Hello,
I want to estimate abundance of the spinner dolphins population off Reunion island through mark-recapture method. I have photoID data from 2012 to 2022. Because the closure tests show me that the population is open from a year to another (i.e., primary period), but closed across June-October of each year (i.e. secondary period), I decided to use a Robust Design method. Depending on the period chosen, I find quite different results:
* study period: 2012-2017 => {φ(.), ɣ”(.), ɣ’(.), p(T), c(T), N(.)}, with N=275 individuals (265-285)
* study period: 2012-2019 => {φ(.), γ"(.), γ'(.), p(t, T), c(t, T), N(T)}, with N varying from 97 ± 36,5 individuals (48 – 198) in 2017 to 211 ± 68,8 individuals (113 – 393) in 2012;
* study period: 2013-2021 => {Φ(.), gamma”(.), gamma’(T), p(t, T), c(t,T), N(T)} with N varying from 76 ± 12,3 individuals (56 – 105) in 2014 to 128 ± 29,4 individuals (82 – 200) in 2021
My question is then, what is the best study period? Is it necessary to have as many data as possible, or do I need to focus on a short period of time?
Thank you for your response.
Vanessa