Fish Population Dynamic and Stock Assessment (2+1)

Points to be noted while drawing curves

1. The intervals on the time axis between the various samples must be proportional to the time elapsed between the sampling dates.
2. The original data must be plotted atleast twice, or more along the time axis, which allows for longer, stabilized growth curves to be drawn and for all relevant age groups to be included in one single line.
3. When several growth curves are drawn(reflecting the production of several broods per year), the various growth curves should have the same shape, and vary only as to their origin.
4. The scale of the ordinate (length) should start at zero, thus allowing approximate spawning periods to be identified.
5. Each growth curve must interconnect several peaks. The more peaks a curve inter connects, the more likely it is to depict the actual growth of the population.
6. The model lengths corresponding to various ages (starting from an arbitrary age) can be read off the curve at regular time intervals, and may be then used to determine the growth parameters.

Alternatively,plot the modes in the form of a scatter diagram against time in successive months and then trace their progression. See whether growth could be traced from the very origin of each brood to its maximum model position and based on which plot age length key (Fig.2)