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Flashcards in Aquatic Ecology final Deck (324)
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181

Importance of letting fish grow big

reproductive output
large fish = higher reproductive output
23"in vermilion can produce 17X more young than 14"

182

Sustaining Sea Otter, kelp forest

protects fish abundance, mussel growth, other inverts and crustaceans, changes to predatory sea bird resources

183

Fish Abundance, sea otter presence

~5X higher w/ S.O. present

184

Mussel Growth, sea otter

~2X w/ s.o. present

185

Gull diet, sea otter

Diet is 90% fish w/ s.o. present
90% macro inverts. without sea otter

186

Bald Eagle diet, sea otter

s.o. present: diet is fish, mammals, birds ~ equal
s.o. absent: ~70% of diet is seabirds

187

control sea urchin populations

sea otter
predatory fish species
spiny lobsters

188

urchin/kelp feedback

lack of predation-- urchin population boom-- urchins feed on kelp holdfast-- kelp wash away in tide-- habitat is lost

189

Anacapa Island MPA

California - predatory fish, lobsters regaining populations- increased urchin predation- sustainable kelp forest

190

Idealized MPA

Equilibrium state:
maximized species diversity
many linkages in food web
redundancy
stability

191

Ecological redundancy

organisms having several food sources

192

"Spillover effect"

= export of adult fish out of MPA
high fish density within MPA - leave protected area (no physical boundary)

193

MPA size determination

dependent on species to be protected
too large detracts from fishery
too small ineffective

194

Sizes of MPAs

not self-sustaining
moderately self-sustaining
completely self-sustaining

195

MPA not self-sustaining

most species lost
high periphery : area
unsustainable
small effect on recruitment and commercial fishing
too much loss out of reserve to be effective

196

MPA moderately self-sustaining

some species lost
adequate periph:area
some individuals retained
significant source of recruits to fished area
some reduction of fishing grounds
good balance of benefits for all

197

MPA completely self-sustaining

all species retained
low perish:area
small spillover
little recruitment outside reserve
severe reduction to fishing ground
little export

198

Where should MPAs be?

vulnerable habitats
important habitat
species rich habitat
spawning grounds

199

MPA and migratory species

doesn't really protect migratory species, better for stationary species (ex. rock cod)
DOES increase salmon prey though

200

MPA vulnerability

currents flow through, pollutants can flow through
MPAs necessary but not adequate

201

Lake Victoria

SA 69500km^2
depth Zm = 39m
several invasives: Nile Perch, water Hyacinth
overfishing (gillnets)
massive loss of endemics
loss of Oreochromis fishery

202

Lake Victoria native population

300 Cichlid fish
most diverse cichlid population
2/3 gone
highest vertebrate extinction rate
Oreochromis sp. (algal feeder) - major protein source

203

Management troubles of Lake Victoria

shared by 3 countries that don't get along
Uganda, Kenya, Tanzania

204

Water hyacinth

mostly near shore environment- highly mixed/dynamic water bodies, sheltered small basins
clog up waterway

205

Major aquatic plants (invasive)

Hydrilla (US)
Elodea (Europe)
Eurasian milfoil (NA)
Purple loosestrife (NA)
Canary Reed Grass (NA)
take over shallow transparent water bodies
huge economic losses

206

Invasive plant management

Herbicides
Mechanical harvesting
biological control

207

Invasive plant management, biological control

introduce something else that will prey on it (kind of like how coopers hawk controls European starlings)

208

Invasive plant management, mechanical harvesting

bulldozers!

209

Nile Perch

large piscivorous fish
introduced in 1960 for British sport fishing
up to 300lbs

210

Lessons of Lake Victoria

introduction of one species changed entire trophic dynamics of one of the largest lakes in the world