Butterfly fish ‘may face extinction’ March 3, 2008
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Scientists have warned that a beautiful black, white and yellow butterflyfish, much admired by eco-tourists, divers and aquarium keepers alike, may be at risk of extinction.
The case of the Chevroned Butterflyfish is a stark example of how human pressure on the world’s coral reefs is confronting certain species with ‘blind alleys’ from which they may be unable to escape, says Dr Morgan Pratchett of the ARC Centre of Excellence for Coral Reef Studies and James Cook University.
In a study published in the journal Behavioural Ecology and Sociobiology Dr Pratchett and Dr Michael Berumen of Woods Hole Oceanographic Institution (USA) warn that the highly specialized nature of the feeding habits of this particular butterflyfish – the distinctively patterned Chaetodon trifascialis - make it an extinction risk as the world’s coral reefs continue to degrade due to human over-exploitation, pollution and climate change.
‘The irony is that these butterflyfish are widespread around the world, and you’d have thought their chances of survival were pretty good,’ Dr Pratchett said today. But they only eat one sort of coral – Acropora hyacinthus – and when that runs out, the fish just disappear from the reef.’
Rather Starve Than Change Diet
The team found it hard to believe a fish would starve rather than eat a mixed diet, so they tested C. trifascialis in tank trials on a range of different corals. The fish grew well when its favourite coral was available – but when this was removed and other sorts of corals offered, it grew thin, failed to thrive and some died.
‘We call these kinds of fish obligate specialists. It means they have a very strong dietary preference for one sort of food, and when that is no longer available, they go into decline. We still don’t have a satisfactory scientific explanation for this, as it seems like rather a risky tactic in evolutionary terms – but it must confer some advantage provided enough of its preferred food is available,’ Dr Pratchett says.
Vulnerable Coral
The A. hyacinthus coral, which the butterfly fish feeds on, is itself highly vulnerable – to attacks by plagues of crown-of-thorns starfish (thought to be triggered by humans releasing excess nutrients onto the reef as sediment, fertilizer or sewage), to storms and to the coral bleaching caused by the heating of ocean surface waters to 32 degrees or more, which is thought to be linked to global warming.
‘Although extremely widespread, the Chevroned butterflyfish may be at considerable risk of extinction following ongoing degradation of coral reefs around the world, because the coral itself is exceptionally vulnerable, Dr Pratchett explains.
‘It is estimated that up to 70 per cent of the world’s coral reefs are now badly degraded, which usually involves the loss of this particular coral – and, when it goes, the C. trifascialis also disappear from the reef.
Targeted by Aquarium Collectors
‘To make matters worse, butterfly fishes are one of the main families of coral reef fishes being targeted by aquarium collectors. However, the specialized coral-eaters are clearly not suitable for keeping in aquaria - and often die because they cannot obtain their main food source.’
A previous case in which a coral-dependent fish vanished occurred in the case of Gobiodon a specialized coral-dweller known only from one site, Kimbe Bay in Papua New Guinea, which was thought by scientists to have possibly become extinct after its habitat was destroyed.
Researchers consider that such extinctions are likely to occur as part of the global mass extinction of species now taking place, and that marine ecosystems may be particularly vulnerable in that small changes in habitat or water quality can have a big impact on their species.
Dr Pratchett and Dr Berumen say theirs is one of the few studies so far to consider the evolutionary and ecological basis of dietary versatility, and has implications for the fate of specialised feeders throughout the animal kingdom.
Shark species face extinction amid overfishing and appetite for fins February 18, 2008
Posted by michaelgreenwell in biodiversity, climate change, conservation, endangered, environment, environment sites, environmentalism, extinction, marine, marine conservation, predators, shark, wildlife, zoology.add a comment
Nine more species of shark are to be added to the endangered list as scientists warn that oceans are being emptied of the fish by overfishing and finning.
The scalloped hammerhead shark, which has declined by 99% over the past 30 years in some parts of the world, is particularly vulnerable and will be declared globally endangered on the World Conservation Union (IUCN) list.
“Sharks are definitely at the top of the list for marine fishes that could go extinct in our lifetimes,” said Julia Baum of the Scripps Institution of Oceanography in California and a member of IUCN shark specialist group. “If we carry on the way that we are, we’re looking at a really high risk of extinction for some of these shark species within the next few decades.”
At the American Association for the Advancement of Science annual meeting in Boston yesterday, Baum said that in addition to the scalloped hammerhead, other shark species that will be added to the revised IUCN endangered list later this year are the smooth hammerhead, shortfin mako, common thresher, big-eye thresher, silky, tiger, bull and dusky. There are already 126 species of shark on the IUCN’s list.
“The perception has been that really wide-ranging species can’t become endangered because if they are threatened in one area, surely they’ll be fine in another area,” said Baum. “But fisheries now cover all corners of the earth and they’re intense enough that these species are being threatened everywhere.”
Recent studies have shown that all shark populations in the north-west Atlantic Ocean have declined by an average of 50% since the early 1970s.
Shark numbers can become depleted very quickly because they take a long time to mature - 16 years in the case of a scalloped hammerhead. Their fins are highly prized in China and can fetch up to £140 a kilogram. Until recently the eating of shark fin was a delicacy restricted to the rich in China, said Baum, but as the country’s middle class has grown in the past 25 years, so has the market for shark fins.
Excessive fishing has caused a 90% decline in shark populations across the world’s oceans and up to 99% along the US east coast, which are some of the best-managed waters in the world, according to Baum.
The decline in predators such as sharks can have devastating consequences for the local marine ecology.
In a case study published last year, Baum found that a major decline in the numbers of predatory sharks in the north Atlantic after 2000 had allowed populations of the sharks’ prey, cownose rays, to explode. The rays in turn decimated the bay scallop populations around North Carolina. “There was a fishery for bay scallops in North Carolina that lasted over a century uninterrupted and it was closed down in 2004 because of cownose rays.”
Fishing for sharks in international waters is unrestricted, but Baum supports a recent UN resolution calling for immediate limits on catching sharks and a ban on shark finning.
Sonja Fordham, of the Shark Alliance, a coalition of 50 scientific and conservation groups, said: “People think these wide-ranging, fast sharks are resilient to fishing; however, this shows this is not the case. Concerned citizens can really help by making their fisheries ministers aware that they support conservation measures such as catch limits.”
Some conservation efforts for sharks will focus on newly identified hotspots where sharks congregate during migrations. Peter Klimley of the University of California, Davis, found that scalloped hammerhead sharks migrate along fixed “superhighways” in the oceans, speeding between a series of “stepping stone” sites near coastal islands ranging from Mexico to Ecuador.
“Hammerhead sharks are not evenly dispersed throughout the seas, but concentrated at seamounts and offshore islands,” he said. “Hence, enforcing reserves around these areas will go far in protecting these species and will provide the public with places for viewing sharks in their habitat.”
One site between Hawaii and Mexico attracts so many sharks it has become known among scientists as “the white shark cafe”, Klimley says.
“We started calling it the cafe because that is where you might go to have a snack or maybe just to ’see and be seen’. We are not sure which,” said Salvador Jorgensen, a researcher at Stanford University’s Hopkins Marine Station.
“Once they leave the cafe they return year after year to the same exact spot along the coast, just as you might return to a favourite fishing hole.”
Tay salmon stocks ‘facing extinction’ November 21, 2007
Posted by michaelgreenwell in Ichthyology, biodiversity, environment, environment sites, fish, fishing, nature, scotland, wildlife, zoology.add a comment
SCOTLAND’S world-famous “queen” of salmon rivers is being fished to extinction, according to its ghillies, who are pleading with its fisheries board to implement new laws to save its depleted fish stocks.
Anglers from across the world have flocked to Perthshire for decades to fish for Atlantic salmon in Scotland’s longest and most renowned river, the Tay.
But the Tay Ghillies Association has revealed it has been “a dreadfully poor salmon fishing season”, with catches down by 50 per cent and expected to fall even further next season. The association accuses the Tay District Salmon Fisheries Board of ignoring a number of warning signs.
A spokesman for the Tay Ghillies Association said: “The annual catch numbers on the River Tay this year with rod and line will not amount to any more than 6,000 fish. The Dee, which is a fraction of the size of the Tay, with a fraction of the anglers, are set to do 5,000.”
However, David Summers, of the Tay District Salmon Fisheries Board, said: “The idea that the Tay has completely collapsed is grossly overblown.”
He said the policy of catch-and-release needed strengthening, adding: “For next season we are advocating that, in the spring, you must put back the first fish every day and you may keep the next one.
“We currently ask that anglers not fish with worms before the end of May and certainly not in September and October. However, we are reviewing this policy.”
In Scotland, 85,901 salmon were reported caught in 2006, with 47,471 - 55 per cent of the total catch - being released.
