Marine Vertebrates: Lecture 13
February 25, 2008
Part 1: Buoyancy and the Spermaceti Organ (Malcom Clarke’s hypothesis)
I.
Anatomy of a sperm whale’s head
A.
Cross section
1.
NOTE: Spermaceti organ is surrounded by a dense capillary network supplied by a
large, posterior artery
B.
Nasal passages (“world’s largest nose”, Cranford, TW)
1.
Left vs. right (right is more complex, passes through spermaceti organ)
II.
Heating and Cooling the Spermaceti Oil
A.
Spermaceti oil: density vs. temperature and pressure (see figure in PP)
B.
Mechanisms of heating and cooling
1.
Cooling
a)
Role of right nasal passage/maxillonasalis muscle
b)
Role of capillaries associated with skin and nasal passages
2.
Heating
a)
Role of increased arterial input from posterior artery
III.
Putting it all together
A.
Descent
B.
At depth
C.
Ascent
IV.
NOTE: Hypothesis has been subject of controversy. Alternate hypotheses…
A.
Spermaceti organ and sound production
1.
The sperm whale's nose: Sexual selection on a grand scale? (Cranford TW, Marine
Mammal Science 15 (4): 1133-1157.)
B.
Key function of aggression? The face that sank the Essex: potential function of the
spermaceti organ in aggression
Part 2: Migration & Navigation (Part 1)
I.
Introduction
A.
Migration defined: To pass, usually periodically, from one region or climate to another,
usually for feeding or breeding
1.
Can occur on daily, monthly, yearly or multiyear cycles.
B.
Migration is a common and spectacular phenomenon
1.
A high proportion of marine species are migratory
II. What are the key questions/subjects of interest for this topic?
A.
Basic descriptions: Where do individuals/groups move over the course of a
day/month/year/lifetime?
1.
Need to find/study on ecologically relevant time scales.
2.
Methods
a)
Population studies in particular areas
b)
Aerial surveys
c)
Tag-release-recapture (rockfish studies off the Oregon Coast)

Why does this method often overestimate populations?
d)
Radio and satellite-tagging/tracking studies
e)
Fixed acoustic sensors (SoSUS array: U.S. Navy): blue whale study

Works only for species producing distinct acoustic signals
B.
Why do they move?
C.
What cues do they use for navigation?
D.
Have migratory patterns changed with global climate change?
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III.
Migratory patterns
A.
Northern hemisphere high latitudes to southern hemisphere high latitudes
1.
Arctic terns and Antarctic terns [see PP]
a)
Where does each breed?
b)
Which has the longest north-south migration known (14,000 miles oneway?)
c)
Are they both in the same hemisphere at the same time? (Think about this
logically.)
d)
How did it happen that one breeds in the N. hemisphere while the other
breeds in the S. hemisphere?
B.
Polar to tropical
1.
Eastern Pacific gray whale [PP diagram] exemplifies migration pattern typical
of Mysticetes
a)
Migratory route
b)
Timing
c)
Hypotheses for why they migrate

Females giving birh/calves

Others?
2.
Many Mysticeti make a similar journey:
a)
Humpback whales

Focus on Australian populations

Note mixing in feeding grounds, separation on return to W. vs. E.
Australia.

Song dialect change due to “lost” males…
3.
Focus: Blue whale migration (Burtenshaw et al., 2004, will post…)
a)
Overview

Vocally distinct population (~2000-3000 whales) in NE Pacific: Gulf of AK
to Central America

Low frequency, high intensity songs travel hundreds of miles
b)
Methods

System of fixed hydrophones throughout the NE Pacific were used in this
study to detect the whale calls (US Navy, SoSUS array)

Frequency and intensity of calls used to approximate the blue whale
density in a particular area

How could this be misleading?

Satellite imagery detects SST and chl a concentration

Net tows and acoustic surveys provide information on krill populations, but
were not included in this study…
c)
Results:

What does the pattern of calling suggest about the migratory pattern?

Why might calling intensity be low in some regions? .

Less seasonality to the residence time of whales off Vancouver I. Why?
d)
Compare with Patterns of primary production. Discuss…

What temporal/spatial pattern of phytoplankton blooms are seen?

Why is there an apparent 5-month time lag between blooms and peak whale
populations?

What type of data is missing?

Why is there less seaonality for Vancouver I. population?

Shifts in the whale populations during El Niño (1997-1998) corresponds with
similar shifts in primary productivity

Reduction in S. California peak

Prolonged stay in central CA and off Vancouver I.
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C.
D.
E.
Migration at same latitude, breeding to feeding grounds
1.
Focus: Atlantic bluefin tuna (Block et al., 2005—link to her paper at
http://www.tunaresearch.org/reprints/bluefinature.pdf)
a)
Overview

Spawning stock of Atlantic bluefin tuna has dropped by 80% or more since
1970 due to overexploitation, with continued decline

Clearly in the “Avoid” category of MBA Seafood Watch!

Management plan currently recognizes two distinct populations, a western
and eastern population, arbitrarily divided at 45W longitude.

Questions: Do these populations overlap in any way? Are there
distinct breeding populations?
b)
Methods

Extensive program of satellite tagging of bluefin tuna in W. Atlantic
(including Gulf of Mexico spawning grounds) and E. Atlantic (including
Mediterranian spawning grounds.)

Now there is a larger “TOPP” program, tagging of Pacific Pelagics
(http://topp.org/)
c)
Results (http://www.tunaresearch.org/nature.html)

Extensive mixing of the two populations in feeding grounds on both sides of
the N. Atlantic

Note that they are occurring roughly in a frontal zone at/near the edge
of the Gulf Stream

Individuals appear faithful to their spawning sites.

Variability in individual tracks

Age-related differences in extent of travel.
d)
Discussion

Spawning grounds: fisheries management issues.
2.
Green sea turtle (other species of sea turtles have similar migrations) [Fig. 4.45]
a)
Breeds on Ascension Island, only 5 miles wide.

Ascension I. served as a refueling ground for Allied forces during
WWII. The saying goes, “If you miss Ascension, your wife gets a
pension.”

Presumably an ideal location for breeding and mating; certainly out
of the way of predators
b)
Travels 1200 miles in open ocean between this breeding location and
feeding grounds in Brazil.
Migratory circuits
1.
Wandering albatross [PP, additional figure]
a)
Find food (fish, squid) in the open ocean, probably following productive
fronts along their migration route and taking advantage of prevailing wind.
b)
Albatrosses caring for young undertake 10-15 day foraging trips
c)
Circuits are from 1800- 9000 miles (determined by satellite tracking data)
Migration between freshwater and seawater
1.
Salmon spend from one to several years (depending upon species and conditions) in
the ocean in order to feed. Probably concentrate in regions where currents meet,
creating “fronts” that contain high concentrations of food.
a)
Compare migration location to Alaska and CA current systems
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