Investigating the South African Bryde’s whale

Balaenoptera edeni

South Africa’s Secretive Giants

Dr Gwenith Penry

Post-doctoral research

The Bryde’s Whale - Balaenoptera edenipronounced “Br-oo-des” Johan Bryde, Norwegian Consul.

Conservation Status, Biology and Distribution

• IUCN ‘data deficient’

• International Whaling Commission (IWC) - 11 management stocks globally

• Number of species / populations unknown

• Limited or no migrations

• Tropical and subtropical distribution

• 2 Ecotypes: Inshore and Offshore

• SA Inshore population restricted to within continental shelf

• Year round feeding and reproduction

IUCN

Map: Best 1977. Two allopatric forms of Bryde’s whales off South Africa

Consolidating 10 years of researchPlettenberg Bay and False Bay

• Abundance estimation- Mark Recapture techniques:

- Estimated population (Plett) = 150 -250 (CV = 0.07-0.38)- Range wide = approx. 500

• Seasonal Variation in occurrenceSeasonal fluctuations in occurrence of inshore Bryde's whales in Plettenberg Bay, South Africa, with notes on feeding and multispecies associations.

GS Penry , VG Cockcroft & PS Hammond , 2011. AJMS

Mean Seasonal Sightings

Season

Mea

n D

aily

Sig

htin

gs

0.1

0.2

0.3

0.4

0.5

0.6

0.7

1 2 3 4

Mean Seasonal Chlorophyll-a Conc

Season

Chl

-a c

onc

(mg/

m**

3)

1.5

2.0

2.5

3.0

3.5

4.0

4.5

1 2 3 4

Mean Seasonal Wind speed

Season

Win

d S

peed

(m/s

)

3.4

3.6

3.8

4.0

1 2 3 4

Mean Seasonal SST

Season

SS

T P

lett

Bay

(Cel

cius

)

1718

1920

1 2 3 4

Hap1

Hap5

Hap2

Hap6

Hap3

Hap4 (SA Offshore)

B.brydei SP

B. brydei EIO

B.brydei NP

B.edeni (Coastal Japan)

B.edeni (Malaysia) – identical to type specimen

SH Sei whale

NH Sei whale

B.omurai (Solomon islands)

Humpback whale (outgroup)

99

98

14

13

14

93

40

29

65

87

40

88

Maximum Parsimony tree.

Pelagic

populations

5 haplotypes

identified for SA

inshore

population

(77%)• Molecular identity and taxonomy

In Prep: Phylogenetic relationships of southern African Bryde’s whales inferred from analysis of the

mtDNA control region: Recommendations for revision of current nomenclature.

Relevance…..

• National Red List Assessment

• Identification of critical habitats (feeding and breeding)

• Spatial and temporal closures

• Prey availability

• Global comparison of available molecular data – SMM taxonomy committee

• Feed into an ecosystem-based approach to fisheries management

• Known threats to the population:• Food source (climate change, fishing

pressure)

• Ship strikes and entanglement

• Disturbance from increasing tourism

Summary • Inshore form is NOT B.edeni

• Small, genetically isolated population

• Threatened by competition for

resources

Arguably South Africa’s largest resident predator!!

Acknowledgements

• MRI – University of Pretoria

• Dr Peter Best

• National Research Foundation (NRF)

• Rufford Foundation, Society for Marine Mammalogy

• Meredith Thornton, Ian Thompson, MaleenHoekstra, Ken Findlay

• Amanda Page and Shayna Brody - interns

• Raggy Charters, Dyer Island Conservation Trust, ORCA foundation, Simons Town Boat Company

• False Bay Yacht Club

Global and local distribution

• Tropical & Subtropical

distribution

• 40o N and 40o S

• 2 Ecotypes

• Coastal

• PelagicMap: Best 1977. Two allopatric forms of Bryde’s whales off South Africa

The Past

• Historical data limited because:– Not heavily targeted by commercial

whaling due to absence from polar waters.

– Targeted from 1970’s onward due to depletion of larger more profitable species

– Confusion with sei whale = incorrect catch statistics

– Falsification of numbers, e.g. by USSR –many more taken than were reported.

• Available estimates are old and of questionable accuracy.

Abundance Estimate

Photo identification - dorsal fins

(2005-2008)

83 marked individuals

Mark recapture models:

Estimated population (Ntotal)

= 150 -250 (CV = 0.07-0.38)

Only relevant to the east coast?

PhD

Results

Methods

• Abundance estimation• Photo identification and genotyping

• Foraging Ecology and Genetics

- Small sample of skin – current diet

- Baleen plates – life record of dietary contribution

Stable isotope analysis

Mean Seasonal Sightings

Season

Mea

n D

aily

Sig

htin

gs

0.1

0.2

0.3

0.4

0.5

0.6

0.7

1 2 3 4

Mean Seasonal Chlorophyll-a Conc

Season

Chl

-a c

onc

(mg/

m**

3)

1.5

2.0

2.5

3.0

3.5

4.0

4.5

1 2 3 4

Mean Seasonal Wind speed

Season

Win

d S

peed

(m/s

)

3.4

3.6

3.8

4.0

1 2 3 4

Mean Seasonal SST

Season

SS

T P

lett

Bay

(Cel

cius

)

1718

1920

1 2 3 4

1 = Spring; 2 = Summer; 3 = Autumn; 4 = Winter

a. b.

c. d.

Seasonality

Feeding

Inshore form - sardine,

anchovy, maasbanker.

Offshore form – euphausiids,

some fish.

Multispecies feeding frenzies:

common dolphins, Cape

gannets, Cape fur seals and

sharks.

G Penry

G Penry

G Penry

Dr GS Penry

Foraging Ecology (past and present)Stable isotope analysis (SIA)Potential for an MSc project, starting in 2013.

Objectives

- Identify past and present diet using ratios of carbon (13C:12C) and nitrogen isotopes (15N:14N) in

baleen and skin samples respectively.- Baleen plates from stranded animals will provide a complete life record of prey type.

- Current prey selection by live animals will be determined from skin samples of biopsy sampled

animals.

- Determine whether the trophic level at which this population feeds has changed over several

decades i.e. from fish to euphausiids.

- Discuss the findings in relation to changes in abundance of inshore Bryde’s whales (since

1983), observed declines in other predators (e.g. African penguin) of small pelagic fish and

ecosystem changes.

- Long term – incorporate findings (dietary requirements of the population) into an ecosystem

approach to conservation and management.

Inshore Bryde’s whale stomach content data

from whaling records showed a complete

dependency on small pelagic fish; primarily

sardine and anchovy.