Warmer Oceans Are No Picnic for Fish

By LIZ DURKEE

Eat fish, we are told, they're good for the body and brain. Eat local fish to support the Island economy and limit the use of fossil fuels used to transport food. But eating traditionally local seafood will become a challenge as marine species struggle to adapt to changes in ocean waters due to human-induced global warming. Some species may not be local for long.

As water temperatures rise, cod, lobsters, and other marine species are migrating north to find cooler water that suits their feeding and breeding needs. As the oceans become warmer and more acidic, some fish find it harder to absorb the oxygen they need to survive.

Fish are already in trouble due to pollution and overfishing. The new climate change stresses are dizzying: changes in water currents and circulation, wind speed and directions, less oxygen, more carbon dioxide, more rain that adds pollutants and freshwater to saltwater systems, sea level rise that floods fish breeding grounds, storms that erode and alter habitats, and hazardous algae blooms.

These impacts will affect the food chain in many ways, from the mix of predator to prey and parasite to host to major ecosystem disruption. Oak Bluffs shellfish constable Dave Grunden cites one example: "Invasive colonial tunicates are carpeting acres of the floor ofthe Georges Bank fishing grounds. Some fish, such as flounder, have tried to eat it but are unable to digest it," he said.

By coating the sea bottom, the tunicates also eliminate valuable spawning grounds.

Phytoplankton is critical to the marine ecosystem. These tiny organisms are, in the words of the Conservation Law Foundation, "the nutrient base for the entire marine food web, [and] alterations in temperature can lead to mismatches in the timing of fish reproduction and phytoplankton availability, and to changes in the kinds of phytoplankton present. This could have a detrimental effect on the life cycles of some marine species."

Cod is the official fish of Massachusetts. A major 2007 study on climate change in New England is titled Confronting Climate Change in the U.S Northeast, prepared by the Northeast Climate Impacts Assessment and the Union of Concerned Scientists. The report concludes that, "Georges Bank, historically the Northeast's most important fishing grounds, is projected ... to become too warm to support the growth and survival of young cod by late this century." And sadly: "Cod are expected to disappear from the region's waters south of Cape Cod during this century."

Local lobsters are in no better shape. The report states that "lobster fisheries in Long Island Sound and the coastal waters off Rhode Island and south of Cape Cod are likely to decline significantly by mid-century." The New England Aquarium reports: "Scientists have also seen evidence linking rising seawater temperatures to the spread of lobster shell disease in Massachusetts' waters."

The news for aquaculture is mixed. According to a report by the Pew Center on Global Climate Change: "Warmer conditions would support faster growth or a longer growing season for aquacultured species, but it might become too warm for some species in a particular region, requiring a change in the species being cultured."

Gregory Skomal is a Massachusetts Division of Marine Fisheries environmental analyst, a shark specialist, and a former longtime Island resident. He explains that fish have very specific temperature ranges they like to inhabit and that there will be a change in the diversity offish and invertebrates we see off New England. "There will be a shift northward of some traditional fish as temperatures become intolerable for them," he says. He adds that while the range of some fish in the area will expand, others will contract. For example, there is not a huge number of summer flounder, or fluke, north of Cape Cod, but that may change. Some fish will move to deeper or shallower waters to survive." Sharks, he notes, will face the same type of population shifts as other fish.

Wind, currents and temperatures may affect the range and spawning habits of prized recreational and commercial catches like striped bass and bluefish. Local fishermen may lose access to some traditional catches, but Mr. Skomal says that more southern species, such as king and Spanish mackerel will likely migrate north.

As the playing field changes, some species will adapt and others will become extinct, locally or globally. The World Wildlife Federation reports: "Climate change could ... well be the knockout punch for many species which are already under stress from overfishing and habitat loss." The PEW report is somewhat brighter: "New combinations of species will interact in unpredictable ways ... there is evidence that marine organisms and ecosystems are resilient to environmental change ... allowing them to respond quickly ... and thus rendering them ecologically adaptable."

These challenges affect not only the ocean but an Island way of life. According to the National Oceanic and Atmospheric Administration (NOAA), "Living marine resources support a $60 billion dollar per year seafood industry and recreational fisheries that annually contribute $12 billion to the economy ... and help attract vast numbers of people to coastal regions for tourism and recreation."

The sad fact is that humans are responsible for disrupting the finely-tuned ocean and land-based ecosystems that sustain us. We didn't foresee this when fossil fuel consumption charged the Industrial Revolution. Now we know. Now we can choose to buy local seafood and boycott species that are at risk. The Home Port Restaurant in Menemsha serves only locally caught fish and shellfish and no threatened species such bluefin tuna. We can also support safe and renewable energy to combat fossil fuel consumption. Protecting marine species is a perfect example of the old adage to think globally but act locally.

This series of 14 essays about climate change was published in the Vineyard Gazette over a period of seven months in 2011. It appears here with permission. Copyright Vineyard Gazette. All rights reserved.

Comments