Safeguarding marine ecosystems as wild food production systems
Maintaining availability of abundant wild seafood starts with taking care of the ecosystems that produce it and the pathways by which it gets from sea to table. This is a deep commitment that exceeds the scope of individual choices about what to eat; it requires working together to promote public policies that protect our wild commons. If you love wild seafood, don't just eat it, get involved in the decisions that affect it! From federal oil drilling decisions to local policies about working waterfronts, as a seafood stakeholder, you have a say.
Understanding and addressing changes in marine ecosystems is complex. Marine ecosystems have sustained various impacts over the centuries, and today's ecosystems are a product of historical as well as present-day impacts. While marine ecosystems are often called "resilient", the cumulative effects of multiple changes can be temporarily or permanently destabilizing. These changes take a toll on regional seafood supply and the wellbeing of fishing communities dependent on local waters.
It is often hard for scientists to pinpoint the precise causes of changes in the availability of seafood in the ocean, because there are so many drivers of change acting at once. Moreover, the regulatory system that governs wild seafood in the U.S. is not set up to address these drivers. With legal authority limited to restricting the impacts of fishing activity on seafood production, U.S. fisheries management is not capable of effectively targeting non-fishing impacts like climate change, pollution, and habitat loss, which also have great influence on ecosystems and seafood. Nor is it set up to foster stability of fishing communities or broaden the reach of local seafood supply chains -- two ingredients integral to maintaining a robust and generous wild regional seafood production system. To address the big picture of sustainable seafood, fishermen and seafood lovers need to influence environmental policies, land use policies, energy and transit regulations, waterfront access rules, food access issues, and many other collective choices that influence the use of our waters for food.
The paragraphs below provide a brief introduction to some drivers of change in marine ecosystems that are not currently addressed by fisheries management regulations.
Climate change and ocean acidification
Carbon dioxide emissions are higher than they have ever been in the last 650,000 years, due to burning of fossil fuels. In addition to CO2, methane and other greenhouse gases continue to accumulate in the atmosphere. Image courtesy of Wikipedia.
The warming waters and changing seasonalities associated with global climate change are making once-familiar marine ecosystems more variable. In New England, these effects are visible in the recent explosion of lobsters in the eastern Gulf of Maine, the movement of Mid-Atlantic species like black sea bass and squid into northern New England waters, and the virtual disappearance of the cold-water-loving Atlantic cod. Fishermen are highly adaptable by nature, but if the market for their catch remains rigid, they will have a hard time pursuing coping strategies.
Water temperature is a decisive factor in determining the geographic ranges of marine species, and as the climate warms, some stocks are beginning to shift northwards or into deeper waters. However, not all species are capable of shifting their ranges successfully, and climate change inevitably will mean major changes in the abundance of some species as well as a hard-to-predict restructuring of food webs. In addition, changing seasonal patterns associated with climate change affect the timing of important events like spawning, migration, and larval development.
HABITAT LOSS AND FRAGMENTATION
A dam in Wilton, Maine. Photo courtesy of Wikipmedia Commons.
Nearshore habitat loss and degradation can result from coastal development, water quality pollution, dredging and dumping of dredge spoils, and hydrological changes caused by ditch-digging and channelization of salt marshes. These impacts are likely to affect inshore species like weakfish, tautog, scup, black sea bass, summer flounder, and winter flounder.
Dams on inland rivers, many of which were constructed during the industrial revolution and are now non-operational, have been a decisive factor in decimating the area’s once-great anadromous fish stocks (fish that spawn in freshwater and migrate to the sea to live out their adult lives). Dams impede access to spawning areas upstream, alter the river flows that cue fish eggs to hatch, lead to increased predation on spawning and juvenile fish by causing delays in mobility. Operational hydroelectric dams can cause direct fish mortality as a result of passage through power-generating turbines.
Non-point-source pollution
A fish kill induced by a low-oxygen event. Photo courtesy of Wikipedia.
Invasive Species
Carcinus maenas, the green crab. Introduced to the Eastern US in the nineteenth century, it is working its way northward as waters become warmer. Presently it is wreaking havoc in the clam flats on the coast of Maine. Photo courtesy of Wikimedia Commons.
Highly selective fishing
Mismatch between the ecosystem and the marketplace is common. Balancing the diversity of ecosystem production with the demand of the seafood marketplace can help.
Non-point pollution can come from anywhere, but it all flows downhill, winding up in our waterways and estuaries. Runoff from impervious surfaces such as roads and parking lots can carry oil and other automotive chemicals. Runoff from farms and lawns can carry pesticides and fertilizers. Sewage can enter waterways through weak sceptic systems and combined sewer overflow systems, carrying not only excess nutrients buy pharmaceutical residues that may contain endocrine disruptors. Power plants can cause fish larval mortality through discharge of heated water, or thermal effluents, into the surrounding water body. And buried under bottom sediments, there are reminders of the wanton disregard that early industry had for the environment: heavy metals that long ago settled out of the water column, but run the risk of being re-suspended during dredging or extreme weather events.
Invasive species alter ecosystems by adding a new predator/competitor to the system – one that often doesn’t have any natural predators of its own. Green crabs (Carcinus maenas), empowered by climate change, are currently wreaking havoc on the Gulf of Maine soft-shell clam industry. Dead man's fingers (Codium fragile) is a non-native seaweed species that now dominate some subtidal zones, and can radically alter subtidal communities. An invasive tunicate species, Didenium, is smothering benthic habitat on Georges Bank, preventing shellfish larvae from settling to the seafloor and making it harder for bottom-dwelling fish to reach invertebrate prey. Freshwater invasives are also a concern for those species that use rivers and lakes for part of their lives: introduced catfish, snakeheads, and other invasives in freshwater systems may impact anadromous fish by increasing predation, and non-native vegetation in rivers and ponds can interfere with anadromous fish passage by restricting navigation. Learn more about invasive species on fact sheets from the Gulf of Maine Council, Save the Bay, and the Massachusetts Office of Coastal Zone Management.
Fishing has many impacts on the marine ecosystem, ranging from a simple removal of fish biomass to alterations in food web structures, changes in the size structures of fish populations, fluctuations in ecosystem productivity, and habitat alteration. An impact that is increasingly coming to light, but has been hitherto overlooked, is the effect of market selectivity on ocean ecosystems. The fact that fishing places greater pressure on some species than on others (e.g., fishing harder on the species that the market most desires) can lead food webs to become skewed (usually, in favor of non-desired fish species). Ocean ecosystems are not like farms where we can remove weeds and cultivate prized crops; instead, when we exclusively remove the prized fish, we inadvertently "cultivate" the "weeds" (of course, these are not actually nuisance species, but delicious species whose delights have simply not been discovered yet by the market!). Additionally, fishing can unleash chain reactions in marine ecosystems, such as trophic cascades, which occur when a decrease in a predator species leads to an increase in its prey species, and so on. Some cutting-edge scientists are now advising a "balanced" pattern of fishing -- one that mimics the natural predation levels in an ecosystem. Expanding your seafood palate can make you a better steward of the ocean: diversity on your plate supports biodiversity in the sea!