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
Session Two: ROCKWEED AS HABITAT: STATE OF KNOWLEDGE
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
- Little is known about potential impacts of habitat structural change and habitat loss on fish habitat.
- Current methods of assessing fish populations have a low probability of detecting changes in abundance.
Fishes in the Rocky Intertidal
- In Passamaquoddy Bay there is low diversity of intertidal fish but high abundance. 31 species representing 19 families have been found in the intertidal. 21 species are commonly found, representing 13 families. There are 104 indigenous species in and around the Bay.
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:
- Imposed changes can lead to permanent shifts in communities.
- If foraging areas are reduced by rockweed harvest, birds may focus on remaining habitat and could overexploit it.
- If rockweed harvest alters predation by birds, community-wide changes could result.
- Need to identify the keystone species in the rockweed community.
Session Three: WORKING GROUPS: WHAT ARE THE CRITICAL GAPS IN OUR KNOWLEDGE OF ROCKWEED AS A HABITAT?
- What are the population dynamics of individual species (life histories)?
- What is the linkage to habitat? Is habitat important?
- What is the degree of complexity? The degree of change as it relates to diversity? Look at relationships which are more subtle.
- What is the response of plants to harvesting?
- Does cutting affect recruitment of rockweed to understory?
- What are the responses of epiphytes to harvesting?
- How important is export of organic carbon?
- What is the effect of cutting whole canopy vs. segments?
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.
- What are the effects of different harvesting methods?
- How can we minimize bycatch (of invertebrates)?
- What is the maximum carrying capacity?
- How do get to the changes in invertebrates?
- From harvesting?
- From modeling? We know diversity and abundance in landed catch and in canopy but how much is in the skiff?
- Are invertebrates limiting for fish?
- Is prey limiting? Example: Is the copepod level limiting for fish?
- Does change in the age of the rockweed community make a difference to invertebrates? Age structure of the rockweed is important-there is less epiphytic growth on young shoots.
- Should we monitor harvest vs. control sites on a long-term basis? Problems with this: It is difficult to find comparable sites. There are a lot of different habitat sites within a harvest area. Sampling design. Different substrates are harvested for various lengths of time.
- Do we need to establish protected sites?
We should look at European studies which document long term change.
- What is the utility of rockweed beds for fish nursery habitats? Do we know this from a landscape ecology perspective? (If we see a change in the community structure are we harvesting too much?)
- What is the effect of periwinkle harvesting, fishing, etc on rockweed? (If the grazers are gone (periwinkles) and you have sewage impacts do you see blooms of green algae?) Complex interactions with other species can alter the population dynamics of the targeted species.
- Does rockweed harvest affect settlement of other important commercial species. Rockweed is an important nursery habitat.
- We need more info on the importance of rockweed to black ducks and purple sandpipers.
- Does harvesting affect the number of floating racks?
- Where does rockweed fit in with importance of other habitats? In other words, eelgrass is very important, is rockweed similar?
- Could we monitor Littorina or Polysiphoria to measure impacts?
- Identify the key species and use them as indicators.
- What?s the biomass of epiphytes after harvesting? Does the removal of epiphytes affect the abundance of amphipods/isopods-If their abundance is reduced does it reduce the amount of fish?
- Structure of beds
- Bycatch changes
- Changes in species abundance
- Need public and harvester involvement-community ownership
- Reference sites vs. impacted sites
- Exploitation rates
- Look at different harvesting methods and gear
- Impacts of different exploitation rates
- Minimize impacts of bycatch
- Characterize attributes that make rockweed valuable habitat
- Is rockweed important for migratory fish?
Session Four: ROCKWEED AND THE COASTAL ECOSYSTEM
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
- Nutrient pollution increases germination of macroalgae
- Found most blooms in areas where grazers have been reduced due to harvesting and the area has been affected by eutrophication
Harvest of snails, harvest of rockweed and eutrophication push the system either to a mussel/barnacle community or a macroalgae bloom.
- Rockweed & snail harvesting can enhance eutrophication effects
- Fish harvesting effects are unknown for the algal community
- There are strong food web linkages
Management objectives should be:
- Control nutrient pollution
- Control unknown harvesting effects
- Have "no harvest zones"- we need baseline
- Limit multiple uses to avoid synergistic effects
Session Five: MANAGEMENT UNDER UNCERTAINTY
John Neilson, DFO, Synopsis of Ecosystem Approaches to Management
The Oceans Act-requires DFO to initiate management of marine ecosystems
- Precautionary principals
- Ecosystem conservation
Single species management plans must have:
- Conservation objectives such as preventing growth overfishing and preventing recruitment overfishing
- Ad hoc ecosystem considerations such as the rockweed experiment, krill, and capelin TAC
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.
- Define Ocean Management Areas. What geographic scale (each species has different sized areas of occurrence)? We need a nested approach-some could be managed locally, others higher up.
- Make the Precautionary Approach operational. We need to define unacceptable outcomes, take uncertainty into account, implement decision making processes. The precautionary approach is more than the sum of the parts. The precautionary approach needs integrated management.
- Define ecosystem features which are to be preserved. Examples include: maintenance of the ecosystem and species diversity, recovery of species at risk of endangerment, maintenance of genetic variability within a species, maintenance of directly impacted species, abundance of key predators. Defining these ecosystem features requires enhanced monitoring such as benthic community surveys, foraging species surveys, and predator-prey linkages.
What are some new management tools we might use?
- Marine Protected Areas
- Establish the governance framework. We know that there is a huge diversity of players and that management actions occur at each level of stakeholder involvement. We need to build on the present advisory committee structure. One example of a new institution might be an Ocean Management Area Council with various structures underneath it such as Fishery Advisory Committees.
Jim Wilson, UMO, How do we know what is the right thing to do?
Voluntary vs. policed compliance
- We would like to have a management system with a high level of voluntary compliance.
- In order to get this we have to make the rule worthwhile or of value to the users of the managed resource.
- With a quota we try to make a contract with fishermen: you restrict your catch and we?ll guarantee a certain amount of fish in the future. We cannot truthfully guarantee this.
- We need to verify that the model we are using is the right one in order to make our quota contracts. Since we can?t we proceed as if our model is the right one.
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.
Session Six: RECOMMENDATIONS FOR MANAGING ROCKWEED IN THE FACE OF SCIENTIFIC UNCERTAINTY
- Do we have confidence in present harvesting levels?
- Do we know critical life stages?
- Do harvesting levels need to be site specific? (spatial scales of management)
- Could we use rotation of harvest areas instead of harvest/no harvest areas?
- Management need to be responsive to changes in the market or changes to the amount of resource.
- The distribution of harvest effort needs to be spread out.
- Are there pollock recruitment areas in rockweed?
- Use community knowledge to fill in the gaps of what we know about a resource.
- Have community representatives sit on management committees.
- Build flexibility into the management plan.
- Set aside no take zones now before the resource is exploited along the entire Maine coast.
- Understanding of rockweed recruitment
- Understanding of nutrient cycling and organic carbon export.
- What about rockweed aquaculture?
- What effects will climate change have on the resource?
- Look at practical ways to minimize by-catch.
- We need long-term monitoring to determine the structure of the invertebrate community.
- We need a systematic approach to develop "no harvest" zones. We need goals and objectives to help determine these zones.
- Will rockweed harvest reduce clam recruitment because detritus will be reduced. If you reduce the biomass and breakage of rockweed will it affect the health of the clam flats?
- Is pollock the only commercially important species which is associated with rockweed at some stage in its life cycle?
Working Group Reports: Management Recommendations
- Knowledge Transfers
- No Take Zones
- Marine Protected Areas
- Precautionary Approach
- Confidence in harvest levels
- No Take Areas (are the existing ones adequate, appropriate?)
- Spread out harvesting effort
- Include community representatives in management structure
- Minimize by-catch
- Protected areas that are permanent serve as cheap insurance
Whole Group Recommendations
- Government agencies should develop a generic policy for managing low trophic level species(Harvesting low trophic level species may be a risk)
- Establish a network of No Take Zones (no impact-including aquaculture was mentioned but there was no general agreement on this)
- Must have community involvement
- Need integrated coastal zone management
- Need ecosystem approach to management-We know that rockweed is extremely important in the nearshore environment-so first do no harm-present levels of harvest seem to be sustainable.
- Assess biomass first and then develop a management plan. Management attributes of the New Brunswick system include: hand method of harvest, assessment of the resource, reporting to government/monitoring.Maine allows mechanical harvest.
Session Seven: WRAP UP AND FINAL RECOMMENDATIONS
Harvesting Low Trophic Level Species
- Need to assess the stock of any given species
- Two characteristics of low trophic level species: very high biomass and very fast growing (rockweed is an exception, it is very slow growing)
- How important are the low tropic species in the recovery of commercially important species?
1.Nutrient Cycling/Nutrient Budget
- We need to identify and quantify components of the budget: floating mat biomass, Maine rockweed biomass, agricultural runoff, aquaculture inputs, atmospheric deposition. The study should be more than one year long.
2.Habitat use by pollock
- Relative abundances in different habitats
- Need at least a 3-5 year study like the one starting in Maine on intertidal fish habitat. This would be a good place to integrate the knowledge of local fishermen. The DFO and the Conservation Council have some of this local knowledge recorded already.
3. Eider Ducks
Ongoing Studies include:
- Aerial surveys to tell which areas are being used by ducklings
- Every second year nesting pairs are counted in the GOM
- Brood areas are recorded
Things we need to know:
- At what scale are eiders selecting their habitat
- Areas being used by the eiders should be clearly designated so that harvesters could avoid them
Return to Cobscook Bay Resource Center homepage.