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c. Zimmermann and G. Hubold
After a synchronization of the parameters, a linear regression between
activity (in terms of movements per unit time, usually 2 min) and
respiration (for the identical interval) was computed. Standard oxygen
consumption rate was determined by extrapolation to zero movements,
following a procedure used earlier this century [20-22] with different setups. With this approach, determination of SOC was possible even when
the fish never displayed phases of inactivity. Standardization to SOC is a
prerequisite to compare the metabolism of active and inactive fish,
although the SOC value has no direct relevance for an active species like
the polar cod.
A number of different variables were recorded in each experiment to
quantify fish activity and respiration as well as experimental conditions.
An intricate pattern of intercorrelations exists between these variables. It
can be assumed that complex factors (such as the "mode of life"), which
cannot be measured directly, are underlying these variables. A factor
analysis was conducted to identify these hypothetical parameters, based on
the correlation matrix of the variables [23-24]. To avoid collinearities,
variables with correlation coefficients >0.75 were excluded. The 9
variables chosen for the factor analysis were:
- parameterizing activity:
• mean movement rate ("move mean")
• quotient of maximum and mean movement rate obtained during one
experiment ("move quot")
• mean duration of phases between two movements ("pause mean")
- parameterizing respiration:
• calculated standard oxygen consumption ("SOC")
• factorial scope for activity, the ratio between respiration during
maximum activity and SOC, which gives a measure for the metabolic
capacity of an animal [25]
• slope of the regression curve between activity and respiration as a raw
measure for the energy requirements of a single move ("slope actJresp")
- parameterizing experimental conditions:
• mean temperature ("temp mean")
• maximum temperature range during one experiment ("temp diff') and
• relation between fish volume and respiration chamber volume, as a
measure for the space available for the specimen ("space").
All values were adequately transformed (reciprocals of "move" and
"pause" and logarithms of all other variables) prior to correlation
computations. Principal components were extracted from the correlation
matrix, orthogonally rotated and orthotranlvarimax transformed. Finally,
the component scores were calculated.
c. Zimmermann and G. Hubold
After a synchronization of the parameters, a linear regression between
activity (in terms of movements per unit time, usually 2 min) and
respiration (for the identical interval) was computed. Standard oxygen
consumption rate was determined by extrapolation to zero movements,
following a procedure used earlier this century [20-22] with different setups. With this approach, determination of SOC was possible even when
the fish never displayed phases of inactivity. Standardization to SOC is a
prerequisite to compare the metabolism of active and inactive fish,
although the SOC value has no direct relevance for an active species like
the polar cod.
A number of different variables were recorded in each experiment to
quantify fish activity and respiration as well as experimental conditions.
An intricate pattern of intercorrelations exists between these variables. It
can be assumed that complex factors (such as the "mode of life"), which
cannot be measured directly, are underlying these variables. A factor
analysis was conducted to identify these hypothetical parameters, based on
the correlation matrix of the variables [23-24]. To avoid collinearities,
variables with correlation coefficients >0.75 were excluded. The 9
variables chosen for the factor analysis were:
- parameterizing activity:
• mean movement rate ("move mean")
• quotient of maximum and mean movement rate obtained during one
experiment ("move quot")
• mean duration of phases between two movements ("pause mean")
- parameterizing respiration:
• calculated standard oxygen consumption ("SOC")
• factorial scope for activity, the ratio between respiration during
maximum activity and SOC, which gives a measure for the metabolic
capacity of an animal [25]
• slope of the regression curve between activity and respiration as a raw
measure for the energy requirements of a single move ("slope actJresp")
- parameterizing experimental conditions:
• mean temperature ("temp mean")
• maximum temperature range during one experiment ("temp diff') and
• relation between fish volume and respiration chamber volume, as a
measure for the space available for the specimen ("space").
All values were adequately transformed (reciprocals of "move" and
"pause" and logarithms of all other variables) prior to correlation
computations. Principal components were extracted from the correlation
matrix, orthogonally rotated and orthotranlvarimax transformed. Finally,
the component scores were calculated.