Marine Food Webs and Fisheries OCN 201 Biology Lecture 9 http://archive.wri.org/image.cfm?id=2648&z=?
Food Chain A series of different species of organisms at different trophic levels in an arrangement such that each species feeds only on organisms one trophic level below and serves as food only for the next level above. Trophic Levels Primary Producer Primary Consumer Secondary Consumer Tertiary Consumer
Trophic Efficiency Much of the biomass consumed by an organism is respired (released as CO 2 and heat) or released as waste products Typically only 10% is used to make biomass This results in the biomass pyramid (or biomass pyramid)
Biomass Pyramid 1 kg 10 kg 100 kg 1,000 kg Top Consumer Phytoplankton Zooplankton Med. Fish Sm. Fish e.g., 10,000 kg
Food Web The complex feeding arrangements among all the organisms in a community that takes into account that any organisms may feed on more than one species of prey and on more than one trophic level.
Simplified Marine Food Web Biomass Pyramid
Trophic Cascades There are many interdependent connections in the marine food web! Disturbance of one component of a food web can have unexpected consequences at many other levels
Simplified Marine Food Web Lots of interdependent links Otters Removing one can alter the entire food web structure
North Pacific Whale Catch
Overharvesting of Whales
Trophic Cascade Springer et al 2003 PNAS Whaling Moratorium
Urchin Barrens
Simplified Marine Food Web Biomass Pyramid
Ocean Fisheries NASA Global Fishing Watch map showing locations of fishing activity
Food from the Sea Seaweed Invertebrates Fish Whales Commercial whaling nominally ceased in 1987 (IWC moratorium) Subsistence whaling by indigenous cultures is permitted Whaling resumed by Norway in 1993, Japan never stopped: whales taken for scientific purposes ; meat and blubber sold to market. New program (since 2015) 300 Minke whales taken from Antarctic waters every year
Food from the Sea Wild caught fisheries - Hunting and gathering from the ocean - Ocean fishing is the last example of catching wild animals on large scale for food Mariculture - A form of aquaculture that involves the farming of marine species
Commercial Fishing Methods GRAB & RUN
Commercial Fishing Methods WWF-Canon / Morten Lindhard HARPOONS AND SPEARS
Commercial Fishing Methods Pole and Line BAITED LINE Longlining Trolling
Commercial Fishing Methods NETS Otter Trawl Purse Seine http://www.legasea.co.nz/images/commercial-fishing-methods.jpg
Factory Trawler Alamy Stock Photo Fish caught, processed, packaged, and frozen all the same ship We have become EXTREMELY efficient at removing fish from the sea
Maximum Sustainable Yield maximum catch of fish that can be harvested without depleting stocks in the future
North Atlantic Cod Fishery
Food and Agriculture Organization of the United Nations Marine Fish Harvest Global marine fish catch has declined since mid-nineties Despite increasing effort Appear to be at or above maximum sustainable yield Effort gw 24 16 8 0
Current Assessments of Sustainability 30% Overfished 90% of fisheries at or above maximum capacity Food and Agriculture Organization of the United Nations
7.7 Billion
Fisheries Issues Overfishing (taking more than m.s.y.) Habitat destruction (bottom trawls) Bycatch (catch of non-target species)
http://coastmonkey.ie/wp-content/uploads/2016/12/super-trawlers.png Super Trawlers Huge factory ships with enormous capacity
Bottom Trawlers Habitat destruction Before After
Bycatch Bottom Trawl Longline Mid-water Trawl
Food from the Sea Wild caught fisheries - We are at the limit of what we can pull from the sea, but human population continues to grow Aquaculture - Marine and freshwater aquaculture are critical areas of growth
Mariculture Oyster Farms Fish Farms
Mariculture Kona-Blue Kona Kampachi Oyster (yellowtail) Farm Fish Farm Kualoa Ranch Oysters (Moli i Fish pond)
Total Fish Supply Figure from Food and Agriculture Organization Marine + Inland Aquaculture is becoming increasingly important Farmed Caught Food and Agriculture Organization of the United Nations
Aquaculture Issues Dependence on fish meal/oils Escape of non-native species Waste effluent (pollution of the environment) Diseases (and antibiotics used to treat them) Research, engineering, and development is helping to mitigate some of these problems
Making Informed Choices Both wild caught and farmed food sources have issues Some wild caught fisheries and aquaculture operations are better managed and more sustainable than others By being informed you can make better choices and minimize damage to the ecosystem
Informed Public
What you can do: Region-specific Consumer Guides