Transcript No Slide Title

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for the NMA by STEP, the
Science Training &
Education Partnership
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Partnership
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National Marine Aquarium
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Fisheries, sustainability &
conservation
Fisheries supply a valuable food
resource, but are seldom managed in a
sustainable manner
Fisheries and fisheries management
Setting and enforcing limits
Related issues
Summary
Fisheries and fisheries management
Setting and enforcing limits
Related issues
Summary
Humans have exploited many different
types of resource species in the sea
Current annual fish catches total 80-90 million
tonnes, and provide 20% of human protein
consumption
Over 100 million people depend on
ocean fisheries and aquaculture for
their livelihoods
Subsistence fisheries usually take
relatively small amounts of fish
This means that the fishery is
sustainable - the fishery does not result
in a long-term decline in the resource
species
Modern fishing equipment means that
far more fish can be caught, to supply
an expanding market
About 50% of exploited fish stocks are
close to their maximum biological
production level
A further 25% of exploited fish stocks
are over-fished
A recent study estimates that ‘industrial’
fishing has reduced the biomass of large
predatory fish to 10-20% of pre-fishery
values, usually within fifteen years
Fishery management should ensure
that fishing does not deplete
populations below sustainable levels,
and should protect endangered
populations
Fisheries and fisheries management
Setting and enforcing limits
Related issues
Summary
Managing a fishery in a sustainable manner
means that catches must be regulated so
that the fish population remains stable
This requires an understanding of the
current status of the population and its
biology
Population size
Population age distribution
Growth rate at given ages
Reproductive rate at given ages
Mortality rate at given ages
Fishery management is designed to ensure
that the fish population does not drop below
the value needed to replace caught fish
Fishery management can use various
approaches to regulate a fishery
Set quotas or allowable catch levels
Establish ‘no-fishing’ areas
Establish a ‘closed season’
Set minimum fish size-limit, or specify net
mesh size
Close fishery entirely
Excluding young fish from the catch is
achieved by using nets that allow small
fish to escape
However, fish may be injured even though
they are not caught
There are several other practical
problems in regulating fisheries
Illegal and unregulated fishing
Inadequate scientific data
Minimum size limits may not be effective in
excluding under-sized fish
Target species may be caught by other fisheries
Natural environmental variability may make
prediction unreliable
In some cases, catches of individual
species may be prohibited, but there is
no way to prevent them being caught
Supposedly protected fish have to be
discarded, even though they are already
injured or dead
Finally, measures to protect fish
populations may have important social
and economic impacts
Fisheries and fisheries management
Setting and enforcing limits
Related issues
Summary
There are several effects associated with
fisheries which also give cause for concern:
Habitat damage
Environmental effects of discarded gear
Incidental mortality and by-catch
Ecosystem effects
Large fishing gear and
dynamite-fishing cause
extensive damage to coral
reefs and other habitats
Discarded and lost
fishing gear and
other materials form
a serious hazard for
marine animals
Few fisheries catch only the intended species
Marine birds and mammals, such as dolphins, can
drown in nets
Long-line fishing is a significant cause of population
decline for some seabirds, such as albatrosses
Fishing for small species may catch young stages of
larger protected species, below their minimum size
Fishing can also compete with other
species in the ecosystem
Some modern fishing regulatory measures
aim to maintain the entire local ecosystem in
balance, rather than simply conserving target
species
Fisheries and fisheries management
Setting and enforcing limits
Related issues
Summary
You have seen that Fishing is an important source of
food
Many fish populations have
been reduced by over-fishing
You have seen that Fishery management aims to
provide a sustainable resource
Various methods are used to
regulate fisheries
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NOTES for USERS
The material in this slide show is designed to support the teaching of science at Key Stage 1
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