percent total body lipid content increases in steller sea lion (eumetopias jubatus) pups during the...
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Percent total body lipid content increases in Steller sea lion (Eumetopias jubatus) pups during the first year of life in a similar pattern to other otariid species.
Lorrie Rea1, Ken Pitcher1, Sean Farley1, Julie Richmond1, Wendy Dunlap-Harding1 and Brian Fadely2.
1Alaska Department of Fish and Game,
Division of Wildlife Conservation2National Marine Mammal Lab, NOAA
Funding provided through NOAA Cooperative Agreements NA17FX1079 and NA04NMF4390170. ADFG research conducted under MMPA permit #358-1564, 358-1769 and 358-1888 and ADFG ACUC #03-002 and 06-07.
Acknowledgments:
We would like to thank the field research teams of both the Alaska Department of Fish and Game and the National Marine Mammal Laboratory (NMFS/NOAA) as well as the crews of the R/V Medeia, P/V Stimson, P/V Wolstad, R/V Tiglax, M/V Pacific Star and the R/V Norseman I and II.
Evidence of poor nutrition in Steller sea lions during the 1980’s:
• body size of sea lions (age 1-10 years) significantly lower in 1980s than in 1970s
• lower pregnancy rates in 1980s than 1970s indicating possible high rate of fetal mortality
• change in diet as seen in stomach contents
• concurrent declines in harbor seals, fur seals and some piscivorous seabirds
Steller sea lion physiology and ecology in the 1990’s: in conflict with the nutritional stress hypothesis
• no evidence of high pup mortality
• no evidence of poor adult female body condition
• similar birth weights of pups in east and west
• faster growth rates of pups in declining population
• no blood chemistry or hematology evidence of poor pup health in east or west
• blood chemistry evidence of longer fasting periods in eastern pups, agrees with longer foraging trips
• longer perinatal period and time spent nursing in western stock
Conclusions from 1990’s data:
1. Adult females in the west were able to secure enough food to adequately nurse their pups within the first 4 to 6 weeks of lactation
2. If food limitation is a problem (in the 1990’s and today), it may affect larger, late lactation pups and newly weaned juvenile sea lions
If nutrient intake has been limiting the recovery of this species due to adult females being unable to support larger late lactation pups we would expect to see:
1) Lower body mass at a given age in western population
2) Lower percent body fat at a given age in western population
Indices of body condition:
• body mass
• standard length, girth at 6 locations
• percent total body lipids (deuterium dilution technique, bioelectrical impedance analysis -BIA)
• blubber depth (imaging ultrasound)
Indices of body condition:
• body mass
• standard length, girth at 6 locations
• percent total body lipids (deuterium dilution technique, bioelectrical impedance analysis -BIA)
• blubber depth (imaging ultrasound)
Indices of body condition:
• body mass
• standard length, girth at 6 locations
• percent total body lipids (deuterium dilution technique, bioelectrical impedance analysis -BIA)
• blubber depth (imaging ultrasound)
Methods
• 382 Steller sea lion pups, 2 to 11 months of age
• captured between 1998 and 2005 in 4 regions of Alaska
• Southeast Alaska (SEA)
• Prince William Sound (PWS)
• Gulf of Alaska (GOA)
• Aleutian Islands (AI)
Methods
• underwater dive capture near haulouts
• deuterium dilution method, injecting sterile D2O IM at a dose of 0.3 to 0.5 g/kg body weight, with post equilibration samples collected at approximately 2 h and 2.5 hours after injection
• sublimation of blood samples produced water sample that was assayed by FTIR spectrophotometry against a standard curve
Lactation Age
Stage (months) SEA PWS GOA AI
1 2 - 3 38 19 -- 16
2 4 - 6 36 71 5 3
3 7 – 9 29 40 20 15
4 10 - 11 32 30 -- 28
Total 135 160 25 62
Males 77 91 17 33
Females 58 69 8 29
Sample sizes by area
Lactation Stage
Mas
s (k
g)
20
40
60
80
100
120
PWS malesPWS females
1 2 3 4
Sexually Dimorphic Species:
Males
Lactation Stage
Mas
s (k
g)
40
60
80
100
120
140
160
AI GOAPWSSEA
1 2 3 4
Females
Lactation Stage
Mas
s (k
g)
20
40
60
80
100
120
140
AI GOAPWSSEA
1 2 3 4
Body mass varies by region
Males: 1 AI > SEA p=0.0012
2 GOA > PWS > SEA p=0.0111
3 AI > PWS, SEA p=0.0002
4 AI > PWS, SEA p<0.0001
Females: 1 AI > PWS, SEA p<0.0001
2 AI > PWS > SEA p<0.0001
3 GOA > SEA p=0.0282
4 AI > SEA p=0.0050
Lactation Stage
Lactation Stage
To
tal
bo
dy
lip
ids
(%)
10
20
30
40
PWS malesPWS females
1 2 3 4
Males
Lactation Stage
To
tal B
od
y L
ipid
(%
)
10
20
30
40
AI GOAPWSSEA
1 2 3 4
Females
Lactation Stage
To
tal
Bo
dy
Lip
ids
(%)
10
20
30
40
AI GOAPWSSEA
1 2 3 4
Total body lipid content varies by region:
Males: 1 p=0.4978
2 p=0.4990
3 AI > GOA, SEA p=0.0006
4 AI, PWS > SEA p<0.0001
Females: 1 p<0.4174
2 p<0.0693
3 AI > SEA p=0.0168
4 AI > PWS > SEA p<0.0001
Lactation Stage
Total body lipids of otariid pups:
0
10
20
30
40
50
To
tal B
od
y L
ipid
s (%
)
0
10
20
30
40
50
Early lactation
AI GOA PWS SEA Z.c. A.p. A.g. A.t. C.u.
0
10
20
30
40
50
Mid lactation
Late lactation
Steller sea lions Other otariids
1) Mean body mass of pups was higher in western stock regions than in SEA at all stages of lactation (males and females)
2) Percent total body lipid content was higher in AI pups than in SEA pups during late lactation (males and females)
3) Compared to other otariid species there was no evidence of poor body condition in Steller sea lion pups during the first year of development
Conclusions:
Western stock Steller sea lion pups can gain adequate nutrition to grow and deposit body fat reserves throughout the first year of life.
Pups in the eastern, stable population are smaller and lower body condition in late lactation.
IS IT FOOD? that currently limits the recovery of the western stock? Unlikely, from a caloric perspective.
Conclusions:
Age (months)
0 2 4 6 8 10 12 14
Per
cen
t to
tal b
od
y lip
ids
(%)
0
10
20
30
40
50
E.j. Southeast AlaskaE.j. Prince William SoundE.j. Gulf of Alaska E.j. Aleutian IslandsZ.c. (Iverson 1988) A.p. (Arnould and Hindell 2002) A.g. (Arnould 2001)A.t. (Beauplet 2003) C.u. (Donohue 2002)
Total body lipids of otariid pups: