Age & Growth

Question 1

What is Somatic Growth?

Answer 1

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

Question 2

Length-Weight models assume growth…

Answer 2

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

Question 3

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

Answer 3

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

Question 4

Isomatic Growth

Answer 4

relative increase in all dimensions is the same as organism grows

most species do not exhibit isometric growth

Question 5

allometric growth

Answer 5

Growth in one dimension is proportional to some power of the other(s)

relative increase in one dimension is greater than others.

Question 6

allometric growth

Answer 6

Growth in one dimension is proportional to some power of the other(s)

relative increase in one dimension is greater than others.

Question 7

What type of data does Allometric Models fit well?

Answer 7

weight-at-length data

Question 8

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

Answer 8

von Bertalanffy Growth Model

Question 9

von Bertalanffy Growth Model

Answer 9

Includes maximum length ( L∞)

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

Can be modified to model
Ontogenetic shifts in growth
Seasonal growth

Question 10

Who introduced the von Bertalanffy Growth Model and when

Answer 10

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

Question 11

Explain the von Bertalanffy Growth Model

Answer 11

Question 12

How to study somatic growth?

Answer 12

Is studied at the individual level but used the physiological process to model growth to understand changes in population biomass

Question 13

Length & weight are measures of growth when related to …?

Answer 13

Age
Length vs Age - How quickly things are growing
Weight vs Age - How heavy things are growing
Length vs Weight

Question 14

Isometry

Answer 14

Same
L,W,D scale up proportionally to each other
Does not happen

Question 15

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

Answer 15

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

Question 16

von Bertalanffy Growth Model

Answer 16

Measures how fast that species will take to get its terminal growth.

Can use this to measure Ontogenetic shifts in growth or seasonal growth.

Question 17

L∞

Answer 17

Fish have indeterminate growth (L infinity)

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

Question 18

t0

Answer 18

sometimes called ‘initial condition’ parameter; fish growth begins at hatching

Question 19

High k (time-1)

Answer 19

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

Question 20

Low k

Answer 20

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

Question 21

What is another common model used?

Answer 21

Gompertz Growth Model

Question 22

Gompertz Growth Model weight at age mostly used for?

Answer 22

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

Question 23

Gompertz Growth Model Lenth at age model used for

Answer 23

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

Question 24

Why do we want to know about age and growth?

Answer 24

Life history
Management application

Question 25

Why is life history important?

Answer 25

Age at maturity
Birthdates
Spawning period
Survival
Growth rate
Habitat suitability

Question 26

Why is age and growth important to management?

Answer 26

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

Question 27

How to measure growth

Answer 27

Length
Weight
Wet or dry mass
Whole or eviscerated

Question 28

Methods of Aging: Length Frequency

Answer 28

Separation of sizes into age
Overlay normal distribution
Modal progression analysis → Growth

Caveats
Better for younger ages
Normality assumption

Question 29

Methods of Aging: Hard Parts

Answer 29

Deposition in alternating rings

Question 30

What are the two zones used for aging hard parts?

Answer 30

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

Question 31

What are the types of hard parts used for again?

Answer 31

scales, vertebrae, spines,

Question 32

What are the caveats for using hard parts for aging?

Answer 32

Loss & regeneration (scales)
Resorption (fin spines)
Validate the frequency of rings
Daily, annually, or not

Question 33

Scales used for aging

Answer 33

Non-lethal
Environmental and spawning marks
Regenerated

Preparation
Removal
Impressions/mounting
Reading (image analysis)

Question 34

What is an otolith?

Answer 34

Organ in the inner ear (Ear stone)

Question 35

What are the three types of otoliths?

Answer 35

Sagittus, lapillus, asteriscus

Sagittus is the one that is often used because it often larger than the other two.

Question 36

What are the benefits of using otoliths for aging?

Answer 36

Cannot be lost/regrown
No resorption or erosion

Question 37

What are downfalls?

Answer 37

Terminal for the fish

Question 38

How to prepare an Otolith:

Answer 38

Sectioning
Mounting
Grinding/polishing
Reading (image analysis)