FISH 475 Lecture Notes - Lecture 19: Marine Ecosystem, Toothed Whale, Forage Fish
10 Jun 2018
School
Department
Course
Professor
Marine Mammal Diet and Foraging Strategies: Review
Food is the driving force that led marine mammals back to the sea
Ex: Oligocene epoch = Circum-Antarctic Current = HUGE blooms of
zooplankton = first baleen whales
○
-
MM diversification heavily influence by diet and foraging strategy
-
Simple solution to aquatic living = capture strategy patterns
Aka its easier to clean a pool with a net or a vacuum than chopsticks
○
-
General types of prey capture strategies
Filter Feeding
○
Suction Feeding
○
Ram/Snap feeing in cetaceans = pierce feeding in pinnipeds
○
Grappling with forearms in sea otters
○
-
Odontocetes:
Suction feeders and ram/snap feeders
○
Cooperative feeding is widespread but not all group feeding is
cooperative
○
-
Mysticetes:
Filter feeders (skim and lunge techniques)
○
Suction feeders (grey whales only)
○
Some cooperative feeding
○
-
Otariids:
Generally shallow divers, specialists on DSL organisms and coastal forage
fish
○
Central place foragers during breeding
○
Pierce feeding via anterior snapping is predominant
○
-
Phocids:
Pierce (via anterior snapping), suction, AND filter feeders
○
Variable mouth anatomy and dentition = variable capture techniques
○
Most do not forage during lactation, so not often considered central place
foragers
○
-
Odobenidae:
The king of suction feeders - mouth and lip anatomy perfectly shaped for
maximum suction
○
Heavy reliance on vibrissae and forelimbs for prey capture
○
-
Sirenians:
Modified pierce/bite feeders
○
All species herbivorous
○
Dentition and digestion suited for processing celluloid plants
○
Manatees (Trichechidae) can feed anywhere in the water column
○
Dugongs are obligate bottom feeders
○
-
Polar Bears:
Primarily forage on phocid seals on stable sea ice
○
Will eat other prey, including vegetation, in an emergency
○
Can be efficient scavengers
○
-
Otters:
Feeding tactic: grappling with forearms
○
Shallow divers, nearshore habitat
○
Primary prey are crustaceans, mollusks, and benthic fish
○
Dentition, skull and digestive anatomy suited for diverse prey that's often
hard/tough to digest
○
Tool users for food "preparation"
○
-
The role of marine mammals in ecosystems
It's extremely complicated and nearly impossible to quantify
-
Marine Mammals in the Food Web:
What we Know:
Marine mammals are consumers
Whales are big and it matters
~15.7 million tons of whale in the world's marine
ecosystem
®
53.4 million tons of krill consumed annually in the
Southern Ocean by 5 whale species
®
□
Killer whales in the Southern Ocean
Type A: Whale Eaters
®
Small Type B: Penguin Eaters
®
Large Type B: Seal Eaters
If they specialized all the time they would eat
72,000 seals/year
◊
®
Type C: Fish Eaters
®
□
§
Marine mammals are prey
The most controversial of the three potential ecological
pathways
□
Killer whale predation may drive:
School size, acoustic behavior, distribution
®
Baleen whale migration
®
Prey abundance… Trophic cascades
Trophic Cascades: powerful indirect interactions
that can control entire ecosystems, occurring
when predators in a food web suppress the
abundance or significantly alter the behavior of
their prey, thereby releasing the next lower
trophic level from predation
◊
®
□
Food web reconstructing through competition:
Killer whale predation in western Australia
Humpbacks in WA have made an amazing
recovery
◊
Prior to 2006, there were only 2 KW attacks
◊
Between 2006-2013, 33 known KW attacks! (64%
of documented attacks resulted in kills)
◊
Extrapolating to KW populations during the 5
months of humpback occupancy = dozens of
calves killed annually
◊
®
Western Australia killer whale and humpback whale
interactions continue….
Large numbers of sharks are seen accompanying
these killer whale attacks
◊
The sharks reduce a whale carcass to a pile of
bones in hours: Whale fall
Whale fall: the gift that keeps on giving
Dead whales that fall to the seafloor
can create complext localized
ecosystems that supply sustenance to
deep-sea organisms for decades
–
}
◊
®
□
§
Marine Mammals are competitors
The impacts of competition
Sources:
Other members of their group
◊
Other animals eating the same prey
◊
Humans using their habitat
◊
Predators hunting them
◊
®
Impact:
Change of habitat
◊
Change in migratory route
◊
Less successful foraging
◊
Prey switching
◊
Fewer offspring
◊
Death
◊
®
□
The "Krill Surplus Hypothesis":
An example of competitive release:
Competitive release occurs when one of two
species competing for the same resource
disappears, thereby allowing the remaining
competitor to utilize the resource more fully than
it could in the presence of the first species
◊
More than 2 million whales removed from the
southern hemisphere in the 1900s
◊
That freed up around 150 million tons of krill per
year
◊
Theoretically, you could support an additional
200-300 million penguins on that surplus
◊
Observed growth in penguin populations
attributed to "krill surplus"
◊
®
□
§
Marine Mammals are ecosystem engineers
Any organism that creates, significantly modifies, maintains,
or destroys habitat
□
§
Size + Abundance = Important
Cetaceans in CA current consume 12% to 15% of net primary
productivity
□
Gray whales, walrus, dugongs, sea otters and others are
ecosystem engineers
They facilitate consumption by seabirds and benthic
scavengers
®
They mix sediment and nutrients in H2O
®
□
Examples:
Dead whales support 350+ species
Create havens in the deep-sea
◊
®
Decline of sperm whales in the Pacific
tropics/subtropics may have led to a shift toward squid
& tuna dominated ecosystem
®
Killer whales may have contributed to sequential
decline of marine mammals in Bering Sea
®
□
§
○
-
The Role of Marine Mammals in Ecosystems: Review
So, how do marine mammals impact their ecosystems?
The remove a huge amount of prey (krill, squid, penguins, and other
marine mammals)
○
They impact other predators of these prey through competition
○
Whale fall creates benthic habitat that lasts for decades
○
-
The act as ecosystem engineers by:
Bringing nutrients into the water column (via sediments and/or poop)
○
Facilitate scavenging and consumption by birds and invertebrates
○
-
Lecture 19: The Role of Marine Mammals in
Ecosystems
Friday, May 11, 2018
10:26 AM
Marine Mammal Diet and Foraging Strategies: Review
Food is the driving force that led marine mammals back to the sea
Ex: Oligocene epoch = Circum-Antarctic Current = HUGE blooms of
zooplankton = first baleen whales
○
-
MM diversification heavily influence by diet and foraging strategy
-
Simple solution to aquatic living = capture strategy patterns
Aka its easier to clean a pool with a net or a vacuum than chopsticks
○
-
General types of prey capture strategies
Filter Feeding
○
Suction Feeding
○
Ram/Snap feeing in cetaceans = pierce feeding in pinnipeds
○
Grappling with forearms in sea otters
○
-
Odontocetes:
Suction feeders and ram/snap feeders
○
Cooperative feeding is widespread but not all group feeding is
cooperative
○
-
Mysticetes:
Filter feeders (skim and lunge techniques)
○
Suction feeders (grey whales only)
○
Some cooperative feeding
○
-
Otariids:
Generally shallow divers, specialists on DSL organisms and coastal forage
fish
○
Central place foragers during breeding
○
Pierce feeding via anterior snapping is predominant
○
-
Phocids:
Pierce (via anterior snapping), suction, AND filter feeders
○
Variable mouth anatomy and dentition = variable capture techniques
○
Most do not forage during lactation, so not often considered central place
foragers
○
-
Odobenidae:
The king of suction feeders - mouth and lip anatomy perfectly shaped for
maximum suction
○
Heavy reliance on vibrissae and forelimbs for prey capture
○
-
Sirenians:
Modified pierce/bite feeders
○
All species herbivorous
○
Dentition and digestion suited for processing celluloid plants
○
Manatees (Trichechidae) can feed anywhere in the water column
○
Dugongs are obligate bottom feeders
○
-
Polar Bears:
Primarily forage on phocid seals on stable sea ice
○
Will eat other prey, including vegetation, in an emergency
○
Can be efficient scavengers
○
-
Otters:
Feeding tactic: grappling with forearms
○
Shallow divers, nearshore habitat
○
Primary prey are crustaceans, mollusks, and benthic fish
○
Dentition, skull and digestive anatomy suited for diverse prey that's often
hard/tough to digest
○
Tool users for food "preparation"
○
-
The role of marine mammals in ecosystems
It's extremely complicated and nearly impossible to quantify
-
Marine Mammals in the Food Web:
What we Know:
Marine mammals are consumers
Whales are big and it matters
~15.7 million tons of whale in the world's marine
ecosystem
®
53.4 million tons of krill consumed annually in the
Southern Ocean by 5 whale species
®
□
Killer whales in the Southern Ocean
Type A: Whale Eaters
®
Small Type B: Penguin Eaters
®
Large Type B: Seal Eaters
If they specialized all the time they would eat
72,000 seals/year
◊
®
Type C: Fish Eaters
®
□
§
Marine mammals are prey
The most controversial of the three potential ecological
pathways
□
Killer whale predation may drive:
School size, acoustic behavior, distribution
®
Baleen whale migration
®
Prey abundance… Trophic cascades
Trophic Cascades: powerful indirect interactions
that can control entire ecosystems, occurring
when predators in a food web suppress the
abundance or significantly alter the behavior of
their prey, thereby releasing the next lower
trophic level from predation
◊
®
□
Food web reconstructing through competition:
Killer whale predation in western Australia
Humpbacks in WA have made an amazing
recovery
◊
Prior to 2006, there were only 2 KW attacks
◊
Between 2006-2013, 33 known KW attacks! (64%
of documented attacks resulted in kills)
◊
Extrapolating to KW populations during the 5
months of humpback occupancy = dozens of
calves killed annually
◊
®
Western Australia killer whale and humpback whale
interactions continue….
Large numbers of sharks are seen accompanying
these killer whale attacks
◊
The sharks reduce a whale carcass to a pile of
bones in hours: Whale fall
Whale fall: the gift that keeps on giving
Dead whales that fall to the seafloor
can create complext localized
ecosystems that supply sustenance to
deep-sea organisms for decades
–
}
◊
®
□
§
Marine Mammals are competitors
The impacts of competition
Sources:
Other members of their group
◊
Other animals eating the same prey
◊
Humans using their habitat
◊
Predators hunting them
◊
®
Impact:
Change of habitat
◊
Change in migratory route
◊
Less successful foraging
◊
Prey switching
◊
Fewer offspring
◊
Death
◊
®
□
The "Krill Surplus Hypothesis":
An example of competitive release:
Competitive release occurs when one of two
species competing for the same resource
disappears, thereby allowing the remaining
competitor to utilize the resource more fully than
it could in the presence of the first species
◊
More than 2 million whales removed from the
southern hemisphere in the 1900s
◊
That freed up around 150 million tons of krill per
year
◊
Theoretically, you could support an additional
200-300 million penguins on that surplus
◊
Observed growth in penguin populations
attributed to "krill surplus"
◊
®
□
§
Marine Mammals are ecosystem engineers
Any organism that creates, significantly modifies, maintains,
or destroys habitat
□
§
Size + Abundance = Important
Cetaceans in CA current consume 12% to 15% of net primary
productivity
□
Gray whales, walrus, dugongs, sea otters and others are
ecosystem engineers
They facilitate consumption by seabirds and benthic
scavengers
®
They mix sediment and nutrients in H2O
®
□
Examples:
Dead whales support 350+ species
Create havens in the deep-sea
◊
®
Decline of sperm whales in the Pacific
tropics/subtropics may have led to a shift toward squid
& tuna dominated ecosystem
®
Killer whales may have contributed to sequential
decline of marine mammals in Bering Sea
®
□
§
○
-
The Role of Marine Mammals in Ecosystems: Review
So, how do marine mammals impact their ecosystems?
The remove a huge amount of prey (krill, squid, penguins, and other
marine mammals)
○
They impact other predators of these prey through competition
○
Whale fall creates benthic habitat that lasts for decades
○
-
The act as ecosystem engineers by:
Bringing nutrients into the water column (via sediments and/or poop)
○
Facilitate scavenging and consumption by birds and invertebrates
○
-
Lecture 19: The Role of Marine Mammals in
Ecosystems
Friday, May 11, 2018
10:26 AM
Document Summary
Lecture 19: the role of marine mammals in. Food is the driving force that led marine mammals back to the sea. Ex: oligocene epoch = circum-antarctic current = huge blooms of zooplankton = first baleen whales. Mm diversification heavily influence by diet and foraging strategy. Simple solution to aquatic living = capture strategy patterns. Aka its easier to clean a pool with a net or a vacuum than chopsticks. Ram/snap feeing in cetaceans = pierce feeding in pinnipeds. Cooperative feeding is widespread but not all group feeding is cooperative. Generally shallow divers, specialists on dsl organisms and coastal forage fish. Pierce (via anterior snapping), suction, and filter feeders. Variable mouth anatomy and dentition = variable capture techniques. Most do not forage during lactation, so not often considered central place foragers. The king of suction feeders - mouth and lip anatomy perfectly shaped for. The king of suction feeders - mouth and lip anatomy perfectly shaped for maximum suction.
