## Linear Recruitment Model

The simplest spawner-recruit model assumes a linear (density-independent) relationship between spawning biomass and recruits:

Under this model, recruitment has no upper limit, which could allow population growth to infinity. For that reason, the linear model is seldom applied to real populations, but its simplicity retains value in theoretical studies.

The versions are equivalent, given a = 1/[ and [ = a/[. Here a is the asymptotic level of recruitment; [, the level of S at which recruitment is half its asymptotic level.

Unfortunately, spawner-recruitment data rarely fit models well, leading to considerable uncertainty. An alternative form of the Beverton-Holt model uses external data to constrain or fix recruitment parameters. In this form (Figure 2a), the two parameters are the recruitment R0 from the stock when unfished and steepness h, defined as the proportion of R0 produced by 20% of S0, the spawning biomass of the unfished stock. (The value of 20% is arbitrary but conventional.) In this parametriza-tion, the model becomes

0.8R0hS

with 0.2 < h <1.0. Steepness quantifies resilience to exploitation, and its values have been estimated by several authors through meta-analysis. Although R0, like a, is

Was this article helpful?

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