Living fishes
Theliving fishes (not a monophyletic
group) include:
the jawless fishes (e.g. lampeys),
cartilaginous fishes (e.g. sharks and rays),
bony, ray-finned fishes (most of the bony
fishes such as trout, perch, pike, carp, etc)
and
the bony, lobe-finned fishes (e.g. lungfishes,
coelacanth).
16.1
16.2
Bony fishes: Osteichthyes
The term osteichthyes does not describe a
monophyletic group, but is a term of
convenience to describe the fishes whose
skeletons are made of bone that replaces
cartilage during embryonic development.
There are two classes the Actinopterygii
(the ray-finned fishes) and the
Sarcopterygii (the lobe-finned fishes)
General characteristics of bony fish
Skeleton made of bone of endochondral
origin (derived from cartilage).
Paired and median fins supported by
dermal rays.
Respiration mainly by gills. Gills covered
with operculum.
Swim bladder often present.
Complex nervous, circulatory and
excretory systems present
Class Actinopterygii (ray-finned
fishes)
Thisis by far the larger of the two living
classes of fishes with more than 27,000
species.
Includes probably every fish you can think
of. E.g. salmon, cod, herring, tuna, marlin,
pike, sardine, clownfish, goldfish.
Divisions of Actinopterygii
The Actinopterygii are divided into two groups
Palaeonisciformes (formerly known as the
“chondrosteans”), which includes the relic species just
mentioned.
Neopterygii, which includes the most derived and
most recent group of ray-finned fishes the Teleostei
and a number of primitive species including the gars
and bowfins. These primitive Neopterygii were once
grouped as the “holosteans.”
Ancestralray finned fishes in the Devonian
were small and heavily armored with
ganoid scales (thick, bony, non-
overlapping, relatively inflexible scales)
and heterocercal tails (shaped like that of
modern sharks).
Palaeonisciformes
“Chondrosteans”
A few relic species still possess such
characteristics.
These include sturgeon and paddlefish
which are included in the
Acipenseriformes and the bichirs
(Polypteriformes).
Palaeonisciformes
Therelatively few surviving
Palaeonisciformes are the remnant of
what was once a much more diverse
group.
Palaeonisciformeswere the first bony
fishes and were most diverse in the
Carboniferous and Permian.
Palaeonisciformes
Extinctpalaeoniscids were mostly small <
0.5m with a fusiform shape which
suggests they were active foragers.
They were covered with small diamond-
shaped scales.
The base of each scale was made of
bone, the middle of dentin and the surface
with an enamel-like substance called
ganoine. Hence the name ganoid scales.
Sturgeons and Paddlefish
These lack ganoid scales except for in
sturgeons the rows of enlarged scales that
run along the sides of the body.
The skeleton is almost entirely
cartilaginous, which has resulted from the
loss of mineralization.
Paddlefish
The two species of Paddlefish are found in fresh
water in North America and China. The Chinese
species is nearly extinct.
About 2m long paddlefish possess an elongated
flattened rostrum, which is believed to be used
to detect tiny, electric fields.
The North American paddlefish is a planktivore.
http://blocs.xtec.cat/englishcornersallaresipla/files/2008/01/paddlefish2.jpg
Sturgeons
There are 24 species of sturgeons and all are
large fish that reach up to 6m in length.
They have a protrusible jaw (evolved
independently of the teleosts) which they use for
suction feeding.
They are commercially important for their meat,
but especially their eggs (caviar).
http://www.fishingmagic.com/news/images/Canada_Record_Sturgeon_lg.jpg
http://fish.dnr.cornell.edu/nyfish/Acipenseridae/shortnose_sturgeon.jpg
http://cordonnoir.com/images/Caviar_fresh.jpg
Bichirs
There are 11 species of bichir and they are
considered the most primitive surviving group of
the ray-finned fishes.
They are heavily armored with dermal bone and
a thick layer of ganoid scales.
Occur in swamps and streams in Africa and
have a swim bladder that acts like a paired
ventral lung. They will drown if unable to gulp
air at the surface.
Armored Bichir
http://www.aquarticles.com/images/Gallo/Armoured%20bichir%202.gif
http://www.fbas.co.uk/Bichir.jpg
Bichirs
Because bichirs have paired fleshy
pectoral fins and lungs they were formerly
classified with the lungfishes, but are now
considered to have evolved these traits
independently.
Neopterygii: “holosteans”
There are two genera of primitive Neopterygians
that were previously grouped together as
holosteans.
Both have more flexible jaws than Palaoniscids,
but less flexible than those of more advanced
Neopterygians.
These are the seven species of gars
(Lepisosteiformes) and the single species of
bowfin (Amiiformes).
Gars
Garsare medium to large (1-4m)
predatory fish with a distinctive elongated
body and long jaws.
They have hard, interlocking, multilayered
ganoid scales which provide excellent
protection and are similar to the scales of
many extinct Paleozoic and Mesozic
actinoptrygians.
http://animals.nationalgeographic.com/staticfiles/NGS/
Shared/StaticFiles/animals/images/primary/gar.jpg
Longnose gar
http://www.biokids.umich.edu/files/12296/gar_large.jpg
Bowfin
There is only one species of bowfin.
Its scales are of a single layer of bone as
in teleosts, but the caudal fin is
asymmetric and similar to that of more
primitive fishes.
Bowfin
http://pond.dnr.cornell.edu/nyfish/Amiidae/bowfin.jpg
Teleosts
The vast majority of modern fishes are
“teleosts.”
They have replaced the heavy armored
scales of their ancestors with much lighter
more flexible scales that overlap each
other and also have evolved homocercal
symmetrical tails.
Teleost characters
Homocercal tail
Circular scales without ganoine
Ossified vertebrae
Swim bladder
Skull with complex jaw mobility
Teleost classification
How the Neopterygii should be subdivided
differs greatly from authority to authority.
We will use the text’s division of the
teleosts into three large groups:
Teleostei
Euteleostei
Acanthopterygii
Diversity of bony fishes: Teleostei
There are three major clades of the Teleostei
Osteoglossomorpha: [greek bony tongue]. About 220
species of tropical freshwater fish. Includes from the
Amazon Osteoglossum or Arawana, and Arapaima the
largest purely freshwater fish (regularly 3m long, but up
to 4.5 m).
Also includes the African elephant nose fish, which are
bottom feeders and that use weak electric signals to
communicate with each other
Arawana
http://media-2.web.britannica.com/eb-media/28/117528-004-6B4BBA33.jpg
Arapaima
http://www.petfishtalk.com/rss_feeds/images/080326_arapaima_1.jpg
Elephant nose fish
http://images.google.com/imgres?imgurl=http://www.bio.davidson.edu/people/
midorcas/animalphysiology/websites/2003/Wilson/cfunspics/
elephant_nose.jpg&imgrefurl=http://www.bio.davidson.edu/people/midorcas/
animalphysiology/websites/2003/Wilson/
GalONE.htm&usg=__yE31La06_D121J4Yga5NHWknr5Y=&h=467&w=1458&sz
=57&hl=en&start=3&tbnid=xQ3Vx636CuW21M:&tbnh=48&tbnw=150&prev=/
images%3Fq%3Delephant%2Bfish%26gbv%3D2%26hl%3Den%26sa%3DG
Teleostei: Elopomorpha
Elopomorpha: includes tarpons,
bonefishes, and eels.
Specializedleptocephalous [Greek small
headed] larvae are a unique feature of the
group. The larvae spend a long time adrift
on the ocean being moved by ocean
currents.
Bonefish
http://www.islaculebra.com/puerto-rico/fishing.html
Tarpon
http://www.wildernessaccess.com/images/
fishn/Tarpon-FISH-Justin-
S-America-Venezuela-Los-Rogos.jpg
Eels
Mostelopomorphs are eel-like and marine,
but some tolerate freshwater.
The American eel has a very unusual life-
cycle. The eels grow to sexual maturity in
rivers and streams (taking 10 years or
more) and then migrate downriver into the
ocean to breed. (They are catadramous.)
Eels
They swim to the Sargasso Sea (an area of the
North Atlantic between the Azores and West
Indies) where they apparently spawn and die,
presumably at depth.
Eggs and larvae float to the surface and drift on
the currents until they reach the near the coast.
Then they transform into miniature eels and
travel up rivers to mature.
http://www.richardcorfield.com/assets/images/silent_landscape/sargasso.jpg
American Eel
http://www.peacefulparks.org/800x600/eels/
Anguilla-rostrata-2.jpg
Eel larvae
http://media-2.web.britannica.com/eb-media/17/54217-004-411C3896.gif
Eels
European eels also spawn in the Sargasso Sea.
Their larvae travel on clockwise currents mainly
of the Gulf Stream and are distributed to North
Africa, Northern Europe, the Mediterranean and
as far as the Black Sea.
Because they drift in cooler waters European
eels grow more slowly than American eels.
Development is slowed less than growth
however, and as a result European eels have
more vertebrae than American eels.
Teleostei: Clupeomorpha
Are a commercially very important group of
about 360 species of marine schooling, silvery
fishes.
They include herring, shad, anchovies and
sardines.
They feed on plankton which they gather using a
specialized mouth and gill-straining apparatus.
Herring
http://pond.dnr.cornell.edu/nyfish/clupeidae/blueback_herring.jpg
Euteleostei
The next major division of the teleosts contains
about 10,000 species.
There are four major groups of the Euteleostei
Ostariophysi: carp, catfish, piranhas: about 7,900
species
Salmoniforms: trout, salmon and relatives: about 366
species
Paracanthopterygii: cod and anglerfishes about 1,300
species.
“Stem Neoteleosts” not a monophyletic group, but
includes just over 900 species of lanternfishes and
relatives.
Euteleostei: Ostariophysi
Ostariophysi (from Greek for bone and
bladder).
Representabout 30% of all living fishes,
about 6500 species.
Displayvery diverse traits, but many have
protrusible jaws and pharyngeal teeth act
as second jaws.
Euteleostei: Ostariophysi
The group possesses two unique derived
features: alarm substances in the skin and the
Weberian apparatus.
When the skin is damaged, pheromones are
released into the water and these stimulate a
fright reaction in other members of the species
and other ostariophysians. In response, they
may quickly seek cover or school together.
Weberian Apparatus
Weberian apparatus: The name ostariophysian
(Greek bone and bladder) refers to a series of
small bones that connect the swim bladder with
the inner ear.
The Weberian apparatus greatly enhances
hearing in these fish and as a result they are
more sensitive to sounds and can hear a wider
range of sounds than other fishes.
Weberian apparatus
When sound waves strike the swimbladder it
vibrates.
A bone (the tripus) in contact with the swim
bladder then conducts this vibration via
ligaments to two other bones, the second of
which moves and compresses a section of the
inner ear against a fourth bone.
This fourth bone (the claustrum) then stimulates
the auditory region of the inner ear.
Weberian apparatus:
http://www.aqua.org.il/pic/Articles/CatFish/12.JPG
Euteleostei: Ostariophysi
The Euteleostei: Ostariophysi includes
piranhas, tetras, carp and minnows, and
catfishes.
Piranha
http://blogs.westword.com/latestword/
piranha.jpg
Carp
http://www.naturephoto-cz.com/photos/
others/carp-20524.jpg
Euteleostei: Salmoniforms
The group includes the esocid and salmonid
fishes.
The salmonids include salmon and trout, which
include many commercially important species.
Many species of salmon are anadromous and
spend their adult lives at sea, but return to breed
in freshwater.
Euteleostei: Salmoniforms
Troutare close relatives of salmon, but
usually live their entire lives in freshwater.
and trout are important
Salmon
commercial and recreational species.
Rainbow Trout:
http://animals.nationalgeographic.com/
staticfiles/NGS/Shared/StaticFiles/
animals/images/primary/rainbow-trout.jpg
Coho Salmon
http://bullsheet.files.wordpress.com/2008/10/coho-salmon.jpg
Euteleostei: Salmoniforms
The esocids are relatives of the salmonids and
among the most primitive of euteleosteans.
They include pike, muskellunge, pickerels and
relatives.
These fish (which superficially resemble gars)
are voracious stealth-hunting predators and
important freshwater game fish.
Northern Pike
http://www.naturephoto-cz.com/photos/others/northern-pike-20529.jpg
Muskellunge
http://www.rudybenner.com/Cochrane%20District%20Scuba%20Divers_files/
Muskellunge.jpg
Euteleostei: Paracanthopterygii
Includesabout 1,340 species of cod,
toadfish and anglerfish.
Cod and their relatives (including pollock
and haddock) are cold water marine fishes
and the basis of some of the most
historically important marine fisheries.
Atlantic Cod:
http://www.codgen.olsvik.info/Images/Cod7.jpg
Anglerfishes
Anglerfishes are named for their method of foraging
which involves using a lure to attract fish close to them.
The lure is a modified spine of the anterior dorsal fin and
can be wiggled like a prey item.
In deep sea anglerfish the lure contains bioluminescent
bacteria that help attract prey from a distance.
Some bottom-dwelling anglerfish depend on camouflage
and these fish have arm-like pectoral fins that they use
to move long the bottom.
Anglerfish
http://scribalterror.blogs.com/scribal_terror/images/2007/06/17/angler_fish.jpg
Black devil Anglerfish
http://oceanexplorer.noaa.gov/explorations/04deepscope/background/
deeplight/media/fig3b_600.jpg
Euteleostei: “Stem Neoteleosts”
About 916 species of lanternfishes and
their relatives.
Barnard's lanternfish, Symbolophorus barnardi
http://www.austmus.gov.au/fishes/faq/images/sbarnardi2.jpg
Lantern Fish photophores
http://people.whitman.edu/~yancey/lanternventral.jpg
Lanternfish
The lanternfish is a common resident of the
upper portions of the deep-sea. It has a series
of light-producing organs along its body,
especially the belly.
The photophores can vary their intensity and the
fish can tailor the illumination to break up its
shadow and make it less visible to predators.
The photophores also appear to be used to
attract mates.
Acanthopterygii
Includes two major groups:
Atherinomorpha: More than 1,600 species of silversides,
killifishes, grunions, flying fish and relatives.
These are mostly small silvery fish that are surface
feeders.
There are about 50 species of flying fish (mostly tropical)
that are members of the Atherinomorpha and they use
their enlarged pectoral fins to glide 50 to 400m
(depending on updrafts from waves) to escape
predators.
Silversides
http://www.aboututila.com/Photos/AdamLaverty/Fish-Silversides.JPG
Flying fish
http://blogs.dispatch.co.za/dispatchnow/files/2008/01/flying-fish.jpg
http://myanimalblog.files.wordpress.com/2008/02/flyingfish.jpg
Acanthopterygii
The second major group is the Perciformes: more than
13,000 species of perch and their relatives.
Range in size from 7mm to 5m long. A paraphyletic
group there is no set of derived traits that groups them
all together, but the they usually have dorsal and anal
fins with anterior spiny portions, whereas the posterior
spines are usually soft rayed. The two portions may be
partially or completely separated.
Snook, sea bass, sunfish, perch, darter, snapper,
cichlids, barracuda, tuna, most coral reef fish.
European Perch
http://www.strikeit.net/USERIMAGES/PERCH.JPG
Black Seabass
http://shiftingbaselines.org/blog/
images/Black%20Sea%20Bass2.jpg
Snook
http://www.floridaadventuring.com/images/snorkeling-school-of-snook.jpg
http://www.practicalfishkeeping.co.uk/pfk/
images/cc_barracuda_national_park_service.jpg
Barracuda
http://www.bubblevision.com/albums/richelieu-rock/images/giant-barracuda.jpg
SpeciaIizations of the teleosts
A major development in the teleosts is the
conversion of jaws from simple devices for
grasping to sophisticated suction devices.
An approaching fish can push prey away,
but a rapid expansion of the orobranchial
cavity creates a flow of water into the
fishes mouth.
Protrusible jaws
Teleosts are characterized by having great
mobility in the skeletal elements of the
mouth. This allows the grasping portion of
the jaws to be quickly extended forward.
Jaw protrusion is achieved by levering
forward the premaxilla from behind.
The premaxilla is attached with ligaments
that allow the bone to slide forward on top
of the skull.
Protrusible Jaws
Based on anatomical comparisons of their
structure in different groups it is clear that
protrusible jaws have evolved independently
multiple in different teleost clades.
Jaw protrusion is widespread among the
perciform fishes, but also occurs in silversides,
cods and anglerfishes, and in minnows.
Pharyngeal Jaws
Mobileand often powerful pharyngeal jaws
have evolved several times in
actinopterygians.
Ancestralray finned fishes possessed
many dermal tooth plates within the
pharynx. Some toothplates over time
became fused together and to parts of
some gill arches.
Pharyngeal jaws
Theearliest pharyngeal jaws were not very
mobile, but could be used to hold prey
before swallowing. Today a variety of
pharyngeal jaws occur in different groups.
Forexample, in minnows the primary jaws
lack teeth but the pharyngeal jaws are
enlarged and close against a horny pad on
the base of the skull. They are used to grind
plant material.
Pharyngeal jaws
In many groups the upper and lower
pharyngeal jaws can move independently
of each other.
For example, in some moray eels the
pharyngeal jaws can be extended from the
throat into the oral cavity to grasp prey and
pull it into the throat and esophagus.
These X-rays show the normal position of the pharyngeal jaws (upper), and
how they can move forward into the mouth to seize food (lower).
(Credit: Rita Mehta, Section of Evolution and Ecology and Candi Stafford,
School of Veterinary Medicine, UC Davis.)
Legend pasted from http://www.sciencedaily.com/r
eleases/2007/09/070905134523.htm
Moray Eel Pharyngeal jaws
http://en.wikipedia.org/wiki/File:Pharyngeal_jaws_of_moray_eels.svg
Pharyngeal jaws
The cichlids of Lake Victoria have diversified
enormously into about 500 species in a period of
only about 14,000 years.
The possession of pharyngeal jaws which can
process food has allowed the outer jaws to be
greatly modified to consume a wide variety of
prey. Foods consumed include, other fish,
plankton, algae, fish scales, bivalves, and
diatoms.
Lobe-finned fishes: Class
Sarcoptrygii
Sarcoptrygians were abundant in
Primitive
the Devonian, but have since declined to a
handful of species.
Unlikein the actinopterygians (where the
rays fan out from the base of the fin) the
rays of the paired fins in Sarcopterygians
extend from a central shaft of bones to
support the fin web.
Fin structure
http://people.eku.edu/ritchisong/RITCHISO//fins2.gif
Lobe-finned fishes: Class
Sarcoptrygii
Sarcopterygians were 20-70 cm
Primitive
long and cylindrical.
They possessed two dorsal fins, paired
pelvic and pectoral fins that were fleshy,
scaled and possessed a bony central axis.
The heterocercal caudal fin had a
epichordal lobe.
Fossil Sarcopterygian
http://www.pc.gc.ca/progs/spm-whs/images/miguasha/mig6b.jpg
http://animals.nationalgeographic.com/staticfiles/NGS/Shared/
StaticFiles/animals/images/1024/coelacanth-swimming.jpg
Lobe-finned fishes: Class
Sarcoptrygii
Sarcopterygian fishes also had massive
jaw muscles in comparison to those of
actinopterygians.
Inaddition, early sarcopterygians were
covered with a dentine-like material called
cosmine.
Lobe-finned fishes: Class
Sarcoptrygii
Today the sarcopterygians are a very
small group that includes only six species
of lungfishes (Dipnoi) and two species of
coelacanths (Actinistia).
However, all of the tetrapods (four-legged
vertebrates) are descended from an
extinct group of sarcopterygian fishes
known as the rhipidistians.
Lungfishes
There are six species of lungfishes: one
South American, one Australian and four
African species.
Astheir name suggests, these fish, as all
sarcopterygians do, possess alveolar
lungs and can breathe air.
Lungfishes
Extant Dipnoi have lost the articulating toothed
premaxillary and maxillary bones of the other
Osteichthyes.
They have crushing dental plates with fan-
shaped ridges and teeth scattered over the
palate. In addition, strong muscles attach the
lower jaw to the chondrocranium. Lungfishes
are thus specialized to feed on hard foods such
as crustaceans and molluscs.
Lungfishes
The dorsal, caudal and anal fins have fused into
a single continuous fin that extends around the
entire rear third of the body.
The change in body form of the lungfishes may
be an example of paedomorphosis.
They were initially considered to be
salamanders when first described.
Lungfishes
The Australian lungfish can gulp air and survive
being in oxygen poor water, but cannot live out
of water.
In contrast, the South American and African
species can survive out of water for long periods
of time.
The African species live in seasonal steams and
ponds that dry out, but the lungfish survives by
burrowing into the mud and forming a cocoon in
which it survives until the water returns.
African lungfish
http://www.amtra.de/images/Lungenfisch415.jpg
South American Lungfish
http://www.ucmp.berkeley.edu/vertebrates/sarco/lungfish1.jpg
Australian Lungfish
http://www.nhm.ac.uk/about-us/news/2007/october/images/
Australian%20lungfish%20copyright%20Jean%20Joss-370_12548_1.jpg
The discovery of living coelacanths
Coelacanths were believed to have been extinct
for perhaps 50 million years (there are fossils
identical in appearance that are 70 million years
old) when one was caught by a South African
fishing boat in 1938.
The curator of a small museum, M. Courtney-
Latimer, recognized the fish was unusual and
she brought it to the attention of the icthyologist
J.L.B. Smith who after some delay in arriving
identified the fish.
The discovery of living coelacanths
Unfortunately, the delay in arriving meant the fish had
badly decomposed and many important structures had
been lost.
Smith named the fish (Latimeria) in honor of Courtney-
Latimer and then embarked on a 14-year quest to find
another coelacanth.
But it wasn’t until 1952 that a second was caught off the
Comoro Islands, north of Madagascar, which is where
the fish occur naturally (the 1938 fish apparently had
drifted far from its normal range). The story is told in
Smith’s book “The search beneath the sea.”
Images from the rediscovery of the
Coelacanth off the Comoros 1952.
Coelacanths
In 1998 another population of Latimeria [but a
different species] was discovered off Indonesia
(10,000km east of the Comoros).
Coelacanths are large fish up to about 5 feet
long, blue-grey in color with white spots.
They live in deep (70-400m) cold water and are
predators feeding mainly on lanternfish.
16.20
Coelacanths
Coelacanths are readily identified from their fins.
The caudal fin has a small median lobe.
Each of the paired fins is very mobile and has a long
fleshy basal lobe.
The anterior dorsal fin’s fleshy lobe is reduced and it
possesses long protective hollow spines (coelacanth
means “hollow spine”).
When they swim coelacanths move their pelvic and
pectoral fins in the same pattern that tetrapods walk.
Coelacanths
Because coelacanths possess an unusual suite
of characters including fat-filled lungs, a high
level of urea in the blood, a liquid filled
notochord, lobed fins, ventral kidneys and a
reduced brain there has been debate about their
phylogenetic affinities.
The consensus today is that coelacanths are a
sister group to the Rhipidistia which gave rise to
the lungfish and tetrapods.
We will discuss the origins of the tetrapods
shortly.
Global fisheries and conservation
Before moving on from fishes to the
tetrapods, I want to devote some time to
fishing.
Itis 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 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 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 conservation
Clearlya different level of fish abundance
than we encounter today.
abundant numbers of fish were
Similarly
described in the waters off New England
and eastern Canada.
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 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 fishery
Therich fishing grounds off the northeastern
U.S. and eastern Canada result from a
combination of factors.
various banks (the Grand Banks, George’s
The
Bank, Brown’s Bank and others) are deposits of
moraine deposited by glaciers.
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 supported cod
and other predators.
The Grand Banks
http://www.immersionpresents.org/photos/albums/userpics/10179/
Grand_Banks_Map.jpg
George’s Bank and Brown’s Bank
http://www.nefsc.noaa.gov/history/timeline/images/georges.jpg
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 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.
http://www.pugetsoundmagazine.com/articles/img001/10024/lituya1FVOA.jpg
Norwegian Cod schooner 1930
http://pro.corbis.com/images/US002037.jpg?size=67&uid=%7B15ED58FC-
EBD7-4EDF-8067-DA989C5D9ECD%7D
Steam Trawler Bellerophon
http://www.maritimelowestoft.co.uk/images/crownies_lowestoft/
bellerophon_large.jpg
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.
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 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 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 an whole season’s
fishing.
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.
Russian factory trawler
http://www.greenpeace.org/raw/image_full/international/
photosvideos/photos/russian-factory-trawler-fishin.jpg
The Grand Banks fishery
Fishingfleets 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 fishery
By1974 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.
Everythingwas taken juvenile or adult,
spawning or not regardless of the future
impact on stocks.
The Grand Banks fishery
Two Canadian fisheries scientists, Jeffrey
Hutchings and Ransom Myers, have estimated
that about eight million tons 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 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.
In1977 following Iceland’s lead the U.S.
and Canada declared a 200-mile limit and
excluded the foreign fishing boats.
The Grand Banks fishery
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 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 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 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 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.
By1992 the estimate was 22,000 tonnes
(<1/3 of 1% of the original population.).
The Grand Banks fishery
Cod have not made a comeback and there is
some debate about why.
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 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.
http://newsimg.bbc.co.uk/media/images/40874000/
gif/_40874232_bottom_trawling_416.gif
Sea bottom habitat in Canada (left) and Australia (right)
before trawling (above) and after (below).
http://coralnotesfromthefield.blogspot.com/2007_05_01_archive.html
The Grand Banks fishery
years of bottom trawling the sea bed
After
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.