Question

Turns out that some of our team have been using the fatmeter not quite as indicated in the manual (Salmon-1 program).

In other words, they have been measuring the fat more or less on the sideline of the fish, not above the sideline as indicated in the manual, and a bit askew from the designated areas. Will this affect our results significantly?

Answer

For a fish of similar  size and weight… if you measure directly on the lateral line of the fish, then the measurements will be much more variable when measured on the lateral line, than if measured above the lateral line.

The reason… directly under the skin on the lateral line there is a strip of brown flesh, which tends to contain more fat and the amount of fat present in this area  can vary significantly,  from one fish to another, and can be caused by seasonal changes.  If you measure above the lateral line then you are measuring directly into the fish flesh / muscle area, and this is much more repeatable / representative, and fat distribution in the flesh / muscle is less variable, from one fish to another, and seasonal changes  are minimal.

What to do… Please select a number of samples of fish, and proceed as follows…

1. The team should take readings ON the lateral line of the fish, as before, and note the measurement values
2. The team should then take readings ABOVE the lateral line, as recommended in Measurement Charts supplied, and note the measurement values.
3. Once you have collected the data, prepare a graph / chart of the measurements for each group, and extrapolate the data accordingly.   You can then compare the data “scatter” from one group, with the other group.
4. You can also compare the “mean” values of the TWO data sets, and use the chart to correct previous data sets.