Kallaida Eggs

From Fortuitous Tides:

It was also discovered that the large, docile fish known as Kallaida, found in many of the lakes and streams, produced delicious eggs that soon became a favourite of travellers to Forraliss. Unbeknownst to them though, these eggs contained an addictive element. The Rogue Trader's Magi Biologis discovered this fact after an incident where a patron lashed out at a number of staff over quantities of the delicacy. Vor began to regulate the amount produced, quickly driving up the price as well as guaranteeing a steady customer base. Unknown to Vor, one of his henchmen has begun selling the eggs on his own in an attempt to establish his own power base. If this trade takes off as he plans, it will allow him to separate from the Rogue Trader and establish his own way.

Forassian Kallaida

These fish grow to between 1 and 4 metres in length and thrive in lakes and streams on Forraliss’s main continent. A striking, blue-green colour dominates their body from head to tail. The fish is very docile, feeding primarily on plants and algae as well as other fish. The highly addictive property of their eggs greatly concerns many residents of the world, however. Some worry that this interaction with human physiology is a deliberate modification, left by xenos ages ago who tampered with the creatures.