Chapter 8 Flashcards
key points of stock assessment
understand the dynamics and distribution of fish populations under varying environmental conditions
Why do stock assessments? (4)
understand human and natural impacts on fish
Interpret status of a population
Recommend sustainable population sizes (conservation)
Forecast expected returns in the futures (fisheries management)
the three prominent tenets of salmon management
1) stock concept- populations are most productive in their home streams
2) Spawner-Recruitment production- relationships, also MSY
3) Hatchery production and unlimited ocean capacity.
4 steps to doing stock assessment
- Data collection
- data analysis
- prediction
- prediction evaluation and re-assess data needs
Name some methods for Juvenile data collection:
- fry traps
- lake hydro accoustics
- rotary screw traps
- smolt fences
- counting boards
Data collection: Spawning Adults. How?
Dead pitching
boat or areial survey
river fences
river swims and stream walks
Data collection: Migrating Adults. How?
test fisheries
sonar
counting towers
aerial surveys
Why is understanding the age composition of a population important?
for defining POPULATION DYNAMICS of that stock. i.e.: we cant determine the age of the spawners, therefore we cant predict the age of return for their young.
What do Otholiths consist of?
three pairs of small carbonate bodies called LAPILLI, ASTERISCI AND SAGITTAE.
what are population dynamics?
- capacity
- rates of reproduction (productivity)
- rates of maturation (role of age estimation in the big picture).
what is the name of the horizontal line in the rickers curve?
line of equal replacement (1:1)
What is the area above the horizontal line in the rickers curve called?
increasing population size
What are the three manners in which salmon are density dependant?
1: Nest superimposition and nest site limitations
2: Predation and competition in FW phase
3: Predation and competition in marine phase
what is ‘nest superimposition’
when a female digs up another female’s nest.
what can occur when there is a large number of fry reared?
competition for food and cover can be high, which leads to reduced growth and ultimately reduced ocean survival.
