Letting Oysters do their Thing (for a time): NRDA Plan 2 Spawning Reefs

In May, Healthy Gulf submitted comments to the US Fish and Wildlife Service in Atlanta on NRDA Plan 2 which featured $10.5 million in oyster restoration work which represented 75% of the plan’s proposed funding. Ten million dollars go to the creation of new hard bottom areas across the Mississippi Sound that the plan calls oyster spawning reefs.

This emphasis on oyster spawning in Plan II is a recognition that after 15 years of massive impacts to the state’s oyster beds from Katrina, the BP Oil Spill and Bonnet Carre Spillway freshwater effects, what is needed, among other things, is a source of mature breeding adult oysters that can be left undisturbed to do their thing. Or… left unharvested for long enough to reproduce a few times and be a source of oyster larvae able to travel on tides and currents so these tiny, planktonic, free-swimming “veligers” might colonize new reefs, mainly in Mississippi.

We do this with redfish in the Gulf States. There are catch limits on the number of large adult brood stock size red drum (redfish) that can be removed from the population so that fishery managers can assure that enough sexually mature red drum are out there  spawning successfully. Turning this example to oysters, if reefs can be established where a good number of oysters reach sexual maturity, can remain healthy and be left undisturbed so they can spawn over a number of years, in theory this can build the Mississippi oyster population back up to a healthy size.

Plan 2 doesn’t call for oyster sanctuaries, where fishing is restricted totally. It calls for spawning reefs to be built in waters that are suitable for oyster growth. And Plan 2 states how many years the oysters should be allowed to grow before they are harvested. You might call these “forbearance goals”.
These refurbished or newly-laid spawning reefs will have moratoriums on harvest. According to Plan 2, oysters in harvestable waters must stay in place on reefs for 3-5 years. Those in non-harvestable waters must remain on reefs for 5-7 years.

The emphasis on creating spawning reefs and the fact that ten million dollars are being applied to this effort out of a total budget of fifteen million for all of Plan 2, are both significant items. The goal is to have oysters colonize newly placed cultch, grow to maturity and spawn so Mississippi can have greater densities of oyster larvae released into its coastal waters. With such a large outlay of money toward the purpose of more spawning, forbearance from harvest must be part of the plan.
Plan 2 will be carried out in the setting of the open waters of the bays and the Mississippi Sound. We know that the Sound is not a controlled laboratory setting and we have seen what has happened here over the past 15 years. In the face of impending doom for oysters, like the Bonnet Carre Spillway water mass from the 2019 Mississippi River Flood that slowly spread west to east across the Sound last summer, some oysters were harvested and relayed to other areas with better water quality in an attempt to prevent 100% mortality.

Plan 2 also has adaptive management built into it, and in Section 3.0 on page 196, Plan 2 contains the statement: “Projects with more uncertainty may require a more active approach to adaptive management.” This statement, no doubt, speaks to the need to leave some options (perhaps relays to healthier waters) open in the face of the threats oysters have been facing in Mississippi and across the Gulf over the past decades.

Maryland and North Carolina have oyster sanctuaries. Maryland’s sanctuaries are part of its Chesapeake Bay Oyster Management Plan. North Carolina is focused on the Pamlico Sound for its oyster sanctuaries. We’re not there yet in Mississippi – it looks like we have a planned, time-limited forbearance from harvest – but our NRDA Plan 2 is calling for spawning reefs, not sanctuaries. What is contemplated in Plan 2 is a sort of reserve. If you leave a reef alone for a specified time, but not forever, it’s a reserve according to Maryland’s definition. There, as in Mississippi, a boost to the numbers of oyster larvae able to colonize new reefs is the overall goal.

Looking at the numbers of years that Plan 2 sets for leaving oysters on the bottom in both harvestable and non-harvestable waters, Healthy Gulf, in comments to NRDA, suggested 6 years of harvest forbearance for reefs in all waters. We met the 3-5 and 5-7 year ranges closer to the middle. Whether this type of suggestion might sway the writers of NRDA Plan 2 is an open question. If the lion’s share of the money is for spawning and boosting larval densities in this plan, then it can be ambitious toward that end.  In any case, giving the oysters more time to grow and reproduce to colonize new areas is the main theme on the spawning reefs. For success this will need to be accompanied by some luck – with water quality, Gulf storms, and the rainfall in the upper Mississippi Basin over the next few years.

Andrew Whitehurst is Healthy Gulf’s water program director and covers Mississippi water and wetland issues.

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