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Aquatic Biodiversity
Nonindigenous speciesThreatened 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 What determines this?
Species Richness 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: between-habitat
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 1800sArizona in 1920 Missouri from 1879 to 1914
Round Goby
Introduced to Great Lakes in 1990svia 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