Fisheries And Marine Habitat

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Published on 15 Mar 2019
School
LSU
Department
Renewable Natural Resources
Course
RNR 1001
Professor
Fisheries and Marine Habitat
-Lentic systems (Still water systems) provide several distinct habitats that can be important for fisheries
production. These Habitats often have different structural complexity, water quality, and biota.
-Thermocline - Where there is a significant drop in temperature in a body of water depth-wise.
-Thermocline formation is related to the annual mixing cycle - critical to lentic fisheries
-The annual cycle depends on water temperature (and density) and wind velocity
-Ex. Lake temp during winter is 4-6 degrees C with a layer of ice at top. Spring overturn
comes, ice melts, and the wind mixes around water (that is all same density). Summer
stratification happens, wind stops blowing as much and the sun warms up the top layer of
water leaving colder water at bottom creating a thermocline (stratified). Develop hypoxia
(low oxygen; less than 2 mg/l). Fall overturn, wind blows mixing water then water becomes
colder and colder until it's winter again.
-Lotic Systems (Flowing water systems) also provide distinct habitats that can be important for fisheries
production. These habitats are typically characterized by differences in depth, flow velocity, and
substrate.
-Riffle - large shallow substrate, shallow, breaks surface, fast flow
-Glide - deeper than riffle, see water flowing, but doesn’t break surface
-Pool - deep substrate, mostly sand
-In most systems, riffles are important as habitat for invertebrates, including aquatic insects such as
mayflies, stoneflies, and caddisflies. Very indicative of stream health. Finding a lot means that water is
very clean, no pollution, right amount of nutrients, ect.
-Black fly - indicative of poor stream health. Too much organic matter, nutrient additions, ect.
-Although some fish prefer riffles, most are found in pools, feeding on invertebrate drift.
-Darter - fish that likes to live in riffles, eats the bugs in riffles.
-Reservoirs have both lotic and lentic characteristics, the most important to humans is that reservoirs
often provide higher DO levels in the profundal zone than lakes.
-Fish that need low temperatures and high dissolved oxygen may not be able to live in a lake but
could live in a reservoir since there's just enough water flow to dissolve more oxygen.
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Document Summary

Lentic systems (still water systems) provide several distinct habitats that can be important for fisheries production. These habitats often have different structural complexity, water quality, and biota. Thermocline - where there is a significant drop in temperature in a body of water depth-wise. Thermocline formation is related to the annual mixing cycle - critical to lentic fisheries. The annual cycle depends on water temperature (and density) and wind velocity. Lake temp during winter is 4-6 degrees c with a layer of ice at top. Spring overturn comes, ice melts, and the wind mixes around water (that is all same density). Summer stratification happens, wind stops blowing as much and the sun warms up the top layer of water leaving colder water at bottom creating a thermocline (stratified). Develop hypoxia (low oxygen; less than 2 mg/l). Fall overturn, wind blows mixing water then water becomes colder and colder until it"s winter again.