Bio 346 - Freshwater Eco. (Chpt 15) --> Use and Abuse and Restoration of Standing Waters Flashcards
What services does standing water provide? (4 things)
- Fisheries (rec and food)
- Drinking water storage and improvement
- Useful
- Recreational
What are the 5 negative effects of standing waters?
- Overfishing
- Eutrophication
- Poor reservoir design and operation
- Introduction of alien species
- Drainage and toxic pollution
What can help decrease the negative effects of standing waters?
Remedies and restoration
What is the solution of overfishing in fisheries?
Only fish the species that can stand up to fishing should be taken (be able to reproduce itself quickly)
What should be done in order to protect the stock?
Monitoring of catch and imposition of regulations on the fisheries
What happens to the yield as the fish are overfished?
Decrease
Why is yield always lower than the production rate?
- Because some fisheries are unsuitable biologically for sustained fisheries
- Hard to catch
- Cant use as food
What 3 things are required to maintain fisheries?
- The biology of the fish should be understood
- Only those species whose populations will stand up to fishing should be taken
- Should be monitoring of the catch and impositions of regulations on the fishery to protect the stocks
What 2 things increase in fish yields?
- Population
2. Economic pressure
What is hatching dependent on?
- Temp
2. Food availability
How much energy is needed to find large amount of food for large fish compared to small?
Less energy
Where do older trout like to hunt?
At the bottom of the water
Where do most species feed?
In mid waters on small species
Eg) zooplankton
What benefit do the dorsal and anal fins provide?
Provides a powerful tail thrust which allows them to have a burst of high speed
What is an example of a defence mechanism on some fish?
Some fish have spiny pectoral fins which would lodge in the throat of a predator when swallowed tail first
- This gives a grater chance to escape while the predator has to turn their prey around
- Also decreases the chance of getting stuck between rock crevices
What do young fish eat compared to older fish?
- Young fish eat only soft, submerged plants
- Older fish tackle the more emergent plants
What are 3 things that breed gin depends on?
- Environment
- Recruitment number
- Quality
What happens if breeding occurs to late?
High chance of failure to bread through early death
What happens if breeding occurs to early?
Fish may be too small and unable to cope with the energy demands
What are the 2 types of spawning?
- Spawning once and then die (putting all of their energy into reproduction)
- Spawn multiple times
What is essential to make a wise choice of species for a sustainable fishery?
Knowledge of the history of the fish
Mortality rate shouldn’t be grater than what 2 things?
- Growth rate
2. Addition of new species
Where do pelagic fish live?
In unstructured waters, with high risk of predators
What does egg guarding and low egg production and mortality mean?
Low recruitment rates
How is the production of fish measured?
Production is estimated as the increase in weight of the population per unit time and usually per unit area
What is the most widely used method of sampling fish?
By using the mark and recapture method
- Works best in smaller sample sizes
What is a length / weight graph beneficial for?
Not having to measure every fish in the future
- Can get as estimate based on the graph