Age & Growth Flashcards
What is Somatic Growth?
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
Length-Weight models assume growth…
is at least a 3-dimensional process
Length, width, and depth
What is the simplest assumption associated with length-weight models?
L, W, D change in proportion to one another = isometry
Isomatic Growth
the relative increase in all dimensions is the same as the organism grows
most species do not exhibit isometric growth
Allometric growth
the relative increase in one dimension is greater than others.
What type of data does Allometric Models fit well?
weight-at-length data
What is the most common length-at-age model applied?
von Bertalanffy Growth Model
Who introduced the von Bertalanffy Growth Model, and when?
von Bertalanffy described model in 1938; introduced by Beverton & Holt in 1957
Explain the von Bertalanffy Growth Model
Rate at which individuals approach L∞ is constant (k)
model fit to data of a long-lived species
When broad size ranges are considered, the allometric model slight, but consistently, overestimates ____________?
weight at length for fish at the extremes (small and large)
L∞
Fish have indeterminate growth (L infinity)
L infinity – is the point where they don’t grow much more.
t0
Sometimes called the ‘initial condition’ parameter, fish growth begins at hatching
von Bertalanffy Growth Model - High k
Shorter life span
Low age & size at maturity
High reproductive output
von Bertalanffy Growth Model - Low k
Longer life span
Greater age & size at maturity
Lower reproductive output
What is another common model used?
Gompertz Growth Model
