Dear Phi Dot Forum,

I have started my analysis of some shark mark-recapture data by exploring p and phi using a CJS model. The 'best' model is one where p is constrained by a measure of sampling effort (and so I know that in my study the level of effort affects capture probability). All credit to "The Gentle Guide..." for teaching me how to do this....

Anyway, my next step is to estimate abundance using a POPAN model. Working from my earlier CJS analysis I have constructed a model where p is again constrained by a measure of effort; but I have hit a hurdle. I can't quite get to grips with how many parameters it should be estimating.

So I have 24 capture sessions, and in my CJS "effort" model {phi[.]p[time - effort constrained]} I get 3 parameter estimates: 1 phi, and 2 p (intercept and slope). Correct?

But in my POPAN model {phi[.]p[time-effort constrained]b[time]N} how do I work out the number of parameters that should be estimated? Is it 1 phi, 2 p, 23 b and 1 N?

I'm sorry to ask, but the Guide doesn't cover linear constraints in POPAN models. Any thoughts/answers will be much appreciated.

Tim