Gulf of Maine Rockweed Conference Notes

Notes taken by the Cobscook Bay Resource Center personnel, not to be confused with official conference proceedings.

Gulf of Maine Rockweed Conference
Management in the face of scientific uncertainty

A Global Programme of Action Coalition for the Gulf of Maine (GPAC) workshop
Huntsman Marine Science Centre, St. Andrews, New Brunswick
December 5-7, 1999

[To view background information about this conference click here to visit the St. Croix Estuary Project's webpage.]

Session One: Welcoming Comments


Bob Vadas, UMO, Impacts of Grazers on Rockweeds and Macroalgae

Grazers of rockweed include perwinkles, limpets, amphipods, isopods, other snails, sea urchins (in the very low intertidal), chitons, and crabs (very rare).

Factors that affect rockweed include mortality, competition, grazers, disease, epiphytes, etc.

Fucoids (types of rockweed) produce a chemical to deter periwinkle grazing.

Wave action removes approximately 95% of newly settled Ascophyllum recruits. Ascophyllum's recruitment is sporadic and is only successful approximately once every seven years. Once a population is destroyed it takes decades to reestablish. It is a long- lived, slow-growing species. Barnacles facilitate the recruitment of Ascophyllum by providing a refuge from grazers for the germlings.

Glyn Sharp, DFO, Rockweed Structure and its Role as a Habitat for Invertebrates

In Southeastern New Brunswick there is 80% cover of Ascophyllum in the rockweed zone.

We see high diversity of species in the Ascophyllum canopy. More highly branched individuals have greater numbers of invertebrates on them. There is geographical variation in the abundance of invertebrates-it is site specific.

Invertebrate abundance is also affected by season. Abundance can change over the short term as well such as in a period of a month. Some of this shor-term change is due to recruitment.

Presence/Absence of epiphytes affects invertebrate abundance.

Bob Rangeley, DFO, Aquatic Macrophytes as Foraging and Refuging Habitats for Fishes

Fishes in the Rocky Intertidal

Young fish recruit to the rocky shore in spring and summer, moving offshore in the winter (example: pollock).

Rockweed is used as a refuge from predators.

Diana Hamilton, University of New Brunswick, Community-Level Interactions Between Birds and Aquatic Macrophytes: Lessons for a Rockweed Harvest?

Eider ducklings feed predominantly on invertebrates found in rockweed. They have been shown to spend more time feeding when rockweed is available. Rockweed harvesting may limit feeding time when the canopy is removed.

Adult eiders may have an indirect positive effect on rockweed by removing blue mussels that have settled and grown on the plant.

Black ducks have been declining in Eastern Canada. We need to find out if rockweed harvesting is affecting their population.

Eiders are at risk. Disturbance by harvesters increases predation by gulls and reduces feeding time. The message here: AVOID DUCKLINGS. Ducklings use rockweed for only a short time-June and July.

Lessons from other systems:



In Canada, management restricts equipment used for cutting to rakes. It makes a vertical cut so it doesn?t change the clump height. Also, harvesters in Canada are restricted from cutting the whole canopy.

Rockweed is very long-lived. Removing the holdfast is not a good idea because rockweed isn?t a big recruiter. So it's important to use rakes with cutters that don?t pull the plant up by its holdfast.

We should look at European studies which document long term change.


Long-term Monitoring

Short-term studies


Raul Ugarte, Acadia Seaplants, Harvest of Macroalgae: A Global and Regional Perspective

The most important use of seaweed is as human food followed by alginate (browns), carrageenan (reds), and Agar (reds) respectively.

The major players are China, Korea, and Japan in harvesting seaweed for food, however, only 20% of this is wild harvest.

In New Brunswick/Nova Scotia only hand harvesting is allowed. Most of the resource is harvested in New Brunswick and southern Nova Scotia. Harvest is done from small skiffs which hold 3-5 tons. This is brought on shore or to a platform near shore and transported to a drying area on shore. In New Brunswick this is an old airport.

Management of rockweed in New Brunswick is the first time a research program and a management regime were established before the fishery was established.

Thierry Chopin, UNB-St. John, Seaweeds, Nutrients and Aquaculture in Coastal Waters?.Let?s Put Things in Perspective

Seaweeds are nutrient scrubbers. Seaweeds act as a buffer between human land-based impacts and the ocean.

Particles released into the Bay of Fundy will remain in the Bay for up to 3.5 months.

Dragging puts nutrients in the sediments back into suspension. Salmon in Cobscook Bay are off their feed during scallop dragging season because the water is so turbid they can?t see the food. Salmon must see the food to eat it.

High levels of phosphorus and nitrogen were found in algae in Cobscook Bay during scallop dragging season. This is natural fertilization for nori growers in South Bay. Also algae growing next to salmon net cages show high levels of nutrients.

We can use seaweed as a bioindicator of an aquaculture site.

The question he was asked was does rockweed harvesting adversely impact nutrient levels in the water. The answer is no. Rockweed naturally releases nutrients when it releases its reproductive structures.

Boris Worm, Dalhousie University, Nutrient Availability, Low-Trophic Level Harvesting and Cumulative Human Impacts on Coastal Ecosystems

We can't look at rockweed in a vacuum-all species are interconnected.

The three stages in the Northwest Atlantic of the rockweed zone are: mussels/barnacles, annual algae, and rockweed.

Grazers prefer annual algae. If there are a lot of grazers it may prevent massive blooms of these green macroalgae. How does this work in a system affected by eutrophication?

Nutrients vs. grazer control

Harvest of snails, harvest of rockweed and eutrophication push the system either to a mussel/barnacle community or a macroalgae bloom.

Management objectives should be:


John Neilson, DFO, Synopsis of Ecosystem Approaches to Management

The Oceans Act-requires DFO to initiate management of marine ecosystems

Single species management plans must have:

With the current management methods genetic diversity is at risk, by-catch species are at risk, and dependent species are at risk.

DFO direction is towards Integrated Ocean Management.

What are some new management tools we might use?

Jim Wilson, UMO, How do we know what is the right thing to do?

Voluntary vs. policed compliance

Complex systems are a lot of different things interacting with one another in a non-linear manner. A complex system can be stable at times and unstable at others. Fishermen adapt to changes in their complex system very readily regardless of whether the change is management based or natural.

We need to determine where we can predict things and where we can?t. Don?t push what we don?t know quantitatively.

So where do we obtain feedback from the system to determine whether we are doing the right thing? We need a nested government structure (like a federalist system) in which each governance unit has a degree of freedom to act within their defined authority. Can we give local units the authority to act, partitioning the ecosystem problem and working from the bottom up/top down simultaneously?

At this point we seem to be pushing ourselves into a management system which is a policed compliance situation. We only look at management options that we can police.

Our uncertainty over whether we are doing the right thing has at least one implication: we have to reform the way we make ecosystem management decisions, it needs to be from the bottom up.

If you give people some power in any research project, then they begin to think of science as supporting their self interest.

Management actions that would have local impacts should be decided locally.

Chris Finlayson, DMR, The Difference Between Uncertainty and Ignorance: A Case Study in Initiating Management Under Conditions of Ignorance

What we are talking about is the difference between uncertainty as risk and uncertainty as an absence of knowledge.

Our expectation is that uncertainty as risk is manageable with our statistical tools. With management using models we assume that past events can predict the future. Our models are based on information from the past. We must be careful about what we can predict with the model.

The Sea Cucumber Example

In Maine we had a very small fishery for sea cucumbers. There were less than 15 boats fishing for them and they were getting about $7 a tote. The markets were all Asian and when the Asian fishery collapsed the price jumped to $12 a tote. Many boats started fishing for cucumbers and fishing hard. The DMR is promulgating new regulations now based on a bill that says DMR can put a moratorium on emerging fisheries that will limit entrance to the fishery to those that can prove they were fishing for cucumber before the market boom.


Working Group

Questions/Knowledge Gaps
Management Recommendations

Working Group Reports: Management Recommendations

Group A

Group B

Group C

Whole Group Recommendations


Harvesting Low Trophic Level Species

Research Areas

1.Nutrient Cycling/Nutrient Budget

2.Habitat use by pollock


3. Eider Ducks


Ongoing Studies include:

Things we need to know:

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