor seals revealed distinct differences between Antarctic phocids and the northern seal species.

The Journal of Experimental Biology, Aug 15, 2008

Our objective was to determine the ontogenetic changes in the skeletal muscles of Weddell seals t... more Our objective was to determine the ontogenetic changes in the skeletal muscles of Weddell seals that transform a non-diving pup into an elite diving adult. Muscle biopsies were collected from pups, juveniles and adults and analyzed for changes in fiber type, mitochondrial density, myoglobin concentrations and aerobic, lipolytic and anaerobic enzyme activities. The fiber type results demonstrated a decrease in slow-twitch oxidative (Type I) fibers and a significant increase in fast-twitch oxidative (Type IIA) fibers as the animals mature. In addition, the volume density of mitochondria and the activity of lipolytic enzymes significantly decreased as the seals matured. To our knowledge, this is the first quantitative account describing a decrease in aerobic fibers shifting towards an increase in fast-twitch oxidative fibers with a significant decrease in mitochondrial density as animals mature. These differences in the muscle physiology of Weddell seals are potentially due to their three very distinct stages of life history: non-diving pup, novice diving juvenile, and elite deep diving adult. During the first few weeks of life, pups are a non-diving terrestrial mammal that must rely on lanugo (natal fur) for thermoregulation in the harsh conditions of Antarctica. The increased aerobic capacity of pups, associated with increased mitochondrial volumes, acts to provide additional thermogenesis. As these future elite divers mature, their skeletal muscles transform to a more sedentary state in order to maintain the low levels of aerobic metabolism associated with long-duration diving.

The FASEB Journal, Mar 1, 2008

Canadian Journal of Fisheries and Aquatic Sciences, Oct 1, 2022

Fisheries management relies on accurate population models for estimating biomass and setting harv... more Fisheries management relies on accurate population models for estimating biomass and setting harvest goals; however, physiological data for estimating reproductive parameters in population models are difficult to acquire. Here, lifetime reproductive (progesterone and estradiol) and stress-related (cortisol) hormones were measured in annually deposited growth increments in female yelloweye rockfish opercula (N = 22 females, sampled ages 1 to 90 years). Analyses of these profiles (~1 year resolution) provided estimates of physiological (complete puberty) and functional age of sexual maturity (females spawn and contribute larvae to the population) and spawning frequency, with lifetime trends of reproduction and stress. The descriptive mean age of physiological sexual maturity was 11 ± 1 years (SE), while functional age of maturity was 17 ± 2 years. The estimate of marginal mean spawning frequency was 45.1 ± 5.1 %. Stress data (~15 % of females experienced distress events) suggested females were potentially resilient or not exposed to chronic stressors. While preliminary, we provide a novel method to estimate agespecific reproductive parameters for proper age-based population modeling of a human targeted teleost.

Zoo Biology, Jul 25, 2012

Rehabilitating pinniped pups are often admitted to care centers as neonates and generally lack ma... more Rehabilitating pinniped pups are often admitted to care centers as neonates and generally lack maternal investment and are in poor body condition. Upon admittance to a rehabilitation facility, pups are typically fed a milk replacement formula via gavage, which is switched to frozen fish upon weaning. While rehabilitation has been successful in terms of recovery and release, preweaning growth rates in captivity are consistently lower than in the wild. Indicators of stress (cortisol and total thyroxine; TT4), and standard morphometrics, of harbor seal pups in rehabilitation (n = 20) were determined for both preweaned and weaned pups. Hormone concentrations and standard morphometrics from pups in care were compared with free-ranging harbor seal pups (n = 59). Pups in rehabilitation gained mass on both milk and fish diets. Preweaned pups had greater mean serum cortisol and similar TT4 concentrations than weaned pups. Freeranging harbor seal pups were heavier and longer than preweaned and weaned pups in rehabilitation. The free-ranging pups had the lowest cortisol and highest TT4 concentrations of any of the pups. These results suggest that weaned pups that have undergone rehabilitation are not physiologically equivalent to free-ranging weaned pups. Additional research is needed regarding physiological changes in endocrine values during early development under captive care conditions. This information should be useful to marine mammal rehabilitation centers in their development of care protocols and release criteria for rehabilitating harbor seal pups. Zoo Biol. 00:1-8, 2012.

Ices Journal of Marine Science, May 27, 2023

Climate change threatens fisheries health through changing ecosy stem dynamics; ho w e v er, the ... more Climate change threatens fisheries health through changing ecosy stem dynamics; ho w e v er, the impacts on the ph y siology and ecology of commercial fish populations are unclear. Here, annually deposited growth increments of female yelloweye rockfish (Sebastes ruberrimus) opercula collected in the Gulf of Alaska were used to successfully reconstruct lifetime (∼1-year resolution) steroid hormone, stable isotope, spawning, and stress data. We assessed how hormone profiles, spawning and distress frequencies related to sea surface temperature (SST), chlorophyll a concentrations as well as climate indices. Further, we assessed whether incorporating indicators of foraging depth and diet, stable isotope values (δ 13 C and δ 15 N), would improve model interpretations. Progesterone and estradiol concentrations decreased with increasing SST, suggesting that increasing SSTs may negatively impact juvenile and subadult f emales ' reproductive development. Spawning frequency was positively linked to changes in the North Pacific Gyre Oscillation (NPGO) index, potentially timed with f a v orable conditions f or larv al surviv al. T his w as supported b y ju v eniles ha ving a lo w er probability of a distress e v ent during positiv e NPGO y ears compared to negativ e NPGO y ears. While relationships among environmental data and y ello w e y e rockfish ph y siology w ere w eak, this study pro vides insight into the en vironmental impacts on the lifetime reproduction and stress of a commercially important teleost species.

Science of The Total Environment

Frontiers in Marine Science

Animals that display plasticity in behavioral, ecological, and morphological traits are better po... more Animals that display plasticity in behavioral, ecological, and morphological traits are better poised to cope with environmental disturbances. Here, we examined individual plasticity and intraspecific variation in the morphometrics, movement patterns, and dive behavior of an enigmatic apex predator, the leopard seal (Hydrurga leptonyx). Satellite/GPS tags and time-depth recorders were deployed on 22 leopard seals off the Western Antarctic Peninsula. Adult female leopard seals were significantly larger (454±59 kg) and longer (302±11 cm) than adult males (302±22 kg, 276±11 cm). As females were 50% larger than their male counterparts, leopard seals are therefore one of the most extreme examples of female-biased sexual size dimorphism in marine mammals. Female leopard seals also spent more time hauled-out on land and ice than males. In the austral spring/summer, three adult female leopard seals hauled-out on ice for 10+ days, which likely represent the first satellite tracks of parturit...

Aquatic Mammals

Pregnancy and lactation are energetically expensive for female mammals and greatly influence the ... more Pregnancy and lactation are energetically expensive for female mammals and greatly influence the evolution of species-specific reproductive strategies. Phocid (“true” seals) lactation is generally short in duration and relies heavily on stored energy, whereas otariid (sea lions and fur seals) lactation is generally much longer, and energy is supplemented by foraging. While a phocid, the smaller body size of the harbor seal (Phoca vitulina) is assumed to preclude the maintenance of lactation solely from stored energy. For this reason, their lactation strategy is believed intermediate to that of otariids and phocids. The purpose of this study was to characterize blubber fatty acids (FAs) of pregnant and lactating harbor seals and determine if lactating blubber FA profiles more closely resemble phocids or otariids. Blubber FA differences between female reproductive states (lactating, n = 18; pregnant, n = 7; non-lactating–non-pregnant, n = 17), mother–pup pairs (n = 6), and families (o...

Conservation Physiology, 2021

Alaskan harbour seal populations are currently listed as a species of special concern. Although t... more Alaskan harbour seal populations are currently listed as a species of special concern. Although there is evidence of recent stabilization or even partial recovery of harbour seal numbers in areas of historic decline, most populations have not made substantial recoveries. To date, few data exist regarding spatial and seasonal changes in blubber fatty acids (FAs) for Alaskan harbour seal populations. The purpose of this study was to qualitatively investigate harbour seal blubber FA profiles for regional, seasonal and age class differences. Blubber FA concentrations were analysed using MANOVA and linear discriminant analysis (LDA) from 760 individual harbour seals across Bristol Bay, Kodiak, Prince William Sound and Southeast Alaska from 1997 to 2010. Our results suggest spatial and seasonal differences are largely driven by monounsaturated FAs, most notably 14:1n-5, 16:1n-7 and 18:1n-7. In addition, our data revealed a progression in blubber FAs from pups to adults, with a shift from ...

Marine Mammal Science, Nov 7, 2020

Carbon (δ 13 C) and nitrogen (δ 15 N) stable isotope analysis is a valuable ecological tool for a... more Carbon (δ 13 C) and nitrogen (δ 15 N) stable isotope analysis is a valuable ecological tool for acquiring information regarding foraging behavior, isoscapes, and trophic position (

The FASEB Journal, Apr 1, 2013

The FASEB Journal, Apr 1, 2011

Frontiers in Marine Science, Aug 24, 2022

Northern elephant seals (Mirounga angustirostris), like many marine mammals, rely on internal lip... more Northern elephant seals (Mirounga angustirostris), like many marine mammals, rely on internal lipid stores, specifically fatty acids (FAs) stored in the blubber layer, to meet metabolic needs. The energetic demands of northern elephant seals vary with ontogeny, as each life-history stage experiences different metabolic requirements due to development, growth, and breeding. To date, no comprehensive study has reported on changes in blubber FA profiles across northern elephant seal age groups or sex. Therefore, our objective was to determine how blubber FAs differ across ontogeny and sex in northern elephant seals. As a sexually dimorphic mammal, northern elephant seals go through sex-specific ontogenetic changes in morphology and physiology; we hypothesized that these changes would be reflected in their FAs profiles. To determine this, FAs profiles were compared from full blubber cores collected from 79 northern elephant seals across four age groups. We provide the first evidence of blubber fatty acids differing across ontogeny as NES transition from young, developing seals to mature fully developed adults. However, we did not find differences in blubber FAs profiles between the sexes. Monounsaturated fatty acids (MUFAs) are found in the highest proportions across all NES age classes and sexes, followed by SFAs and PUFAs; this highlights the important role MUFAs play in maintaining fluidity of the blubber layer and in thermoregulation. The individual FAs with the highest concentrations (C16:1, C18:1n9 and C16:0) in northern elephant seal blubber are similar to those in other marine mammals. Weaned pup FAs profiles were significantly different from all other age classes; adults and juveniles also showed age-specific differences. Specifically, weaned pups had the highest proportions of SFAs and the lowest proportions of PUFA, suggesting use of PUFAs to aid development. Each life history stage of NES is interconnected to previous and future stages, making FA accumulation, mobilization, and storage an important process throughout an individual's life. Further, any changes to this Frontiers in Marine Science frontiersin.org 01

The FASEB Journal, Apr 1, 2007

Frontiers in Physiology, 2012

Diving mammals, are under extreme pressure to conserve oxygen as well as produce adequate energy ... more Diving mammals, are under extreme pressure to conserve oxygen as well as produce adequate energy through aerobic pathways during breath-hold diving. Typically a major source of energy, lipids participate in structural and regulatory roles and have an important influence on the physiological functions of an organism. At the stoichiometric level, the metabolism of polyunsaturated fatty acids (PUFAs) utilizes less oxygen than metabolizing either monounsaturated fatty acids or saturated fatty acids (SFAs) and yields fewer ATP per same length fatty acid. However, there is evidence that indicates the cellular metabolic rate is directly correlated to the lipid composition of the membranes such that the greater the PUFA concentration in the membranes the greater the metabolic rate. These findings appear to be incompatible with diving mammals that ingest and metabolize high levels of unsaturated fatty acids while relying on stored oxygen. Growing evidence from birds to mammals including recent evidence in Weddell seals also indicates that at the whole animal level the utilization of PUFAs to fuel their metabolism actually conserves oxygen. In this paper, we make an initial attempt to ascertain the beneficial adaptations or limitations of lipids constituents and potential trade-offs in diving mammals. We discuss how changes in Antarctic climate are predicted to have numerous different environmental effects; such potential shifts in the availability of certain prey species or even changes in the lipid composition (increased SFA) of numerous fish species with increasing water temperatures and how this may impact the diving ability of Weddell seals.

Physiological and Biochemical Zoology, Nov 1, 2008

Mammals balance heat dissipation with heat production to maintain core body temperatures independ... more Mammals balance heat dissipation with heat production to maintain core body temperatures independent of their environment. Thermal balance is undoubtedly most challenging for mammals born in polar regions because small body size theoretically results in high surface-area-to-volume ratios (SA:V), which facilitate heat loss (HL). Thus, we examined the ontogeny of thermoregulatory characteristics of an ice-breeding seal (Weddell seal Leptonychotes weddelli). Morphology, blubber thickness, rectal temperature (T(r)), muscle temperature (T(m)), and skin temperatures on the trunk (T(s)) and flipper (T(f)) in 3-5-wk-old pups, yearlings, and adults were measured. Adults maintained the thickest blubber layers, while yearlings had the thinnest; T(r) and T(m) fell within a narrow range, yet T(r) and T(m) decreased significantly with body length. All seals maintained skin temperatures lower than T(r), our index of core body temperature. The T(s)'s were positively correlated with environmental temperatures; conversely, T(f)'s were not. Although pups had the greatest proportion of blubber, their greater SA:V and limited ability to minimize body-to-environment temperature gradients led to the greatest calculated mass-specific HL. This implies that pups relied on elevated metabolic heat production to counter HL. Heat production in pups and yearlings may have been aided by nonshivering thermogenesis in the skeletal muscle via the enhanced muscle mitochondrial densities that have been observed in these segments of this population.

The Journal of Experimental Biology, 2013

In 1940, Scholander suggested that stiffened upper airways remained open and received air from hi... more In 1940, Scholander suggested that stiffened upper airways remained open and received air from highly compressible alveoli during marine mammal diving. There are few data available on the structural and functional adaptations of the marine mammal respiratory system. The aim of this research was to investigate the anatomical (gross) and structural (compliance) characteristics of excised marine mammal tracheas. Here, we defined different types of tracheal structures, categorizing pinniped tracheas by varying degrees of continuity of cartilage (categories 1-4) and cetacean tracheas by varying compliance values (categories 5A and 5B). Some tracheas fell into more than one category along their length; for example, the harbor seal (Phoca vitulina) demonstrated complete rings cranially, and as the trachea progressed caudally, tracheal rings changed morphology. Dolphins and porpoises had less stiff, more compliant spiraling rings while beaked whales had very stiff, less compliant spiraling rings. The pressure-volume (P-V) relationships of isolated tracheas from different species were measured to assess structural differences between species. These findings lend evidence for pressure-induced collapse and re-inflation of lungs, perhaps influencing variability in dive depth or ventilation rates of the species investigated.

Polar Biology, Mar 17, 1998

The diet of adult and juvenile Weddell seals (Leptonychotes weddellii) in McMurdo Sound, Antarcti... more The diet of adult and juvenile Weddell seals (Leptonychotes weddellii) in McMurdo Sound, Antarctica, was determined from both scat and stable isotope analyses, to ascertain if foraging behavior varied with age, season, or diving pattern. Scats were collected over 6 years and recovered hard parts identi®ed. Stable carbon and nitrogen isotope values were determined for seal blood samples and potential prey items and used to identify primary prey species and assess trophic interactions. Pleuragramma antarcticum remains were recovered from between 70 and 100% of the scats, and there was little evidence for inter-annual or age-speci®c variation in foraging behavior. However, stable isotope and dive data analyses indicated that while most seals foraged predominantly on pelagic ®sh and squid, some juveniles concentrated on shallow benthic Trematomus spp. Combining these three methods permitted ®rm conclusions about diet and foraging behavior to be drawn.

The FASEB Journal, Mar 1, 2008

Polar Biology, May 1, 2004

The diets and trophic interactions among Weddell, crabeater, Ross, and leopard seals in the easte... more The diets and trophic interactions among Weddell, crabeater, Ross, and leopard seals in the eastern Ross Sea, Antarctica, were investigated by the use of stable isotope techniques during the 1999-2000 summer seasons. The d 13 C and d 15 N values in seal serum clearly distinguished the three Antarctic pack-ice seal species at different trophic positions (Weddell>Ross>crabeater). These patterns appeared to reflect a close linkage to their known foraging ecology and diving behaviors, and agreed well with their presumed dietary diversity. The more enriched d 13 C and d 15 N values in male Weddell seals than those in females suggested differences in foraging preferences between them. Significant differences in d 15 N were also found among different age groups of Weddell seals. A strong correlation between the C:N ratios and serum cholesterol was probably due to extremely high cholesterol levels in phocids. Comparisons of isotope data with harbor seals revealed distinct differences between Antarctic phocids and the northern seal species.

The Journal of Experimental Biology, Aug 15, 2008

Our objective was to determine the ontogenetic changes in the skeletal muscles of Weddell seals t... more Our objective was to determine the ontogenetic changes in the skeletal muscles of Weddell seals that transform a non-diving pup into an elite diving adult. Muscle biopsies were collected from pups, juveniles and adults and analyzed for changes in fiber type, mitochondrial density, myoglobin concentrations and aerobic, lipolytic and anaerobic enzyme activities. The fiber type results demonstrated a decrease in slow-twitch oxidative (Type I) fibers and a significant increase in fast-twitch oxidative (Type IIA) fibers as the animals mature. In addition, the volume density of mitochondria and the activity of lipolytic enzymes significantly decreased as the seals matured. To our knowledge, this is the first quantitative account describing a decrease in aerobic fibers shifting towards an increase in fast-twitch oxidative fibers with a significant decrease in mitochondrial density as animals mature. These differences in the muscle physiology of Weddell seals are potentially due to their three very distinct stages of life history: non-diving pup, novice diving juvenile, and elite deep diving adult. During the first few weeks of life, pups are a non-diving terrestrial mammal that must rely on lanugo (natal fur) for thermoregulation in the harsh conditions of Antarctica. The increased aerobic capacity of pups, associated with increased mitochondrial volumes, acts to provide additional thermogenesis. As these future elite divers mature, their skeletal muscles transform to a more sedentary state in order to maintain the low levels of aerobic metabolism associated with long-duration diving.

The FASEB Journal, Mar 1, 2008

Canadian Journal of Fisheries and Aquatic Sciences, Oct 1, 2022

Fisheries management relies on accurate population models for estimating biomass and setting harv... more Fisheries management relies on accurate population models for estimating biomass and setting harvest goals; however, physiological data for estimating reproductive parameters in population models are difficult to acquire. Here, lifetime reproductive (progesterone and estradiol) and stress-related (cortisol) hormones were measured in annually deposited growth increments in female yelloweye rockfish opercula (N = 22 females, sampled ages 1 to 90 years). Analyses of these profiles (~1 year resolution) provided estimates of physiological (complete puberty) and functional age of sexual maturity (females spawn and contribute larvae to the population) and spawning frequency, with lifetime trends of reproduction and stress. The descriptive mean age of physiological sexual maturity was 11 ± 1 years (SE), while functional age of maturity was 17 ± 2 years. The estimate of marginal mean spawning frequency was 45.1 ± 5.1 %. Stress data (~15 % of females experienced distress events) suggested females were potentially resilient or not exposed to chronic stressors. While preliminary, we provide a novel method to estimate agespecific reproductive parameters for proper age-based population modeling of a human targeted teleost.

Zoo Biology, Jul 25, 2012

Rehabilitating pinniped pups are often admitted to care centers as neonates and generally lack ma... more Rehabilitating pinniped pups are often admitted to care centers as neonates and generally lack maternal investment and are in poor body condition. Upon admittance to a rehabilitation facility, pups are typically fed a milk replacement formula via gavage, which is switched to frozen fish upon weaning. While rehabilitation has been successful in terms of recovery and release, preweaning growth rates in captivity are consistently lower than in the wild. Indicators of stress (cortisol and total thyroxine; TT4), and standard morphometrics, of harbor seal pups in rehabilitation (n = 20) were determined for both preweaned and weaned pups. Hormone concentrations and standard morphometrics from pups in care were compared with free-ranging harbor seal pups (n = 59). Pups in rehabilitation gained mass on both milk and fish diets. Preweaned pups had greater mean serum cortisol and similar TT4 concentrations than weaned pups. Freeranging harbor seal pups were heavier and longer than preweaned and weaned pups in rehabilitation. The free-ranging pups had the lowest cortisol and highest TT4 concentrations of any of the pups. These results suggest that weaned pups that have undergone rehabilitation are not physiologically equivalent to free-ranging weaned pups. Additional research is needed regarding physiological changes in endocrine values during early development under captive care conditions. This information should be useful to marine mammal rehabilitation centers in their development of care protocols and release criteria for rehabilitating harbor seal pups. Zoo Biol. 00:1-8, 2012.

Ices Journal of Marine Science, May 27, 2023

Climate change threatens fisheries health through changing ecosy stem dynamics; ho w e v er, the ... more Climate change threatens fisheries health through changing ecosy stem dynamics; ho w e v er, the impacts on the ph y siology and ecology of commercial fish populations are unclear. Here, annually deposited growth increments of female yelloweye rockfish (Sebastes ruberrimus) opercula collected in the Gulf of Alaska were used to successfully reconstruct lifetime (∼1-year resolution) steroid hormone, stable isotope, spawning, and stress data. We assessed how hormone profiles, spawning and distress frequencies related to sea surface temperature (SST), chlorophyll a concentrations as well as climate indices. Further, we assessed whether incorporating indicators of foraging depth and diet, stable isotope values (δ 13 C and δ 15 N), would improve model interpretations. Progesterone and estradiol concentrations decreased with increasing SST, suggesting that increasing SSTs may negatively impact juvenile and subadult f emales ' reproductive development. Spawning frequency was positively linked to changes in the North Pacific Gyre Oscillation (NPGO) index, potentially timed with f a v orable conditions f or larv al surviv al. T his w as supported b y ju v eniles ha ving a lo w er probability of a distress e v ent during positiv e NPGO y ears compared to negativ e NPGO y ears. While relationships among environmental data and y ello w e y e rockfish ph y siology w ere w eak, this study pro vides insight into the en vironmental impacts on the lifetime reproduction and stress of a commercially important teleost species.

Science of The Total Environment

Frontiers in Marine Science

Animals that display plasticity in behavioral, ecological, and morphological traits are better po... more Animals that display plasticity in behavioral, ecological, and morphological traits are better poised to cope with environmental disturbances. Here, we examined individual plasticity and intraspecific variation in the morphometrics, movement patterns, and dive behavior of an enigmatic apex predator, the leopard seal (Hydrurga leptonyx). Satellite/GPS tags and time-depth recorders were deployed on 22 leopard seals off the Western Antarctic Peninsula. Adult female leopard seals were significantly larger (454±59 kg) and longer (302±11 cm) than adult males (302±22 kg, 276±11 cm). As females were 50% larger than their male counterparts, leopard seals are therefore one of the most extreme examples of female-biased sexual size dimorphism in marine mammals. Female leopard seals also spent more time hauled-out on land and ice than males. In the austral spring/summer, three adult female leopard seals hauled-out on ice for 10+ days, which likely represent the first satellite tracks of parturit...

Aquatic Mammals

Pregnancy and lactation are energetically expensive for female mammals and greatly influence the ... more Pregnancy and lactation are energetically expensive for female mammals and greatly influence the evolution of species-specific reproductive strategies. Phocid (“true” seals) lactation is generally short in duration and relies heavily on stored energy, whereas otariid (sea lions and fur seals) lactation is generally much longer, and energy is supplemented by foraging. While a phocid, the smaller body size of the harbor seal (Phoca vitulina) is assumed to preclude the maintenance of lactation solely from stored energy. For this reason, their lactation strategy is believed intermediate to that of otariids and phocids. The purpose of this study was to characterize blubber fatty acids (FAs) of pregnant and lactating harbor seals and determine if lactating blubber FA profiles more closely resemble phocids or otariids. Blubber FA differences between female reproductive states (lactating, n = 18; pregnant, n = 7; non-lactating–non-pregnant, n = 17), mother–pup pairs (n = 6), and families (o...

Conservation Physiology, 2021

Alaskan harbour seal populations are currently listed as a species of special concern. Although t... more Alaskan harbour seal populations are currently listed as a species of special concern. Although there is evidence of recent stabilization or even partial recovery of harbour seal numbers in areas of historic decline, most populations have not made substantial recoveries. To date, few data exist regarding spatial and seasonal changes in blubber fatty acids (FAs) for Alaskan harbour seal populations. The purpose of this study was to qualitatively investigate harbour seal blubber FA profiles for regional, seasonal and age class differences. Blubber FA concentrations were analysed using MANOVA and linear discriminant analysis (LDA) from 760 individual harbour seals across Bristol Bay, Kodiak, Prince William Sound and Southeast Alaska from 1997 to 2010. Our results suggest spatial and seasonal differences are largely driven by monounsaturated FAs, most notably 14:1n-5, 16:1n-7 and 18:1n-7. In addition, our data revealed a progression in blubber FAs from pups to adults, with a shift from ...