Basic Forces

The simplest representation of the dynamics of a fish stock, represented in units of biomass, is that due to Russell:

where B is stock biomass, t denotes time (conventionally measured in years), G is somatic growth of individuals, R

is biomass increase due to recruitment (addition of young individuals to the stock), Y is yield (catch in weight) from fishing, and D is loss of biomass from deaths due to other causes. These are the four basic forces considered in models of fish population dynamics.

An equation parallel to eqn [1] can be written for stock size in numbers. Notably, it would omit the term expressing somatic growth.

Generally, external influences such as environmental forcing are either assumed unimportant or modeled as modifying one of the four basic forces. Because eqn [1] models a closed stock, migration in or out is excluded by definition. Stock mixture is usually modeled as exchange between two otherwise independent stocks.

Was this article helpful?

0 0
Oplan Termites

Oplan Termites

You Might Start Missing Your Termites After Kickin'em Out. After All, They Have Been Your Roommates For Quite A While. Enraged With How The Termites Have Eaten Up Your Antique Furniture? Can't Wait To Have Them Exterminated Completely From The Face Of The Earth? Fret Not. We Will Tell You How To Get Rid Of Them From Your House At Least. If Not From The Face The Earth.

Get My Free Ebook

Post a comment