Quiz 6 Flashcards
Unique aspects of stocks
- life history characteristics
- demographics
- morphology
- genetic distribution
Was is a fish stock
-a group of fish that is distinct in space or time
Natural marks for stock discrimination
- naturally occuring differences
- includes morphology pattern, coloration, life-histor, chemistry
- all fish get tagged
Artificial marks for stock discrimination
- conventional/electronic/chemical tags
- individual fish require tagging
- mark/recapture issues
Stock discrimination
-the ability to recognise a group of fish as separate groups
Assumptions to natural marks
- marks are characteristic and reproductible
- all groups contributing to group mixing are classified
- the mark is stable
Genetic analysis with nuclear material
- allozymes
- microsatellite markers
- mitochondrial DNA
Microsatellite markers
- much more diverse
- provides info about population structure, migration/dispersal
Mitochondrial DNA
-good for evolutionary applications, especially rapid evolution
Gel electrophoresis
- sorts DNA fragments according to length
- DNA visualized by staining and illuminating under UV light
Unit stock is a discrete group of individuals:
- from the same gene pool
- self-perpetuating
- fished and managed as a stock
Different methods of sampling
- uniform
- random
- aggregated
- gradient
How to get an unbiased estimate of population
-stratifying sampling effort
Different ways to estimate abundance
- direct estimates (visual counts
- hydroacoustic surveys
- indirect estimates (calculations)
CPUE
- catch per unit of effort
- used for long-term monitering
- important to standardize effort
passive vs active gear
- passive: trap nets - organisms wander in
- active: trawliing or seining
swept area method
vol swept = (size of net opening) * speed * duration
Mark-recapture method
- collect fish under assumption of the unit stock
- mark fish, return them so they can mix evenly back into pop
Peterson method
-estimates pop abundance N(hat) = (MC)/R M = # of fish marked N = total # of fish in pop C = # of fish collected 2nd time R = # of recaptures -error occurs when R = 0
Bailey’s method
-used when pop abundance sampling with replacement
= (M(C+1))/(R+1)
Chapmans method
-sampling for pop abundace is done without replacement
=(((M+1)(C+1))/(R+1)) + 1
Why would we do repeated marking techniques
-to avoid being biased towards N
How can marked fish dissapear
- mark retention is poor
- fish are trap-shy
- difficult to recognize marked fish
- immigration and death
Schnabel estimator
= sum(CM)/sum(R)