Document 2696103

Aquatic habitats
National Geographic
Freshwater habitats
Freshwater habitats
- lotic -
small streams
mature rivers
wetlands
Freshwater habitats
- lentic -
large lakes
Ponds, small lakes
ice
Aquatic environment
mean
depth
extreme
depth
area
volume
fresh
1%
0.01%
few
meters
1,600 m
(Baikal)
salt
70%
97%
3,790 m
11,000 m
(trenches)
Marine Conservation Society UK
Aquatic environment
• salinity – from 0 to 70 ppt
Fresh water = 0-2 ppt
Brackish (estuarine) = 2-30 ppt
Salt water = 35 ppt
– in fresh water, fish must resist osmotic intake of water
– in salt water, fish must retain water and excrete salts
Aquatic environment
• salinity – from 0 to 70 ppt
• temperature - < 0 to > 30 C
– water has high heat adsorbance, 4 x that of air
– fish are metabolically adapted to different temperature ranges; few
are widely eurythermal
– a few fish are adapted to temperatures below freezing
Aquatic environment
• salinity – from 0 to 70 ppt
• temperature - < 0 to > 30 C
• motion – stagnant to torrents
– various morphological adaptations to moving water
Aquatic environment
•
•
•
•
salinity – from 0 to 70 ppt
temperature - < 0 to > 30 C
motion – stagnant to torrents
dissolved materials - gases, solids
–
–
–
–
oxygen in water relatively unavailable, compared to air
methods to acquire oxygen are varied
too little oxygen >> air breathing
too much oxygen >> gas supersaturation problems
Aquatic environment
•
•
•
•
•
salinity – from 0 to 70 ppt
temperature - < 0 to > 30 C
motion – stagnant to torrents
dissolved materials - gases, solids
pressure – deepest water is 11,000 m (6.9 miles, 11 km)
– pressure increases 1 atm for every 33’ (10 m) of depth
– to maintain buoyancy, fish must compensate with air or lipids
– skeletal structure of deep sea fish is reduced due to support by
water
Aquatic environment
•
•
•
•
•
•
salinity – from 0 to 70 ppt
temperature - < 0 to > 30 C
motion – stagnant to torrents
dissolved materials - gases, solids
pressure – deepest water is 11,100 m (6.9 miles, 11 km)
viscosity – water is 800x more dense than air
– requires much more effort to move through water than air
– streamlining is critical; max. speed (tuna) is ~ 21 m/sec
Aquatic environment
•
•
•
•
•
•
•
salinity – from 0 to 70 ppt
temperature - < 0 to > 30 C
motion – stagnant to torrents
dissolved materials - gases, solids
pressure – deepest water is 11,100 m (6.9 miles, 11 km)
viscosity
light - attenuates with depth, turbidity
– many fishes adapted to zero light conditions
– some fishes generate their own light
– issues for color
Aquatic environment
•
•
•
•
•
•
•
•
salinity – from 0 to 70 ppt
temperature - < 0 to > 30 C
motion – stagnant to torrents
dissolved materials - gases, solids
pressure – deepest water is 11,100 m (6.9 miles, 11 km)
viscosity
light
sound - travels 4 x faster in water than air
– directionality is difficult to achieve