OCEAN 320 Lecture Notes - Marine Protected Area, Shifting Baseline, Continental Shelf
Unit 3B: How Much Has the Ecosystem Changed?
Daniel Pauly’s TED Talk: The ocean’s shifting baselines
• Charles Darwin
o Wrote that the Galapagos fish was “common;” now it is on the IUCN Red List
• Field work in Sakumo Lagoon, Ghana
o Lagoon had black chin tilapia, but was overfished; fish species shrunk to 5 cm
• RV Mutiara 4 in Semarang (Java), Indonesia
o Europeans impose industrial fishing on other smaller countries
o Caught mostly fish and animals from the bottom of the sea: 90% sponges and
other reef fish
o When we overfish, the reefs turn muddy and cannot stay fixed on the bottom of
the ocean; other animals were retrieved already dead from related complications
o Way of adjusting a baseline
• The shifting baseline syndrome (1995)
o Want to sustain “what is left” as best as possible; as baseline decreases, we hold
onto what little is left
• Fishing down marine food webs
o Baseline shrinks because what once was abundant becomes rare, and then we lose
rare species, so it doesn’t seem like a huge loss
o We don’t know past and we don’t trust non-scientific evidence (ie: sailor’s
observations)
o Marine protected areas can recreate the past; we can see the baselines (which has
shifted very very low)
• Simulating Visual Oceans
o Use movies/film to explain these shifting baselines to people who have no access
to marine protected areas
Counting the Last Fish
• Nova Scotia, Canada: used to have huge variety of fish, bow fishermen scrape the bottom
clean, often bringing up supporting substrates (sponges)
o Also catch last sharks, swordfish, tuna
o Population sizes are dwindling, many fish are captured before maturity
o Fishers must work farther off shores and in deeper waters to make quota
• 1982 UN’s Convention on the Law of the Sea: allows countries bordering the ocean to
claim exclusive economic zones reaching 200 nautical miles into open waters; includes
the highly productive continental shelves of ~200 m in depth where most fish live
o Ended fighting over fishing grounds, but placed responsibility for managing
marine fisheries on maritime countries
o US and Canadian governments have subsidized the growth of domestic fishing
fleets to supplant excluded foreign countries
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▪ Canada build new off-shore fleets to replace those nations pushed out by
convention; fleets are even larger and more modern than domestic, in-
shore fleets; fish year round, rather than seasonally
▪ Demand for fish makes countries seek agreements to allow foreign fleets
in waters that don’t belong to them; creates overfishing, as foreign fleets
have no incentive to preserve local marine resources long-term
o Convention and technological advancements (acoustic fish finder) temporarily
boost fish catches; by 1980’s, trend reversed despite China overreporting (trying
to meet political productivity increases)
• 2001: examine where catches differed significantly from those taken from similarly
productive waters at same depths and latitudes elsewhere
o Figures from Chinese waters much higher than predicted; 40% of deviations from
the statistical model
o When readjusted to include misrepresentations: concluded that world fish
landings have declined slowly since the late 1980’s, by ~700,000 metric tons a
year
o Other countries over/underreport too, but they usually cancel each other out
• Nations gather data in variety of ways (surveys, census, logbooks)
o In some countries (China) data is forwarded to national government offices;
throughout the processes, officials manipulate statistics to meet production
targets, which creates the huge gap
o Other countries have systems for cross-checking fish landings against
import/export data and info on local consumption
• “Fishing down the food web”
o Occurs when fishers deplete large predator fish at top of food chain (tuna,
swordfish) until they become rare and then target smaller species that would
usually be eaten by fish
o Position on food web is determined by size, anatomy of mouth parts and feeding
preferences
o Layers of food web (trophic levels) ranked according to how many steps they are
removed from primary producers at base of web (phytoplanktonic algae, TL 1)
o Phytoplankton eaten by zooplankton (TL 2); small fishes (sardines, herring,
anchovies) between 20-50 cm are TL3; table fish (cod, snapper, tuna, halibut) are
predators of small pelagics and have TL of 3.5-4.5 (not whole numbers bc they
consume prey on several trophic levels)
o First evidence of fishing down: in North Atlantic, off Patagonian coast of South
America, near Antarctica, Arabian Sea, parts of Africa and Australia; experienced
TL declines of 1 or greater between 1950-2000
o Conclusions based on analysis of global database of marine fish landings created
& maintained by UN Food & Ag Org; information is often inaccurate or not well
differentiated, so use global distribution of fish from FishBase and knowledge
about fishing patterns
find more resources at oneclass.com
find more resources at oneclass.com
