Saving Seafood

Why Don’t Fish Swim Upside Down?

November 10, 2017 — There is no up or down in space, yet in shows like Star Trek, ships are always oriented the same way: right side up. It’s a scientifically unnecessary trope that has become a running joke among science fiction fans.

Yet here on Earth, fish find themselves in a strikingly similar situation. As a fish glides through its weightless, three-dimensional, watery world, it almost always stays right side up. The question—for both starships and fish—is why?

It’s an easier question to answer for fictional spaceships than real-life fish.

In movies or on television, directors show ships the way they do because it makes the scene more understandable to viewers, creatures accustomed to a gravity-bound world. “We have a fixed idea that everything should be right side up,” says Frank Fish, a functional morphologist at West Chester University in Pennsylvania. But what about fish? It’s a puzzle.

“I can’t get into the mind of a fish—despite my name—and determine why it would particularly do that,” says Fish.

Deepening the mystery is that scientists know few reasons why a fish would swim in any particular orientation—yet they clearly have a preference. Unlike land animals, fish don’t push against the ground to move. And, while moving, fish are no more streamlined in one orientation than another. What’s more, most fish are top heavy, says Brooke Flammang, who studies fish biomechanics at the New Jersey Institute of Technology. Like a child balancing on a beach ball in the pool, gravity wants them to flip. So why don’t they?

The leading explanation is that fish began life right side up, evolutionarily speaking, and so most never had a reason to change. “Just between us, yeah, they never bothered,” says Milton Love, a semi-retired marine zoologist at the University of California, Santa Barbara.

A fish’s preferred orientation “goes back to those very early steps of building a left side and a right side, a head end [and] a tail end,” says Peter Wainwright, who studies fish morphology and behavior at the University of California, Davis.

There are two groups of animals that have distinct left and right sides, Wainwright says. The first group, protostomia, includes most invertebrates, like insects and mollusks. Early on in development, as embryos, these animals develop a cavity that goes on to become the mouth.

Read the full story at Hakai Magazine

 

How Ocean Aquaculture Could Feed the Entire World – and Save Wild Fish

Marine researchers at the University of California, Santa Barbara, mapped out the potential of the open ocean to support farmed fish and came to some surprising conclusions.

August 21, 2017 — About five out of every six fisheries worldwide has reached or passed the limit of what it can sustainably produce, according to the World Wildlife Fund. Drought, dams, agricultural runoff and other pressures have depleted wild salmon populations in the Eastern Pacific, while on the east coast of North America, wild Atlantic salmon exists mainly in the memories of the Greatest Generation. Bluefin tuna, the preferred delicacy of the world’s finest sushi chefs, is at 2.7 percent of its historical population – about the same as the Bengal tiger.

Meanwhile, seafood farmed in coastal regions has been infected with sea lice, pollutes neighboring ecosystems with waste, sometimes produces fewer nutrients than are fed into the system, often destroys carbon-sequestering mangroves and can require large amounts of antibiotics to stave off disease.

But according to a new study from the University of California, Santa Barbara’s Bren School of Environmental Science and Management, aquaculture could feed a global population expected to grow to nearly 10 billion by 2050. Lead author Rebecca Gentry, a newly minted PhD in marine ecology, and her colleagues wrote that the open ocean “is largely untapped as a farming resource,” representing “an immense opportunity for food production.” In the study published August 14 in the journal Nature Ecology & Evolution, they found that the entire world’s current output of wild-caught seafood could be farmed in areas that in total would comprise just 0.015 percent of the ocean’s surface area, if grouped together in a way that the authors note would not be realistic or recommended. That’s the equivalent to the size of Lake Michigan.

“People assume the oceans are big but no one had quantified it,” Gentry said. “There’s not that much broad-scale ecological research on marine aquaculture, so we needed a base of information to get an idea of where we can do it.”

Read the full story at Aquaculture Magazine

Global ocean health relatively stable over past five years

July 5, 2017 — While global ocean health has remained relatively stable over the past five years, individual countries have seen changes, according to a study published July 5, 2017 in the open-access journal PLOS ONE by Benjamin Halpern from University of California Santa Barbara, USA and colleagues.

The Ocean Health Index has been used to assess ocean health on the local and regional scale, measuring factors such as biodiversity, coastal protection, and clean waters to help inform regional policies. In this study, Halpern and colleagues analyzed five years’ worth of Ocean Health Index data for 220 countries, seeking potential drivers and implications for the changes that they observed.

As expected, global ocean health has been fairly stable over the past five years, since the health of the world’s oceans cannot change rapidly over a relatively short time period. However, there were notable changes in individual countries. For example, the authors found declines in overall ocean health in many Arctic and sub-Arctic countries, possibly because the rapid loss of sea ice has resulted in reduced coastal protection. The researchers suggest that improvements in wild-caught fishery management, the creation of marine protected areas, and decreases in harvesting of fish and other natural products may have stabilized ocean health scores in other regions.

While the Ocean Health Index was capable of predicting short term changes in global ocean health, the authors suggest that investment in additional resources for measuring changes on a global scale would greatly help with management and protection of ocean health now and in the future.

Read the full story at Science Daily

New study examines how China maintains large catches and what it means for fishery management elsewhere

January 19, 2017 — China, the world’s largest seafood producer, has done something extraordinary. For the past 20 years, despite minimal management and some of the most intense industrial fishing in the world, it has maintained large catches of key species in its most productive waters.

That same kind of intense, lightly managed industrial fishing has collapsed other fisheries, such as Newfoundland’s cod fishery in the 1990s. China’s ability to sustain its catches has puzzled scientists, some of whom have even questioned the accuracy of the country’s catch reports.

A new study from UC Santa Barbara, published in the Proceedings of the National Academy of Sciences, suggests another explanation: By reducing the population of predatory fish, China has increased populations of preyed-upon species.

“If you fish down the large predatory fish, then you can catch more small prey fish, because they are no longer being eaten before you get to them,” explained lead author Cody Szuwalski, a fisheries scientist in UCSB’s Sustainable Fisheries Group. The group is a collaboration of the campus’s Marine Science Institute and Bren School of Environmental Science & Management.

Read the full story at Phys.org