global fisheries and conservation l.
Skip this Video
Loading SlideShow in 5 Seconds..
Global fisheries and conservation PowerPoint Presentation
Download Presentation
Global fisheries and conservation

Loading in 2 Seconds...

play fullscreen
1 / 38

Global fisheries and conservation - PowerPoint PPT Presentation

  • Uploaded on

Global fisheries and conservation. Before moving on from fishes to the tetrapods, I want to devote some time to fishing. It is a sad fact that global fish stocks have been enormously depleted and in most places fish populations are a pale shadow of their former abundance.

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

PowerPoint Slideshow about 'Global fisheries and conservation' - hafwen

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
global fisheries and conservation
Global fisheries and conservation
  • Before moving on from fishes to the tetrapods, I want to devote some time to fishing.
  • It is a sad fact that global fish stocks have been enormously depleted and in most places fish populations are a pale shadow of their former abundance.
global fisheries and conservation2
Global fisheries and conservation
  • For example: Captain John Smith describing tributaries of the Chesapeake in 1608 “… in diverse places that abundance of fish lying so thicke with their heads above the water, as for want of nets we attempted to catch them with a frying pan, but we found it a bad instrument to catch fish with. Neither better fish more plenty or variety had any of us ever seene, in any place swimming in the water than in the Bay of the Chesapeack, but there not to be caught with frying pans.”
global fisheries and conservation3
Global fisheries and conservation
  • Captain John Smith again: Having grounded on an oyster bed in the Potomac as the tide was going out “…we spied many fishes lurking amongst the weeds on the sands, our captaine sporting himself to catch them by nailing them to the ground with his sword, set us all a fishing in that manner, by this devise, we tooke more in an houre than we all could eat.”
global fisheries and conservation4
Global fisheries and conservation
  • Clearly, a different level of fish abundance than we encounter today.
  • Similarly abundant numbers of fish were described in the waters off New England and eastern Canada.
the grand banks fishery
The Grand Banks fishery
  • John Cabot voyaged to Newfoundland in 1497. The Milanese ambassador to London reported what he had heard from Cabot about the fishing there: “they assert that the sea there is swarming with fish, which can be taken not only with the net, but in baskets let down with a stone, so that it sinks in the water. I have heard this Messer Cabot state so much.”
the grand banks fishery6
The Grand Banks fishery
  • Two centuries later Pierre de Charlevoix in 1719 described the Grand Banks of Newfoundland “What is called the great bank of Newfoundland … you find on it a prodigious quantity of shell-fish, with several other sorts of fishes of all sizes, most part of which serve for the common nourishment of the cod, the number of which seems to equal that of the grains of sand which cover this bank. For more than two centuries since, there have been loaded with them two to three hundred ships annually, notwithstanding the diminution is not perceivable.”
the grand banks fishery7
The Grand Banks fishery
  • The rich fishing grounds off the northeastern U.S. and eastern Canada result from a combination of factors.
  • The various banks (the Grand Banks, George’s Bank, Brown’s Bank and others) are deposits of moraine left there by glaciers.
the grand banks fishery8
The Grand Banks fishery
  • The water above them is relatively shallow (60-300 feet in most places) and they occur at the confluence of the cold nutrient rich northern Labrador current and the warm southern Gulf Stream.
  • The mixing of these currents combines warmth and nutrients to produce massive blooms of plankton that supported huge schools of mackerel and herring that in turn support cod and other predators.

The Grand Banks



George’s Bank and Brown’s Bank

the grand banks fishery11
The Grand Banks fishery
  • In 1992 the Canadian Government placed a two year moratorium on cod fishing, which was extended indefinitely and remains in place today. In 2003 the two main populations of Atlantic cod were added to Canada’s endangered species list.
  • In U.S. waters cod populations have similarly plummeted.
  • What happened? Industrial fishing happened.
the grand banks fishery12
The Grand Banks fishery
  • Up until the early 20th century, cod-fishing had been almost exclusively by schooners using hand lines but then steam trawlers were introduced to North America. With their greater fishing power the steam trawlers soon replaced the schooners and had become common by the 1920’s.
  • Around the same time fast-freezing technology was developed and the frozen fillet entered the marketplace.

Fishing schooner Olympic about 1911.


Norwegian Cod schooner 1930



Steam Trawler Bellerophon


the grand banks fishery16
The Grand Banks fishery
  • One of the first fish to be targeted by ships using the new technology was haddock.
  • Haddock freezes well (but salts poorly and previously had been thrown away by fishermen).
  • Huge spawning aggregations were discovered on the Georges Bank and heavily fished for.
  • Catches soared through the 1920’s peaking at 120,000 tonnes in 1929. [1 tonne is 1,000kg about 2,200 lbs]
the grand banks fishery17
The Grand Banks fishery
  • In 1930 an estimated 37 million haddock were landed in Boston. However, even more were discarded because small mesh nets caught fish indiscriminately and more than two juvenile haddock were discarded for each adult landed.
  • Not surprisingly, haddock numbers crashed falling to 28,000 tonnes by 1934. Landings of about 50,000 tonnes per year were sustained into the 1960’s but only because the fishermen began fishing in new waters.
the grand banks fishery18
The Grand Banks fishery
  • In the 1960’s fishing pressure increased immensely as distant-water fishing fleets from Europe moved in to fish (national fishing limits were only 3 miles).
  • Fleets from Britain, Spain, Portugal, Romania, France, West Germany, Poland, East Germany and Russia crowded into the fishing grounds.
the grand banks fishery19
The Grand Banks fishery
  • The European fishing fleets consisted of groups of factory trawlers supplying mother ships that processed the catch and these had immense fishing and processing capacity (thousands of tons a day) much greater than local fleets.
  • In an hour a single factory trawler could catch 200 tons of fish, twice as much as a 16th century ship could have caught in a whole season’s fishing.
the grand banks fishery20
The Grand Banks fishery
  • Onboard the mother ships, fish was machine-filleted and frozen or turned into fishmeal. These ships could fish in any kind of weather and stay at sea for months on end.
  • In 1965 the Soviet Union had 106 factory trawlers and 425 smaller trawlers supplying 30 mother ships and together these took 872,000 tonnes of fish [7x the peak annual haddock catch in 1929].

Russian factory trawler


the grand banks fishery22
The Grand Banks fishery
  • Fishing fleets were able to work cooperatively to exhaust aggregations of fish. When a concentration of fish was found (using the most sophisticated available search equipment) the trawlers would aggregate to fish it into oblivion before dispersing again to seek new schools.
the grand banks fishery23
The Grand Banks fishery
  • By 1974 more than 1,000 European vessels were fishing the banks. Their catch was more than 2 million tonnes, which was 3x the Canadian catch and 10x the New England catch.
  • Everything was taken--juvenile or adult, spawning or not, regardless of the future impact on stocks.
the grand banks fishery24
The Grand Banks fishery
  • Two Canadian fisheries scientists, Jeffrey Hutchings and Ransom Myers, have estimated that about eight million tons [7.25 million tonnes] of northern cod were caught between Cabot's arrival in 1497 and 1750, over the course of 25 to 40 cod generations.
  • Factory trawlers took the same amount in only 15 years, a period less than the lifetime of a single cod.
the grand banks fishery25
The Grand Banks fishery
  • Catches of fish far exceeded sustainable yields and fisheries began to collapse. The haddock fishery in the Gulf of Maine collapsed in the 1970’s.
  • In 1977 following Iceland’s lead the U.S. and Canada declared a 200-mile limit and excluded the foreign fishing boats.
the grand banks fishery26
The Grand Banks fishery
  • But instead of attempting to hold down fishing efforts both countries expanded their fleets.
  • Between 1977 and 1982 the number of New England trawlers increased from 825 to more than 1,400 boats. Domestic overfishing replaced foreign overfishing.
the grand banks fishery27
The Grand Banks fishery
  • By the early 1980’s fishing catches had risen to twice the level that was sustainable, but by investing in more sophisticated equipment fishermen could still make a living.
  • However, at this point fishermen were killing 60-80% of all the cod, haddock and flounder in the Gulf of Maine every year.
the grand banks fishery28
The Grand Banks fishery
  • In the mid-1980’s U.S. fisheries scientists saw the collapse coming and pushed for major cuts in fish landings, but the fishing industry resisted cuts and it wasn’t until the mid 1990’s that reductions were imposed.
the grand banks fishery29
The Grand Banks fishery
  • A similar process played out in Canadian waters. Canadian fisheries scientists overestimated sustainable yields of cod based on a series of bad assumptions. In the 1980’s 5x times as many cod were being taken as should have been removed.
  • Calls to cut back the fishery were ignored and by 1992 the fishery was finished.
the grand banks fishery30
The Grand Banks fishery
  • Estimates of the size of the original population suggest that there were about 7 million tonnes of cod off the Atlantic coast of Canada in 1505.
  • By 1992 the estimate was 22,000 tonnes (<1/3 of 1% of the original population.).
the grand banks fishery31
The Grand Banks fishery
  • Cod stocks are showing signs of recovery. In 2010 cod stocks in the Grand Banks were estimated to have increased 69% since 2007.
  • However, that level is still only about 10% of 1960’s levels.
the grand banks fishery32
The Grand Banks fishery
  • There is some debate about why stock recovery is slow.
  • However, habitat transformation almost certainly has played a major role.
  • Before trawling, the sea bottom on the banks was not a layer of mud. Rocks outcrops, boulders and stones provided structure, places for young fish to hide and rich communities of sponges, crabs, mussels, anemones, tube worms and other invertebrates flourished.
the grand banks fishery33
The Grand Banks fishery
  • A bottom trawler’s net is held open by large metal doors weighing thousands of pounds and the bottom of the bag is kept on the seabed by a weighted metal cable. Each pass of a net drags boulders and rocks, buries and crushes invertebrates and leaves behind a virtual moonscape.
  • Bottom trawling is the ecological equivalent of clear-cutting, but carried out on a much more massive scale and out of view.



Sea bottom habitat in Canada (left) and Australia (right)

before trawling (above) and after (below).

trawl net damage
Trawl net damage
the grand banks fishery37
The Grand Banks fishery
  • After years of bottom trawling the sea bed has been converted from a rich diverse ecosystem to a sterile one.
  • Unfortunately, the tragedy of the cod fishery is just one example of failed fisheries and the pattern has been repeated worldwide.
suggested additional reading
Suggested additional reading
  • “The end of the line” Charles Clover
  • “The unnatural history of the sea” Callum Roberts
  • “The empty ocean” Richard Ellis
  • “Four fish: the future of the last wild food” Paul Greenberg