20 January 2010
Red Grouper create home for many animals
Researchers from Florida State University have found that Red Grouper (Epinephelus morio) dig out and maintain complex structures at the bottom of the sea. They remove sand, exposing hard rocks that are crucial to corals and sponges and the animals that rely on them. The work demonstrates that Red Groupers modify their environment, much as beavers do, creating habitat for many other animals including lobster and commercially important fish."Watching these fish dig holes was amazing enough,” says Felicia Coleman, lead researcher, “but then we realised that the sites served to attract mates, beneficial species such as cleaner shrimp that pick parasites and food scraps off the resident fish and a variety of prey species for the Red Grouper. So it's no surprise that the fish are remarkably sedentary. Why move if everything you need comes to you?”
“The research is incredibly valuable because it demonstrates how interconnected species are in the sea,” says Dr. Susan Williams, a professor at the University of California, Davis. “Red Groupers are the 'Frank Lloyd Wrights' of the sea floor because they are critical habitat architects. The species that associate with them include commercially valuable species- such as vermilion snapper, black grouper, and lobsters. If the groupers are overfished, the suite of species that depends on them is likely to suffer.”
Working along the West Florida Shelf, the authors observed the excavating behaviour of the Red Grouper during both their juvenile stage in inshore waters as their adult stage at depths of 100 m. The study serves to document this behaviour and its apparent impact on the biological diversity of the ocean. Their article on the study, “Benthic Habitat Modification through Excavation by Red Grouper, Epinephelus morio, in the Northeastern Gulf of Mexico,” is published in the most recent issue of the journal The Open Fish Science Journal.
Red Grouper (Epinephelus morio) is an economically important species in the reef fish community of the southeastern United States, and especially the Gulf of Mexico. It is relatively common in karst regions of the Gulf.
As juveniles, Red Grouper excavate the limestone bottom of Florida Bay and elsewhere, exposing “solution holes” formed thousands of years ago when sea level was lower, and freshwater dissolved holes in the rock surface. When sea level rose to its present state, these solution holes filled with sediment. By removing the sediment from these holes, Red Grouper restructure the flat bottom into a three dimensional matrix.
Spiny lobsters are among the many species that occupy these excavations, especially during the day when they need refuge from roving predators.
“What are the consequence of overfishing these habitat engineers?” asks co-author Koenig. “You can't remove an animal that can dig a hole five meters across and several meters deep to reveal the rocky substrate and expect there to be no effect on reef communities. The juveniles of a species closely associated with these pits, vermilion snapper, are extremely abundant around the offshore excavations. It is possible that the engineered habitat is significant as a nursery for this species, which other big fish rely on as food. One could anticipate a domino effect in lost diversity resulting from the loss of Red Grouper-engineered habitat.”
Red Grouper clearly remove sufficient sediment to transform an otherwise two-dimensional area into a three-dimensional structure below the seafloor, providing refuge for themselves and for other organisms. In the process, they expose hard substrate, thus creating settlement sites for corals, sponges, and anemones, allowing the creation of three-dimensional structure above the seafloor as well. Addition of these roles to their contribution as resident top predators suggests that they might have a disproportionately large per capita influence on the ecosystem within which they live.
Red Grouper have been harvested in the United States since the 1880s and are currently the most common grouper species landed in both commercial and recreational fisheries of the Gulf of Mexico.
Excessive fishery removals can and often do have cascading effects in marine communities that ultimately result in the loss of many species. This situation arises when the captured species has a disproportionately large influence on the system within which it lives. The Red Grouper has been shown to be one such species.
Further Reading:
Benthic Habitat Modification through Excavation by Red Grouper, Epinephelus morio, in the Northeastern Gulf of Mexico
pp.1-15 (15) Authors: Felicia C. Coleman, Christopher C. Koenig, Kathryn M. Scanlon, Scott Heppell, Selina Heppell, Margaret W. Miller
doi: 10.2174/1874401X01003010001
Florida State University
What do you think of this news item? Join a discussion.
Labels: America, coral, fish, marine biology, research, SCUBA News
Subscribe to SCUBA News (ISSN 1476-8011) for more news, articles, diving reports, reviews and marine creature of the month.
(SCUBA News is published by SCUBA Travel once a month. Will will keep your e-mail address confidential and only use it to send you the monthly newsletter.)
2 December 2009
'Shocking' 95% Decline of Fish Populations
Populations of numerous migratory fish species - those that move between freshwater and saltwater during the course of their lives - have declined by more than 95 percent in the North Atlantic . This threatens food supplies and economic systems, and is worse than was thought as people have tended to compare numbers over too short time scales, according to a paper published this month in the journal BioScience. "It's shocking," said Dr. Karin Limburg, a fisheries ecologist at the SUNY College of Environmental Science and Forestry in Syracuse, N.Y., who is the paper's lead author.
Limburg and her co-author report that a combination of habitat loss (caused largely by the construction of dams that prevent fish access to traditional spawning areas), urban sprawl, overfishing, pollution and climate change have led to the precipitous decline. Compounding the problem, they say, is the evolving knowledge of the humans who make decisions about how natural resources are managed.
"We're looking at shifting baselines here," Limburg said. "Every human generation gains knowledge about the world and establishes a baseline for what's normal. But there is no institutional memory about how things used to be."
As an example, Limburg pointed to a graph that depicts the status of the American shad between 1887 and 1997. It indicates the species was more than 10 times as plentiful during most of the early years of that period as it was during the middle of the 20th century. But a second chart shows that the levels in the 1880s were just 10 percent of what they had been 50 years earlier.
"We can't envision salmon being a thing of the past," she said. "That was once the case with shad. It was the most important fish in U.S. fisheries, after cod." In fact, the shad's Latin name (Alosa sapidissima) reflects the species' high status as a food fish: "sapidissima" means "most delicious."
In their findings, the authors wrote: "Loss of historical baselines contributes to marginalization of the species, as social customs relating to bygone (collapsed) fisheries also perish, and ecosystems unravel at rates that go unnoticed."
Declines were seen in all but two of the fish populations studied. Striped bass, already the subject of protective measures, increased in North America, and lampreys were found to be more abundant in some rivers in France.
The analysis showed that the once-abundant allis shad, a member of the herring family that lives most of its life in coastal waters but migrates into rivers to spawn, plummeted by 99.9 percent in the Rhine River in the Netherlands between 1886 and 1933; the same species dropped by 99.4 percent in the Minho River in Portugal between 1925 and 1988. The European eel's population plunged 95.4 percent in the Ems River, which flows through the Netherlands and Germany, and in the Vidå River in Denmark between 1960 and 1997; it decreased by 99.5 percent in the Yser River in Belgium between 1974 and 2004
When viewed as a group, the magnitude of the migratory species' declines appears even more serious than that of marine predatory fishes, which has received far more attention, Limburg said.
She said the study highlights the importance of a relatively new school of thought in the scientific community: ecosystem services.
"We want to put this in the context of the new way many ecologists are now thinking, to say that ecosystems have a value by themselves," Limburg said.
In particular, she said, the study highlights the interwoven relationship between marine and freshwater ecosystems. The two are linked in the North Atlantic by the 24 species of fish whose populations were analyzed; they are migratory fish that move between freshwater and saltwater during the course of their lives. "Sadly, the links are largely broken today because of the enormity of declines in abundances," she said.
The findings were reported after Limburg and Waldman analyzed data formerly reported in scholarly literature and collected over the years by government agencies and management organizations in nations whose waters flow into the North Atlantic basin, which includes the Atlantic Ocean north of the equator, plus the Caribbean Sea and the Gulf of Mexico.
Further Reading:
SUNY College of Environmental Science and Forestry
What do you think of this news item? Join a discussion.
Labels: fish, research, SCUBA News
Subscribe to SCUBA News (ISSN 1476-8011) for more news, articles, diving reports, reviews and marine creature of the month.
(SCUBA News is published by SCUBA Travel once a month. Will will keep your e-mail address confidential and only use it to send you the monthly newsletter.)
23 September 2009
Killer Whales Die without Chinook Salmon
When you mention killer whales, the image of one ambushing a terrified seal often springs to mind. But there are populations of killer whales who live exclusively on fish. And not on just any fish: they are very specialised in which fish they will eat. According to research published in Biology Letters, two populations studied in the northeastern Pacific Ocean prefer to eat Chinook salmon (Oncorhynchus tshawytscha). So much so that if the numbers of Chinook salmon drop this directly affects the numbers of killer whales. The whales seem unable to adopt a new food, become weak and have a higher mortality.
The authors conclude that other killer whale populations may be similarly constrained to one or two prey species, because the young whales will have learnt their fishing strategies from the rest of the group. They too will be limited in their ability to switch to new food if necessary.
Journal Reference:
John K. B. Ford, Graeme M. Ellis, Peter F. Olesiuk, and Kenneth C. Balcomb
Linking killer whale survival and prey abundance: food limitation in the oceans' apex predator?
Biol Lett 2009 : rsbl.2009.0468v1-rsbl20090468.
What do you think of this news item? Join a discussion.
Labels: fish, marine biology, SCUBA News, whale and dolphins
Subscribe to SCUBA News (ISSN 1476-8011) for more news, articles, diving reports, reviews and marine creature of the month.
(SCUBA News is published by SCUBA Travel once a month. Will will keep your e-mail address confidential and only use it to send you the monthly newsletter.)
15 July 2009
Creature of the Month: Dragonet, Callionymus lyra
One hundred and eighty-six species of the "Little Dragon" fish live from Iceland in the North to the Indo-Pacific oceans in the South. You will find the species we are concentrating on today, Callionymus lyra, from Norway to Senegal: in the Eastern Atlantic and the North, Irish, Mediterranean, Black, Baltic, Aegean and other Seas.
The adult male C. lyra is colourfully patterned in orange and blue. The females are smaller and a mottled brown. They have an interesting courtship ritual. The male performs an elaborate display, darting around the female, spreading his brightly coloured fins and pulling faces! If the female is impressed the pair then swim side-by-side, almost vertically up to the surface. There they release the eggs and sperm into the water, spawning at dusk. Dragonet males are thought to mate only once in a lifetime.
Dragonets spend most of their lives on sandy or rocky bottoms. They live from the shallows down to 100 m. They are sometimes confused with gobies but have a much broader triangular, head and a long dorsal ray on their backs. If you see slender fish meeting this description darting away from you on the bottom it is probably a dragonet.
Further Reading:
Great British Marine Animals, by Paul Naylor
Labels: fish, marine biology, SCUBA diving, SCUBA News, SCUBA Travel, UK
Subscribe to SCUBA News (ISSN 1476-8011) for more news, articles, diving reports, reviews and marine creature of the month.
(SCUBA News is published by SCUBA Travel once a month. Will will keep your e-mail address confidential and only use it to send you the monthly newsletter.)
25 June 2009
Third of Pelagic Sharks Threatened with Extinction
The first study to determine the global conservation status of 64 species of open ocean (pelagic) sharks and rays reveals that 32 percent are threatened with extinction, primarily due to overfishing, according to the IUCN Shark Specialist Group.“Despite mounting threats, sharks remain virtually unprotected on the high seas,” says Sonja Fordham, Deputy Chair of the IUCN Shark Specialist Group and Policy Director for the Shark Alliance. “The vulnerability and lengthy migrations of most open ocean sharks mean they need coordinated, international conservation plans. Our report documents serious overfishing of these species, in national and international waters, and demonstrates a clear need for immediate action on a global scale.”The report comes days before Spain hosts an international summit of fishery managers responsible for high seas tuna fisheries in which sharks are taken without limit. It also coincides with an international group of scientists meeting in Denmark to formulate management advice for Atlantic porbeagle sharks.
The study reports the Great Hammerhead (Sphyrna mokarran) and Scalloped Hammerhead (Sphyrna lewini) sharks, as well as Giant Devil Rays (Mobula mobular), as globally Endangered and facing a very high risk of extinction in the wild. Smooth Hammerheads (Sphyrna zygaena), Great White (Carcharodon carcharias), Basking (Cetorhinus maximus), Oceanic Whitetip (Carcharhinus longimanus), two species of Mako (Isurus spp.) and three species of Thresher (Alopias spp.) sharks are classed as globally Vulnerable to extinction ( facing a high risk of extinction in the wild).
Scalloped hammerhead (Sphyrna lewini)
(Image: Simon Rogerson)
Many open ocean sharks are taken mainly in high seas tuna and swordfish fisheries. Once considered only incidental “bycatch”, these species are increasingly targeted due to new markets for shark meat and high demand for their valuable fins, used in the Asian delicacy shark fin soup. To source this demand, the fins are often cut off sharks and the rest of the body is thrown back in the water, a process known as “finning”. Finning bans have been adopted for most international waters, but lenient enforcement standards hamper their effectiveness.
Oceanic Whitetip (Carcharhinus longimanus)
(Image: Simon Rogerson)
Sharks are particularly sensitive to overfishing due to their tendency to take many years to mature and have relatively few young. In most cases, pelagic shark catches are unregulated or unsustainable.
The IUCN Shark Specialist Group is calling on governments to set catch limits for sharks and rays based on scientific advice and the precautionary approach. It further urges governments to fully protect Critically Endangered and Endangered species of sharks and rays, ensure an end to shark finning and improve the monitoring of fisheries taking sharks and rays.
Silky (Carcharhinus falciformis)
(Image: Jeremy Stafford-Deitsch)
The IUCN uses a series of categories to classify species
| EXTINCT | The last individual has died |
| EXTINCT IN THE WILD | Only survives in captivity or cultivation |
| CRITICALLY ENDANGERED | Facing an extremely high risk of extinction in the wild |
| ENDANGERED | Facing a very high risk of extinction in the wild |
| VULNERABLE | Facing a high risk of extinction in the wild |
| NEAR THREATENED | Likely to qualify for, a threatened category in the near future |
| LEAST CONCERN | Does not qualify for any of the above |
is the world’s largest global environmental network. It is a
membership union with more than 1,000 government and
non-governmental member organisations and almost 11,000
volunteer scientists in more than 160 countries.
Further Reading:
The Conservation Status of Pelagic Sharks and Rays: Report of the IUCN Shark Specialist Group Pelagic Shark Red List Workshop
IUCN Red List Categories and Criteria booklet
Related Stories:
EU launches shark protection plan
Caribbean Big Fish Disappearing
Mediterranean Sharks Declining Fast
Mexico Passes Shark Finning Ban
Four Times more Sharks caught than Officially Reported
What do you think of this news item? Join a discussion.
Labels: fish, marine biology, research, SCUBA News, sealife, sharks
Subscribe to SCUBA News (ISSN 1476-8011) for more news, articles, diving reports, reviews and marine creature of the month.
(SCUBA News is published by SCUBA Travel once a month. Will will keep your e-mail address confidential and only use it to send you the monthly newsletter.)
3 March 2009
Loss of small fish may be starving the oceans
According to a report by Oceana, there is widespread malnutrition in fish, marine mammals and seabirds because of the global depletion of the small fish they need to survive. These "prey fish" underpin marine food webs and are being steadily exhausted by heavy fishing, increasing demand for aquaculture feed, and climate change. The report finds that 7 of the top 10 fisheries in the world target prey fish. These fisheries have emerged as populations of bigger fish have become overexploited and depleted. The report concludes that the impacts of fishing activity over the past decades has been so great that the nearly all prey fisheries now cannot withstand increased fishing pressure. It also finds that aquaculture is increasingly the driver behind overfishing of prey fish, as salmon, tuna and other carnivorous farmed fish become the fastest growing seafood products in the world. Changing ocean temperatures and currents caused by climate change also make prey fish populations more vulnerable.
Ricardo Aguilar, Director of Investigation for Oceana Europe, says: "When it comes to managing a fishery or talking about overexploitation, we often forget that the disappearance of one species due to overfishing has severe impact on stocks of other species. A clear example is bluefin tuna, which disappeared from Norwegian coasts after herring populations collapsed. Nowadays the absurdity is that both tuna and its prey are overexploited in order to feed these very tunas in fattening cages".
Oceana conclude that more responsible management is needed to prevent predators from going hungry. It proposes a series of measures including a moratorium on new fisheries targeting prey species, conservative catch limits for existing fisheries, first priority for the needs of ocean predators and stopping fishing for prey in predator breeding hotspots.
Further Reading: Hungry Oceans Report
-
What do you think of this news item? Join a discussion.
Labels: environment, fish, SCUBA News
Subscribe to SCUBA News (ISSN 1476-8011) for more news, articles, diving reports, reviews and marine creature of the month.
(SCUBA News is published by SCUBA Travel once a month. Will will keep your e-mail address confidential and only use it to send you the monthly newsletter.)
17 February 2009
When fish farms are built along the coast, where does the waste go?
If you are a fish eater, it's likely that the salmon you had for dinner was not caught in the wild, but was instead grown in a mesh cage submerged in the open water of oceans or bays. Fish farming, a relatively inexpensive way to provide cheap protein to a growing world population, now supplies, by some estimates, 30 percent of the fish consumed by humans. Two hundred and twenty species of finfish and shellfish are now grown in farms.
Intuitively, it seems a good idea—the more fish grown in pens, the fewer need be taken from wild stocks in the sea. But marine aquaculture can have some nasty side effects, especially when the pens are set near sensitive coastal environments. All those fish penned up together consume massive amounts of commercial feed, some of which drifts off uneaten in the currents. And the crowded fish, naturally, defecate and urinate by the tens of thousands, creating yet another unpleasant waste stream.
The wastes can carry disease, causing damage directly. Or the phosphate and nitrates in the mix may feed an algae bloom that sucks the oxygen from the water, leaving it uninhabitable, a phenomenon long associated with fertilizer runoff.
It has been widely assumed that the effluent from pens would be benignly diluted by the sea if the pens were kept a reasonable distance from shore, said Jeffrey Koseff, a professor of civil and environmental engineering and co-director of Stanford's Woods Institute for the Environment. But early results from a new Stanford computer simulation based on sophisticated fluid dynamics show that the icky stuff from the pens will travel farther, and in higher concentrations, than had been generally assumed, Koseff said.
"What we've basically debunked is the old adage that 'The solution to pollution is dilution,' " he said. "It's a lot more complicated."
The computer modelling (with new Stanford software that goes by the acronym SUNTANS) was conducted by Oliver Fringer, an assistant professor of civil and environmental engineering. He created a virtual coastal marine area resembling California's Monterey Bay.
Previous software, he said, has not been up to the task of accurately predicting where the unhealthy effluent from fish pens will end up, and should probably not be used by state or federal regulators when they approve locations for fish farms.
Existing software is typically derived from models that attempt to describe the drift of effluent from sewage outfall pipes, even though the substances and situations are different from fish farms. (Sewage outflow, for example, is often warmer than the ocean water.)
The fine details of modeling the flow of dissolved fish poop from a submerged cage are not as simple as they may seem. The design of the cage itself can affect the outcome. How much of the current flows through the cage, and how much goes around? Does the moving water swirl into eddies at the edges of the pen? Even the effects of the rotation of the earth on the waste plume comes into play.
The fish farmer would prefer that currents flush out his pens frequently, but as those currents take out the garbage they might unfortunately deliver it to a mangrove ecosystem or a public beach. On the other hand, insufficient flow through the pen can create a "dead zone" on the ocean floor as the fecal matter and uneaten food pile up beneath the fish.
Fringer is designing his software so that it can be used to asses any site—Puget Sound, perhaps—where sufficient digital mapping of the area already exists. SUNTANS comes just in time, said Stanford oceans expert Rosamond Naylor, as federal and local officials begin spelling the details of new health and environmental regulations for fish pens.
Further Reading:
EurekAlert
-
What do you think of this news item? Start a discussion.
Labels: environment, fish, SCUBA News
Subscribe to SCUBA News (ISSN 1476-8011) for more news, articles, diving reports, reviews and marine creature of the month.
(SCUBA News is published by SCUBA Travel once a month. Will will keep your e-mail address confidential and only use it to send you the monthly newsletter.)
5 November 2008
A million tonnes of North Sea fish discarded every year
A million tonnes of fish and other sea creatures caught in the North Sea are thrown overboard every year, according to a new report from WWF-Germany.The study, Sea Creatures Are Not Rubbish, shows that one-third of North Sea catch is discarded and calls for a gradual ban on the practice of discarding in the European Union.
This practice occurs when boats decide to dispose of fish which they catch but cannot land or derive income from, or when they have caught more fish than they are allowed to land, or they discard the less valuable fish in order to make more space for more valuable fish.
For example, the report cites the situation with Dover sole, for which six kilos of sea creatures are caught incidentally and discarded for every kilo found in the fishmonger. Similarly, catching one kilo of Norwegian lobster or scampi results in five kilos of bycatch.
The European Union recently declared that 88 per cent of the fisheries stocks of the EU are overfished, compared with 25 per cent on average globally. Bycatch is a major contributor to overfishing, and this unsustainable and illogical practice should be addressed.
WWF is calling for a European-wide discard ban and a bycatch action package. In the future every fish caught should be landed and allocated to the catch quota.
At the same time fishermen should be obliged to use better catch technologies and in this way the bycatch in some fisheries could be reduced by up to 90 per cent.
A legislative initiative against discard practice, announced by the European Commission, was only recently torpedoed by the powerful fishery lobby of some member countries.
You can download the report from the WWF site at http://assets.panda.org/downloads/studie___meerestiere_sind_kein_muell_.pdf
--
What do you think of this news item? Start a discussion.
Bookmark with: del.icio.us | Digg | Newsvine | NowPublic | Reddit
|
Slashdot It! | Facebook | StumbleUpon --
Subscribe to SCUBA News (ISSN 1476-8011) for more free news, articles, diving reports and marine life descriptions - http://www.scubatravel.co.uk/news.html
Subscribe to SCUBA News (ISSN 1476-8011) for more news, articles, diving reports, reviews and marine creature of the month.
(SCUBA News is published by SCUBA Travel once a month. Will will keep your e-mail address confidential and only use it to send you the monthly newsletter.)
7 July 2008
Cleaner fish create safe havens
Both cleaner and cleaned fish benefit from this behaviour. Cleaner fish are also thought to benefit from immunity to predation. They stroke their "clients'" with their fins to help persuade the predators not to eat them. Researchers in Australia have found that the more stroking the calmer the predator. And it wasn't just the cleaner fish who benefited. Other fish nearby the cleaner station experienced less aggressive behaviour from the predators. The suggests that cleaner stations act as safe havens from predator aggression.
Further Reading: Behavioral Ecology, doi:10.1093/beheco/arn067
Cleaner fish do clean!
--
What do you think of this news item? Start a discussion.
Bookmark with: del.icio.us | Digg | Newsvine | NowPublic | Reddit
|
Slashdot It! | Facebook | StumbleUpon --
Subscribe to SCUBA News (ISSN 1476-8011) for more free news, articles, diving reports and marine life descriptions - http://www.scubatravel.co.uk/news.html
Labels: fish, marine biology, research, sealife
Subscribe to SCUBA News (ISSN 1476-8011) for more news, articles, diving reports, reviews and marine creature of the month.
(SCUBA News is published by SCUBA Travel once a month. Will will keep your e-mail address confidential and only use it to send you the monthly newsletter.)
13 March 2008
Mediterranean leaders urged to save tuna
A new WWF report shows that the international fleets hunting this species to extinction have twice the fishing capacity of current quotas and are netting more than three and a half times the catch levels recommended by scientists to avoid stock collapse.
"WWF's new report uncovers the absurdity of a system long out of control, where hundreds of hi-tech boats are racing to catch a handful of fish," says Dr Sergi Tudela, Head of Fisheries at WWF Mediterranean.
"It is crazy - the numerous new fleets are so modern and costly that fishermen are forced to fish illegally just to survive - and worse still they are fishing themselves out of a job," added Tudela.
To keep fishing capacity within the 2008 legal catch limits imposed by the International Commission for the Conservation of Atlantic Tunas (ICCAT), the Mediterranean fleet would need to shed 229 vessels - almost a third of the current 617-vessel fleet. Reducing fishing effort to scientifically recommended levels would require the decommissioning of 283 vessels.
WWF is calling on concerned countries to dramatically reduce capacity in this fishery as a matter of urgency ahead of the 2008 fishing season that starts at the end of April.
WWF also urges ICCAT, the body tasked with sustainably managing the fishery, to take a lead in proposing radical solutions. Until the fishery is under control and sustainably managed, WWF continues to advocate a fishing ban - and to applaud responsible retailers, restaurants, chefs and consumer groups who are boycotting Mediterranean bluefin in increasing numbers.
"The fishery is unsustainable in every way - economically, socially, and ecologically. When will the situation be brought under control? The time to act is now - while there are still bluefin tuna to save in the Mediterranean," Tudela concluded.
What can you do? If you want to buy a tin of tuna off the supermarket shelf don’t worry – you almost never find bluefin tuna in a tin. Most tinned tuna is yellowfin or skipjack. If you buy fresh tuna ask your fishmonger whether the tuna is Atlantic bluefin, and whether it comes from the Mediterranean. If it does come from the Med, don't buy it. And at the Japanese restaurant check where they source the Atlantic bluefin tuna. If it is from the Mediterranean, avoid it.
Note: the tuna caught in the Med is called "Atlantic Bluefin Tuna" (Thunnus thynnus). Don't think that because it has the word Atlantic in the name that means it was caught there.
Further Reading:
Bluefin tuna in crisis
Race for the last bluefin: Capacity of the purse seine fleet targeting bluefin tuna in the Mediterranean
-
What do you think of this news item? Start a discussion.
Bookmark with: del.icio.us | Digg | Newsvine | NowPublic | Reddit
|
Slashdot It! | Facebook | StumbleUpon --
Subscribe to SCUBA News (ISSN 1476-8011) for more free news, articles, diving reports and marine life descriptions - http://www.scubatravel.co.uk/news.html
Labels: fish, Mediterranean
Subscribe to SCUBA News (ISSN 1476-8011) for more news, articles, diving reports, reviews and marine creature of the month.
(SCUBA News is published by SCUBA Travel once a month. Will will keep your e-mail address confidential and only use it to send you the monthly newsletter.)
12 March 2008
Global warming turns fish deaf
Is it important that global warming turns fish deaf? Yes. For coral reef fish, sound is vital for them to judge where to settle down and live.After hatching, reef fish larvae are dispersed by ocean currents for a few weeks. The larval fish must then find their way back to a suitable reef to make their home.
It's thought that the young fish home in on high-frequency noises. Coral reefs are extremely noisy environments, with the crackle of snapping shrimps and the chatter of fish set against a backdrop of wind, rain and surf. Sound carries well underwater, and most fish have great hearing.
Global warming and more acidic oceans, though, can cause fish to be born with deformed earbones. Reasearchers at the Australian Institute of Marine Science in Townsville and the University of Edinburgh, suspected that it might be harder for these fish to pinpoint the origin of a sound, increasing the chance they would get lost in the ocean. And, indeed, their results show that this is so.
Journal References and Further Reading:
Proceedings of the Royal Society, Volume 275, Number 1634 / March 07, 2008
Animal Behaviour, doi:10.1016/j.anbehav.2007.11.004
SOUND: The essential navigation cue for young reef fishes to find their way home
--
What do you think of this news item? Start a discussion.
Bookmark with: del.icio.us | Digg | Newsvine | NowPublic | Reddit
|
Slashdot It! | Facebook | StumbleUpon --
Subscribe to SCUBA News (ISSN 1476-8011) for more free news, articles, diving reports and marine life descriptions - http://www.scubatravel.co.uk/news.html
Labels: coral reef, environment, fish, marine biology, research, sealife
Subscribe to SCUBA News (ISSN 1476-8011) for more news, articles, diving reports, reviews and marine creature of the month.
(SCUBA News is published by SCUBA Travel once a month. Will will keep your e-mail address confidential and only use it to send you the monthly newsletter.)
30 October 2007
No sunglasses required for fish supper
Fishermen are always looking for a tasty catch - but it is the fish that have a natural advantage when it comes to spotting dinner, according to new research from The University of Manchester.
In a paper published this month in the Biophysical Journal, Dr Nicholas Roberts reports how individual light sensitive cells within the retina of goldfish are able to detect polarised light.
It's believed this type of polarisation vision improves visual contrast and can help an animal catch its prey more easily.
Researchers say this latest research is important because it is the first direct experimental evidence of a polarisation detection mechanism in any normal vertebrate eye.
Dr Roberts says: "Vision is the primary sense of many animals and the way they see their world is of fundamental importance to understanding aspects of their behaviour.
"Numerous animals have amazing visual abilities, which allow them to see the world in very different ways. One such ability is polarisation vision.
"Just as fishermen wear Polaroid sunglasses to help improve contrast, many different animals - including fish - have evolved to do the very same thing without the need of sunglasses. It is a surprisingly common ability throughout the animal kingdom."
Journal Reference: Biophys J. 2007 Nov 1;93(9):3241-8.
Photo Credit:US National Oceanic and Atmospheric Administration
What do you think of this news item? Start a discussion.
Bookmark with: del.icio.us | Digg | Newsvine | NowPublic | Reddit
|
Slashdot It! | Facebook | StumbleUpon --
Subscribe to SCUBA News (ISSN 1476-8011) for more free news, articles, diving reports and marine life descriptions - http://www.scubatravel.co.uk/news.html
Labels: fish, research, sealife
Subscribe to SCUBA News (ISSN 1476-8011) for more news, articles, diving reports, reviews and marine creature of the month.
(SCUBA News is published by SCUBA Travel once a month. Will will keep your e-mail address confidential and only use it to send you the monthly newsletter.)
24 September 2007
Blue Tang is Creature of the Month
Blue Tangs are often found roaming the reef, in search of their favourite food - algae. They are surgeonfish which may appear either singly or in large schools, which can contain hundreds of individuals.
The name surgeonfish comes from the defensive spines located on the caudal peduncle (the part of the fish between the tail and the rest of the body) which are as sharp as a surgeon's scalpel. They are herbivorous, eating plants and algae, so their spines are used only for defense.
Blue Tangs are sometimes found schooling with other members of the surgeonfish family. These schools form around dusk when nocturnal predators, such as moray eels, begin to hunt. These schools provoke an aggressive reaction from the smaller damselfishes defending patches of algae.
The true Blue Tang is Acanthurus coeruleus, which found in the Caribbean Sea. Other fish are also sometimes referred to as Blue Tang. In the Red Sea, for example, there is Zebrasoma xanthurum, more properly known as Yellowtail Tang. Also in the Indo-Pacific masquerading as Blue Tang is the Palette Surgeon, Paracanthurus hepatus; familiar if you've watched the "Finding Nemo" film.
As you might expect, blue tangs are largely blue. The Caribbean Blue Tang, Acanthurus coeruleus, has a bright yellow or white spine. It lives between 3 and 28 m on rocky or coral reefs. As it is unafraid of divers you can usually get quite close to it.
The Blue Tang, and other surgeonfish, are important on a shallow coral reef because they help keep the algae in check. Without them the algae would grow so fast that coral larvae settling and trying to make a start on the reef would soon be overgrown.
Further reading:
Beautiful Oceans Coral Reef Architecture & Organisms,
The Blue Planet
What do you think of this news item? Start a discussion.
Bookmark with: del.icio.us | Digg | Newsvine | NowPublic | Reddit
|
Slashdot It! | Facebook | StumbleUpon --
Subscribe to SCUBA News (ISSN 1476-8011) for more free news, articles, diving reports and marine life descriptions - http://www.scubatravel.co.uk/news.html
Labels: fish, marine biology, sealife
Subscribe to SCUBA News (ISSN 1476-8011) for more news, articles, diving reports, reviews and marine creature of the month.
(SCUBA News is published by SCUBA Travel once a month. Will will keep your e-mail address confidential and only use it to send you the monthly newsletter.)
4 July 2007
How fish punish queue jumpers
Fish use the threat of punishment to keep would-be jumpers in the mating queue firmly in line and the social order stable, a new study led has found.Studying small goby fish at Lizard Island on Australia's Great Barrier Reef, Dr Marian Wong and colleagues have shown the threat of expulsion from the group acts as a powerful deterrent to keep subordinate fish from challenging those more dominant than themselves.
In fact the subordinate fish deliberately diet - or starve themselves - in order to remain smaller than their superiors and so present no threat that might lead to their being cast out, and perishing as a result.
"Many animals have social queues in which the smaller members wait their turn before they can mate. We wanted to find out how they maintain stability in a situation where you'd expect there would be a lot of competition," says Dr Wong.
In the case of the gobies, only the top male and top female mate, and all the other females have to wait their turn in a queue based on their size - the fishy equivalent of the barnyard pecking order.
Dr Wong found that each fish has a size difference of about 5 per cent from the one above and the one below it in the queue. If the difference in size decreases below this threshold, a challenge is on as the junior fish tries to jump the mating queue - and the superior one responds by trying to drive it out of the group.
Her fascinating discovery is that, in order to avoid constant fights and keep the social order stable, the fish seem to accept the threat of punishment - and adjust their own size in order to avoid presenting a challenge to the one above them.
"Social hierarchies are very stable in these fish and in practice challenges and expulsions are extremely rare - probably because expulsion from the group and the coral reef it occupies means almost certain death to the loser.
"It is clear the fish accept the threat of punishment and co-operate as a way of maintaining their social order - and that's not so very different to how humans and other animals behave."
Dr Wong said that experimentally it has always proved extremely difficult to demonstrate how higher animals, such as apes, use punishment to control subordinates and discourage anti-social activity because of the difficulty in observing and interpreting their behaviour.
In the case of the gobies the effect is much more apparent because they seek to maintain a particular size ratio relative to the fish above them in the queue, in order not to provoke a conflict.
"The gobies have shed new light on our understanding of how social stability is maintained in animals," she says.
The paper entitled "The threat of punishment enforces peaceful cooperation and stabilizes queues in a coral-reef fish" was co-authored with Dr Philip Munday and Professor Geoff Jones of CoECRS and Dr Peter Buston of the Biological Station of Doñana, Spain. It appears in Proceedings of the Royal Society B, 274.
What do you think of this news item? Start a discussion.
Bookmark with: del.icio.us | Digg | Newsvine | NowPublic | Reddit
--
Subscribe to SCUBA News (ISSN 1476-8011) for more free news, articles, diving reports and marine life descriptions - http://www.scubatravel.co.uk/news.html
Labels: environment, fish, marine biology, research, sealife
Subscribe to SCUBA News (ISSN 1476-8011) for more news, articles, diving reports, reviews and marine creature of the month.
(SCUBA News is published by SCUBA Travel once a month. Will will keep your e-mail address confidential and only use it to send you the monthly newsletter.)
11 May 2007
Egypt Stops Reef Fish Exports
Egypt have cancelled a decree which allowed companies to collect reef fish and export them to Europe and other markets .
According to the Hurghada Environmental Protection and Conservation Association (HEPCA), the previous decision had a devastating effect on nature and on the coral reef condition in the whole area. HEPCA launched a huge campaign against this decision and lobbied with other agencies, enthusiastic individuals, and major media representatives.
As a result of the decision HEPCA have ceased legal actions against the Minister's old decree.
Further Reading: http://www.hepca.com/
What do you think of this news item? Start a discussion.
--
Subscribe to SCUBA News (ISSN 1476-8011) for more free news, articles, diving reports and marine life descriptions - http://www.scubatravel.co.uk/news.html
Labels: environment, fish, Red Sea, SCUBA Travel, sealife
Subscribe to SCUBA News (ISSN 1476-8011) for more news, articles, diving reports, reviews and marine creature of the month.
(SCUBA News is published by SCUBA Travel once a month. Will will keep your e-mail address confidential and only use it to send you the monthly newsletter.)
4 May 2007
The Seahorse is Creature of the Month
Seahorses are delightful to spot, curling onto sponges, coral or sea grass. They range in size from the tiny Hippocampus denise which is just 16 mm, to the 35 cm (1 foot) Pacific seahorse.
Seahorses are not easily seen as they blend in with their surroundings. They can change skin colour to match their environment and even grow skin filaments to imitate seaweed or sea grass growths.
The seahorse is remarkable as the male becomes pregnant. The female seahorse deposits her eggs into the male's pouch where they are fertilised. The eggs remain in the male's pouch until they hatch, when the male gives birth to tiny seahorses. The time to hatching takes between 10 days and four weeks, depending on the species and water temperature. Male seahorses are often pregnant for as many as 7 months in the year. The natural lifespan of seahorses is not known, but believed to be from one year for small species to five years for a larger species.
Seahorses are opportunistic predators, sitting and waiting until prey come close enough and then sucking them rapidly from the water with their long snouts. Their eyes move independently of each other, maximizing their search area. They will eat anything small enough to fit into their mouths
The name hippocampus comes from the ancient Greek, loosely hippos meaning horse and campus meaning sea monster. Hippocampi refer to the mythical creatures on which the sea gods rode. Early zoologists initially classified seahorses as insects not fish.
All seahorses for which data is available are listed on the IUCN Red List of Threatened Species as either Vulnerable or Endangered. This means they are facing a high risk of extinction in the wild. There are many reasons for their vulnerability. Seahorses are exploited for traditional medicines and the aquarium trade. Male brooding means that young depend on parental survival for far longer than in most fish. Many species are monogamous so widowed animals don't reproduce until they have found a new partner. Their low population density and low mobility means that this can take some time. Habitat degradation is also a real threat to populations as they mainly inhabit shallow, coastal areas, which are highly influenced by human activities.
Further Reading
IUCN 2006. 2006 IUCN Red List of Threatened Species. <www.iucnredlist.org>. Downloaded on 20 April 2007.
Project Seahorse - http://seahorse.fisheries.ubc.ca/
Seahorse photo taken in Dominica, copyright Harald Jahn.
What do you think of this news item? Join a discussion.
Labels: Caribbean, Dominica, fish, seahorse, sealife
Subscribe to SCUBA News (ISSN 1476-8011) for more news, articles, diving reports, reviews and marine creature of the month.
(SCUBA News is published by SCUBA Travel once a month. Will will keep your e-mail address confidential and only use it to send you the monthly newsletter.)
7 March 2007
Geometric Moray Eel is Creature of the Month
The Geometric moray has a long body with one continuous fin along its back. Like other morays it has elongated nostrils. You can easily recognise it by the dashed lines patterning its face, as shown in our photo.
Morays live in holes and generally hunt by night, locating
their prey by their excellent sense of smell. Moving with
snake-like motions, they are extremely quick. When at rest
you may see them rhythmically opening and closing their
mouths. They do this to maintain a respiratory current
past the gills.
The Geometric moray is the most common eel in the Red Sea.
It is also found throughout the Western Indian Ocean:
Madagascar, Mauritius, Oman, Mozambique, Seychelles,
South Africa, etc.
Quite small for a moray, the Geometric moray reaches
65 cm long. It lives at depths down to 40 m on coral and
rocky reefs. You may see groups of up to 10 young eels
sheltering in rock crevices.
The black dashes on the face and body of this moray mark
its pores. These are part of its lateral line system which
detects changes in pressure and so can be used to detect
movement and vibration in the surrounding water.
The Geometric moray, Siderea grisea is also known as the Grey Moray and Gymnothorax griseus.
What do you think of this news item? Start a discussion.
--
Subscribe to SCUBA News (ISSN 1476-8011) for more free news, articles, diving reports and marine life descriptions - http://www.scubatravel.co.uk/news.html
Labels: fish, marine biology, sealife
Subscribe to SCUBA News (ISSN 1476-8011) for more news, articles, diving reports, reviews and marine creature of the month.
(SCUBA News is published by SCUBA Travel once a month. Will will keep your e-mail address confidential and only use it to send you the monthly newsletter.)
