September 18th, 2011

thinking

Jellification

...Massive growth of jellyfish populations threaten fish stocks, as they compete with fish for food, eat fish eggs, and poison or swarm fish, and can survive in oxygen depleted environments where fish cannot; they wreak massive havoc on commercial fisheries. Overfishing eliminates a major jellyfish competitor and predator exacerbating the jellyfish population explosion. http://en.wikipedia.org/wiki/Overfishing

I've heard this horror story a zillion times: overharvested oceans are becoming depleted of large predatory fish; their place is being taken by jellies. Soon our oceans will become a giant swarm of jellies. Jellies can grow large and numerous with impunity, as no animal preys on them because they are mostly water; the caloric content is too low to make the predation effective (unless you take them out of water and sun-dry them). This allows the jellies to have large bodies with little cost incurred, helping them to spread their stinging net. Fishing in such seas is a new experience altogether:

...In 2009, a 10-tonne fishing trawler, the Diasan Shinsho-maru, capsized off Chiba on Tokyo Bay as its three-man crew tried to haul in a net containing dozens of Nomura's Jellyfish. The species can grow up to 2 meters in diameter and weigh 450 lb. The last time Japan was invaded on a similar scale, in the summer of 2005, the jellyfish damaged nets, rendered fish inedible with their toxic stings and even caused injuries to fishermen. http://www.telegraph.co.uk/earth/6483758/Japanese-fishing-trawler-sunk-by-giant-jellyfish.html

There are other, less obvious dangers:

...In 2007, jellyfish stung and asphyxiated more than 100,000 farmed salmon off the coast of Ireland as aquaculturists on a boat watched in horror. The jelly swarm reportedly was 35 feet deep and covered ten square miles.

...Jellyfish have halted seafloor diamond mining off the coast of Namibia by gumming up sediment-removal systems. By clogging cooling equipment, jellies have shut down nuclear power plants in several countries; they partially disabled the aircraft carrier USS Ronald Reagan. On the night of December 10, 1999, the Philippine island of Luzon, home to the capital, Manila, and some 40 million people, abruptly lost power. Some 50 dump trucks’ worth of jellyfish had been sucked into the cooling pipes of a coal-fired power plant, causing a cascading power failure. In 2005, jellies struck the Philippines again, this time incapacitating 127 police officers who had waded chest-deep in seawater during a counterterrorism exercise... http://www.smithsonianmag.com/specialsections/40th-anniversary/Jellyfish-The-Next-Kings-of-the-Sea.html


First salmon, then police... Of course, one can see in such developments nature's negative feedbacks in action: excessive predation (overfishing) gives opportunistic species a chance to bloom in the rapidly emptying niches, and in this way undermines the key adaptation of the predator (such as using fishing nets and power plants), restoring the balance. Unfortunately for the jellies, the rumors of their domination might be premature. It seems that the self-propagating horror story is the garden variety case of biased sampling. There is, in fact, no solid evidence that overfishing results in the depletion of, specifically, the top predators:

...The most widely adopted marine indicator is mean trophic level (MTL) from catches, intended to detect shifts from high-trophic-level predators to low-trophic-level invertebrates and plankton-feeders. This indicator underpins reported trends in human impacts, declining when predators collapse (“fishing down marine food webs”) and when low-trophic-level fisheries expand (“fishing through marine food webs”). Catch MTL is interpreted to track changes in the underlying ecosystem, but its usefulness as an indicator has been questioned because catches are influenced by changes in economics, management, fishing technology and targeting patterns. Here we combine model predictions with global assessments of MTL from catches, trawl surveys and fisheries stock assessments and find that catch MTL trends often diverge from ecosystem MTL trends obtained from surveys and assessments. In contrast to previous findings of rapid declines in catch MTL, we observe recent increases in catch, survey and assessment MTL. http://www.ecomarres.com/downloads/Fingerprint.pdf
http://www.nature.com/nature/journal/v468/n7322/full/468385a.html

...New research questions whether humans are in fact eating up the ocean's big, predatory fish, then moving on to smaller marine species further down the food chain. In 1998, Pauly put forth the paradigm when they reported that the MTL of fish sold had declined from 1950 to 1994, particularly in the Northern Hemisphere. But according to Branch and his colleagues' critique, the MTL of fish catches does not reliably show what is going in ecosystems. They came to this conclusion by comparing the MTL of catches with data from trawl surveys — conducted by researchers — and stock assessments for fish populations. Both of these are measures of the abundance of fish in the ocean, rather than what is coming up as catches in fishermen's nets. The new study found that on a global scale, predatory fish are not being replaced in nets by prey fish. Rather, catches of many big predator fish, like bigeye tuna, have increased along with those of many smaller species. http://www.livescience.com/11199-fish-story-doubt-cast-depletion-big-ocean-species.html


The study indicates rapid growth of the populations (and catches) of large squid, tuna and flatfish, blue whiting, scads, etc. They suggest a simple rationale: new, expanding fisheries first target the most accessible species yielding the highest revenue — mussels, shrimps and small fish — before expanding to high-trophic-level fish. There is another reason to doubt the jellification: the jellyfish may find that their defense strategy fails with the top (if often misguided) predator on the planet -

...Stripped of tentacles and scraped of mucous membranes, jellyfish are typically soaked in brine for several days and then dried. In Japan, they are served in strips with soy sauce and vinegar. The Chinese have eaten jellies for 1,000 years. Lately, the Japanese government has encouraged the development of haute jellyfish cuisine — jellyfish caramels, ice cream and cocktails. Some enthusiasts compare the taste of jellyfish to fresh squid. Pauly says he’s reminded of cucumbers. Others think of salty rubber bands. Another paper hailed jellyfish flesh as “the ultimate modern diet food.” http://www.smithsonianmag.com/specialsections/40th-anniversary/Jellyfish-The-Next-Kings-of-the-Sea.html?c=y&page=4

I see the future: the news articles reporting the collapse of cannonball jellies in the Atlantic, the horror stories of jelly overharvesting, of fat-ladden, barely edible salmon taking over the commercial fisheries.

Will human greed deprive the children of our children of their jellyfish cookies and ice cream?


thinking

Полундра

...Восклицание "полундра" стало предупреждением у пожарных и моряков, обозначающим надвигающуюся опасность. Произнося “полундра”, человек подразумевает "берегись" или "отойди прочь". Само слово произошло во времена императора Александра I. Одним из развлечений царя было наблюдать за пожарами, поэтому на каждую подобную трагедию Александр приезжал лично. Во время одного из пожаров Александр увидел, как на пожарного сверху упала балка. Царь предложил с этого момента ввести в употребление слово, произнося которое люди могли предупредить остальных о подобной опасности. Из множества вариантов царь выбрал именно "полундру", которая была перенята в дальнейшем и моряками. На море слово несколько изменило свое значение и стало обозначать срочный сбор для всей команды. В своем этимологическом словаре Фасмер утверждает, что слово "полундра" происходит от голландского "van onderen", которое переводится как "cнизу". http://korneslov.ru/publ/polundra/19-1-0-360

Интересно, какими соображениями руководствовался Александр I, выбирая из многих (!) вариантов полундру, и почему он выбрал снизу, если балка падет сверху?
thinking

О зайцах


Месяц назад я гулял по бельгийскому городу Генту, сильно устал и решил прокатиться на трамвае. Билетная машина у остановки не приняла мою карточку, и я сел на трамвай, рассчитывая купить билет у кондуктора. Кондуктора, однако, не оказалось. На сл. день я поехал на поезде. И опять не было кондуктора. И я стал замечать, что кондукторов как-то удивительно мало, а то и вовсе нет. В Чикаго так бы дело не пошло. В соседней Голландии и Франции, пожалуй, тоже. Я составил в голове простую теорию: если Х→1 покупают билет, то выявление (1-Х)→0 зайцев может быть существенно дороже, чем потери на безбилетников, и тогда кондуктора невыгодны. Вероятно, вместо этого устраивают редкие проверки, как когда-то в Москве. В конце концов, я попал на такую проверку. И опять подумал. В России билет стоил гроши (транспорт субсидировался государством), так что Х было низким, и риск определялся не столько зарплатой кондуктора, сколько размерами штрафа. По-логике, в виду более высокой платы проезда в Генте, кондуктора они могли себе позволить, если бы Х не было уж совсем близко к 1. С чего бы такая исключительная честность у населения?

Потом я зашел в местную крепость, Gravensteen. Там были выставлены многочисленные орудия пыток, которыми пользовались в позднем средневековье на попавшихся воришках. Особенно впечатлили двойные головные колодки для сварливых баб: их оставляли на несколько дней выяснять отношения, периодически обливая водой. Колодки были статегической длины: достать руками они друг друга не могли, хотя, вероятно, при некотором навыке могли доплюнуть. Самыe почетные экспонаты (под стеклом с сигнализацией) были небольшой топорик и здоровенный нож. Табличка сообщала, что орудия служили для отрубания конечностей, и музею были завещаны сыном последнего муниципального палача: oни бережно передавались из поколения в поколение 400 лет. Вспомнил я и вафельщика из "Тилля Уленшпигеля", прочтенного в далеком детстве.

Вот что, оказывается, нужно делать, чтобы Х устремилось к единице...