Transcript Aquatic Biodiversity

Aquatic Biodiversity
Nonindigenous species
Threatened and endangered
species
Outline





Determinants of community structure
Measuring biodiversity
High diverse ecosystems
Role of introduced species
Extinctions and threatened species
What is community structure?




Different sites have different compositions of
species
If communities have structure, then they
must be more than a group of randomly
selected individuals of different species
Is it random? Or is it not? What evidence do
we have?
Species pool
Assessing Community
Structure

Species Pool


Species Richness


What determines this?
What determines this?
Evenness
Measuring Diversity

Shannon-Weaver
Index



S=total number of
species
Pj is proportion of
total population that
is species j
Evenness

E=H’/lnS
Types of diversity


α diversity:
within-habitat
β diversity:
betweenhabitat
Effects of sample size and
drainage basin
Effect of latitude

Predatory
Gastropods


A) molluscs
B) fish
Diverse Aquatic Ecosystems

African rift lakes

Lakes Tanganyika
and Malawi – cichlid
species look similar
but are genetically
dissimilar
Introduced aquatic species

Biotic groups


How many species?
Examples?


How did they get introduced?
What is being done to control them?
Introduced aquatic species
The problem is getting BIGGER
Where do they come from?
How do they get here?
Brook trout
Stocked for sportfishing since
the 1800s
Arizona in 1920
Missouri from 1879 to 1914
Round Goby
Introduced to Great Lakes in 1990s
via freighter ballast
Has undergone population explosion
Grass carp




Stocked for biological control of vegetation.
First imported in 1963 to aquaculture facilities in Alabama and
Arkansas.
The first release into open waters took place in Arkansas, when
fish escaped the Fish Farming Experimental Station
Spread rapidly




widely scattered research projects
stockings by federal, state, and local government agencies
legal and illegal interstate transport and release by individuals, etc.
Stocking of grass carp as a biological control against nuisance
aquatic plants in ponds and lakes continues.
 thousands of grass carp are reared and sold by fish farmers
in Missouri and Arkansas
Grass Carp indirect effects




better growth of rainbow trout due to increases in phytoplankton and
zooplankton production
also higher predation on rainbow trout by cormorants due to lack of
cover, and changes in diet, densities, and growth of native fishes.
Increases in phytoplankton populations is a secondary effect

A single grass carp can digest only about half of the approximately
45 kg of plant material that it consumes each day. Nondigested
material causes algal blooms, which can reduce water clarity and
decrease oxygen levels (Bain 1993).
may carry several parasites and diseases known to be transmissible to
native fishes

Asian tapeworm; thus responsible indirectly for the infection of the
endangered woundfin
Triploid grass carp

Considered to be sterile and incapable of
reproduction



some researchers have questioned the sterility of
triploids
can produce some viable gametes, but the
proportion of such gametes is extremely low
Nevertheless, techniques used to induce triploidy
are not always totally effective and every
Triploid grass carp are indistinguishable in
external morphology from normal (fertile)
diploids