When salmon is farmed in large-scale monocultures, the fish tend to become susceptible to disease and parasites. Researchers working for the organization Nofima have now found a way of combating the parasite salmon lice in fish farms without using any dangerous toxins. Wrasse loves to eat lice, so the researchers simply added wrasse to the salmon populations and the result was astonishing.

During the trials, the most efficient lice eater turned out to be the Ballan wrasse (Labrus bergylta). In addition to being highly efficient, it also gathered lice at lower temperatures than the other Wrasse species that took part in the experiment.

When Ballan wrasse was used, roughly 2-5% wrasse was needed for salmon living in sea cages. This means that a population of 100 000 salmon will need somewhere between 2 000 and 5 000 wrasse to stay deloused. A new larger project will now be prepared to make sure there is an adequate supply of the lice eaters in Norway. The project will go on for three years and has received funding from The Fishery and Aquaculture Industry Research Fund (FHF).

The effort which is now commencing is unique in both a Norwegian and global context. Norway is the only salmon-producing country that is using wrasse on a large scale to combat salmon lice,” says Arne Karlsen, managing director of FHF.

Removing large amounts of Ballan wrasse from the wild to keep in salmon farms could cause serious damage to the wild populations and the goal of the Norwegian project is therefore to cover at least 25% of the demand with farmed wrasse by 2013.

In addition to Nofima and FHF, the project will also involve SINTEF Fisheries and Aquaculture, the Institute of Marine Research and the Norwegian University of Science and Technology.

Several Norwegian projects are already taking a closer look at the Ballan wrasse, including a research venture concerning Ballan wrasse farming that started last year with funding totaling NOK 12 million from the Research Council of Norway, FHF and industry partners.

” It is estimated that the total Norwegian effort on Ballan wrasse farming is in the vicinity of NOK 100 million,” says Kjell Maroni, research and development director at FHF

The researchers will now have to find out how to carry out large-scale wrasse farming without being plagued by the same problems with disease and parasites as the salmon farms.



“Perhaps part of the reason the males are so likely to cheat is that females never punish males”, marine scientist says.

Male Labroides dimidiatus cleaner fish punish females that bite instead of clean (thus driving off the bigger fish) but females never punish males for doing exactly the same thing.

The Bluestreak cleaner wrasse (Labroides dimidiatus) lives on coral reefs where it feeds by removing parasites and dead tissue from the skin of larger fish. Most of the time the wrasse provides bigger fish with a valuable service, but sometimes the tasty mucus in front of the cleaner turns into an irresistible temptation, prompting the wrasse to bite off a mouthful. This is naturally not appreciated by the bigger fish and a cleaner wrasse who can’t control his or her urges will have to watch the big fish take off in a jiffy, taking all the nutritious parasites with it.

When a male fish notice a female fish scaring off the big fish they are cleaning together he will promptly punish her for her injudiciousness. This might seem altruistic, but the male fish is actually pissed off at her for making his dinner swim away.

“The male’s dinner leaves if the female cheats,” says Nichola Raihani from the The Zoological Society of London who has been studying Labroides dimidiatus together with research partner Redouan Bshary.

“By punishing cheating females, the males are not really sticking up for the clients but are making sure that they get a decent meal,” Raihani explains.

Raihani believes true altruism is rare.

“When you see something that looks like it’s altruistic, if you look hard enough, there’s normally going to be a benefit somewhere down the line for the person that’s doing that supposedly altruistic act,” she says.
Interestingly enough, a female fish that has to watch her dinner swim away because a male wrasse couldn’t leave the mucus alone never punishes the culprit.

“The males are less well behaved than the females a lot of the time but perhaps part of the reason the males are so likely to cheat is that females never punish males,” Dr Raihani told the Science podcast.

Males tend to be larger than females and this might be why the female finds it safer not to discipline him. All Bluestreak cleaner wrasses start out as females and in a group of 6-8 wrasses you will never find more than one male. If the male dies or is removed from the group, the strongest female will change into a male and take his place.

The wrasse study has been published in the journal Science.
You can download the podcast here: http://podcasts.aaas.org/science_podcast/SciencePodcast_100108.mp3

A new species of wrasse living off the Brazilian coast has been described by Osmar Luiz, Jr, Carlos Ferreira and Luiz Rocha. The new species has been named Halichoeres sazimai after Brazilian ichthyologist Ivan Sazima from Universidade Estadual de Campinas in São Paolo.

Halichoeres sazimai inhabit the Western South Atlantic off the southern and south-eastern coasts of Brazil where researchers regularly saw it foraging solitary on sand bottoms immediately adjacent to the lower end of rocky reefs. Occasionally, harems consisting of 5-10 specimens were also spotted. The fish was sometimes observed over the reefs as well, but usually stayed at a dept of at least 20 metres. According to the researchers, this may have to do with a preference for water colder than 18° C.

Halichoeres sazimai separates itself from its close relatives by having a white body adorned with a zigzag patterned midline stripe which is yellow or golden in females and juveniles and black and brownish in terminal males.

Sorry i have not found a pic of this species.

The paper has been published in the journal Zootaxa.
“OJ, Jr, Luiz, CEL Ferreira and LA Rocha (2009) Halichoeres sazimai, a new species of wrasse (Perciformes: Labridae) from the Western South Atlantic. Zootaxa 2092, pp. 37–46.”