##
Recent Developments in Larval Fish Trophodynamic
Modeling

Francisco E. Werner, John A. Quinlan
Greg Lough, Larry Buckley,
Jeff VanKeuren and
Christopher E. Naimie

One of our objectives is to explain observed larval distributions
and growth rates during the 1995 Stratification Experiment. We will
simulate field estimates of light, turbulence, temperature and prey
distribution in a trophodynamic model of larval cod and haddock. In
particular, we want to see if we can reproduce observed growth rates
of 10-15% per day (in weight) for larvae initially 8mm in length
(approximately 300 micro-gm in weight). We use a one-dimensional
point model (t vs. z; Naimie, 1996) forced by winds and sea-level
gradients to obtain turbulent dissipation rates and
stratification. The trophodynamic model is based on Laurence's
bioenergetic formulation extended to include effects of turbulence
on encounter and capture success, preferred prey size range (Werner
et al. 1996), temperature effects on metabolism (Laurence, 1981),
and light limitation (Huse, 1994; VanKeuren, 1997). We find, using
idealized prey and light fields that we can reproduce (and exceed)
field derived growth rates of 10-15% per day in certain regions of
the water column. Our next step will be to input observed, depth
and time-dependent prey fields for May 1995. We will also explore
alternative formulations for temperature effect on metabolism and
begin to develop behavioral rules based on choices (of position in
the water column through active swimming) that optimize growth
rates, intake rates, and reduce metabolic costs.