Log data - which process to use

siggasig

Hi,
I am new to data mining but I think it can be just the tool for analyzing my data. It consists of records of landings of fish. Each row has  columns with date, vessel number, harbor, amount of fish #1, amount of fish #2 and quota for fish #2. I suspect that some vessels are discarding fish #2 (dumping it back to the sea) if they don't have quota for it (permit to hold it once it has been landed - NB, all catch is mandatory to land). This could be confirmed by looking at records for other vessels that have landed fish #2 at the same harbor and at the same day (it is suspicious that one vessel catches fish #2 on the same day and same place another vessel does not catch any).

What would be a good process to choose to investigate this?

Many thanks,
SS