Fisheries conservation.PPT

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					     World Dependence on Fish
• Fish account for 15% of world protein supply
• One billion people rely on fish as their main source of animal
• Dependence on fish is higher in coastal areas
• Some small island nations depend on fish almost exclusively
• 95 million tons of fish production are harvested directly from wild
  populations (salt and fresh water)
• Another 35 million tons are harvested from aquaculture
• Most fish are used directly for food
                – although increasingly fish provide animals feeds etc
• 35 million people are directly employed in fishing
• International trade in fish products was $US 55 billion which is
  greater than the individual gross domestic product of over 70% of
  the world’s nations

                    [Food and Agriculture Organisation of the United Nations (2002)]
Major depletion of world fish stocks
•A recent paper in PLOS Biology reviews some of the
current problems with the fishing industry and fish stocks
around the world [Gewin (2004)]
Key points cited in the paper include:

A recent Food and Agriculture Organisation (FAO) states

“28% of global [fish] stocks are significantly
depleted or overexploited,
and 47% are either fully exploited or meet the
target maximum sustainable yields.
Only 24% of global [fish] stocks are either
under- or moderately exploited.”
• “Most of the line fish around the coast of
South Africa are depleted to 5-15% of
pristine levels”

•“[Asian] commercial fish species have been
depleted to 10-30% of what they were 30-40
years ago.”

•“FAO estimates that roughly one-quarter of
the marine commercial catch destined for
human consumption                        –
some 18-40 million metric tons of fish -
is thrown back into the sea, a harvest catch
that is never utilized or counted.”
•“It is estimated that the illegal, unreported
and unregulated (IUU) fisheries surpass
allowed fishing quotas by 300%”.

•“Even sustainable harvest rates reduce fish
populations quickly. If the goal is a
productive fishery, we’re automatically
talking about up to a 70% decline across the

•Atlantic cod have declined by almost 90%
“Atlantic cod in Canadian waters suffered a
total population collapse and are now on
Canada’s endangered species list.”
•“By the time a significant declining trend has
been detected by traditional catch
assessments, [fish] stocks are likely to be in
poor shape, if not already depleted.”

•“The global ocean has lost more than 90% of
large predatory fishes, such as marlin, sharks
and rays.”

•“Based on the available information, it is not
unusual for fish populations to show little or
no recovery even after 15 years [after
exploitation ceases].”
•“ In the case of Antarctic species, some
overexploited populations remain at less than
5% pre-exploitation abundance after 30 years.”

The paper does however have some positive
• “In a review of 89 studies of [Marine
Protected Areas]…the average number of fish
inside a reserve increases between 60% -and
        Other signs of decline
• Industrialized fisheries typically reduce
  community biomass by 80% within 15 years
  of exploitation
• 55 species of marine fish have lost at least
  part of their geographical range
• 3 species of marine fish have gone extinct
  over the past two centuries
• An analysis of 230 fish populations showed
  an 83% reduction from known historic levels.
  Researchers point out that ‘known historic
  levels’ often underestimates true historic
  population [Hutchings and Reynolds (2004)]
       Historical Populations
• Humans have been disturbing marine
  ecosystems since they first learned how to

• There have been major changes in the
  structure and nature of coastal marine
  ecosystems over many centuries

• Overfishing and ecological extinction
  predate and precondition modern studies on
  marine ecosystems and recent collapses of
  fish stocks etc.
                                  Jackson et al. (2001)
         Historical Populations
• Fisheries management based on recent data
  only may be misleading

  e.g. the earliest data on surveys on fish
  stocks may already be on over exploited

• Jackson et al. (2001) suggest using historical
  data measured in centuries rather than
  decades to:
  – Can provide the missing baseline for future restoration efforts
  – Raise the possibility that many more marine ecosystems may be
    vulnerable to collapse in the near future

                                                  Jackson et al. (2001)
Jackson et al. (2001)
          Are our estimates correct?
                 An example
• In 1996, Red Snapper was put under strict management
  in the U.S. after overexploitation
• This created an incentive to substitute less valuable
  fish on the Red Snapper market
• A recent study showed that three-quarters of the fish
  sold in the United States as ‘red snapper’ belonged to
  another species Marko (2004)
• It’s unclear where the mislabelling occurred but could
  cause incorrect estimates of stock size if it influences
  the reporting of catch data Marko (2004)
• It also creates an impression among the public that
  there is a plentiful supply of that fish
• And finally, the substituted fish may be not monitored
  causing a large scale but unidentified exploitation of
  the substitute species
   Fishing Down the Food Web
• The mean trophic level of commercial
  species declined from 1950 to 1994

• This reflects a gradual transition from:

  long-lived, high trophic level, piscivorous
  (fish eating) bottom fish

  toward short-lived, low trophic level
  invertebrates and planktivorous pelagic fish
                                 [Pauly et al. (1998)]
  Fishing Down the Food Web
• Large predatory fish biomass today is
  estimated to be only about 10% of pre-
  industrial levels
  (sharks, skates, rays, and marlin)
                     [Myers and Worm (2003)]

• These effects are most pronounced in the
  Northern Hemisphere

• This has serious consequences for
                                   [Pauly et al. (1998)]
Fishing Down the Food Web
    Recovery from Exploitation
• Various studies suggest that fish do not
  recover rapidly from overexploitation

• Research for 90 fish stocks revealed that 15
  years after collapse, 40% of gadids (haddock,
  cod, and flatfishes) had little, if any, recovery

• Only 12% exhibited full recovery
  – All were clupeids (herring and related species)
  – attributable to earlier maturity, reduced vulnerability to incidental
    exploitation or bycatch, and possibly reduced probability of
    habitat destruction by fishing gear due to pelagic lifestyle
                       [Hutchings (2000); Hutchings and Reynolds (2004)]
   Recovery from Exploitation

• It is not unusual for populations
  that have declined more than 60%
 (over 15 years)
 to exhibit little or no recovery as
 much as 15 years later
             [Hutchings (2000); Hutchings and Reynolds (2004)]
  Problems that Prevent Recovery
• slow response by managers to address

• inability to reduce anthropogenic
  removals/mortality to zero (e.g., by-catch

• public/user-group perceptions that are
  unsupported by science that delay or alter the
  nature of the managerial response;

• the allee effect
  (small population sizes lead to proportionally
  increased rates of predation, reduced mating success
  and reduced fertility);
                              [Hutchings and Reynolds (2004)]
  Problems that Prevent Recovery
• reduced numbers of adults can lead to
  increased predation of juveniles and inter-
  specific competition and predation;

• reduced abundance of top predators causing
  a shift in ecosystems that may impact

• selective harvesting - the largest most
  successful animals are targeted whereas
  animals with lower fitness stay in the
  [ Hutchings and Reynolds (2004)]
Problems that Prevent Recovery

The impacts of inappropriate fisheries
management are illustrated by the Canadian
stock of Atlantic cod –

within 30 years the stock declined by 99.9%
in some areas.
                        [ Hutchings and Reynolds (2004)]
  What does recovery require?
• Reductions in fishing are necessary, but
  not always sufficient, for recovery

• It is near impossible to reduce fishing
  mortality to zero because of bycatch

• Closed fisheries must remain closed until
  a target level is reached
  -rather than being reopened at the first
  sign of population growth
 Difficulties in detecting decline
• Researchers in the North Sea investigated the
  statistical power to detect declines in fish

• They discovered that the ability to detect a
  decline in fisheries with a period less than
  decades was low

• Also the ability to detect declines that could
  prompt listing under the IUCN Red Lists was
  also low                   [Maxwell & Jennings (2005)]
Difficulties in detecting decline and
• Also at least 5-10 years of dedicated
  monitoring needed to tell if a population has

• Conservationists cannot rely on statistical
  certainty to show that a population is in
  if a decline is statistically recognizable it may
  be too late
• This reinforces the need for the
  precautionary principle        Maxwell and Jennings (2005)
      The Role of Economics
• Many global fisheries overshot their
  economic threshold some time in the past

 - i.e. that have become financially
 unprofitable because of:
      -declining fish numbers,
      -declining value of fish and
      - expense of harvesting

 But government subsidies have allowed
 fishing to continue so that the “ecological”
 threshold has now also been exceeded
      The Role of Economics
• A consequence of the subsidies is that
  energy efficiency is plummeting
• On average, for every metric ton of fuel
  consumed, only 1.5 metric tons of fish are

• Some fisheries are orders of magnitude

• For example, catching a metric ton of shrimp
  may cost 100 metric tons of fuel.
      The Role of Economics
• But governments keep subsidizing large
  scale fishing operations and vessels,
  with better technology to find fish and

• Small scale operations would be more
  efficient and less damaging to fish stocks
  and the environment

• But big companies are better are lobbying
   Atlantic Cod
     Hutchings ( 2004b)

• In the early 1960s, Gadus morhua extended
  from southeastern Labrador south to the
  northern half of the Grand Bank
• The population numbered almost two billion
  breeding individuals and comprised 75% to
  80% of Canada’s cod
• Landings were highest at 800,000 tons in 1968
• In 1976, establishment of the EEZ (Exclusive
  Economic Zone) excluded foreign ships from the
  cod fishery and reduced total landings
• Through the 1980’s, landings were 250,000
  Atlantic Cod
• Since 1983, the population declined more
  than 99.9%

• The primary cause for decline was over-

• Significant reductions in age and size at
  maturity were brought on by fishery induced
  genetic changes
  - due to catches there was selective pressure
  for smaller faster maturing animals
                                [Olsen et al. (2004)]
   Atlantic Cod

• The directed commercial fishery was closed
  in 1992

• The fishery remains open for individual
  sustenance needs under strict controls

• In 2001, two out of every three cod older than
  1 year were still being caught by the fishery
Atlantic Cod
   Atlantic Cod
• Main threats to recovery include:
  – Directed fishing
  – Non-directed fishing
  – Bycatch
• Other Threats:
  – Altered biological ecosystems
  – Changes to the magnitude and types of
    species interactions
  – Fishery-induced changes to life history
Peruvian Anchoveta
         Clark (1976)

• After WWII, a large anchoveta (Engraulis ringens)
  market developed in the Peru upwelling
• The anchovy catch doubled each year from
  100,000 tons in 1955 to 8 million tons in 1965

• The first fishery assessment (1965) showed
  the stock was fully exploited
• The catch was limited to this amount for the
  next few seasons.
Peruvian Anchoveta
        Clark (1976)

• Later studies showed the stock could yield
  10 million tons per year so the quota was
  raised in 1968

• By 1971, the fishery appeared to be a model
  of successful management

• In 1972, recruitment failed and a severe El
  Nino event crowded the adults near the coast
  where they were subject to heavy fishing and
  the fishery collapsed
 Peruvian Anchoveta
• Subsequent research showed that in the Pacific, air and
  ocean temperatures, atmospheric carbon dioxide, fish
  landings, and the productivity of coastal and open ocean
  ecosystems have varied over periods of about 50 years.

• Large-scale changes in ocean temperatures result in
  fluctuations between a warm sardine regime and a cool
  anchovy regime with each regime lasting approximately 25

• In the 20th century, there were:
    – cool phases 1900 to 1925, 1950 to 1975
    – warm phases 1925 to 1950, 1975 to the mid-1990s

• This matches up perfectly with the collapse of the
  California sardine fishery in the early 1950’s
                                                 [Chavez et al. (2003)]
          Lessons Learned
• Large-scale, naturally occurring variations
  must be taken into account when
  considering human-induced climate
  change and the management of ocean
  living resources

• Sustainability requires that each system
  falls within its normal range of natural
          Lessons Learned
• Commercial species cannot be managed
  in isolation from the ecosystems that they

• Humans must be considered part of
  ecosystems and the biosphere, subject to
  the same natural laws and benefiting from
  the same supporting services as other
 Damage caused by fishing gear

• Although the impacts of over-fishing
  are a cause for concern, damage
  caused by fishing gear on benthic
  marine species and habitats are also a
  major issue.

• Generally mobile, bottom-fishing gears
  are considered to cause more habitat
  damage then pelagic gear.
                            [Chuenpagdee et al. (2003)]
 Damage caused by fishing gear
• It is suggested that ecosystem-based
  fisheries management include shifting from
  damaging to non-damaging fishing gear
• In cases where collateral impacts cannot be
  addressed by alternative fishing gears and
  practices, implementing closed areas is the
  only way to protect health ocean ecosystems
  and species.
• It has been suggested “emphasis be given to
 educating both the fishing industry and the
 public about the importance of the
 ecosystem impacts of fishing and the need for
 ecologically friendly practices.” [Chuenpagdee et al. (2003)]
        By-catch and conflict
• Incidental by-catch discarded after capture
  (as much as ¼ the total catch = 18-40
  million tons!)
• Affects on predatory fishes, turtles, birds
  and mammals

• Also as available fish stocks for human
  use decrease, control of natural predators
  causes conservation management
Human impacts on ecosystems may
  be more severe than previously
Roberts (2003) discusses five major shifts in perspective
   “that reveal [human] impacts [on ocean ecosystems] to
   be more severe and persistent than previously
   appreciated”. Theses include:
 (1) Historical analyses indicate that “the global
   expansion of European nations across the planet
   caused a large scale loss of marine megafauna.”
   Also in the past century the “expansion of industrial
   scale fishing has continued the process, massively
   reducing the biomass of exploited species.”
(2) “Once depleted we are finding that populations
   rarely rebound rapidly, contrary to a widespread
   belief in greater resilience of marine compared to
   terrestrial species”.
(3) “Marine ecosystems are being shifted into alternative
   states that are less desirable from the human
   perspective.” Moreover, “it could be difficult, or
   impossible in some cases, to reverse impacts once
(4) There is a high risk of extinction for many marine
   species, and shallow water marine habitat loss is
   “proceeding as rapidly as on land”, and the
   distribution and ecology of many shallow marine
   species make them “highly susceptible to
(5) Technological advances are allowing exploitation of
   deep sea resources and inevitable collateral habitat

  To reverse these trends, to protect biodiversity and to
  stimulate the recovery of the world’s fisheries the
  Roberts suggests the instigation of “large-scale
  networks of marine reserves that are off limits to
  damaging activities and fishing.”
                                      [Roberts (2003)]
   Re-Thinking Fisheries Management
Gewin (2004) discusses the rising issue that
uncertainty needs to be incorporated into
fisheries management models
(i.e. there is a lot that we don’t know)
Currently this is rarely into account and may
be endangering stocks.

Also environmental changes can have major
impacts fish stocks (e.g. Peruvian anchoveta)
and this is rarely taken into consideration.
   Re-Thinking Fisheries Management

Likewise managers do not recognise how
competitors can overtake a depleted species
niche making recovery difficult.

Finally, Gewin notes that fisheries managers
in the northeast Atlantic data are collected on
only 55 of 250 species – issues that make full
ecosystem-based management difficult at
                                       Gewin (2004)
              IUCN Resolution
At the 3rd IUCN Congress, a resolution on sustainable
   management of the High Seas was passed that called
• Members to implement the FAO Code of Conduct for
   Responsible Fishing and to enforce measures from
   several international agreements to ensure sustainable
   use of High Seas marine resources;
• The development of new international mechanisms
   (via UNCLOS) for the governance, management,
   protection and restoration of marine biodiversity and
   productivity in the High Seas;
• The taking of immediate action to eliminate illegal,
   unreported and unregulated fishing;
• An upgrading of regional fisheries management
   organisations to adopt procedures that take into account
   ecosystem-based, precautionary approaches to
   minimise impacts on marine ecosystems;
              IUCN Resolution
• Investigation into ways to enforce actions on flag states
  that fail to control domestically registered vessels;
• Establish a global network of marine protected areas
  beyond national jurisdictions and to develop scientific
  and legal bases for their establishment, by 2012;
• Support of scientific research into high seas
  biodiversity and ecological processes to ensure the
  sustainability of human activities.

  (SOURCE: IUCN 2004. CGR3. RES057-REV1. Conservation and
  Sustainable Management of High Seas Biodiversity. 3rd IUCN
  Congress, 17-25 November 2004, Bangkok, Thailand)
But one scientist is quoted in Gewin (2004)

  “…it’s naïve to think that modifying and
 improving models will necessarily lead to
 improved natural resource management.”

             Another stated:

“The big mistake is suggesting that you can
manage fish stocks….we can only manage
             human activity.”
•   Chavez, F.P., J. Ryan, S.E. Lluch-Cota, and M. Niquen C. 2003. From anchovies
    to sardines and back: a multidecadal change in the Pacific ocean. Science
•   Chuenpagdee, R., Morgan, L.E., Maxwell, S.M., Norse, E.A. and Pauly, D. 2003.
    Shifting gears: assessing collateral impacts of fishing methods in US waters.
    Front. Ecol. Environ. 1:517-524.
•   Clark, W.G. 1976. The lessons of the Peruvian anchoveta fishery. California
    Cooperative Oceanic Fisheries Investigations. 19:57-63
•   Food and Agriculture Organisation of the United Nations. 2002. The State of
    World Fisheries and Aquaculture. FAO Fisheries Department. FAO Rome.
•   Gewin, V. 2004. Troubled waters: the future of global fisheries. PLoS Biol.
•   Hutchings, J.A. 2000. Collapse and Recovery of Marine Fishes. Nature 406:882-
•   Hutchings, J.A. 2004. Marine fish population collapses: consequences for
    recovery and extinction risk. Bioscience 5: 297-309
•   Hutchings, J.A. 2004b. The cod that got away. Nature 428:889-89.
•   Jackson, J.B., M.X. Kirby, W.H. Berger, K.A. Bjorndal, L.W. Botsford, B.J.
    Bourque, R.H. Bradbury, R. Cooke, J. Erlandson, J.A. Estes, T.P. Hughes, S.
    Kidwell, C.B. Lange, H.S. Lenihan, J.M. Pandolfi, C.H. Peterson, R.S. Steneck,
    M.J. Tegner, R.R. Warner. 2001. Historical Overfishing and the Recent Collapse
    of Coastal Ecosystems. Science 293:629-638
•   Marko, P.B., S.C. Lee, A.M. Rice, J.M. Gramling, T.M. Fitzhenry, J.S. McAlister,
    G.R. Harper, and A.L. Moran. 2004. Mislabelling of a depleted reef fish. Nature
    430: 309-310
•   Olsen, E.M., Heino, M., Lilly, G.R., Morgan, M.J., Brattey, J. Ernande, B.,
    Dieckmann, U. 2004. Maturation trends indicative of rapid evolution preceeded
    the collapse of northern cod. Nature 428: 932-935.
•   Pauly, D., V. Christensen, J. Dalsgaard, R. Froese, F. Torres Jr. 1998. Fishing
    down marine food webs. Science 279:860-863
•   Maxwell, D. and Jennings, S. 2005. Power of monitoring programmes to detect
    decline and recovery of rare and vulnerable fish. Journal of Applied Ecology
    42: 25-37.
•   Myers, R.A. and B. Worm. 2003. Rapid worldwide depletion of predatory fish
    communities. Nature 423:280-283
•   Roberts, C.M. 2003. Our shifting perspectives on the oceans. Oryx 37:166-177.

•   Thanks to Sue Heath for many of the slides

See also chapters in:
Norse & Crowder (2005) Marine Conservation Biology. Island Press.

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