Hello,

I am estimating the population abundance of the federally endangered Atlantic Sturgeon using long term capture-recapture data. The sampling area is a one kilometer stretch of river that is sampled 30-40 times a year over a five-month period. These fish are very mobile and move in and out of the sampling area frequently. For estimates I am using the open population model POPAN and my parameter of interest is the superpopulation size each year. I know that one of the assumptions of this model is that emigration is permanent which is violated in our analysis because my fish move in and out of the sampling area so much. My question is how strong of an effect is this violation likely to have on my population estimates. Would there be a strong bias and if so is there anything I can do to avoid it?

I cannot use a robust design for several reasons. I cannot assume closure because my sampling area is so small and my sampling period is so long. Also, there are years in the study that have a lot of capture data and many years with little to no capture data. Thank you for the help.