dolphin abundance from photo ID using POPAN (Mark)

[lemdva]

Hello

I would like to ask for advice or help in the statistical analysis of a 7-yr dataset of spinner dolphins from photo ID. My team and I have been going back to the same area (southern Tanon Strait) and same season (April-June) and taking photos of dorsal fins for photo ID from 2004 to 2010.

We used the POPAN feature of Mark to estimate annual abundance. We used the p(t)phi(t)pent(t) model; and the following parameter-specific link function values are p:sin, phi: sin, pent: Mlogit(1), and N=log. Are we going the right track? Or should we use more appropriate functions for the parameters?

How are derived estimates corrected for c-hat calculated per year? Can we do it using Mark or we do it manually? The POPAN only gives us a 'super population' estimate that is corrected for c-hat for the entire period.

Any help or advice will be greatly appreciated.

Lem

[geryan]

Hi Lem,

One of the recent developments in the field is renewed utility of mark-resight models (Chapter 18 in 'A Gentle Introduction', I think) - these have a lot of potential for use in the field of dolphin photo ID because, unlike a robust design-type modle (e.g. POPAN), you can use every sighting of a dolphin within the period, and incorporate sightings of individuals that you can't identify directly into the model. You can then estimate, as well as total abundance, survival, number of unmarked animals, resighting rates and probabilities of transitioning into, or out-of an observable state (i.e. the study area). I've been part of one such study for Irrawaddy dolphin and found this method really useful. The final report of that study hasn't been yet released, but it will be soon and I'm happy to send you a copy if you're interested as the analyses might be very transferrable to your case. With regards to the model outlined below, you probably want to consider comparing a number of models other than p(t)phi(t)pent(t), like constant rates for p, phi and/or pent to see if any are better supported.

Best of luck

gerry ryan

[lemdva]

Thanks Gerry Ryan

Please send me a copy of your manuscript, if you don't mind.

Lem
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Lemnuel V Aragones, PhD
Associate Professor
Institute of Environmental Science & Meteorology
University of the Philippines
Diliman, Quezon City 1101
PHILIPPINES

email: lemdva2001@yahoo.com or lvaragones@up.edu.ph