Saving Seafood

How is climate change affecting fishes? There are clues inside their ears

May 15, 2019 — Climate change affects all life on Earth, but it poses unique challenges for aquatic species. For example, as water warms it holds less dissolved oxygen than cooler water. As a result, the world’s oceans, coastal seas, estuaries, rivers and lakes are undergoing a process known as “deoxygenation.”

When dissolved oxygen levels fall to about 2 milligrams per liter – compared to a normal range of roughly 5 to 10 mg/L – many aquatic organisms become severely stressed. Scientists call this low oxygen threshold “hypoxia.”

Globally fisheries generate US$362 billion annually. Scientists are already forecasting loss of fish biomass due to warming water. But can we measure effects on fish directly?

For some climate change impacts, the answer is yes. Increasingly, a window on the secret lives of fishes is opening up through study of tiny, calcified formations inside fish skulls called otoliths – literally, “ear-stones.”

Rocks in fish heads

Many people may be surprised to learn that fish have ears, and in many cases an acute sense of hearing. Modern fishes have three pairs of otoliths that form inside small sacs underneath the semi-circular canals of their inner ears and function as part of the fish’s hearing and balance system. (Species with skeletons made of cartilage, such as sharks and rays, lack otoliths.)

Otoliths are made of calcium carbonate, mostly in a form called aragonite, which is similar to the material that makes up hard corals and clam shells. Otoliths can be smaller than sand grains or as large as a fava bean. They grow as the fish grows throughout life, which makes them interesting for fish biologists. In environments where water temperature changes seasonally, sequences of opaque and translucent zones form in fishes’ otoliths over the course of a year, like tree rings. And amazingly, young fish deposit tiny increments on a daily basis.

Read the full story at the Times Union

Life in the North Atlantic depends on this floating seaweed

May 15, 2019 — ‘THERE’S NOTHING LIKE it in any other ocean,’ says marine biologist Brian Lapointe. ‘There’s nowhere else on our blue planet that supports such diversity in the middle of the ocean—and it’s because of the weed.’

Lapointe is talking about a floating seaweed known as sargassum in a region of the Atlantic called the Sargasso Sea. The boundaries of this sea are vague, defined not by landmasses but by five major currents that swirl in a clockwise embrace around Bermuda. Far from any mainland, its waters are nutrient poor and therefore exceptionally clear and stunningly blue.

The Sargasso Sea, part of the vast whirlpool known as the North Atlantic gyre, often has been described as an oceanic desert—and it would appear to be, if it weren’t for the floating mats of sargassum.

The seaweed may seem unremarkable at first glance—just bunches of drifting plant matter—but as Lapointe has helped illuminate through his work, sargassum is the basis of a complex ecosystem that nurtures a stunning array of marine life. It serves as a mobile shelter and a movable feast.

For 36 years Lapointe, a biologist with Florida Atlantic University’s Harbor Branch Oceanographic Institute in Fort Pierce, has combed the Sargasso Sea, observing sargassum by satellite and experiencing it firsthand in scuba gear. He wanted to figure out where the weed comes from, how it moves, what it sustains, and what sustains it—and to unravel the complex relationship sargassum has with other forms of marine life, from seahorses to great white sharks. Only by learning about this vital resource, he says, can we protect it from potential threats, such as ocean acidification and pollution.

Read the full story at National Geographic

New Research Reveals Clearer Picture of Upwelling That Feeds West Coast Marine Ecosystem

May 13, 2019 — The following was released by NOAA Fisheries:

Great volumes of nutrient-rich water welling up from the deep ocean fuel the West Coast’s great diversity of marine life. Now scientists using satellite images, research buoys, ocean models, and other ocean monitoring tools have brought the upwelling into much sharper focus, measuring even the velocity of the water and the amount of nutrients that it delivers.

Scientists described new “upwelling indices,” which represent a breakthrough in understanding the biological engine that drives the West Coast marine ecosystem.

“Upwelling is vital to marine life along the West Coast, but the tools we were using to monitor it hadn’t changed much in almost 50 years,” said Michael Jacox, a research scientist at NOAA Fisheries’ Southwest Fisheries Science Center who developed the new indices. “Now we’re bringing state-of-the-art tools and the latest science to bear to help us understand how upwelling supports and shapes the California Current Ecosystem.”

Given the ecological importance of upwelling, scientists and managers are eager for indices that allow them to monitor its variability and understand its impacts on coastal ocean ecosystems.

Jacox, of the Southwest Fisheries Science Center and NOAA’s Earth System Research Laboratory, and other researchers from NOAA Fisheries, and the University of California at Santa Cruz, recently published the new upwelling measurements new upwelling measurements in the Journal of Geophysical Research: Oceans and the indices are also available online. Maps based on the indices reveal through color-coding where upwelling is most pronounced, such as off Cape Mendocino in California.

Upwelling occurs along certain coastlines around the world where winds and the Earth’s rotation sweep surface waters offshore, drawing deep, cold, and salty water full of nutrients up to the surface. These nutrients fuel growth of phytoplankton that form the base of the marine food web, and ultimately nourish the West Coast’s ocean ecosystem from sardines to sperm whales.

Read the full release here

Shipwrecks may help tropical fish adapt to climate change

May 10, 2019 — When Chris Taylor presses play, footage of blue wrasse and greater amberjack fills the screen. The fish whirl and spin against a vivid backdrop of corals, sponges, and algae. When Taylor, an ecologist at NOAA’s National Centers for Coastal Ocean Science in Beaufort, North Carolina, asks visitors to the Centers where they think the video was taken, he’s not surprised to hear the Florida Keys or the Caribbean. But the guesses are invariably wrong.

“These highly structured reefs are right off our coast,” Taylor says. “There are all of these brightly colored fishes that defy expectations.”

A new study in Nature Communications Biology by Taylor and Avery Paxton, a marine ecologist who divides her time between NOAA and the Duke University Marine Laboratory, shows artificial deepwater reefs off the coast of North Carolina increased the number of tropical and subtropical fishes at the northern edge of their ranges. These findings have important implications for fishes in warming waters. As ocean temperatures rise, artificial reefs may facilitate the movement of these species towards the poles, where they may be able to find a habitat that is more suitable in the future.

Read the full story at National Geographic

Study: Fishery consolidation in Alaska leaves fishermen vulnerable

May 9, 2019 — Alaskan commercial fishermen are specializing more and more, leaving them more vulnerable to the immense uncertainty fishermen have to contend with, according to a new study.

Targeting a diverse array of fish types in different regions can allow fishermen to weather the ups and downs instigated by fish population changes, new regulations, deflating markets and environmental disasters. But fishermen in Alaska are increasingly specializing. Fewer fishermen are on the water than three decades ago, and those who remain are participating in fewer fisheries, according to the study, which was published in Fish and Fisheries.

“Across different fisheries and regions of Alaska, there are fewer people fishing than there used to be and their fishing portfolios have become less diverse,” Anne Beaudreau, the lead author of the study and an associate professor at the University of Alaska Fairbanks, told SeafoodSource.

Individual fishery quota systems, plus the high cost of permits and other institutional barriers, have made it more difficult for new players to enter Alaskan fisheries, according to the study.

Though fishermen could, in theory, diversify their portfolio of permits, those management restrictions and high costs often prevent them from doing so, leading to more specialization. Permits can cost hundreds of thousands of dollars depending on the fishery, Beaudreau said.

Read the full story at Seafood Source

UN report: Humans accelerating extinction of other species

May 7, 2019 — People are putting nature in more trouble now than at any other time in human history, with extinction looming over 1 million species of plants and animals, scientists said Monday.

But it’s not too late to fix the problem, according to the United Nations’ first comprehensive report on biodiversity.

“We have reconfigured dramatically life on the planet,” report co-chairman Eduardo Brondizio of Indiana University said at a press conference.

Species loss is accelerating to a rate tens or hundreds of times faster than in the past, the report said. More than half a million species on land “have insufficient habitat for long-term survival” and are likely to go extinct, many within decades, unless their habitats are restored. The oceans are not any better off.

“Humanity unwittingly is attempting to throttle the living planet and humanity’s own future,” said George Mason University biologist Thomas Lovejoy, who has been called the godfather of biodiversity for his research. He was not part of the report.

“The biological diversity of this planet has been really hammered, and this is really our last chance to address all of that,” Lovejoy said.

Conservation scientists convened in Paris to issue the report, which exceeded 1,000 pages. The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) included more than 450 researchers who used 15,000 scientific and government reports. The report’s summary had to be approved by representatives of all 109 nations.

Read the full story at the Associated Press

North Atlantic Ocean productivity has dropped 10 percent during Industrial era

May 7, 2019 — Virtually all marine life depends on the productivity of phytoplankton — microscopic organisms that work tirelessly at the ocean’s surface to absorb the carbon dioxide that gets dissolved into the upper ocean from the atmosphere.

Through photosynthesis, these microbes break down carbon dioxide into oxygen, some of which ultimately gets released back to the atmosphere, and organic carbon, which they store until they themselves are consumed. This plankton-derived carbon fuels the rest of the marine food web, from the tiniest shrimp to giant sea turtles and humpback whales.

Now, scientists at MIT, Woods Hole Oceanographic Institution (WHOI), and elsewhere have found evidence that phytoplankton’s productivity is declining steadily in the North Atlantic, one of the world’s most productive marine basins.

In a paper appearing today in Nature, the researchers report that phytoplankton’s productivity in this important region has gone down around 10 percent since the mid-19th century and the start of the Industrial era. This decline coincides with steadily rising surface temperatures over the same period of time.

Matthew Osman, the paper’s lead author and a graduate student in MIT’s Department of Earth, Atmospheric, and Planetary Sciences and the MIT/WHOI Joint Program in Oceanography, says there are indications that phytoplankton’s productivity may decline further as temperatures continue to rise as a result of human-induced climate change.

“It’s a significant enough decine that we should be concerned,” Osman says. “The amount of productivity in the oceans roughly scales with how much phytoplankton you have. So this translates to 10 percent of the marine food base in this region that’s been lost over the industrial era. If we have a growing population but a decreasing food base, at some point we’re likely going to feel the effects of that decline.”

Osman and his colleagues looked for trends in phytoplankton’s productivity using the molecular compound methanesulfonic acid, or MSA. When phytoplankton expand into large blooms, certain microbes emit dimethylsulfide, or DMS, an aerosol that is lofted into the atmosphere and eventually breaks down as either sulfate aerosol, or MSA, which is then deposited on sea or land surfaces by winds.

Read the full story at MIT News

Place-Based Management Can Protect Coral Reefs in a Changing Climate

April 30, 2019 — Researchers from the state Department of Health and the University of Hawai‘i at Mānoa have developed and applied a new technology in Hawai‘i that identifies where coral reef ecosystems and associated fisheries are vulnerable to human activities and where to focus management actions to minimize anthropogenic impacts.

The authors of the newly published study in the journal Ecological Applications identified specific locations on land where improved wastewater management and landscape practices would yield the greatest benefits for downstream reefs in terms of mitigating harm to coral communities and associated reef fish populations.

Expansion of coastal development, along with wastewater discharge and fertilizers, can harm coral reefs and their fisheries through increases in sediment and nutrient runoff. Consequent reef degradation directly affects ecological resilience, food security, human well-being, and cultural practices in tropical island communities around the world.

The researchers focused on the ahupua‘a (land divisions) of Hāʻena on Kaua‘i and Ka‘ūpūlehu on Hawai‘i Island, at opposite ends of the main Hawaiian Islands, where native Hawaiian communities are taking action to manage their resources through a place-based management approach.

Read the full story at Big Island Now

N.C. Study: Warmer Water Linked to Higher Proportion of Male Flounder

April 30, 2019 — If southern flounder live in warmer water during a critical window of early development, a higher percentage become male – more than 90 percent in some cases – research from North Carolina State University found. Having a high proportion of adult males over the long term could threaten both wild populations and the valuable commercial fishing industry, which depends on larger female flounder.

Field research and lab experiments showed that a four-degree Celsius difference in average water temperature during juvenile development shifted the male-female ratio from about 50-50 to as much as 94-6, says Jamie Honeycutt, an NC State postdoctoral researcher and lead author of an article about the research in Scientific Reports. That difference is within the range of expected ocean temperature increases under climate change models.

Environmental factors such as water temperature influence sex determination in southern flounder, as well as in other fish and reptiles, Honeycutt explains. Flounder stick to shallow waters that serve as nurseries until after they become male or a female, hanging around estuaries until reaching maturity before returning to the ocean to spawn at about age 2.

“We think that southern flounder have a genetic sex-determining system similar to humans, who have two X chromosomes for a female and an X and a Y for a male. In flounder, if an individual is a genetic male, it is destined to be male,” Honeycutt says. “However, if a genetic female is exposed to temperature extremes, then it can develop as a functioning male.”

Read the full story at North Carolina State University

During abrupt warming, lobsters in acidic water have reduced heart function, fewer infection-fighting cells

April 25, 2019 — Ocean acidification and warming may be an unhealthy combination for lobsters, say University of Maine scientists.

The heart rates of lobsters (Homarus americanus) who lived 60 days in water with predicted end-century  pH levels became erratic significantly sooner during an abrupt warming event than those of lobsters in ocean water with current pH levels.

The findings could be “likened to putting people on a treadmill and finding that people exposed to  fell off the treadmill from exhaustion much sooner than those not exposed,” says Heather Hamlin, a reproductive endocrinologist and associate professor in the School of Marine Sciences.

The lobsters exposed to acidic ocean conditions also had fewer cells that fight infection in their hemolymph (similar to blood), says Amalia Harrington, a recent marine biology Ph.D. graduate.

So while lobsters in acidic  may look and act normal, they experience physiological challenges when exposed to multiple stressors, says Hamlin.

She and Harrington tested adolescent female lobsters transitioning to adulthood. Effects of environmental stressors during this stage could have major impacts on the population of the species, say the researchers, who believe this is the first such study of its kind.

“We’re really trying to get at the ‘hidden’  on this understudied but extremely important stage of the American lobster,” says Harrington.

“Most of the previous work exploring climate change impacts on American lobster has focused on early developmental stages (eggs and larvae). While this is helpful for understanding how environmental change might impact the number of baby lobsters that survive their time in the plankton and make it to the seafloor, it doesn’t really tell us what impact that will have on the population as a whole.”

Read the full story at PHYS.org