Science Behind Sustainable SeafoodSolving the Ecosystem Problem

Alaska Fisheries Science Center

What is the effect of removing a primary food source in Alaskan waters?

2

Organisms are interconnected by what they consume.

Free write

• Write down what comes to your mind when I say the word food web.

• Underline three things you wrote which are important to a food web

http://www.afsc.noaa.gov/REFM/REEM/Manuals/Default.htm

Krill video

• http://video.nationalgeographic.com/video/animals/invertebrates-animals/crabs-lobsters-shrimp/krill/

• What animals ate krill in the video? • Describe a food chain they saw in the video• How does a food web differs from a food chain?

http://jonbowermaster.com/blog/2009/01/krill-baby-krill/

Parts of the Bering Sea ecosystem• The sun’s energy is converted into nutrients for plants through

a process called photosynthesis.

• Phytoplankton are microscopic plants that drift in the ocean. They are at the base of all food chains in the Bering Sea

• Zooplankton are microscopic animals and are found near the bottom of the Bering Sea food chain. • Zooplankton like amphipods and copepods are prey to

many small fish.• Big baleen whales eat zooplankton (Humpback whales)

Parts of the Bering Sea ecosystem• Small fish like herring and juvenile walleye pollock can be

both predator and prey since they sit in the middle of the food chain.• Feed on zooplankton

• Adult walleye pollock can also be both predator and prey. they are not the top predator. • Feed on krill and juvenile pollock

• Humans are at the top of the food chain.

• In the Bering Sea, northern fur seals are also a top-predator• Feed on walleye pollock, Atka mackerel and Pacific cod

Stomach data• To better understand the relationships between predators

and prey in the Bering Sea, scientists at the Alaska Fisheries Science Center annually collect and examine the stomachs of thousands of fish.

• What they see tells them a lot about how important all species in the Bering Sea are to maintaining balance within the entire ecosystem.

http://www.afsc.noaa.gov/REFM/REEM/Manuals/Default.htm

year 1999

stomachs 2839

hauls 164

Prey name Percent weight

zooplankton 56.96

pelagic invertebrates 4.34

squids 2.24

forage fish 8.45

flatfish 0.44

rockfish 5.5

other fish 5.62

pollock 2.19

benthic invertebrates 4.06

shrimp 14.47

crab 0.54

glopp 0.69

Sum 105.5

Walleye Pollock

WALLEYE POLLOCK STOMACH DATAhttp://www.afsc.noaa.gov/species/pollock.php

year 1999

stomachs 1401

hauls 136

Prey name Percent weight

zooplankton 3.94

pelagic invertebrates 0.41

squids 0.74

forage fish 2.73

flatfish 6.79

other fish 9.4

pollock 24.29

cod 0.72

arrowtooth 0.02

benthic invertebrates 14.11

shrimp 6.99

crab 29.21

glopp 0.64

Sum 99.99

Pacific cod

PACIFIC COD STOMACH DATA

http://www.afsc.noaa.gov/species/Pacific_cod.php#

year 1999

stomachs 148

hauls 39

Prey Name Percent Weight

zooplankton 8.47

forage fish 4.47

flatfish 0.05

other fish 16

pollock 60.4

benthic invertebrates 1.16

shrimp 5.91

crab 3.51

glopp 0.02

Sum 99.99

Arrowtooth flounder

ARROWTOOTH FLOUNDER STOMACH DATAhttp://www.dfw.state.or.us/MRP/finfish/sp/flatfish.asp

year 1999

stomachs 232

hauls 38

Prey Name Percent Weight

zooplankton 6.31

pelagic invertebrates 0.03

flatfish 0.27

other fish 0.94

pollock 15.63

benthic invertebrates 52.19

shrimp 12.06

crab 12.31

glopp 0.26

Sum 100

Flathead sole

FLATHEAD SOLE STOMACH DATAhttp://www.dfw.state.or.us/MRP/finfish/sp/flatfish.asp

Stomach Data Discussion

WALLEYE POLLOCK, PACIFIC COD, ARROWTOOTH FLOUNDER, FLATHEAD SOLE

•Which animals have similar diets?•Which prey species occurs in all of the diets?•Which prey species occurs in most of the diets?•Which predator has the most different or specialized diet?

Why do you think a predator has multiple types of prey?

1. What advantages would more prey types in a diet give an animal?

2. Do Pacific cod eat the same prey in all 3 places?3. Do cod eat the most of the same prey in all 3 places?

Make your own food web

http://access.afsc.noaa.gov/REEM/WebDietData/DietTableIntro.php

http://www.sciencedirect.com/science/article/pii/S096706450700197X

Bering Sea Ecosystem

U.S. Department of Commerce | National Oceanic and Atmospheric Administration | NOAA Fisheries | Page 18