The Skimmer & MPA News

The Skimmer on Marine Ecosystems and Management

Aquaculture production is an increasingly important component of global seafood production. Seafood production from aquaculture has expanded nearly six-fold since 1990, while capture fisheries production has remained relatively stagnant. According to the UN Food and Agricultural Organization’s most recent analysis of global fisheries and aquaculture, seafood production from aquaculture (excluding seaweeds) exceeded production from marine capture fisheries for the first time in 2016.[i]

Aquaculture’s reputation is mixed, however. It obviously has the potential to feed many people, but it has is associated with a number of observed and potential negative environmental impacts, including:

  • Altering and destroying habitat, such as mangrove forests, for aquaculture facilities
  • Escapes of farmed species into the wild, enabling species invasions and altering the genetics of wild populations
  • Spreading diseases and parasites to wild populations
  • Releasing fecal waste, uneaten food, and pesticides into the local environment, decreasing water quality
  • Contributing to the overfishing of wild fish populations because of the use of wild fish to feed farmed fish.

This negative view obscures the incredible diversity of aquaculture types and their diverse interactions with marine environments. Aquaculture enterprises vary in:

  • What species are cultivated (e.g., seaweeds, mollusks, crustaceans, finfish) and what they feed on (e.g., whether they are photosynthesizers, filter feeders, deposit feeders, herbivores, carnivores)
  • How intense production is (e.g., total biomass per cage, the degree to which fertilizer and supplementary feeds are used)
  • The type of environment production takes place in (e.g., freshwater streams or lakes, fully enclosed tanks, ponds, intertidal, sheltered bays, open ocean, sea pens, ponds, tanks).
The Skimmer on Marine Ecosystems and Management
The Skimmer on Marine Ecosystems and Management

Editor’s note: Thierry Chopin is a professor of marine biology and director of the Seaweed and Integrated Multi-Trophic Aquaculture Research Laboratory at the University of New Brunswick in Canada. He is also president of Chopin Coastal Health Solutions Inc. His research focuses on the ecophysiology/biochemistry/cultivation of seaweeds and the development of Integrated Multi-Trophic Aquaculture (IMTA) for environmental sustainability, economic stability, and societal acceptability.

The Skimmer: Can you tell us a little bit about what IMTA is?

Chopin: With IMTA, farmers cultivate species from different trophic levels and with complementary ecosystem functions in proximity. They combine fed species (e.g., finfish that need to be provided with feed) with extractive species (e.g., seaweeds, aquatic plants, shellfish, and other invertebrates that extract their food from the environment) to take advantage of synergistic interactions among them. In these systems, biomitigation operates as part of a circular economy (i.e., nutrients are no longer considered wastes or by-products of one species, but instead are co-products for the other species).

The Skimmer on Marine Ecosystems and Management

By Tundi Agardy, Contributing Editor, The Skimmer. Email: tundiagardy [at] earthlink.net

A recent publication “Marine zoning revisiting: How decades of zoning the Great Barrier Reef has evolved an effective spatial planning approach for marine ecosystem-based management” published in Aquatic Conservation: Marine and Freshwater Ecosystems distills important lessons from Australia’s evolving commitment to manage the world’s most iconic multiple use marine protected area. It casts a critical eye on what has worked and what has not, and it pushes us beyond our marine comfort zone to face the challenge of true ecosystem-based management (EBM), which neither ocean zoning nor marine spatial planning (MSP) in their current applications can adequately provide. With this publication, Jon Day and his coauthors have given the world a valuable gift that will keep on giving if we can acknowledge this gift and heed it.

Day and his colleagues (including Richard Kenchington, who like Day has been intimately involved in the design and management of the Great Barrier Reef Marine Park [GBRMP] through its various iterations over the years) recount how zoning both set the stage for multiple use management and evolved to provide the legal framework for regulations to protect the world’s largest barrier reef. The use of zoning had to be adapted over decades because the GBRMP Authority was a pioneer in spatial management and the allocation of space to uses of the marine environment. Zoning on land may have provided a glimpse of the possible, but adapting zoning approaches to the fluid and obscured ocean realm required experimentation and a fair amount of risk taking.

The Skimmer on Marine Ecosystems and Management

Editor’s note: In 2016, roughly one-third of the total value of the world’s trade of fish and fish products was invertebrates. (They were approximately one-fifth of the global fish trade by live weight.) To learn more about the state and future of invertebrate fisheries management, The Skimmer interviewed Heike Lotze, a professor in the Department of Biology at Dalhousie University in Halifax, Canada. In this interview, we discuss several of her papers published over the past decade on the recent expansion, ecosystem effects, and management of invertebrate fisheries, including a recent synthesis “Ecosystem effects of invertebrate fisheries” published in Fish and Fisheries in 2017.

The Skimmer: As global catch of invertebrates increases, what impacts are invertebrate fisheries having on marine ecosystems?

Lotze: Invertebrate catches have increased more than six-fold globally since the 1950s. Catches include all major species groups – from lobster, shrimp, and crabs (crustaceans) to octopus, cuttlefish and squid (cephalopods) to mussels and snails (mollusks) to sea urchins and sea cucumbers (echinoderms). In many countries, invertebrates are some of the most lucrative commercial fisheries and provide coastal communities with valuable livelihoods and associated benefits. The global increase in catches has been accompanied by the spatial expansion of invertebrate fisheries: many more countries are engaging in fishing invertebrates, and many more areas within countries are now fishing invertebrates. For example, sea urchin and sea cucumber are now fished around the globe, and fishing for invertebrates has expanded from shallow to deeper waters to maintain or enhance catch levels. Fisheries have further shifted from large- to smaller-sized individuals and from high- to lesser-valued species, usually in response to declining catches and following a ‘fishing down the value-chain’ pattern.

Many people may think it is ‘just’ invertebrates, but these species play important ecological roles in marine ecosystems. These roles are often more diverse than the roles that fish play, consequently the impacts of invertebrate fisheries on other species and marine ecosystems are more varied than those of finfish fisheries. For example:

  • Many invertebrates are important prey for higher trophic level species, such as fish, whales, turtles, and seabirds, and reducing invertebrate abundance can have ripple effects through marine food webs, comparable to those of forage fish;
  • Many mussels, oysters, and sponges enhance biodiversity by creating three-dimensional structures that are important habitat for other species – for settlement, finding food, finding shelter, breeding, and nursery grounds;
  • Many invertebrates filter feed which improves water quality and clarity and provides benefits to other organisms, including humans;
  • Herbivore grazers, such as many urchins and gastropods, act as lawn mowers keeping algal carpets in check; and
  • Detritivore sea stars and sea cucumbers clean up ocean floors as the scavengers of the sea.
The Skimmer on Marine Ecosystems and Management

Editor’s Note: From the Archives calls attention to past Skimmer/MEAM articles whose perspectives and insight remain relevant.

Coverage of social media usually focuses on how social media platforms (e.g., Twitter, Facebook) can be used to communicate with and educate stakeholders and the general public. But social media also provides publicly available information on how people are using and feeling about the marine environment. Learn how social media and other digital data are being used for marine conservation and management.

The Skimmer on Marine Ecosystems and Management

Editor’s note: We’ve all read about how ocean noise can harm marine mammals. New research reveals that it can have profound impacts on lower trophic levels as well, with likely consequences for marine ecosystems. Catch up on the latest research with this month’s Skimmer.

A little background on sound in the ocean

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