Hi Phidot users,
I have a question that has been bugging me for a while. I use the a spatial version of the CJS model to estimate survival of outmigrating juvenile salmon in rivers. In one of my study years, I have reasonable (>0.5) detection probability at my furthest upstream detection location, then terrible (<0.1) detection probability for many detection locations in a row (12), then reasonable detection probability again in the lowest parts of the river. Program MARK estimates perfect survival (1) for all the river reaches that have poor detections on their downstream end, EXCEPT for the first one in that row, which was given an unusually low survival estimate (with somewhat reasonable confidence intervals). I think it's unrealistic to think that all the salmon survived through those 11 other reaches (total >150 km long), and I also feel that the survival estimate for the first reach is too low, so I'm wondering if the CJS model attributed all the mortality of the stretch of poor detection reaches to just the first reach? Is this a model behavior that others have noticed?
Finally, any suggestions to fix this behavior?
Thanks.
Cyril