Modelling Fish Populations for Sustainability By: James Bernard Supervisors: Charles Twardy, David Green and Charles Todd (From the Department of Sustainability and Environment)

Murray Cod Information  Murray Cod reside in the Murray River  Murray Cod that reside in the Murray River are a biological mystery!

Murray Cod Information  How the Fish Population Works: Eggs Young Fishling (0 – 4 Years Old) Mature Fish (5+ Years Old)

Murray Cod Information  How the Fish Population Works: Eggs Young Fishling (0 – 4 Years Old) Mature Fish (5+ Years Old)

Problems!  What if the fish are caught before they mature, and consequently cannot reproduce? –Murray River Rules and Regulations stipulate the Murray cod must be at least 500mm before eligible for fishing. –Are they old enough to reproduce at this age?

Problems!  How can we find out whether they are old enough to reproduce and contribute any fish back to the population? –First step is by producing an Age-Growth Curve

Age-Growth Curve  An example of an Age-Growth Curve for the Murray Cod.

Snob  A graph produced using Snob

 What comes after the Age-Growth curve? More Problems! Age Growth Model ? Recruitment Process

 How many eggs will each mature fish produce? –Analyse using different models –Analyse using aquaculture information Recruitment Process

 What comes after the Recruitment Process? More Problems! Age Growth Model Population Model Recruitment Process

Progress …  A graph produced using MS Excel (Individual) Fish Length

 YES! –What age do the Murray Cod start producing? –What triggers the Murray Cod’s reproduction? –Limited recapture data –Inaccurate recapture data Potential Problems?

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