Ecology - University of California, San - Ecology.pdfآ  Ecology Lisa T. Ballance Marine Mammal Biology

Ecology

Lisa T. Ballance

Marine Mammal Biology – SIO 133

Spring 2012

Ecology – the study of the relationships

of organisms to each other and to their

surroundings

“Ecology” is a HUGE field

Today

1. Marine mammal relationships with:

a) Physical and biological environment

b) Prey

c) Competitors

d) Predators

2. Marine mammal roles in marine ecosystems

--Case Studies: Cetaceans --Please pay special attention to readings for a more general overview (*complementary* to lecture material)

1a) Marine mammal relationships with the physical and biological

environment

Case Study: Cetaceans in the eastern tropical Pacific and California Current

Fiedler and Talley 2006

Oceanographic Data

Species Data

• 1986 – 2005

• 400,000 km surveyed

• 17,000 cetacean sightings

• Species-habitat relationships quantified for 12 and 15 spp. in the CA Current and ETP, respectively

Environmental Data

• Oceanographic - In situ – SST – SSS – Thermocline depth, strength – SS Chl

• Oceanographic - Remotely sensed – SST – “Fronts” (CV of SST)

• Geographic – Latitude – Longitude – Depth – Bottom slope

Analytical Approaches

• Modeling Framework – GLM – GAM – Tree-based

• Error Structure – Poisson – Quasi-likelihood – Negative binomial

• Model Selection – AIC – Cross-validation

• Generalized Additive Models – Incorporate environmental variables

to model abundance along sampled trackline, model used to predict abundance in areas not sampled

• Environmental information must be available throughout study area (latitude, longitude, depth)

– Non-random distribution of effort

– Non-linear relationships between species and environmental parameters

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Results: GAMs versus GLMs

Striped Dolphins

Results: Remotely Sensed versus In- situ Environmental Variables

Striped Dolphins

Inclusion of mid-trophic data

Without

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Marine Mammal Protection Act, Endangered Species Act, National Environmental Policy Act require users of the marine environment to conduct environmental assessments regarding impact of activities on marine mammals.

The Question: How Many?

The Problem: Numbers are either unavailable or based on geographic areas outside the relevant area.

Example: Naval operations on the high seas – potential impacts on beaked

whales

Cuvier’s beaked whale density estimates available for “eastern Pacific”

No sightings, little data in area of interest!

Marta Guerra

How many Cuvier’s Beaked Whales might be impacted by these operations?

Using Species-Habitat Relationships for Conservation/Management:

Species-Habitat Relationships Allow for

Prediction

Physical and Biological Data Cuvier’s Beaked Whale Sightings

x Cuvier’s Beaked Whales in Area of

Concern

Coming to a website soon

1b) Marine mammal relationships with prey

Prey of marine mammals include:

When we think of consumers in an ecological context, we ask questions

like:

• What is eaten?

• How much?

• How does this consumption impact the ecosystem?

Case Study: Cetaceans as consumers in the Southern Ocean*

*South of the Polar Front

Krill

E. superba, E. crystallorophias, T. macrura

“Krill-based ecosystem” in about one quarter of the ~32 million sq. km of the Southern Ocean (Siegel & Loeb 1995)

Estimated Abundance Mean Mass (tons)

Ingestion Rate/Day

(1,000 kcal)

No. Days Spent

Feeding % Krill in

Diet

Total Krill Consumed Annually (millions of

tons)

Antarctic Blue Whales 2,300 83 3,708 120 100 1.1

Fin Whales 15,000 48 2,415 120 100 4.7

Sei Whales 20,000 17.5 1,096 120 80 2.3

Humpback Whales 55,000 26.5 1,517 120 100 10.8

Antarctic Minke Whales 500,000 7 535 120 100 34.5

53.4

How much krill is consumed?

Sources: RL Brownell pers. comm.; synthesis by Hewitt and Lipsky 2009

~53.4 million tons krill consumed annually by 5 species of whales

• For some perspective, annually: – 104,182 – 211,984 metric tons harvested: 2000 – 2011 (SC-CAMLR

2011) – 190 million tons consumed by baleen whales alone prior to

commercial exploitation (Laws 1985) – 250 million tons consumed by current populations of all krill predators

(whales, birds, pinnipeds, fish, squid: Miller and Hampton 1989)

• Despite much careful attention, estimates of krill consumption are invariably associated with a great degree of uncertainty (e.g., Leaper and Lavigne 2007)

• How does this consumption impact the ecosystem?*

*remember for later

Squid • Sperm whales

– 10,000 males (Brownell, pers. comm.)

• Beaked whales – 599,300 Ziphiid whales (almost all H.

planifrons) in the Southern Ocean (Kasamatsu & Joyce 1995)

– H. planifrons – the most abundant cetacean in the Southern Ocean?

• Killer whales? (Type B)

• How much squid is consumed?*

• How does this consumption impact the ecosystem?*

*Big Unanswered Questions Durban & Pitman, unpublished data

Other Species

• Killer whales as consumers of:

Fish, penguins, seals, whales

Fish - Ross Sea KWs “Type C”

Krahn et al. 2008

Penguins – Gerlache KWs “Mini Type B” Pitman & Durban 2010

Seals - Pack Ice KW “Big Type B” Pitman & Durban 2011

Whales – “Type A” Pitman & Ensor 2003

How much of these species do killer whales consume?

• ~ 25,000 killer whales in the Southern Ocean (Branch & Butterworth 2001)

Prey specialization (?)

• What is the distribution and abundance of KW ecotypes?*

• How does this consumption impact the ecosystem?*

*Big Unanswered Questions

1c) Marine mammal relationships with competitors

Case Study: Marine Mammals as competitors in the Southern Ocean*

*South of the Polar Front

Competitive Release: The “Krill Surplus” Hypothesis

• > 2 million whales removed from Southern Hemisphere (Clapham and Baker 2006)

• Up to 150 million tons krill/yr unconsumed (Laws 1977)

• Theoretically could support addition of 200-300

million penguins per year (Sladen 1964; Emison 1968)

• Growth in penguin populations attributed to “krill surplus” (Sladen 1964; Emison 1968; Conroy 1975; Croxall and Kirkwood 1979; Croxall et al. 1981; Laws 1985; Rootes 1988)

Antarctic Fur Seals: the best example of competitive release?

• Remarkable recovery from commercial exploitation at South Georgia

• Populations above pre-exploitation levels?

Hodgson and Johnston 1997

South Georgia • Range expansion to

Signy, South Orkneys, due to population increase

• Numbers 78-94% > than during past 6570 (±60) radiocarbon years – exceeding range of natural variability

Boyd 1993

Competition for krill is occurring.

• At Anvers Island, there are significant relationships between humpback whale abundance, the size- frequency distribution of krill target