There should be an initial base lines so that we could compare the data of prevalence of a particular species. this will steer us in comparing the acquired data and formulation of future management strategies.
OK, related to the stocks of freshwater-species of commercial interest we have several studies, so if You are interested I can make a list of the available publications (related to this topic) and send You the pdf-copies.
P.S. Actually, during this year, we are performing a stock-assessment in the Danube Delta, consequently, the comparative data will probably be available next year.
Do You have a certain (well-delimited) area where You are assessing the fish-stocks?
well I am interested in Indus Mahseer distribution in Indus river system in Pakistan. One of my PhD student is working on ichthyobiodiversity of Indus River in KPK province in pakistan.
I will certainly appreciate your collaboration in this regard.
Fish fauna at Indus is actually very rich but I itend to focuss on very important angling fish which is under threat also although not on IUCN list.