Nature Conservation
(semester course)
Threat by Hunting
doc. Jiří Schlaghamerský, Ph.D.
Dept of Botany and Zoology, Fac. of Science, MU
MODULARIZACE VÝUKY EVOLUČNÍ A EKOLOGICKÉ BIOLOGIE
CZ.1.07/2.2.00/15.0204
Characteristic traits of particularly endangered species (1)
• very small range
- birds restricted to one or few oceanic islands
- fish restricted to a single lake (pool!) or a single river systém
• with a single or a small number of populations
• with small populations / low density
- large predators
- highly specialized species
• requiring a large home range
• of large body size (the largest within its taxonomic group)
• with slow population growth (K-strategists)
• lacking effective mechanisms of dispersal (e.g. unable to fly)
Which species are under threat?
Characteristic traits of particularly endangered species (2)
• living in stable environments (e.g. in tropical primeval forests, in cavities
of ancient trees)
• migratory species
• living permanently or temporarily in groups
- herds of hoofed animals (bison, wild horse, onager, kulan)
- bats (caves),
- migratory birds (e.g. passenger pigeon),
- birds breeding in collonies,
- fish (salmon),
- sea turtles (laying eggs),…
• hunted or collected by man
Which species are under threat?
Decline of megafauna or lemures in dependance on the arrival of humans
North
America
(megafauna;
genera in %)
Africa
(megafauna;
genera in %)
Madagascar
(lemures;
species in %)
Threat to species by hunting
Comparison of the size of extinct birds, Aepyornitids (elephant birds)
and Moas in comparison with other birds incapable of flight and man
Threat to species by hunting
extinct species species alive
Euryapterix curtus
Anomalopteryx
didiformis
The Moa Birds (Diornithiformes)
- New Zealand
- about 10 species (2 families)
- mostly woodland species
- from 20 kg up to over 230 kg (2 m at the withers)
- last one killed in 1785?
Threat to species by hunting
The Haast’s eagle
(Harpogornis moorei)
- New Zealand
- females up to 13 kg, wing spread 3 m
- youngest bones ca 500 years old
Threat to species by hunting
The Elephant birds (Aepyornitidae)
- Madagascar
- at least 7 species (2 genera)
- up to 400 (500?) kg (height 3 m)
- last one died in 1649?
- contribution of hunting and climatic change (drought) to extinction?
Threat to species by hunting
Threat to species by hunting
The Elephant birds (Aepyornitidae)
- eggs: volume 10 l, length 35 cm
Threat to species by hunting
The lemur Megaladapsis edwardsi
- Madagascar
- the largest lemur – gorilla-sized (the genus included
another two large species, in total some 17 “giant” lemur
species got extinct)
- woodland species
- 600 years before present still alive
- contribution of hunting, clearing of forests
and climate change to extinction?
The lemur Megaladapsis edwardsi
Threat to species by hunting
Threat to species by hunting
The Dodo (Raphus cucullatus)
- The Isle of Mauritius (Indian Ocean)
- extinction due to hunting by man and introduced
animals - cats, pigs and macaques
- first landing of seafarers in 1507
- colonisation of the island in 1644
- last birds observed in 1662, survival until 1681?
Only drawing by a person that
actually saw the bird alive
(François Leguat, 1708)
Skeleton of female and male
Reconstruction according to Leguat’s description
(Frederick William Frohawk)
Threat to species by hunting
The Rodriguez Solitaire (Pezohaps solitaria)
- Rodrigzuez Island (Indian Ocean)
- discovered in 1691, in 1730 common, in 1755 very rare, in 1761 not found
- hunted to extinction by man and introduced cats
The Réunion ibis
(Threskiornis solitarius = Borbonibis latipes)
- Réunion Island (Indian Ocean)
- Discovered in 1613, last one died in 1791
- Real appearance?! Systematic position?!
- For long referred to as the Réunion solitaire (Raphus solitarius)“, a dodo-like
species that probably never existed!
It might have looked like this: Hypothetical
restoration based on contemporary descriptions,
subfossil remains, and extant relatives (Wikipedia).
Misleading image (short beak!):
Frohawk's 1907 restoration of the
Réunion solitaire, based on
Sieur Dubois’ description
It certainly did not look like this, but
was often depicted as a white dodo!
Here Frederick William Frohawk's 1907
restoration of the Réunion solitaire,
adapted from Withoos' white dodo.
Threat to species by hunting
The Great Auk(Penguinus impennis)
- The largest auk (5 kg, height 75-92 cm)
- Originally occurring on the coasts and islands of the Nothern Atlantic
- Massive hunting and egg collecting
- The birds served not only for food of the inhabitants of the coast and sailors but also as fishing
bait and fuel (much fat), later as a source of dune feathers in high demand
Threat to species by hunting
The Great Auk (Penguinus impennis)
- Before the end of the 13th century extinct on the Norwegian
mainland
- Dramatic population decline at the end of the 16th century
- in N. America erradicated at the end of 18th century (last population
on Funk Island off the coast of Newfoundland ceased to exist between 1785 and 1800)
- 1808 erradicated on the Faroer Islands
- 1812 erradicated on the Orkney Islands
- 1813 erradicated on the British Isles
- 1815 erradicated in Greenland
- 1821 erradicated on the Hebrides
- 1830 Geirfuglakor island with last breeding colony submerged due to volcanic activity
- 1835 a colony of surviving birds (less than 50) discovered close-by on Eldey Island
- 1840 one bird killed on the isle Stac an Armin (St. Kilda Archipelago, Outer Hebrides)
- 1844 last nesting pair on Eldey Island beaten to dead, egg destroyed
- 1852 one bird reported off the coast of Newfoundland – last sighting ever reported
- in the last decades the demand of museums and private collectors for skins and eggs
contributed substantially to the erradication of the species
Eldey Island southwest of Iceland
Threat to species by hunting
Threat to species by hunting
The Labrador Duck (Camptorhynchus labradorius)
- occuring along the northern part of the North American Atlantic coast (Labrador)
- egg collecting and hunting by man (meat, down feathers)
- antropogennic decrease of mollusc populations in its wintering grounds
- last bird killed in r. 1875
The Short-tailed Albatross (Phoebastria [=Diomedea]
albatrus)
- original range: Bonin (Izu) archipelago and Ryuku (Japan), Taiwan,
islands close to Chinese coast, Pacific coast of North America
- at the end of the 19th cent. population of ca. 5 million (on Bonin = Izu)
- intensive hunting for feathers (pens, feather beds)
- 1939: 30-50 birds on Torishima island, last nesting pairs disappeared
concurrently with the se prohibition of hunting
- 1949: declared extinct (however, juveniles survived at the open sea)
- 1954: return of 25 birds to Torishima, at least 6 pairs, first eggs
- 2008: 1922 birds (ca 426 pairs) on Torishima, 442 birds on Minami-kojima (Senkaku
archipelago)
Tori shima
Threat to species by hunting
The Passenger Pigeon (Ectopistes migratorius)
- original range in North America east of the Rocky Mountains
- original population size ca 2 million
- in the 2nd half of the 19th century decline of population due to
massive hunting, total protection declared
- last individual died in 1914 (Cincinnati Zoo)
Distribution area: nesting red,
wintering orange
Threat to species by hunting
The American Bison (Bison bison)
(Pre-)Historic distribution of the bison
Present distribution
(continuously increasing due to reintroductions)
- population size before arrival of Europeans ca 60 million
(still valid in ca 1800)
- mass killing since the 18th century
- in 1832 exterminated east of the Mississipi
- in 1870 exterminated in the Southern Plains
- in 1870-1875 2.5 million animals shot per year
- in 1889 only 1091 individuals alive (635 in the wild)
Threat to species by hunting
The plains indians were totally dependent on bison
(after the expansion of horse keeping and the
corresponding cultural changes)
The American Bison (Bison bison)
Threat to species by hunting
Bizon (Bison bison)
- The hides were processed
on a large scale, the skinned
corpses were left behind.
The famous buffallo hunter
William F. Cody alias
Bufallo Bill
- The construction of the
transcontinental railway
contributed substantially to the
almost total extermination of
bison.
- The last utilization
was the collecting
of bones (e.g. for
fertilizer production).
J. Schlaghamerský: Ochrana přírody – ohrožení druhů lovem
The Wisent or European Bison (Bison bonasus)
Three subspecies:
- The European / Lowland Bison (B. b. bonasus) – today ca. 1000 animals,
ca. 70 % „in the wild“
- The Caucasian Bison (B. b. caucasus) , pure-blood subspecies extinct,
a breed of hybrids with the lowland subspecies with some genes of the
American Bison (B. bison) has survived
- The Carpathian bison (B. b. hungarorum), extinct around 1790 (the last one
perhaps killed as early as 1762 in the Rodna mountains (presently in northern
Romania), valid subspecies?
Threat to species by hunting
Original distribution: Euroasia
Reconstruction of distribution area in the Holocene (light green) and
high middleages (dark green); last endemic populations in red
1 AD - ranging from the British Isles to Siberia and the Caucasus (there
are doubts about the western border of the distribution area, in the
Caucasus represented by another subspecie, i.e. B. b. caucasus)
7th cent. - in the West still present in the Vosges mountains
1100 - 1500 - exterminated in the British Isles, Apennine Peninsula and Sweden
11th cent. - still present in northern Switzerland
until 16th cent. - still present in Brandenburg
until 18th cent. - in Poland / Eastern Prussia and Transilvania
early 19th cent. - last lowland wisents living in the Białowieża Forest (formerly
the Polish king’s, then the Russian tsar’s hunting reserve)
1850 - ca 1920 - decline and extinction of the lowland subspecies population in the
wild : 1850 - 1500 individuals; 1910 - 600 ind.
1923 - The international Society for the Protection of the European Bison
founded in Berlin, 54 (56?) specimens in captivity, of those 12 able
to reproduce
2006 - 3200 pure-blood wisents in the breed registry, including also the
lowland-Caucasus line (of those ca 60% “in the wild”)
Bison bonasus (bonasus)
Threat to species by hunting
The Causacian Wisent
(Bison bonasus caucasicus)
1831 - population of the Caucasian subspecies
discovered in the north-western Caucasus (SZ Kavkaz)
ca 1860 - 2000 individuals
1914 - 800 individuals
1917 - 500-600 individuals
1921 - 50 individuals (fast declined due to hoof and mouth disease, anthrax,
poaching and excesses of Soviet revolutionaries)
1924 - reserve established
1927 - last three pure-blood individuals killed
2002 - ca 2200 hybrids of the Caucasian and lowland subspecies, most of those
also with genes of the American Bison (all genes of the Caucasian subspecies
come from a single bull held in captivity, which died in 1925)
Threat to species by hunting
The Aurochs (Bos primigenius)
Reconstruction of original range
Several subspecies:
- B. p. primigenius – ancestor of taurine or European cattle (B. taurus)
- B. p. namadicus (India) – ancestor of the Indian cattle - the zebu
• Size at the withers up to 185 cm in bulls (1000 kg), 150 cm in cows
• Domestication from 6500 B.C. onwards
• The wild form became extinct in Asia in antiquity, in western and central Europe
between the 12th and 14th century (after large-scale forest clearing between the 9th
and 11th century)
Threat to species by hunting
Reconstruction of bull and cow
after 1300 BC – not present (exterminated?) in the British Isles
after 400 BC – not present (exterminated?) in the Netherlands
ca 1 AD - exterminated in northern Italy (30 BC still hunted there)
- exterminated in Jutland (mainland Denmark)
800 AD - still present in France
1000 AD - still present in Switzerland
ca 1250 - exterminated in Hungary (Pannonian Plain)
12th or 13th cent. - exterminated in Russia
1406 and 1408 - last reliable records from Germany
1476 - last two herds of wild aurochs become the property of the Polish
king (received from the Duke of Mazovia)
The Auerochs (Bos primigenius)
Threat to species by hunting
The Aurochs (Bos primigenius)
Last population in the Jaktorow royal hunting enclosure
(south of Warsaw):
1564 - 38 individuals (8 bulls, 22 cows, 3 immatures, 5 calfs)
1566 – 24 individuals remaining
1602 - 4 individuals (3 bulls, 1 cow)
1620 – last individual (cow) – died in 1627
An attempt to get the original Aurochs back by cross-breeding of several primitive races
of domestic cattle was undertaken in 1920-1940 (the Heck brothers, Zoos in Munich
and Berlin) - today some 2000 individuals of an stabilized breed exist in various
zoological gardens and game enclosures. The bulls reach „only“ 150 cm at the withers.
Threat to species by hunting
The Quagga (Equus q. quagga)
- southern subspecies of E. quagga
- orig. range NW to the Oranje river, NE to the Vaal river,
SE to Great Kei River
- massive hunting by white settlers (for meat and hides,
as competitors of domestic animals on range-land)
- last live individuals captured in 1870
Plains Zebra
(E. quagga burchelii)
Mountain Zebra
(E. zebra)
Grevy’s Zebra
(E. grevyi)
Threat to species by hunting
Zebra kvaga (Equus q. quagga)
- last animal shot in the wild in 1878
- last animal died in captivity in 1883 (Amsterdam Zoo)
- only later it became clear that this had been the last
quaggakvagu
Threat to species by hunting
Since 1987 there is a project attempting to obtain zebras
of quagga phenotype by breeding selected individuals of
the adjacent subspecies captured in Namibia (apparently
carrying genes of the nominate subspecies).
Franz Roubal, 1931
- up to 9 m long, up to 6 tonnes body mass
- discovered in 1741 on a single island in the Bering Sea (formerly also present on
the Kamtchatka peninsula – erradicated by tribesman)
- erradicated by sailors within 27 years – in 1768 (scientific description 12 years
hereafter)
Steller’s Sea Cow (Hydrodamalis gigas)
Threat to species by hunting
- original range included Australia and New Guinea (erradicated by the aborigines and
by competition of dogs and the ferralized dingo)
- at the time of the colonization by Europeans only occurring (demonstrable) in Tasmania
- from 1830 to 1909 bounty was paid for killed thylacines (said to attack sheep)
- from 1888 to 1909 2184 bounties were paid (minimal number of killed individuals)
- last known shot in the wild in 1933
- in 1936 the last individual died in Hobart Zoo, absolute protection of the species was
decreed in the very same year
The Tasmanian Wolf or Tiger (Thylacinus cynocephalus)
Threat to species by hunting
Three subspecies of the tiger: Panthera tigris
virgata, P. t. balica, P. t. sondaica
- the 2nd largest subspecies
- orig. range: Turkey - N. Iraq – Iran – Aserbajdzhan, Russian
Central Asia, Turkhmenistan, Uzbekistan, Afghanistan, Mongolia
- intensive hunting incl. a campaing of the Russian army at the Caspian Sea in the early
20th century
- last(?) shot in 1959 (Iran?, Iraq?) or as late as 1970 (Turkey) or 1997 in northern
Afghanistan?
Tiger distribution area in 1900
The Caspian Tiger (Panthera tigris virgata)
Threat to species by hunting
The Bali Tiger (Panthera tigris balica)
- subspecies of smallest body-size, only on the island of
Bali (rather small population)
- last kill in 1937
- reports on sightings up to 1952 (questionable ones
from 1970 and 1972)
The Java Tiger (Panthera tigris sondaica)
- only on the island of Java, in the early 19th century
very abundant
- in 1940 only in mountainous areas – decline due to
hunting, poisoning, deforestation
- 20-25 individuals remaining
- 1979: last footprints found (max. 3 ind.)
Java
Threat to species by hunting
Bali
- were also on the brink of extinction,
today their populations remain mostly
small but are rising in many areas due
to their protection and reintroductions.
Threat to species by hunting
Large Carnivores in Europe
Threat to species by hunting
Current problems of threats to species by hunting or collecting:
poaching and international trade
• trading with ivory (elephant, mammoth (subfossile), narwhal, wealrus, and
hippopotamus tusks/teeth; rawmaterial for artistic objects)
• trading with rhinoceros horns, bones and other body parts of tigers and other
objects used in traditional medicine (in particular Chinese)
• capturing or collecting (e.g. eggs, marine molluscs, but also plants such as
cacti and orchids) for sale to zoological and botanical gardens, at present
mostly to private keepers, breeders (falconers, parrot breeders, etc.) or
collectors.
• hunting for subsistance and trade („bushmeat“) in developing countries
• too intensive use of wild populations by fishing, hunting or similar activities by
“developed” countries, often based on international agreements but also on
the brink of illegality (e.g. whaling).
Ivory Trade
Threat to species by hunting
CITES and the ivory trade
1975 Convention on the International Trade in Endangered Species of Wild Fauna and Flora):
The African Elephant listed in Annex II (allowing monitored international trade with ivory and other
products); The Asian Elephant listed in Annex I (not allowing trade with ivory or any other products).
1989 (valid from 1990) CITES transferrs all African Elephant populations from Annex II (threatened) to Annex I
(endangered)
1997 CITES (COP 10) transfers populations in Botswana, Namibia and Zimbabwe to Annex II, to allow an
one-time sale of ivory stocks (done in 1999).
2000 The Republic of South Africa, Namibia, Botswana and Zimbabwe withdrew their applications for a
permit of trading with ivory, which they had filed earlier. Kenia a India withdrew their applications to
transfer the elephant populations of other countries from Annex II back to Annex I. Southafrican
population transferred from Annex I to Annex II.
2002 The Republic of South Africa, Namibia, Botswana and Zimbabwe asked for the permit to sell their
existing ivory stocks and to receive annual quota for the sales of elephant tusks. Zambia did not ask
for annual quota but for a permit to sell existing stocks only.
2006 CITES put aside the requests of South Africa, Namibia and Botswana to sell their ivory stocks.
2007 African Elephant populations in South Africa, Namibia, Botswana and Zimbabwe transferred to Annex II.
This allows non-commercial trophy hunting, trade with live individuals (restricted by given rules), trade in
skins, hair, leather products, limited trade with ivory products under compliance with explicit rules, trade
with registred raw ivory (tusks and their parts) from state-owned stocks (except ivory that had been confiscated
or of unknown origin) to checked buyers (max. one sale to one buyer), in a one-time transaction
– followed by a 9-year moratorium on further sales .
Threat to species by hunting
Threat to species by hunting
The African Elephant (Loxodonta africana)
The development of regional populations of the African
Elephant from 1900 and estimates of present regional
population sizes
Present (2007) distribution of the African Elephant
Total population ca 550 000 (2007)
cca 60 000
cca 160 000
cca 300 000
cca 8 000
Threat to species by hunting
Foto: Bodenseemann
The Asian Elephant (Elephas maximus)
Number of elephants poached in India in 1991-2001
Asian Elephant population world-wide
(estimate, 1996) and in India (1991-2001)
Threat to species by hunting
Rhinoceroses – victims to superstition about the healing power
of their horns
White Rhinoceros (Ceratotherium simum)
In 2010 scientific evidence was presented, indicating that the northern
subspecies, Cotton’s, deserves the status of an independent species.
Black Rhinoceros (Diceros bicornis)
Population estimates for rhinos living in the wild in Africa as of Dec. 2007
Threat to species by hunting
Thanks to strict protection the populations of African rhinos grew in the last decades
(the population of the Southern Wide Rhinoceros increased from 20-50 animals in 1885
to ca 20 000; the population of the Black Rhino had dramatically decreased from ca 300 000
in 1950 dramaticky poklesla, but even here an increase to ca 5 000 was reached).
However a dramatic breaking point was reached in 2007.
Rhinoceroses – victims to superstition about the healing power of their horns
Poaching victim
Development of rhino populations in Zimbabwe reflects poaching intensity
The demand for rhino horns on the black market – mainly in China and further South Asian countries
(use in traditional Chinese medicine) and in Yemen (used for handles of traditional daggers) – started to rise
steeply, once the superstitious belief that they presented effective medicine against cancer spread in Vietnam.
Since than the price of rhino horn has increased manifold (35 USD / kg in 1975, 65 000 USD / kg in 2004) .
Threat to species by hunting
Minimal numbers of rhinos poached in Africa
(2006 – Feb. 2013)
dle údajů AfRSG, TRAFFIC a CITES Rhino Working Group
Numbers of rhinos poached in Africa (2006–2009)
broken down to countries and way of killing
98% of all African rhinos now live in four countries
in southern Africa: South Africa, Namibia,
Zimbabwe and Botswana.
The Czech Republic plays an important role in
the illegal trade with rhino horns (large vietnamese
community, feigned trophy hunting by
Czech citizens, theft of horns from exhibitions,
stepping stone on the way to Asia).
Numbers of rhinos poached in South Africa (2000 – Oct. 2014)
Rhinoceroses – victims to superstition about the healing power of their horns
Threat to species by hunting
Rising numbers of poached rhinos and arrested
poachers in South Africa from 2010 to Sept. 2014.
One measure to protect rhinos against poachers is the careful removal of their horns. However, to prevent
injury, the ceratin base of the horn (which is growing into the bone), has to be left intact. Even this remaining part
attracts poachers as the price per kg horn is very high.
In the Republic of South Africa, paid trophy
hunting of rhinoceroses is still legal,
usually in private game reserves
(ca 23% of rhinos in South Africa have
private owners). According to official
sources legal trophy hunting makes up for
100-160 rhinos killed per year. The export
of private trophies, however, serves as a
disguise for their further trade and for the trade with
poached horns. In the meantime South
Africa has prohibited trophy hunting by
citizens of Vietnam and Czechia!
Threat to species by hunting
Rhinoceroses – victims to superstition about the healing power of their horns
Rhino horns on the black market in Africa
Percentages of horns entering the illegal trade,
and confiscated by security forces in Africa.
The fight against the well-organized and armed
groups of poachers is dangerous and requires
sufficient numbers of well-trained and equipped rangers.
Threat to species by hunting
Rhinoceroses – victims to superstition about the healing power of their horns
Estimate of Asian rhino populations in the wild as of Sept. 2009 (trends since 2007)
Number of photo trap records of Lesser One
Horned (= Javan) Rhinoceros in Vietnam
Greater One Horned (= Indian)
Rhino population development
(1910-2005)
On the 24th October 2011
the WWF announced that the
last Lesser One Horned
Rhinoceros in Vietnam
had been poached.
Threat to species by hunting
In many developing (poor!) countries, wild animals are hunted, often illegally, as an
supplementary or even main source of food (proteins!) – so-called „bushmeat“ (in Africa)
– however, this meat reaches increasingly also the European market!
Apes are among the hunting game.
Threat to species by hunting
Example: Bioko Island (Equatorial Guinea): what ends on the market and eventually in the kitchen!
Threat to species by hunting
The sale of animals, their parts or
products made of them as souvenirs
or collector items can lead to dramatic
decline in populations.
Legal trophy hunting (“sport”) can provide
substantial funding for national or private
reserves, and thus co-fund nature conservation.
However, the longing for trophies can also lead
to illegal hunting, corruption etc. The existence
of legal products obtained from animals killed
for trophy makes it easier to trade with such
products obtained illegally.
Threat to species by hunting
The orchid trade in Laos
Trade with wild-growing orchids seriously threatens many species
Threat to species by hunting
Photo: Stan Shebs
Photo: Ansgar Walk
Photo: Zenwort
Whaling – most populations of large species decreased dramatically
Nowadays mostly subsistence hunting by
indigenous peoples is permitted (above
Eskimoes or Inuit in Greenland)
Whale meat in a grocery shop in Japan, where
Whaling is still done for “research purposes”
Threat to species by hunting
Species Natural population size Present population
(pre-hunting estimates) (estimates of the number of individuals)
Baleen whales
Blue whale 200 000 9 000
Common minke whale 140 000 850 000
Sei whale 100 000 55 000
Fin whale 475 000 123 000
Grey whale 23 000 21 000
Bowhead whale 56 000 8 200
Humpback whale 150 000 25 000
North Atlantic right whale ? 1 300
Southern right whale 100 000 1 500
Toothed whales
Beluga ? 50 000
Narwhal ? 35 000
Sperm whale 2 400 000 1 950 000
Assessement of the impact of human hunting on whale populations
Threat to species by hunting
Photo: Erik Christensen
Catch of Atlantic white-sided dolphin
(Lagenorhynchus acutus) na the island of Hvalba
(Faroe Islands, 26. Aug. 2006)
Numbers of Minke whale (Balaenoptera
acurostrata) catches by Norwegian
whalers (red) and quotas of allowed
catches (blue)
Hunting, fishing, harvesting:
about the use of populations
Living / growing in the wild
Threat to species by hunting
Threat to species by hunting
Hunting, fishing, harvesting: about the use of populations living / growing in
the wild
Threat to species by hunting
Hunting, fishing, harvesting: about the use of populations living / growing in
the wild
Threat to species by hunting
Hunting, fishing, harvesting: about the use of populations living / growing in
the wild
Threat to species by hunting
Hunting, fishing, harvesting: about the use of populations living / growing in
the wild
Threat to species by hunting
Hunting, fishing, harvesting: about the use of populations living / growing in
the wild
Net recruitment (increment) curveof a hypothetical population
To reach a maximal yield
while not damaging the
population we have to
keep population size at
Nm.
hm is the highest
yield that the population
is able to support by its
own increment = maximum
sustainable yield (MSY)
Threat to species by hunting
The highest frequence
of harvesting at
a medium population
density
Hunting, fishing, harvesting: about the use of populations living / growing in
the wild
Threat to species by hunting
Hunting, fishing, harvesting: about the use of populations living / growing in
the wild
The MSY approach was used by the International Whaling Commission to set fixed
annual whaling quota in 1949-1960.
An alternative to fixed quota is the regulation of harvesting effort.
h = g * E * N
h = yield from a harvest
g = harvesting efficiency
E = level of harvesting effort
N = population size
Threat to species by hunting
Hunting, fishing, harvesting: about the use of populations living / growing in
the wild
Threat to species by hunting
Hunting, fishing, harvesting: about the use of populations living / growing in
the wild
Threat to species by hunting
Hunting, fishing, harvesting: about the use of populations living / growing in
the wild
Threat to species by hunting
Hunting, fishing, harvesting: about the use of populations living / growing in
the wild
Threat to species by hunting
Hunting, fishing, harvesting: about the use of populations living / growing in
the wild
Surplus Yield Models
(all introduced above)
Alternative approach (more complicated):
Dynamic Pool Models
(the very first one formulated in 1957)
Available data on the population (empirical and theoretical) are
arranged in such a way to reflect the dynamics of a structured
population.
Recommendation for the practise includes not only harvesting
effort but also its break down to the individual age classes.
Threat to species by hunting
Hunting, fishing, harvesting: about the use of populations living / growing in
the wild
Threat to species by hunting
Hunting, fishing, harvesting: about the use of populations living / growing in
the wild
Garrod a Jones made at the the turn of
the 1970s a dynamic pool model for
the northernmost part of the cod
population in the Atlantic ocean – the
subpopulation in Norwegian Arctica:
- They assessed the age class
structure in the late 1960s.
- They forcasted the medium-term
effect of various fishing intensities
and mesh sizes in the trawl nets on
the catch.
- The temporary peak after five years
was the effect of the large year-class
hatched in 1969.
- Recommendation: low intensity
fishing using a large mesh size (let
the fish grow and reproduce for a
longer time).
Threat to species by hunting
Hunting, fishing, harvesting: about the use of populations living / growing in
the wild
What happened with the recommendations given by Garrod and Jonese?
- The mesh size was not modified before 1979 when it was increased from
120 mm to 125 mm (according to Garrod and Jonese already the use of a
mesh size of 130 mm led to an overexploitation of the population!).
- Cod fishing intensity never dropped below 45% (in the late1970s annual
catches of 900 000 tonnes were taken).
At the end of the 1980s the subpopulation of cod in Norwegian Arctica
was seriously depleted – similarly as all other cod stocks in the North
Atlantic.
For more details see Chapter 15 in Begon et al. (2006): Ecology: from individuals to ecosystems. 4th
ed. Blackwell Publishing Ltd.