The development of a low cost refrigerated flow-through seawater system for at-sea estimation of post-release mortality

The post-release mortality of discarded fish can represent an additional source of mortality that is important to understand for effective marine fisheries management. To best estimate these mortality rates under near-natural conditions, a refrigerated flow-through seawater system was developed for short-term holding experiments at-sea aboard commercial fishing vessels, using accessory tanks containing heat exchanging coils cooled by an ice slurry. Ice was added to these tanks in one to two-hour intervals based on the cooling requirement. This system was capable of maintaining temperatures within one degree Celsius of target conditions for 93-96% of operation, creating an environment where post-release mortality could be evaluated without additional thermal stress.