Problems with fish data

[Raizel]

I'm doing research on habitat preferences of a certain species of fish, and the data was collected using trotlines. A trotline is basically a fishing line that's placed along the bottom of the lake with hooks at evenly spaced intervals. I'm assuming that each hook is a site and each time we put it in the water is a sampling event. The problem with trotlines is two-fold:

1. Sometimes a fish steals a worm from a hook without being caught. I can't assume that it was the species I was looking for, but it's also more likely to be that species than any other species. Sometimes, worms would be missing from the entire line. Is it better to treat the missing worm as a non-detection, a detection, or to treat it the same as if we didn't sample there that time?

2. Once a fish is hooked, it's not possible for another fish to be caught on that same hook. Part of what I want to look at is differences between sizes and sexes. However, if I catch a female on a particular hook, I can't catch a male on the same hook and vice versa. Any advice on how to use my data to get the best results?

[darryl]

How did you plan to analyse this data when you were planning the study. How far apart are the hooks and do you have any idea about the effective area being sample by a hook?
Darryl

[Raizel]

I wasn't the one who planned the study. The ichthyology professor I'm working with for the summer collected the data last year with some undergraduate students. There were three trotlines in different areas, each with thirty hooks spaced a meter apart. I have no idea about the effective area being sampled by a hook. The professor is assuming that each hook will only sample one square meter.