Navigating Oyster Tank Systems: A Comprehensive Guide to Hatcheries, Wet Storage, and Depuration

With the rise of oyster farming, questions around oyster tanks are becoming a normal part of every day at APS. This article is intended to help address some of the most common concerns and questions raised during our discussions with oyster producers regarding oyster wet storage and depuration. There are three main types of tank systems used for oysters on land: hatcheries, wet storage tanks, and depuration systems.

OYSTER HATCHERIES Hatcheries and nurseries are used to breed oysters and produce

spat / seed for subsequent ocean ranching. Given the increasing need for spat and the increasing difficulty and consistency with wild spat collection, expect to see more and more of these established over the next few years. Perhaps the key message around hatcheries should be that they require daily attention (in most cases, expect that to be more than an 8 hour day - with no weekends off during the production cycle). Ideally, the operator is a science-y type person with a nurturing soul. As designers and builders of these systems, we can make the system operation as straight-forward as following a checklist, but there is daily interaction required between the operator and the oyster.

OYSTER WET STORAGE "Wet storage" tanks are used to hold oysters ready for market. The tanks help to smooth out supply and demand cycles and/or to avoid interruptions in harvesting due to impending heavy rains, ice formation or break-up, or high bacterial counts. These operations are by far the simplest to operate of the three types looked at in this article. There seems to be some confusion in the industry as to what is required for a wet storage tank that commonly seems to result in a system capable of depuration being oversold to the oyster producer when a simpler wet storage system is appropriate. However, the governing bodies (CIFA or FDA) both outline their requirements quite clearly. Two of the key principles that are missing or insufficient on the systems I have seen out there are a proper oxygenation system and a temperature control system. A lack of oxygen is going to stress any animal. When an animal is stressed it produces 'stress responses' such as cortisol. Cortisol then affects glycogens, which then affects taste. Temperature control is key for reducing stress, both from temperature fluctuations, but also with the water quality fluctuations that come with a temperature change. As oysters metabolism changes with temperature, a lack of temperature control can also contribute to changes in taste.

DEPURATION SYSTEMS Depuration systems are used to enable harvesting and sale during periods where high bacterial counts would otherwise result in a closure of harvesting. The biggest misconception about depuration is that a depuration system exists that CFIA or FDA has pre-approved. Building a system that meets the guidelines is the easiest part of this process. By far, the largest chunk of work involved in establishing a depuration system is the documentation of the processes. One needs to establish a process for making sure the oyster is safe to eat. And a process to make sure that each part of that process is working perfectly. And a process to give everyone confidence that the process that makes sure that the process is working, is actually followed each step of the way. And then, a process is needed to fix any deficiencies found in or by the above processes... It is the creation and auditing of these processes that is really the reason why so few, if any, depuration systems actually operate in Atlantic Canada.

IN CONCLUSION First, the plug. APS designs and builds all three of these tank systems. As with all of our systems, we do so with a special care for effectiveness and efficiency. Secondly, don't forget the paperwork. Being a ready-to-eat product, this cannot be stressed enough. Skimping on paperwork or filling it out with a doctor's illegible handwriting can be detrimental to an operator, but also the industry as a whole. The oyster industry has the ability to market based on 'merroir' and the incredible stories that surround the production of oysters and contribute to their taste. Consumers are putting a premium on traceability. Instead of seeing it as the bane of your existence imposed by the overlords, look at the paperwork as a direct contributor to getting top dollar for your product.