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Fish Management > Final > Flashcards

Final Flashcards

1
Q

name some examples of fishing effort for CPUE

A
  • troller days
  • seine sets
  • gillnet hours
  • demersal trawl hours
  • skate sets
  • trap or pole sets
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2
Q

demersal trawl hours, complications

A

the amount of time a trawler drags its net across the bottom, but it is complicated by factors such as the power of the fishing vessel, speed, etc

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3
Q

skate sets, complications

A

skates are long line, which have hooks distributed along them with various spacing
C: hook spacing.

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4
Q

trap or pole sets, complications

A

this is the catch in a passive fishing gear as is used for crabs, lobsters, prawns, and fish like black cods.
C: variation in spacing of the traps as competition btwn traps occur.

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5
Q

describe the varying degrees of refinement of CPUE

A
  • # fishers using gill nets.
  • kg of fish/fisher/month
  • kg of fish/day (masks different fisher power)
  • kg of fish/fisher/day/100m length of gill net. (most refined)
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6
Q

Describe Mortality Rate**, what two types are there,

what is the equation

A

the rate at which fish are lost from the population due to death.
-Fishing mortality: mortality caused by a fishery (F)
-Natural mortality: mortality due to natural causes
Z=F+M

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7
Q

Leslie Plot of Stock Depletion is used to calculate what?

A

catch per unit effort

fish abundance, catchability

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8
Q

Name the assumptions for CPUE

A
  • no changes in fishing gear
  • no changes in operating strategies
  • no seasonal and daily weather affecting efficiency
  • no immigration/emigration
  • uniform fish distribution
  • no recruitment
  • no natural mortality
  • no different gear types operating on a single fishery with different fishing power
  • no catchability changes
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9
Q

what is the most important bias of all assumptions for CPUE? why?

A

Changes in gear
-as a fishery develops the gear develops as well, so a modern fishery may have the same numbers as a virgin fishery, even thought the modern fishery may have significantly reduced stocks.

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10
Q

in order to conduct 2 or 3 pass removals, how does the stream get divided?

A

into stratums, which may be riffle, glide, pool, or other. Then each stratum is randomly sampled to estimate the number of fish in it.

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11
Q

when electrofishing, how many passes should be made?

Ideally, what percentage of the population should be sampled in the first pass?

A
  • 2, but 3 will give best results

- 80% on the first pass

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12
Q

name the 3 assumptions for removals method (EFing, etc)

A
  • the population is closed
  • the probability of capture (p’i’) in the ‘i’th samle is the same for each individual exposed to capture
  • the probability of capture ‘p’ remains constant from sample to sample
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13
Q

why must the population be closed for the removals method?

A

because it depends on the decrease of the CPUE, so no immigrating/emigrating populations

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14
Q

what are two population data categories that serve to increase the biomass of a stock of fish as opposed to mortality which reduces biomass

A

growth of fish, recruitment

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15
Q

what is the difference between Linf and Lmax?

A

Linf is a size at which the increase in length is minimal (species)
Lmax is the measure of a specific stock

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16
Q

what is the equation for the weight/length relationship?

A

W=aL^b
W=weight
L=length
a and b= constants

17
Q

when preserving fish, what happens when preserved in:

  • alcohol/formalin?
  • freezing?
A
  • a/f=shortening

- f=lengthening

18
Q

when would you use a condition factor?

A

when comparing different stocks of fish, or a stock at different times of the year/years.

19
Q

what does a condition factor compare?

A

how heavy a fish is for its length

20
Q

in the equation:
W=aL^b
which coefficient is the condition factor?

A

the intercept, a.

21
Q

what are the four common units of growth?

which one is only used for selmelparous fish?

A
  • absolute growth rate
  • specific growth rate
  • instantaneous growth rate
  • von Bertalanffy growth coefficient

-instantaneous

22
Q

what is the name of this equation?

W1-W0/t1-t0

A

absolute growth rate

23
Q

what is the name of this equation?

W1-Q0)*100/W0(t1-t0

A

specific growth rate

24
Q

the three main means to determine a fish’s size and age are:

A
  • examination of hard parts such as otoliths
  • mark, recapture studies
  • size frequency distributions
25
Q

name common hard parts for analysis

A
  • otoliths
  • scales
  • vertebrae
  • fin spines
  • clithra
  • shell marks in mollusks
  • statoliths in cephalopods
  • teeth in marine mammals
26
Q

for hard part analysis, name three ways of obtaining time verification

A
  • mark recapture
  • otolith or scale marking with tetracycline
  • shell notching
27
Q

why use lea’s formula?

A

by using the space of a hard part between checks, it can determine the length of the actual fish.

28
Q

why use the swept area method?

A

used to estimate the abundance of demersal species wit a uniform distribution within their habitat.

29
Q

what is the swept area method?

A

a transect survey in which a trawl net is dragged along the bottom and the area covered by the trawl related to the amount of fish captures.
-measures abundance

30
Q

what is the traditional vs modern means of conducting a swept area method?

A

trawl nets vs ROVs

31
Q

how should the strata be divided for swept area method?

A

high, medium and low density, or sometimes just high and low.

32
Q

the area swept by the trawl, for swept area method, are a function of:

A
  • the velocity of the trawl
  • the time of the trawl
  • the size of the trawl opening
33
Q

what factors must be taken into consideration for swept area method?

A
  • which fish get caught compared to out swim
  • different species are more or less vulnerable to trawl gear
  • different sized fish
  • duration of trawl (which fish get tired faster)
34
Q

How do ROVs differ from trawl surveys for swept area method?

A
  • ROV estimates are often higher with lower variability for fish that are associated with the bottom which trawls have a difficult time capturing
  • ROV give lower abundance for patchy distributed fish
  • ROV give higher abundance variance b/c they only sample a narrow path
35
Q

MSY

A

maximum sustainable yield- made from trawl surveys

Fish Management (3 decks)

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