JINAN -- Fish byproducts have often been regarded as fish offal or waste, but researchers in eastern China's Shandong province are turning them into treasure.

The Qilu University of Technology has signed a cooperation agreement with Shandong Zhonglu Oceanic (Yantai) Food Co Ltd to turn the company's annual production of around 6,000 tonnes of fish byproducts into more than 10 commodities.

A research team of the university, led by professor Zhao Xiangzhong, has successfully extracted collagen peptide, which benefits skin and joint health, from byproducts of tuna processing.

The team has also turned tuna bones and skin into other products ranging from fish oil and sauces to biscuits.

The processing of aquatic products like tuna will generate a large number of byproducts from the head, tail, bone, skin and internal organs, which contain nutritional ingredients including protein. They are often fashioned into feed for shrimp and fish, or sometimes are even discarded, which can be a big waste.

Zhao estimated the entire Shandong Peninsula could produce around 200,000 tonnes of fish byproducts each year.

Currently, the byproducts are priced at no more than 2,000 yuan (around $292) per tonne. The price could grow six-fold to 10-fold if they can become sources of collagen peptide, according to Zhao.