Sharks swim closer to extinction

[[R_H]]

BBC

More than half of the world's ocean-going sharks are at risk of extinction, a new analysis concludes.

Specialists with IUCN (formerly the World Conservation Union) found that 11 species are on the high-risk list, with five more showing signs of decline.

Sharks are particularly affected by over-fishing as they reproduce slowly.

The scientists are calling for global catch limits, an end to the practice of removing fins, and measures to minimise incidental catches (bycatch).

"There's this idea that because these are widely ranging species, they're more resilient to fishing pressure," said Sonja Fordham, deputy chair of the IUCN Shark Specialist Group (SSG) and policy director for the Shark Alliance conservation group.

"In fact they're becoming species of serious concern because there are no international catch limits for sharks. There are intense fisheries on the oceans, and they remain pretty much unprotected."

New threats

The SSG assessed data on the 21 species of sharks and their close cousins, the rays, that swim in upper portions of the open ocean where they are exposed to fishing fleets.

Of the 21, one - the giant devilray - is assessed as Endangered, and 10 are Vulnerable.

A further five are listed as Near Threatened, which means the signs of decline are not serious enough yet to merit a full listing.

The classifications are based on a range of criteria that look at past or forecast declines in population size. For example, a population shrinking by 50% in 10 years would usually qualify as Endangered.

Some of these species have been assessed before; but for others, including the three species of thresher sharks with their spectacularly long tails, the dangerlisting is new.

Fin cuts

The main threat to sharks is fishing, both accidental and targeted.

"They used to be taken as bycatch by boats targeting tuna and swordfish," said Ms Fordham. "But now as those species are declining we're seeing more fishermen targeting sharks.

"Porbeagle and shortfin mako are targeted for fins and meat; species like blue shark are likely to be finned, but particularly in Europe we're seeing more blue shark being landed."

Several of the bodies that regulate fisheries in international waters - the Regional Fisheries Management Organisations (RFMOs) - have set up measures to curb shark finning, but there are different standards in place, a situation that enables fishermen to work around the regulations.

As East Asian economies boom, conservation groups say the market for fins is increasing.

"Fishery managers and regional, national and international officials have a real obligation to improve this situation," commented Nicholas Dulvy from Simon Fraser University in Vancouver, the report's lead author.

"But it doesn't have to be like this. With sufficient public support and resulting political will, we can turn the tide."

The report was released at the Convention on Biological Diversity (CBD) meeting in Bonn, and will be published in the journal Aquatic Conservation: Marine and Freshwater Ecosystems.

The new risk assessments will be included in the IUCN Red List of Threatened Species when it is published later this year.

[weemadando]

The shark fin fishing industry disgusts me, always has. And that is a massive cause of shark population decline.

[Broomstick]

>sigh<

I gave up eating shark 15 years ago, when the populations started falling... It seems the situation is no better, and in some cases worse.

[Illuminatus Primus]

Are people fucking dumb? They're loaded with mercury anyway.

[Broomstick]

No, that's tuna.

Seriously, though - do you have a cite for that, or are you just making assumptions?

[Vaporous]

It's the general assumption that the higher a fish is on the food chain, the more mercury it is likely to contain.

[Broomstick]

That's an assumption but in fact mercury levels can vary widely from one fish to another, which is why we don't test just one tuna we test many.

Has anyone actually tested shark meat for actual mercury levels, and if so, are they within tolerable/acceptable ranges or not?

Keep in mind that the age of a shark also has an effect - a young animal usually has less mercury. Thus, younger/smaller sharks should have less, but again, has anyone done the actual research?

Different shark species also eat different prey - the plankton-eating whale shark probably has less toxic shit in it than a big great white.

[Ace Pace]

That's an assumption but in fact mercury levels can vary widely from one fish to another, which is why we don't test just one tuna we test many.

Has anyone actually tested shark meat for actual mercury levels, and if so, are they within tolerable/acceptable ranges or not?

Keep in mind that the age of a shark also has an effect - a young animal usually has less mercury. Thus, younger/smaller sharks should have less, but again, has anyone done the actual research?

Different shark species also eat different prey - the plankton-eating whale shark probably has less toxic shit in it than a big great white.

Can we trust the FDA on that count?

Nearly all fish contain trace amounts of methyl mercury, some more than others. In areas where there is industrial mercury pollution, the levels in the fish can be quite elevated. In general, however, methyl mercury levels for most fish range from less than 0.01 ppm to 0.5 ppm. It's only in a few species of fish that methyl mercury levels reach FDA limit for human consumption of 1 ppm. This most frequently occurs in some large predator fish, such as shark and swordfish. Certain species of very large tuna, typically sold as fresh steaks or sushi, can have levels over 1 ppm. (Canned tuna, composed of smaller species of tuna such as skipjack and albacore, has much lower levels of methyl mercury, averaging only about 0.17 ppm.) The average concentration of methyl mercury for commercially important species (mostly marine in origin) is less than 0.3 ppm.

FDA toxicologists have determined that for persons other than pregnant women and women of childbearing age who may become pregnant, regular consumption of fish species with methyl mercury levels around 1 part per million (ppm)--such as shark and swordfish--should be limited to about 7 ounces per week (about one serving) to stay below the acceptable daily intake for methyl mercury.

[Shroom Man 777]

This is a damn shame since sharks are really beautiful creatures - like, the best-looking fishies in the world. Goddamn humanity!

[The Vortex Empire]

This is a damn shame since sharks are really beautiful creatures - like, the best-looking fishies in the world. Goddamn humanity!

Clearly, the only way to solve this problem is to make Human Arm Soup and supply it to the sharks. Let's see how we like it.

[Singular Intellect]

This is a damn shame since sharks are really beautiful creatures - like, the best-looking fishies in the world. Goddamn humanity!

Clearly, the only way to solve this problem is to make Human Arm Soup and supply it to the sharks. Let's see how we like it.

Evidence suggests sharks don't generally like the taste of humans, and furthermore, next to their primary sources of food like blubber rich seals, humans are just a skin and bone meal.

[The Vortex Empire]

This is a damn shame since sharks are really beautiful creatures - like, the best-looking fishies in the world. Goddamn humanity!

Clearly, the only way to solve this problem is to make Human Arm Soup and supply it to the sharks. Let's see how we like it.

Evidence suggests sharks don't generally like the taste of humans, and furthermore, next to their primary sources of food like blubber rich seals, humans are just a skin and bone meal.

Then we use obese people, and flavor it with Seal blood.

[Darth Yoshi]

It'll cut down on obesity, anyway. "Keep in shape, or you'll get fed to the sharks!"

[Broomstick]

That's an assumption but in fact mercury levels can vary widely from one fish to another, which is why we don't test just one tuna we test many.

Has anyone actually tested shark meat for actual mercury levels, and if so, are they within tolerable/acceptable ranges or not?

Keep in mind that the age of a shark also has an effect - a young animal usually has less mercury. Thus, younger/smaller sharks should have less, but again, has anyone done the actual research?

Different shark species also eat different prey - the plankton-eating whale shark probably has less toxic shit in it than a big great white.

Can we trust the FDA on that count?

Nearly all fish contain trace amounts of methyl mercury, some more than others. In areas where there is industrial mercury pollution, the levels in the fish can be quite elevated. In general, however, methyl mercury levels for most fish range from less than 0.01 ppm to 0.5 ppm. It's only in a few species of fish that methyl mercury levels reach FDA limit for human consumption of 1 ppm. This most frequently occurs in some large predator fish, such as shark and swordfish. Certain species of very large tuna, typically sold as fresh steaks or sushi, can have levels over 1 ppm. (Canned tuna, composed of smaller species of tuna such as skipjack and albacore, has much lower levels of methyl mercury, averaging only about 0.17 ppm.) The average concentration of methyl mercury for commercially important species (mostly marine in origin) is less than 0.3 ppm.

FDA toxicologists have determined that for persons other than pregnant women and women of childbearing age who may become pregnant, regular consumption of fish species with methyl mercury levels around 1 part per million (ppm)--such as shark and swordfish--should be limited to about 7 ounces per week (about one serving) to stay below the acceptable daily intake for methyl mercury.

In other words, occasional consumption of shark by non-breeding adult humans is a reasonable health risk.

So my two or three times a year 4-6 oz serving of mako was unlikely to cause a health problem, right?

[Mayabird]

It's the general assumption that the higher a fish is on the food chain, the more mercury it is likely to contain.

It's called biomagnification. Organisms at lower trophic levels accumulate small amounts of mercury, or PCBs, or DDT back in the day, things like that, and when they're eaten, all those toxins accumulate in the bodies of the predators. A teeny amount in each little plankton, a small fish eats a thousand of them and gets all their toxin loads, a larger fish eats a thousand small fish and gets a thousand thousand times the plankton load, etc.

Since sharks are mostly at the top of the food web, they get really high levels, as do the other top predators.

[JBG]

"Evidence suggests sharks don't generally like the taste of humans, and furthermore, next to their primary sources of food like blubber rich seals, humans are just a skin and bone meal."

That is true. Coming from Australia, where most things are bitey or poisonous, it is important to learn what is aggressive and what isn't. Sharrks are dangerous but the danger is largely avoidable as long as you don't make it too hard for the shark to work out what is it's natural prey ( seals for Great Whites, for instance ) and what are humans.

In this part of the world a significant cause of decline in shark numbers is hunting sharks for their dorsal fin. When that is cut off they leave the rest of the shark to die. That really pisses me off.

[Broomstick]

It's the general assumption that the higher a fish is on the food chain, the more mercury it is likely to contain.

It's called biomagnification. Organisms at lower trophic levels accumulate small amounts of mercury, or PCBs, or DDT back in the day, things like that, and when they're eaten, all those toxins accumulate in the bodies of the predators. A teeny amount in each little plankton, a small fish eats a thousand of them and gets all their toxin loads, a larger fish eats a thousand small fish and gets a thousand thousand times the plankton load, etc.

Since sharks are mostly at the top of the food web, they get really high levels, as do the other top predators.

As do humans - people don't like to think about it, but in many cases human flesh would be considered unfit for consumption and highly contaminated. Of course, cultural resistance to eating eat other renders it somewhat a moot point. However, there have been instances of women wishing to donate to breast milk banks being turned away due to high levels of toxins in their milk. It's also a reason why we do need good infant formulas, since such mothers probably should not be breast feeding and we just don't have enough human milk banks.

[Maxentius]

This is a serious shame; I have such fond memories of snorkeling with sharks when I was younger. They're incredibly beautiful animals. It amazes me that so many people can attribute malevolence to these creatures.

I really do wonder how much human perception has hinged on sensationalist depictions of sharks. Would shark population levels be this low if, say, Jaws was never released?

[Eulogy]

As do humans - people don't like to think about it, but in many cases human flesh would be considered unfit for consumption and highly contaminated. Of course, cultural resistance to eating eat other renders it somewhat a moot point. However, there have been instances of women wishing to donate to breast milk banks being turned away due to high levels of toxins in their milk. It's also a reason why we do need good infant formulas, since such mothers probably should not be breast feeding and we just don't have enough human milk banks.

Damn. I really hope this means that such people aren't poisoned for life. Are there ways to purify oneself of mercury, etc.?

[Broomstick]

Well... it's possible to remove some, but as a practical matter there are some people for whom that would take years to reduce the level significantly. And it's not just mercury - there's quite a few pollutants that can build up, such as PCB's, dioxins, lead, and other heavy metals. It is possible to have an "unsafe" level of various substances in your body without overt acute symptoms - meaning you could have a level that is dangerous long term without even realizing it.

[Eulogy]

Well... it's possible to remove some, but as a practical matter there are some people for whom that would take years to reduce the level significantly. And it's not just mercury - there's quite a few pollutants that can build up, such as PCB's, dioxins, lead, and other heavy metals. It is possible to have an "unsafe" level of various substances in your body without overt acute symptoms - meaning you could have a level that is dangerous long term without even realizing it.

It's still better to purify. How would one go about sensibly removing poisons?

[Broomstick]

Heavy metals, including lead and mercury, are removed through a process called chelation therapy. This binds the metal to substances that allow the body to excrete the poison. Chelation therapy does take time, and it can have severe side effects up to and including death. Long-term, since it depletes calcium, it can also seriously weaken bones, and it can also cause kidney damage.

Certain other toxins are just not readily removed from the body. Sometimes they're stored in body fat, in which case any weight loss should be gradual - abrupt changes in body fat percentage may make a person who is asymptomatic suddenly very seriously ill as toxins are dumped back into circulation. Sometimes the least dangerous course is simply letting the body remove substances over time, even if it can be very slow and inefficient.

Clearly, avoiding contamination is best however it is also impractical - we ALL carry a burden of toxins accumulated over a lifetime. Even doing something as obvious as becoming a vegetarian and eating lower on the food chain won't entirely solve the problem since crops do absorb heavy metals and toxins from the soil, even when organically grown, and there are still issues with air and water pollution. This is NOT a new problem - preserved animal tissues from ancients sources (think "frozen in glaciers" and natural mummification) reveal that in the past animals accumulated toxins and the higher in the food chain the more they had. Of course, that is exactly why your body has some capacity to remove toxins and why animals have things like livers and kidneys. Animals evolved the capacity to deal with normal background levels of toxins, and that includes us. The trick is to not exceed the body's capacity for these things.

[Illuminatus Primus]

No, that's tuna.

Seriously, though - do you have a cite for that, or are you just making assumptions?

No, the mechanism for mercury accumulation in seafood is not particular to tuna. Were you making assumptions?

[Broomstick]

While all fish accumulate mercury to greater or lesser extent - and don't think it's just ocean fish, river and streams also carry a toxic burden - it varies considerably by location and species. For example, some species of tuna carry higher mercury burdens than other species of tuna. Of course I would expect greater toxin levels in sharks than in, say, anchovies but I was interested in what actual research had been done on actual sharks.