Six Fish That Are Smarter Than We Give Them Credit For

The Crux

Six Fish That Are Smarter Than We Give Them Credit For

By Yao-Hua Law | March 3, 2015 11:34 am


Name a smart animal. Perhaps dogs, or dolphins, or chimpanzees came to mind. But why not goldfish, salmon, or moray eels?

Most people don’t associate intelligence with fishes. Blame it on the misconception that evolution is linear, with fishes sunk at the primitive end and primates raised near the top. Increasingly, though, scientists are appreciating the full spectrum of fish behaviors in their natural environments, thanks to advances in technology such as underwater ROVs and better recording equipment.

“In the past ten years, there has been a sea change in how scientists view fish intelligence,” says Culum Brown, who studies fish behavior at Macquarie University. Brown notes that some scientists would still deny that fishes possess basic cognitive skills.

Scientists have found that not only can fishes perceive their environments using complex senses, but that they can also coordinate hunts, use tools, and remember and learn – sometimes better than rats and toddlers.


I See – and Smell and Hear – You

We humans see in three bands of the light spectrum – blue, green and red. That makes our vision trichromatic. Most fish, however, are tetrachromats, able to see in the same three colors and also ultraviolet. Many fishes see objects as clearly as we do.

What’s more, fish can smell and taste impressively well. Chemicals permeate easily in water, and fishes have equipped their gills, fins and mouths with lots of receptors. For example, the yellow bullhead has 175,000 taste buds across its body; our tongue has only 10,000.

And though we don’t often think of it, fish are incredible auditory creatures. We now know about a thousand fish species that make and use sounds to facilitate mating, feeding and group dispersal. Some, like the meagre (Argyrosomus regius), a fish that weighs up to 110 pounds, make such loud grunts during mating that they expose their location to eavesdropping fishermen.


Making Connections

A basic sign of intelligence is so-called associative learning – basically, what Pavlov demonstrated with his dogs.

Fish can also accomplish this feat. For instance, pet fishes often demonstrate time-place learning: they remember when and at which ends of the aquarium their feeding occurs.

And lab experiments have found that in some cases fish are better at this than mammals. Galaxias, a common freshwater fish, accomplish time-place learning in 14 days while rats need 19. In another example of associative learning, wild rainbowfish learn to link food with lights-on in 14 trials, whereas rats need 40 trials to associate food with a sound.

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Goby fish. Image by  Khoroshunova Olga/ Shutterstock

Learning the Layout

Fishes are better navigators than most human toddlers. After encountering an object, many fishes associate the object with the location’s basic geometry (e.g., always in the oblong corner of a chamber). Fishes can also combine salient features of the environment, say a patch of grass next to the object, with geometric information to augment memory. In contrast, children learn to use featural cues only after five years old.

Gobies that live in rock-pools provide a classic demonstration of such spatial learning. Researchers simulated high and low tides in the lab and let gobies explore neighboring pools during high tide. During low tide, if these gobies were startled (i.e., the researchers poked them with a stick) they overwhelmingly jumped into adjacent pools. Spatial learning in this instance saved them from falling onto a sandbank.

Atlantic salmon. Credit J. Helgason/ Shutterstock

Fish Schooling

That salmon on your plate may very well have been a mentor in his past life.

In captivity, young Atlantic salmon often wait a few minutes before they strike at a new food item. But after being in a tank with experienced salmon, who strike immediately, the youngsters become far bolder than if they are housed with other naïve salmon.

Scientists think that imitation allows younger fishes to acquire other kinds of crucial knowledge, for instance migration routes and foraging locations, from older fishes, and helps retain tradition in fish schools.

Grouper. Credit Sergey Dubrov/ Shutterstock

Trust and Teamwork

Cooperation requires some complex brainpower. In fact some scientists speculate it was the force that sparked the human brain to get so big.

And it turns out, with their tiny brains, fish are capable of pretty advanced alliances too. Groupers and moray eels are the only known example of two different species working together to hunt.

It works like this: The eel snakes into the crevices of the reef, flushing out reef fishes into the open waters, while the grouper patrols outside, scaring fishes into the reefs. Whichever way the fishes escape, they are likely to swim in the direction of a gaping mouth – either of a grouper or eel. Both groupers and eels catch more prey hunting together than alone.

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Black-spotted tuskfish. Image by Wild Singapore via Flickr

Using Tools

Tool use was once heralded as the cognitive leap that only humans had made. Then, beginning with chimpanzees, scientists discovered tool use across a diverse range of animals: crows, vultures, otters, and octopi. What’s less known is that fishes, too, use tools.

The black-spotted tuskfish has got its feeding routine down to a science. It feeds on animals that protect their soft bodies in hard shells: crustaceans, snails and clams. Clamping a clam in its mouth, a tuskfish whams it into the rock – left, right, left, right – until the clam shell breaks. In a similar approach, some species of wrasse crush urchins against corals to break their spines and feed on their soft insides.


Native Hawaiians Provide Lessons In Fisheries Management

Roughly three-quarters of the Earth’s surface is covered with water. As I stand on a beach in Hawaii and look out over the vast, blue expanse in front of me, I am overwhelmed by the immensity of the Pacific Ocean. My brain wrestles with numbers far beyond its capacity to visualize. In that moment, it is incomprehensible that even seven billion humans could deplete such a boundless and unimaginable resource. Yet, I know that we are. We are emptying the oceans of their fish, one species at a time.

Today, 85 percent of the world’s fisheries are either fully exploited, overexploited or have already collapsed. Combined, the world’s fishermen catch 2.5 times the sustainable number of fish every year. Scientists predict that if current trends continue, world food fisheries may collapse entirely by 2050. “We are in the situation where 40 years down the line we, effectively, are out of fish,” explains Pavan Sukhdev, special advisor to the UN Environment Programme.

What we need are better management strategies. Now, researchers from the Center for Ocean Solutions at Stanford University are turning to the past for advice. Loren McClenachan and Jack Kittinger used historical records to reconstruct fish catches for the past seven hundred years to see if earlier civilizations did a better job than we are at managing their fisheries. The authors were able to characterize historical catch rates in the Florida Keys and Hawaii by reviewing a variety of historical sources, including species-specific catch records from the 1800s and archaeological reconstructions of population densities and per-capita fish consumption.

“Seven hundred years of history clearly demonstrate that management matters,” said Loren McClenachan, co-author of the study and assistant professor of environmental studies at Colby College. In Florida, fisheries were characterized by years of boom and bust through sequential collapse of high-value species, many which are still endangered or extinct today. The Keys fisheries were set up for failure – unlike other historical island communities, the Keys were highly connected to other markets, increasing fisheries demand. Furthermore, they have historically lacked a centralized management system. But, while fisheries in the Florida Keys have always been poorly supervised, fisheries in Hawaii were once far better than they are today.

“Before European contact, Native Hawaiians were catching fish at rates that far exceed what reefs currently provide society,” said Kittinger, co-author and early career fellow at the Center for Ocean Solutions. Native Hawaiians pulled in over 15,000 metric tons of fish per year, and these high yields were sustained over several hundred years, despite a dense Hawaiian population. “These results show us that fisheries can be both highly productive and sustainable, if they’re managed effectively.”

Much of the management system in Hawaii was tied to class and gender. For example, most offshore fishing was done by a professional fishing class who were familiar with their local environment. If they wanted to fish, they had to ask their chiefs, who regulated the fishing gear and canoes. The most valuable (and vulnerable) species like turtles and sharks were reserved for high chiefs and priests, reducing fishing pressure.

The key to the Hawaiian’s success lay in using a diverse suite of management measures. Many of the methods they used are similar to strategies employed in fisheries management today, including protected areas, community-based management, regulation of gear and effort, aquaculture, and restrictions on vulnerable species.

Perhaps the greatest difference between management then and now, however is that in native Hawaiian society, rules were strictly enforced. “Rules were accompanied by robust sociocultural institutions,” the authors write. The ancient Hawaiians did not hesitate, and punished transgressors with corporal punishment. “Clearly, we don’t recommend this,” said Kittinger, “but it’s easy to see there’s room to tighten up today’s enforcement efforts.”


He’eia Fishpond in Kane’ohe Bay, Hawaii. Image c/o Paepae O He’eia


Other differences exist as well. For example, while aquaculture was used by the native Hawaiians, these fishponds were maintained for different reasons than we farm fish today. Fishponds did not contribute substantially to total fish production, but instead served as food security during tough times. As such, Hawaiians stocked fishponds with very different species than modern farms. Fishponds contained small, algae-eating species, requiring little from the sea to support them. Modern aquaculture, in contrast, relies heavily on wild-caught feeder species to support lucrative, luxury species like salmon. Five pounds of wild-caught fish are needed to produce one pound of farmed salmon, and instead of acting as a backup for when wild fish are scarce, fish farms make up a whopping 50% of our consumed fish production.

Kittinger and McClenachan hope that understanding successful management strategies by historical societies will lead to better management of our current resources. “The evidence we present from historical reconstructions shows that reef fishery sustainability has been achieved in the past,” they write, “which can guide actions for a more sustainable future for reefs and the communities that depend on them.” 

Sunlight Could Lower Your Blood Pressure

Surrounded by winter’s gloomy gray skies, many of us believe that a little bit of sunshine will be good for our health — helping our bodies synthesize vitamin D and improving mood. And now scientists have found a new way that sunshine may be good for our health: Exposure to the ultraviolet components of sunlight can lower blood pressure.

For decades, scientists have noticed a link between geography and risk of high blood pressure. The average blood pressure in a population increases as distance from the equator increases, as does the prevalence of hypertension, or abnormally high blood pressure. Researchers have also noted that people with mild hypertension have higher blood pressure measurements in the winter. What scientists couldn’t figure out was whether sunlight or temperature was causing these differences.


Controlling Blood Pressure

A clue came in the form of a signaling molecule known as nitric oxide.

In 2009, a group of Scottish scientists discovered a vast repository of nitric oxide in the surface of the skin — far greater than anything in the blood. They also showed that exposure to a component of ultraviolet radiation known as UVA light could make the nitric oxide biologically active, converting it to nitrate or nitrite.

Martin Feelisch, a biologist at the University of Southampton in England, believed that these results could explain why individuals living nearer the equator were less prone to hypertension. He hypothesized that the UVA rays from sunlight activated the nitric oxide, which entered the bloodstream and lowered blood pressure by dilating blood vessels.Image

New Study Looks at Norovirus Removal in Oysters


UK – The Food Standards Agency is inviting tenders to design and execute a research study to identify and evaluate possible enhancements to improve norovirus removal from live oysters during shellfish depuration processes.

The FSA wants to commission work to quantify and optimise the effectiveness of standard UK depuration practices in reducing norovirus in oysters and to explore the potential for novel approaches to significantly improve the effectiveness of this process.

The foodborne viruses’ research programme aims to gather data to provide a robust science and evidence base to inform development of a risk management programme on foodborne viruses, with a particular focus on norovirus.

The study should include reviews of relevant available evidence (published and unpublished) as the starting point for a fully justified laboratory-based project which will improve the controls that can be applied to current UK depuration practices, to reduce the levels of norovirus in oysters sold for public consumption.

2014 Whiteleg Shrimp Exports Continue to Push Up

VIET NAM – In 2013, Viet Nam’s whiteleg shrimp exports hit $1.58 billion, up 113 per cent year on year and making up 50.7 per cent of the country’s total shrimp exports which surpassed black tiger shrimp sales with $1.33 billion, up only 6.3 per cent and occupying 42.7 per cent of total shrimp sales. In the first month of 2014, the trend was continued.

In January 2014, Vietnam earned over US$258.6 million from shrimp exports including US$157.6 million of whiteleg shrimp sales (making up nearly 61 percent of total shrimp exports) and US$80.64 million of black tiger shrimp sales with the proportion of 31.18 per cent.

In 2013, demand for whiteleg shrimp in main consuming markets (the US, Japan and EU) soared due to short supply. Sharp decline in global shrimp production, particularly whiteleg shrimp in 2013 was caused by Early Mortality Syndrome (EMS) outbreak in two largest shrimp producers of Thailand and China.

EMS on farmed shrimp in Viet Nam was well-controlled in 2013, leading a significant increase in the shrimp production. 2013 witnessed a sharp expansion of whiteleg shrimp farming area to 66,000 hectares from 41,800 hectares of 2012 while total shrimp farming area up only 1.6 per cent year on year with 666,000 hectares. Accordingly, the output of whiteleg shrimp rose 50.5 per cent year on year to 280,000 MT from 186,000 MT in 2012.

In the late 2013, many Mekong Delta provinces stocked shrimp, mainly whiteleg for third crop of the year. In the first shrimp crop in 2014, many households shifted to farm whiteleg shrimp instead of farming black tiger shrimp.

Whiteleg shrimp sales to the US up 337.6 per cent

In January 2014, shrimp exports to the US totaled $86.88 million, up 163 per cent year on year. The US is the leading importer of Viet Nam shrimp. In January 2014, shrimp sales to the US made up 33.6 per cent of the country’s total shrimp exports while in the same month of 2013, the proportion of exported shrimp to the market was only 22.2 per cent, equal to exports to Japan.

Positive growth in whiteleg shrimp sales to the US in Jan 2014 showed that Viet Nam’s whiteleg shrimps are favored in the US market.

In Jan 2014, shipment of Viet Nam whiteleg shrimp to the US touched over $67.4 million, up 337.6 per cent from Jan 2013 ($15.4 million).

In the month of 2014, shrimp exports to other major markets also reported a sharp surge: exports to Japan and EU up 64.3 per cent, exports to South Korea up 143.5 per cent, to Australia up 96 per cent; however, shrimp exports to China downed 37.7 per cent.


Eating Fish Saves Water

US – Researchers in the US have, for the first time, quantified the amount of freshwater that would be needed to replace marine protein in our diets with protein produced on land. Jessica Gephart and her colleagues from the University of Virginia, US, believe that quantifying water footprints in this way is an important tool for evaluating food and water security.

“Marine fish production requires little or no freshwater, whereas generating terrestrial protein such as meat, eggs or crops requires large amounts of water,” Ms Gephart told environmentalresearchweb. “So consuming marine protein instead of terrestrial protein represents a freshwater saving and contributes to a low water footprint diet.”

Calculating the water footprints of different food groups also helps to identify countries that may struggle to produce adequate supplies of protein should populations of marine fish decline.

Gephart and her colleagues found that, globally, replacing marine protein with terrestrial protein would require an additional 350 cubic km of water per year. As an estimated 7600 cubic km of water per year is used for human food production, marine protein currently provides water savings of 4.6 per cent.

While this global figure is relatively small, the researchers found that in some countries the saving can be as high as 50 per cent.

“We found the highest water saving from marine protein in the Maldives,” said Ms Gephart. “This figure shows that the Maldives are very dependent on marine protein and as the amount of land available for capturing freshwater and producing terrestrial protein is small, the Maldives may struggle to generate enough terrestrial protein domestically should fish stocks decline.”

As well as the Maldives, the team rated the Republic of Korea and Barbados as receiving the greatest water benefit from marine protein, and consequently as most vulnerable to the loss of this protein. Only four countries have sufficient renewable water resources but insufficient land: Japan, Brunei Darussalam, Trinidad and Tobago, and Bangladesh.

“These countries may be able to increase terrestrial food production if yield can be increased on available agricultural land,” said Ms Gephart. “But they may be more likely to import terrestrial protein.”

The researchers also identified countries that have sufficient land, but insufficient water. These include much of the Middle East and North Africa, and parts of Sub-Saharan Africa.

Ms Gephart hopes the study, which has been published in Environmental Research Letters (ERL), will highlight the fact that water resources and food security are often linked, directly or indirectly.