POPAN and CJS question...

questions concerning analysis/theory using program MARK

POPAN and CJS question...

Postby Fish_Boy » Tue Jan 22, 2019 4:24 pm

This is applicable to any encounter history I am sure, but I focus on POPAN and CJS... So how does MARK 'know' when individuals out grow a sample gear type? For example, our netting surveys are consistent in season, duration, location etc. and the age of individuals susceptible to the mesh sizes is about 10-12 years old. Once an individual's encounter history get to >12 years, how do we tell MARK that individual is no longer available?

This same issue is relevant for our longer term data sets that are pushing 23 years, where certain tag series are no longer captured (as the individuals have died or been harvested). Any advice on how to deal with this would be greatly appreciated.
Fish_Boy
 
Posts: 65
Joined: Fri Oct 28, 2005 2:12 pm
Location: Winnipeg

Re: POPAN and CJS question...

Postby cooch » Tue Jan 22, 2019 6:31 pm

This sounds like a particular application of 'individual covriates'. If you are willing to 'flip a switch' for any animal a certain number of years since marking, such that after that number of years, p=0, then you can probably get there from here. Clever use of the IF functions: eq (equal to), gt (greater than), ge (greater than or equal to), lt (less than), le (less than or equal to).
cooch
 
Posts: 1628
Joined: Thu May 15, 2003 4:11 pm
Location: Cornell University

Re: POPAN and CJS question...

Postby murray.efford » Wed Jan 23, 2019 2:51 am

Just thinking out loud, and in ignorance of MARK ... isn't this more in the nature of an offset rather than an individual covariate, in that there should be no need to _estimate_ a coefficient if fish become untrappable deterministically at a known age? Or you might build an age-related binary covariate in the design matrix and then fix any coefficient (cutoff age?) at a known value.
Also, does the attrition of ancient cohorts in a long term study need anything more than the usual probabilistic mortality?
Murray
murray.efford
 
Posts: 686
Joined: Mon Sep 29, 2008 7:11 pm
Location: Dunedin, New Zealand

Re: POPAN and CJS question...

Postby Fish_Boy » Wed Jan 23, 2019 1:09 pm

Thank you for the responses! I will need to RTFM and brush up on design matrix applications. As I have not gotten that far under the hood since the MALCLLIK example at a workshop 11 years ago.

I suspect Murray is correct for the older cohorts in the the long-term study, conceivably these fish can be >100 years old, so it may not ever become an issue.
Fish_Boy
 
Posts: 65
Joined: Fri Oct 28, 2005 2:12 pm
Location: Winnipeg


Return to analysis help

Who is online

Users browsing this forum: No registered users and 14 guests