"Kago"
as they are called in Japan are a wide range of small net, plastic, and steel baskets used to dispense chum in the water, such as krill and shrimps, dead or alive. Most sabiki fishers use them either at the top or bottom of rigs. Many have weighted bottoms for casting or boat fishing and they can be used under floats too.
Tip - If you can't obtain shrimps then cat food can also help to bring fish in close.