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

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  • 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

    With

  • 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