Oneida Lake: Long-term Dynamics of a Managed Ecosystem and Its Fishery

Chapter 22: Growth Parameters as Growth Indices in Time-varying Environments: a Comparison among Four Approaches to Using the von Bertalanffy Growth Function

Ji X. He, Donald J. Stewart, and Lars G. Rudstam

doi: https://doi.org/10.47886/9781934874431.ch22

The growth rate of fish can be a useful indicator of environmental changes when fish growth is influenced by biotic environmental conditions such as prey and competitor abundances, and abiotic environmental conditions such as water temperature and clarity (Weisberg 1993; Rudstam et al. 1996). Fish growth in a given year, however, also depends on previous growth history because animal physiology is size dependent (Peters 1983). In practical applications, it is often difficult to separate year-specific environmental impacts on fish growth from the contribution of cohort-specific growth over time (Weisberg et al. 2010).

A simple descriptive statistic such as an average annual length increment can be used as a growth index (Hile 1941; Forney 1965). An elaboration of this index is the year effect from general linear models that treat annual size increment at a given age as being the result of additive effects of the age and year (Weisberg 1993; Ostazeski and Spangler 2001; Coffin et al. 2003). Size affects growth, however, and the effect of past growth history on current growth are not included in these growth indices (Weisberg et al. 2010). Neither can these indices capture the situations where the environment has different effects on different sizes of fish, and time trends of size-at-age can differ among age classes (Forney 1965; He and Bence 2007). For example, annual growth of Oneida Lake Walleye Sander vitreus from 1944 to 2000 increased for age-0 and age-1 fish, did not change for fish of intermediate ages and decreased for older fish (He et al. 2005). A simple index of average growth across age groups cannot account for such patterns in fish growth over time.