A new method for distinguishing between tuna species has been presented in a paper co-authored by Dr Jordi Viñas, a fish genetics specialist at Girona University in Spain and Dr Sergi Tudela, Head of Fisheries of WWF Mediterranean.

The new method is based on gene sequencing and the researchers hope that it will support fisheries management and make trade restrictions possible for endangered species of tuna, since it can be used to accurately identify the species from any kind of processed tuna issue. It works for all eight recognized species of tuna, including highly endangered species like the Southern and Pacific bluefin tuna.

The true tunas belong to the genus Thunnus and are among the most endangered of all commercially exploited fish. They are also high priced, so when you pick up some cheap tinned fish in the supermarket the box will rarely contain Thunnus; the content will in most cases have been made from fish belonging to related families such as mackerels.

The Principality of Monaco has already lodged an application before the Convention on International Trade in Endangered Species (CITES) for a trade ban on the endangered Atlantic (Northern) bluefin tuna.

The paper – “A Validated Methodology for Genetic Identification of Tuna

Species (Genus Thunnus)” – was published on October 27 in the journal PLoS ONE.

http://www.plosone.org/

The Monterey Bay Aquarium has launched a national campaign asking top U.S. chefs and culinary decision makers to take a “Save Our Seafood” pledge not to serve items listed in the “avoid” section of the Monterey Bay Aquarium Seafood Watch List.

Seafood Watch is one of the best known sustainable seafood advisory lists, compiled by the Monterey Bay Aquarium. The origin of the list can be traced back to the “Fishing for Solutions” exhibit which ran at the Monterey Bay Aquarium from 1997 to 1999.

The list consists of an avoid list and a good-alternative list and is updated twice a year. The website (http://www.montereybayaquarium.org/cr/seafoodwatch.aspx ) is updated even more frequently.

“Ocean life is still in decline and we clearly need to take urgent action to turn things around,” said aquarium Executive Director Julie Packard. “The good news is that we know what it will take, and that key players are working more closely than ever to solve the problems. I’m confident that we can and will create a future with healthy oceans.”

So far, about two dozen top culinary professionals from across the nation have agreed to adhere to the list, including Susan Spicer (Bayona, New Orleans), Rick Bayless (Frontera Grill/Topolobampo, Chicago), Suzanne Goin (Lucques, Los Angeles), Mary Sue Milliken and Susan Feniger (Border Grill/Ciudad, Los Angeles), Fedele Bauccio (Bon Appetit Management Co., Palo Alto), Rick Moonen (rm seafood, Las Vegas), Michelle Bernstein

(Michy’s, Miami), Alton Brown (Be Square Productions, Atlanta), and Michel Nischan (The Dressing Room, Westport, Conn.).

Monterey Bay Aquarium is also working with 14 nonprofit organizations across the United States and Canada as part of the Conservation Alliance for Seafood Solutions (www.solutionsforseafood.org). Participating organizations have crafted a Common Vision for Environmentally Sustainable Seafood to help seafood buyers and suppliers develop comprehensive, corporate policies on sustainable seafood. Since the debut of the Common Vision in 2008, more than 20 major companies across North America have pledged their support.

Researchers from Emory University have identified the first fish to have switched from ultraviolet vision to violet vision, i.e. the ability to see blue light. This fish in question – a type of scabbardfish – is also the first example of an animal where a deleted molecule has resulted in a change in visual spectrum.

Many species, including humans, have violet vision but our common vertebrate ancestor had UV-vision and could not sense the blue colour spectrum.

All fish studied before the scabbardfish have been found to have UV vision. The scabbardfish is believed to have switched from UV vision to violet vision by deleting the molecule at site 86 in the chain of amino acids that makes up the opsin protein.

“Normally, amino acid changes cause small structure changes, but in this case, a critical amino acid was deleted,” Yokoyama explains.

Vision is of particular interest to evolutionary geneticists since it is a comparatively straight-forward sensory system with a low number of genes involved. Human vision is for instance made possible by no more than four genes.

“It’s amazing, but you can mix together this small number of genes and detect a whole color spectrum,” says evolutionary geneticist and research team leader Shozo Yokoyama. “It’s just like a painting.”

In their study, the Emory researchers linked molecular evolution to functional changes and the possible environmental factors driving them.

“This multi-dimensional approach strengthens the case for the importance of adaptive evolution,” says Yokoyama. “Building on this framework will take studies of natural selection to the next level.”

The Scabbardfish spends most of its life at a depth of 25-100 meters and at these depths UV light is less intense then violet light, something which may have prompted the change in vision. Living deep down in the ocean will however not necessarily make you benefit from a vision switch; the Lampfish has for instance retained its UV vision – most likely because it swims up to the surface at night to feed on translucent crustaceans that are easier to locate if you have UV vision.

“The finding implies that we can find more examples of a similar switch to violet vision in different fish lineages,” says Yokoyama. “Comparing violet and UV pigments in fish living in different habitats will open an unprecedented opportunity to clarify the molecular basis of phenotypic adaptations, along with the genetics of UV and violet vision.”

The article has been published in the October 13 issue of Proceedings of the National Academy of Sciences.

http://www.pnas.org

In addition to evolutionary geneticist Shozo Yokoyama, the research team also included post-doctoral fellow in biology Takashi Tada and post-doctoral fellow in biology and computational chemistry Ahmet Altun.

A research team from the National University of Singapore announced this week that they have created the world’s first semi-cloned fish – a female medaka fish named Holly.

Holly is the result of so called semi-cloning; an approach that leads to the formation of a new and unpredictable combination of genetic traits from both parents, similar to normal fertilization.

The research team also announced that Holly has produced normal offspring that carry a genetic marker also found in her and her parents. According to the team, this indicates that the new technique retains genetic stability.

Holly may aid researchers working with reproductive medicine and technology to find new ways of helping people with infertility problems.

The findings will be published in the October 16 issue of Science Journal.

www.sciencemag.org

The National Marine Aquarium in Plymouth, UK has received some attention in the press after chartering a Boeing 767 to fly in a 42-tonne cargo of Caribbean fish for a new exhibition.

The fish – 100 specimens from 18 different species – was purchased from the Ocean World aquarium in Barbados and will arrive to the UK in 19 purpose-built tanks. The sharks, rays and other fish will then be escorted by the police to their new homes in the National Marine Aquarium.

Chartering a Boeing 767 for this type of tropical import costs roughly £100,000, which is almost 160,000 USD.

An international team of researchers have shown how one single gene mutation is capable of making the medaka, a Japanese killifish, loose its attractive colours and display a drab grey colour which renders them significantly less attractive to medakas of the opposite sex – unless that potential mate is grey too.

In the wild, medakas come in a wide range of colours, including orange, brown and drab grey.

“We observed that the grey medaka were often rejected in favor of their brown or orange rivals“, says lead author Shoji Fukamachi. “This is the first demonstration of a single gene that can change both secondary sexual characteristics and mating preferences“.

As mentioned above, you don’t have to fear ending up without a mate just because you happen to be a grey medaka – you just have to go out looking for another grey specimen since the study showed greys to be preferentially selective for each other. This preference for choosing a member of your own colour suggests that sympatric speciation could occur in medakas as the colour determining gene is mutated, i.e. new species may form as the medakas choose to mate with specimens of their own colour.

The research is a collaborative effort by researchers from the University of Konstanz, Germany and from the University of Tokyo, Japan. The study has been published in the open access journal BMC Biology.

Telling a wild salmon from a farmed one can be tricky, especially if you don’t want to kill or injure the fish in question. To solve this problem, Dr Elizabeth Adey of the Scottish Association for Marine Science (SAMS) have developed a way of using fish scale analysis to determine the origin of a salmon.

Fish scales grow like tree rings and preserves a chemical record of the water in which the fish lived as each new section of the scale was formed. The new method, which was developed in collaboration with the National Oceanography Centre in Southampton, checks the amount of manganese present in the fish scale. During her work, Dr Adey discovered that the scales of farmed salmon have a very high manganese content compared to the levels found in scales coming from their wild counterparts.

“This is probably caused by manganese supplements in fish food, and also because conditions underneath the fish cages promote recycling of manganese in the water column,” Dr Adey explains. Using the new method, Dr Adey and her team was able to distinguish between farmed and wild salmon with 98% accuracy.”Because of its non-destructive nature, this technique could be used to assess the proportion of farmescape salmon present in any river, and therefore identify where additional conservation and wildlife protection measures are needed,” says Dr Trueman, a geochemist with the University of Southampton’s School of Ocean and Earth Science, based at that National Oceanography Centre. “Salmon farming is a big, intensive business. In 2006, around 130,000 tonnes of salmon were farmed in Scotland for the table. Wild populations of Atlantic salmon are in serious decline across their whole range and the total wild population returning to Scottish rivers in the same year is estimated at less than 5000 tonnes. Wild fish are rare and expensiveso there is a strong incentive for fraudulent labeling. Farmed fish also escape into rivers, harming the wild population. Unfortunately, it can be difficult to distinguish between farmed and wild fish.“

In the future, the new technique may also be able to point out which individual fish farms that need to implement more efficient methods for keeping their salmons in. In some Norwegian rivers, more than 50 percent of the salmon are now escapees. Escaped fish can carry disease to wild populations, and there is also a risk of genetic pollution since farmed fish haven’t gone through the same natural selection process as wild fish.

The gar family, famous for containing the largest fresh water fishes in Mexico, is currently at risk of becoming extinct – something which Mexican researchers are working hard to prevent.

“This fish is native to our country and the United States”, Doctor Eduardo Mendoza Alfaro explains. “Currently, its populations are threatened due to excessive hunting, — for there are no rules that regulate its fishing — urban expansion, pollution, and particularly the dams´ construction, which caused the destruction of their breeding grounds. These factors led this species to reduce to only forty adult specimens in the country — in inventory and considered national patrimony.”

Doctor Eduardo Mendoza Alfaro*, a member of the ‘Eco-physiology Group,’ from the Universidad Autonoma de Nuevo Leon’s (UANL) School of Biological Sciences Ecological Department, is currently researching gar reproduction and diet in order to find ways of efficiently raising gars in captivity. The team also works with several other types of endangered fish, but the gar – which can reach a length of three meter and is highly esteemed by sport fishers – is arguably the most iconic.

Lepisosteus platostomus – Shortnosed gar, Copyright www.jjphoto.dk

One of the hurdles that must be overcome to ease gar raising in captivity is how to distinguish males from females. In a reproductive facility you want to keep an ideal sex ration – with gars this is four males for each female – but this is difficult to accomplish without reliable sexing methods.

“We could not identify females and males, because, morphologically, they are

Identical”, says Dr Alfaro. “Even though most of the fish can be cannulated in order to know their gender and maturation status, for gar is not the same process, that is what represents

the first obstacle for scientifics when they were carrying out the reproduction

studies and establishing fish’s gender. Most of the fish can be cannulated by introducing them a catheter in the oviduct in order to take the oocytes (ovules). However, this process cannot

be carried out with the gar. They are so primitive fish, which date since 189 million years ago and their urinal tract which ends with the oviduct in a kind of sewer that cannot allow the

cannulation.”

To overcome the problem, Dr Alfaro and his team devised a new technique based on a molecule known as vitelogenine. Vitelogenine is present only in females from puberty and onwards, and can be used as a biochemical marker.

First, the team purified the molecule. Then, they created antibodies against the molecule for recognizing and quantifying it.

“Currently, we got an extremely sensitive method which allows us to dose this molecule with only a small sample of fish’s skin mucus, says Dr Alfaro. “So, we not only identified if it is a female or a male, but we can follow up females’ sexual maturation.”

Gar facts

· The gar family evolved during the cretaceous.

· A gar can weigh up to 220 lbs.

· The gar is a predatory fish with an elongated jaw. It is sometimes referred to as alligator fish due to its resemblance to the predatory reptile. It has numerous sharp teeth and a body protected by hard scales.

· Gars spawn in swamps during the wet season and destruction of wetlands poses a problem for them.

· In the wild, several males follow the female wanting to fertilize her eggs as she deposits them.

· Mexico is the world’s leading gar specimen producer.

*Roberto Eduardo Mendoza Alfaro is a professor at the UANL´s School of Biological Sciences Ecology Department in Leon, Mexico.

If you’ve ever wondered how the eyes of flatfish like flounder and sole ended up on one side of the head, you should take a closer look at a newly published article by Dr Matt Friedman.

Dr Friedman, who recently took up a post at Oxford University, has been investigating this mysterious eye migration using 50-million-year-old fossilized Acanthomorph fishes from Italy and France, and has managed to show that the change was slow and gradual rather than abrupt. Over millions of years, the positions of the flatfish eyes have gradually changed, little by little.

Addressing the Society of Vertebrate Palaeontologists’ (SVP) annual meeting at the University of Bristol today, Dr Friedman said: ”Flatfishes and their profoundly asymmetrical skulls have been enlisted in many arguments against gradual evolutionary change, precisely because it is difficult to imagine how intermediate forms might have been adaptive. My work provides clear evidence of the kinds of intermediates deemed ‘impossible’ by earlier workers and answers this long-standing riddle in vertebrate evolution.”

The most ancient Acanthomorph fishes had asymmetrical skulls, but the eyes were still located on both sides of the head. From these foregoers, intermediate species evolved and one of the eyes gradually moved across the head until both eyes ended up on the same side – millions of years later.

The flatfish group puzzled 19^th century scientists trying to grasp the new Darwinian ideas, because during that epoch, the group’s fossil record was incomplete and it was unclear how the gradual migration of one eye could have come about. Today, a much broader range of fossil fish is available to science and Dr Friedman’s study included over 1,200 fossil specimens belonging to over 600 different species.

According to Australian Southern Bluefin Tuna Association chief executive Brian Jeffriess, industry experts expect the tuna stocks to have recovered by 2013.

The statement was made during a Korean tuna meeting involving industry representatives from Australia, Japan and New Zeeland.

To make sure that over-catching does not restart, Jeffriess said the Commission for the Conservation of Southern Bluefin Tuna has focussed heavily on new enforcement measures.

“For example, from January 2010, every fish has to be tagged at harvest with each fish having its own individual number,” he said. “This tag would also be backed up by documents for each fish showing the date of harvest, weight and length.”