Survey on fish mortality

Yes, absolutely. This will result in death from "old age" occurring at any time in the study and such statistical noise should be easy to adjust for if enough data is collected.

I could have asked people to tell how old their fishes are, but unfortunately, most people don't know this except for fish that show clear morphological differences as they age (e.g. angels), so I am afraid that this would exclude most people from participating.

 

Actually, this is a difficult topic. We don't really know much about lifespans in nature, and a lot of what we believe is extrapolated from studies from captivity .

There are some methods, though, for estimation of age of fish in the wild, and there are some publications on the variation in biological life span among wild fish species.

 

I'm not sure on your stats background, but there are some factors that won't "even out"... for instance, price of fish. For example, are inexperienced keepers as likely to buy the most expensive fish as experienced keepers are?

I haven't looked at the survey, but linking size of tank to the fish that were put into that tank might give you an idea of experience or research put in as a variable control.

 

Yes, good point. When the results are presented (curves that show relative death distribution between different species) it will not necessary be easy to explain all the peaks and valleys. Some of these might be explained by some fish being pricier than others, or for other reasons not bought by inexperienced hobbyists. So people need to keep this in mind when trying to interpret the data.

That might have been a reasonable correcting factor, but it's too late now. The survey is rolling. I'll present some preliminary data in a few days if people keep up participating and hopefully we'll get a better idea of the value of the results then.