Age & Growth Flashcards

1
Q

What is Somatic Growth?

A

The mechanism and results of fish adding weight
At the individual level: eating more food
Results in an increase in biomass of the stock
Links size and age

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2
Q

Length-Weight models assume growth…

A

is at least a 3-dimensional process
Length, width, and depth

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3
Q

What is the simplest assumption associated with length-weight models?

A

L, W, D change in proportion to one another = isometry

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4
Q

Isomatic Growth

A

the relative increase in all dimensions is the same as the organism grows

most species do not exhibit isometric growth

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5
Q

Allometric growth

A

the relative increase in one dimension is greater than others.

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6
Q

What type of data does Allometric Models fit well?

A

weight-at-length data

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7
Q

What is the most common length-at-age model applied?

A

von Bertalanffy Growth Model

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8
Q

Who introduced the von Bertalanffy Growth Model, and when?

A

von Bertalanffy described model in 1938; introduced by Beverton & Holt in 1957

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9
Q

Explain the von Bertalanffy Growth Model

A

Rate at which individuals approach L∞ is constant (k)

model fit to data of a long-lived species

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10
Q

When broad size ranges are considered, the allometric model slight, but consistently, overestimates ____________?

A

weight at length for fish at the extremes (small and large)

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11
Q

L∞

A

Fish have indeterminate growth (L infinity)

L infinity – is the point where they don’t grow much more.

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12
Q

t0

A

Sometimes called the ‘initial condition’ parameter, fish growth begins at hatching

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13
Q

von Bertalanffy Growth Model - High k

A

Shorter life span
Low age & size at maturity
High reproductive output

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14
Q

von Bertalanffy Growth Model - Low k

A

Longer life span
Greater age & size at maturity
Lower reproductive output

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15
Q

What is another common model used?

A

Gompertz Growth Model

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16
Q

Gompertz Growth Model weight at age mostly used for?

A

Used to model the growth of invertebrates, skates, rays & some sharks

17
Q

Gompertz Growth Model Lenth at age model used for

A

Used to model the growth of young fish (within the first year)

18
Q

Why do we want to know about age and growth?

A

Life history
Management application

19
Q

Why is life history important?

A

Age at maturity
Birthdates
Spawning period
Survival
Growth rate
Habitat suitability

20
Q

Why is age and growth important to management?

A

Catch- or size-at-age
Selectivity of gear types
Age-structured stock assessments
Recruitment/year class strength

21
Q

How to measure growth

A

Length
Weight

22
Q

What are the two zones used for aging hard parts?

A

Hyaline zone – translucent, protein-rich ring
Opaque zone – calcium-rich layer

23
Q

What are the types of hard parts used for again?

A

scales, vertebrae, spines,

24
Q

What are the caveats for using hard parts for aging?

A

Loss & regeneration (scales)
Resorption (fin spines)
Validate the frequency of rings

25
Scales used for aging
Non-lethal Environmental and spawning marks Regenerated
26
What is an otolith?
An organ in the inner ear (Ear stone)
27
What is the most common otolith used?
Sagittus because it often larger than the other two.
28
What are the benefits of using otoliths for aging?
Cannot be lost/regrown No resorption or erosion
29
What are downfalls?
Terminal for the fish
30
How to prepare an Otolith:
Sectioning Mounting Grinding/polishing Reading (image analysis)