Abstract
Selection of installation sites for fish-ways often adapts previous experience of locating fish-ways. Therefore, with the goal of developing a fish population dynamics model designed for networking of water areas, we investigated applicable values of the important parameter r which represents the growth rate of fish populations on newly connected areas. The target species was field gudgeon, Gnathopogon elongatus elongatus. We calculated survival rates using cohort life tables obtained by assuming a stable age distribution, based on the results of field surveys of their total length, and past studies about reproduction. To consider the uncertainty of these survival rates, we performed Monte Carlo simulations on a newly connected area under density-independent condition, giving survival rates some random fluctuation. The range of introduced fluctuation was derived from past studies about other fish species. A value for r of 0.36 is thought to be an applicable and conservative value on average that avoids overestimating the effects of networking of water areas. The range of fluctuation of r should be determined depending on the length of time over which computations are performed.
