Residence time derived parameters MSJS model

questions concerning analysis/theory using program MARK

Residence time derived parameters MSJS model

Postby plelong » Sat Apr 01, 2023 4:13 pm

Hi everyone,

I'm currently fitting a Multi-State Jolly-Seber model on immature green turtles CMR dataset with 6 states (3 size classes on 2 sites).
These turtles spend several years on their feeding grounds before leaving definitively. I'm interesting in the time spent on foraging grounds before migration.

In the derived parameters of the MSJS model, I have two estimates of the residence time from 2 different methods but the values are very different and I don't know what is the best method to use in the context of this study.

According to the Mark help, the method 2 assumes no time or state effects in the model.
For the method 1, the estimate is really different compared to the method 2.

Does anyone know the difference between these two methods ?

I don't know either how can I interpret the ingress and egress time. If anyone has some clues for that, I will be grateful !

Thank you very much by advance.
Pierre
plelong
 
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Re: Residence time derived parameters MSJS model

Postby Bill Kendall » Tue Apr 04, 2023 7:52 pm

Your confusion is understandable. The MSJS model is new in Mark. Right now the help file is the only documentation, but we're working on a chapter for it in the Gentle Introduction. I delayed before responding to this because Gary and I found a couple of issues with the model and needed to work them out. By tomorrow he will have a corrected version of Mark on his website, so install that new version before returning to the analysis.

So your data consist of one capture period per year, with six states? I assume over time you have transitions among size classes, and maybe between sites? The specific answer to your question is that yes, Method 2 is appropriate only when egress from the system (the collection of six states), by death or transitioning to a life stage that doesn't utilize these sites, is strictly a function of the number of years since entering the system. In either case, residence time incorporates both survival and permanent emigration. In addition, with either Method 1 or Method 2, it represents an index to residence time, both methods assume no individuals were in the study area before the study began, and Method 1 assumes no individuals are left after the study ends. These residence times are most directly applicable where the model is being applied to data from a single season (e.g., sea turtles arriving to nest and using more than one monitored beach over the span of the season).
Bill Kendall
 
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Re: Residence time derived parameters MSJS model

Postby plelong » Tue Apr 11, 2023 11:12 am

Hi M. Kendall,

Thank you for your fast reply, I'm currently rerunning my models with the corrected version of Mark.

I will use the residence time method 2 since this estimate is the most suitable in my case. The only problem is that I can't assume that there is no individual before the study began and I think it could create a bias for the estimation of the residence time (lower estimate than reality since some large individuals are considered as new at the beginning of the study, unless I'm mistaken).

Thank you very much for your help.

Pierre
plelong
 
Posts: 6
Joined: Sat Jul 09, 2022 3:04 pm
Location: France


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