Small cleaner fish keep coral reefs healthy

This 2012 video says about itself:

This tiny bluestreak cleaner wrasse looks pretty brave by swimming into that big potato cod‘s mouth, but don’t worry. These two fish have a deal!

The cleaner wrasse helps out bigger fish by eating any parasites and dead tissue that might be clinging to them. In exchange for the wrasse’s assistance, the bigger fish refrain from snacking on them. The wrasse gets a free meal from the cod, and the cod stays healthier because of the wrasse.

Relationships like this, where different plants or animals work together and help each other out is called “mutualism” because both organisms mutually benefit from the other being around. In fact, these little cleaner wrasses are so good at what they do, that these bigger fish will actually seek them out– they’ll deliberately pay visits to wrasse cleaning stations along reefs, much the same way people will line up to have their cars cleaned on a nice summer day!

From the Université de Montréal in Canada:

Staying clean keeps seafish smart

March 7, 2018

“Vet” service provided by smaller fish is key to keeping coral reefs healthy, a Canadian study finds.

A team of international researchers led by a Canadian biologist has found that infection with parasites makes it harder for seafish living in coral reefs to think.

The study, conducted at the Lizard Island Research Station in Australia and led by Assistant Professor Sandra Binning of Université de Montréal’s Department of Biological Sciences, was published today in Proceedings of the Royal Society B: Biological Sciences.

It highlights the important role of both parasites and cleaning organisms in the decision-making abilities of reef fish.

Binning and her team found that sick seafish can get well again by seeking out other animals like the blue-streaked “cleaner wrasse”, a common aquarium fish that eats harmful parasites off their “clients”, helping keep them healthy.

“We collected wild damselfish with or without access to cleaner wrasse and tested their ability to solve a feeding test in the lab”, Binning recalled. “We then compared their performance to fish that we infected with parasites experimentally.”

“We found that infection with parasites, especially in high numbers, really affects the ability of fish to learn.”

These results may not be surprising to anyone who’s been sick and tried to do activities requiring thinking and concentration. “When we’re sick, our body diverts resources away from our brain towards fighting off the infection”, Binning noted. “This makes it harder for us to think and learn.”

Humans may also benefit from staying parasite-free. “Studies have found that schoolchildren with stomach worms perform worse on standardized tests that their parasite-free peers,” said Binning. “Treating these kids with anti-parasite medication improves their performance.”

Although fish can’t take medication when they’re feeling under the weather, they can enlist the help of cleaners to help rid them of their parasites. This access to cleaning services can dramatically improve a fish’s performance in a learning test.

According to Dr. Binning, “cleaner wrasse act like the vets of the sea. Clients visit cleaners to get their parasites removed, and this helps boost their ability to think and solve the test.”

Interactions with cleaner wrasse are also known to reduce client stress levels and increase local recruitment of coral reef fishes.

However, this vital role in maintaining healthy reef communities may be under threat: cleaner wrasse are among the top marine fishes caught for the aquarium industry, due to their colourful patterns and charismatic behaviour.

“It’s important that we understand the impacts of reduced access to cleaners on client fishes”, said Binning. “Cleaners may not be the largest or most abundant fish on the reef, but they affect the well-being of thousands of their clients. This needs to be taken into consideration when setting collection limits and managing marine parks.”

The study was done in collaboration with several groups of researchers: Derek Sun and Alexandra Grutter of the University of Queensland in Australia; Dominique Roche, Simona Colosio and Redouan Bshary of the University of Neuchatel in Switzerland; and Joanna Miest of the University of Greenwich in the U.K.


Zambian fish working together to get food

This 2013 aquarium video is called Neolamprologus obscurus.

From ScienceDaily:

How a fish species in Lake Tanganyika works together to secure additional food sources

March 6, 2018

Cooperative behaviour to acquire food resources has been observed in hunting carnivores and web-building social spiders. Now researchers have found comparable behaviours in a fish species. A tiny striped fish called Neolamprologus obscurus only found in Lake Tanganyika in Zambia excavates stones to create shelter and increase the abundance of food for all fish in the group. Led by Hirokazu Tanaka of the University of Bern in Switzerland and the Osaka City University in Japan, this study is the first to document how team work in fish helps them to acquire more food. The research is published in Springer’s journal Behavioral Ecology and Sociobiology.

Neolamprologus obscurus is a highly sociable species of cichlid found only in the southern reaches of Lake Tanyanika. These zebra-striped fish feed mainly on shrimp and other invertebrates found along the bottom of the lake. At night, shrimp move into the water column, but by dawn they sink back to the lake bottom to hide in crevices and holes, including the shelters that the fish have dug out under stones. Such excavation work is always done as a group, as is subsequent maintenance efforts. Breeding fish seldom leave these safe havens and are supported by up to ten helpers from their family group. The helpers protect the brood, and constantly remove sand and debris that fall into the cavities.

“The function of these excavated cavities is much like that of the webs of social spiders, which live in groups and share the trapped prey among group members,” explains Tanaka.

In this study, Tanaka and his colleagues wanted to find out if the size of the cavities at the bottom of the lake relate to the abundance of food available in the area, and if the presence of helpers influences the size. Through hours of scuba diving in Lake Tanyanika, the researchers created artificial cavities and examined the stomach contents of some of the fish. In another experiment, the researchers removed helpers that were assisting breeding fish. Within a week, enough sand had fallen into the cavities to decidedly shrink these spaces. This effect was augmented when the helpers removed were big.

One of the key findings was that the size of an excavated crevice had an influence on the amount of shrimps that subsequently gathered in it. When there were more helpers around, the space that could be created was bigger and more shrimps could be gathered.

“Helpers in Neolamprologus obscurus extend and maintain the excavated cavities, and by doing so, contribute to an increase in food abundance inside the territory of breeding females”, explains Tanaka.

“Fish living in groups may be able to increase and maintain considerably larger excavated cavities per capita compared to solitary living fish. Consequently, group living enables Neolamprologus obscurus to efficiently increase the prey abundance in their territory. This increases the body condition and future reproductive success of breeders and/or helpers”, adds Tanaka, who suggests that there is a clear benefit to group living for this species of fish.

Triplefin fish’ light in their eyes

This video says about itself:

Snippet: Watch a fish create sparks of light with its eyes

20 February 2018

These shallow-water fish can use their eyes like flashlights. Triplefins likely send out “sparks” to sense prey.

Read more here.

Korea, import radioactive Fukushima fish, WTO demands

This Associated Press video says about itself:

31 July 2015

South Korea is banning imports of all fishery products from Japan’s Fukushima region because of what it calls growing public worry over radiation-contaminated food that has reportedly prompted a sharp decline in fish consumption.

The Ministry of Oceans and Fisheries said on Friday that it made the move because of Tokyo’s uncertain progress on stopping contaminated water from flowing into the ocean and worries about how the clean-up will advance.

“This measure is due to the public’s growing concerns regarding the fact that hundreds of tons of polluted water, coming from the recent accident scene of Fukushima nuclear disaster, is flowing into the sea everyday”, said government spokesman Shin Joong-don on Friday.

Seoul imposed a partial ban on Japanese fish following the March 2011 earthquake that led to the meltdown of a nuclear reactor in Fukushima.

The new measure now includes all fishery products from Fukushima and seven other nearby Japanese prefectures.

Japan has acknowledged that contaminated underground water has been flowing into the Pacific Ocean.

From daily The Morning Star in Britain:

Saturday, February 24, 2018

WTO tells South Korea to allow in Japanese nuclear fish

SOUTH KOREA said today that it will appeal against a World Trade Organisation (WTO) decision against bans on imports of Japanese fishery products after the Fukushima nuclear meltdowns.

The government said it wanted to protect public health and safety and would maintain its existing regulations on imports of Japanese seafood.

Japan had complained to the WTO about South Korea’s ban, saying it violated WTO rules, was discriminatory and served as a trade barrier.

In 2013, South Korea banned imports of all fishery products from eight Japanese provinces near Fukushima after Tokyo Electric Power reported leaks of radiation-contaminated water.

That tightened restrictions already imposed after the nuclear disaster at the Fukushima Dai-Ichi nuclear power station in March 2011, when a tsunami wrecked the plant and caused its reactors to melt down.

It also required inspection certificates for food products from Japan if small amounts of radioactive cesium or iodine were detected.

China also bans seafood and other agricultural products from Fukushima and nine other prefectures, including Tokyo. It requires certificates on foods from the rest of Japan.

Do birds transport fish eggs?

This 2012 video says about itself:

Here are minnows, Gulf killifish, hatching under the microscope. In the wild they lay their eggs on marsh grasses at a full moon high tide and then 30 days later when the next full moon high tide comes they get wet and hatch.

From the Universität Basel in Switzerland:

Dispersal of fish eggs by water birds – just a myth?

February 19, 2018

How do fish end up in isolated bodies of water when they can’t swim there themselves? For centuries, researchers have assumed that water birds transfer fish eggs into these waters – however, a systematic literature review by researchers at the University of Basel has shown that there is no evidence of this to date.

Small lakes with a surface area of less than 100 m2 represent the majority of global freshwater ecosystems. Many of these lakes are found in remote, often mountainous areas with no inflow and outflow. Yet in most of these lakes, there are fish. So how do fish reach lakes and ponds that are not connected to other bodies of water?

This question was already addressed by some of the leading natural scientists of the 19th century such as Charles Darwin, Alfred Russel Wallace and Charles Lyell, who all came to the same conclusion – water birds must be responsible for fish dispersal.

And they had a plausible explanation for this: fish eggs of some species are sticky and can survive for some time out of water. The theory is thus that the fish eggs stick to water birds’ feathers or feet; the birds then fly from one body of water to the next, where the fish hatch from their eggs.

Conclusive studies are lacking

A study carried out by environmental scientists from the University of Basel has now shown that although the research community considers this to be a proven theory, no studies have been published to confirm it.

To objectively measure the lack of evidence, the Basel research team conducted a systematic literature review. The result shows that no in-depth scientific studies exist to prove that water birds disperse fish eggs.

To rule out the possibility that the unsuccessful search was due to their method, the researchers also used the same approach to look for evidence of the dispersal of aquatic invertebrates. In this case, they found numerous scientific publications supported by experiments and field studies.

Still widespread today

For their study, the Basel researchers also reviewed online forums and surveyed around 40 experts from research, private institutions, and enviromental NGOs. Their aim was to determine the prevalence of the theory of fish dispersal by water birds both inside and outside the research community. The majority of experts that took part in the survey found the theory so plausible that they deemed the mystery to have been solved. However, none of them could draw on any empirical evidence.

“The lack of evidence does not mean that water birds are not responsible for the dispersal”, says Dr. Philipp E. Hirsch from the University of Basel. “But we simply do not yet know what roles are played by birds, humans and other processes.”

Understanding the way that fish are dispersed in remote bodies of water is important for the maintenance of biodiversity. The knowledge of how species colonize new habitats forms the basis for the preservation of refuges and targeted reintroduction and also helps prevent the spread of invasive species.

Deep-sea rays use hydrothermal vents for incubating eggs

This video says about itself:

Deep-Sea Skates Incubate Eggs Near Hydrothermal Vents | Nautilus Live

8 February 2018

In June 2015, a team of researchers aboard E/V Nautilus made a surprising discovery while exploring the seafloor northwest of the Galapagos Islands. Large numbers of skate egg cases were observed near hydrothermal vents emitting volcanically-heated fluids. Researchers believe the warmer water helps to incubate and speed development of the embryos–the first time this behavior has been observed in marine animals. The Bathyraja spinosissima, commonly known as Pacific white skate, is a relative of sharks and rays. As one of the deepest living skate species, this species is rarely seen but has been documented from the Galapagos Islands to the Pacific Northwest.

The research team from Charles Darwin Research Station, University of Rhode Island, and the Galapagos National Park Directorate collected video surveys and specimens using ROV Hercules, recently publishing their findings in Scientific Reports.

From Penn State university in the USA:

Deep-sea fish use hydrothermal vents to incubate eggs

February 12, 2018

Summary: An international team of researchers have discovered egg cases of deep-sea fish near hydrothermal vents. The team believes that deep-sea skates, a relative of sharks and rays, use the warm water near the vents to accelerate the typically years-long incubation time of their eggs.

Some deep-sea skates — cartilaginous fish related to rays and sharks — use volcanic heat emitted at hydrothermal vents to incubate their eggs, according to a new study in the journal Scientific Reports. Because deep-sea skates have some of the longest egg incubation times, estimated to last more than four years, the researchers believe the fish are using the hot vents to accelerate embryo development. This the first time such behavior has been seen in marine animals.

“Hydrothermal vents are extreme environments, and most animals that live there are highly evolved to live in this environment,” said Charles Fisher, Professor and Distinguished Senior Scholar of Biology at Penn State and an author of the paper. “This study is one of the few that demonstrates a direct link between the vent environment and animals that live most of their life elsewhere.”

Among the least explored and unique ecosystems, deep-sea hydrothermal fields are regions on the sea floor where hot water emerges after being heated in the ocean crust. In their study, an international team of researchers, led by Pelayo Salinas-de-León of the Charles Darwin Research Station, used a remotely operated underwater vehicle (ROV) to survey in and around an active hydrothermal field located in the Galapagos archipelago, 28 miles north of Darwin Island.

“The first place the ROV landed on the sea floor was on a ridge, in the plume of a nearby hydrothermal vent that we had specifically come to investigate — a black smoker,” said Fisher. “When we panned the camera down, we found something we did not expect: These giant egg cases, also known as mermaid purses. And we found several layers of them, indicating that whatever was laying these eggs had been coming back to this spot for many years to lay them. As the dive progressed, we saw more and more of these egg cases and realized that this was not the result of a single animal, but rather a behavior shared by many individuals.”

The researchers found 157 egg cases in the area and collected four with the ROV’s robotic arm. DNA analysis revealed that the egg cases belonged to the skate species Bathyraja spinosissima, one of the deepest-living species of skates that is not typically thought to occur near the vents. The majority — 58 percent — of the observed egg cases were found within about 65 feet of the chimney-like black smokers, the hottest kind of hydrothermal vents, and over 89 percent had been laid in places where the water was hotter than average. The researchers believe that the warmer temperatures in the area could reduce the typically years-long incubation time of the eggs.

While several species of reptiles and birds lay their eggs in locations that optimize soil temperatures, only two other groups of animals are known to use volcanically heated soils: the modern-day Polynesian megapode — a rare bird native to Tonga — and a group of nest-building neosauropod dinosaurs from the Cretaceous Period.

Because of their long lifespan and slow rate of development, deep-water skates may be particularly sensitive to threats to their environment, including fisheries expanding into deeper waters and sea-floor mining. Understanding the development and habitat of the skates is vital for developing effective conservation strategies for this poorly understood species.

“The deep sea is full of surprises,” said Fisher. “I’ve made hundreds of dives, both in person and virtually, to deep sea hydrothermal vents and have never seen anything like this.”