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hem es almost entirely fromeavesdropping on their songs； but even these are a mystery。 blue whales will sometimes breakoff a song； then pick it up again at the same spot six months later。 sometimes they strike upwith a new song； which no member can have heard before but which each already knows。
how they do this is not remotely understood。 and these are animals that must routinely eto the surface to breathe。
for animals that need never surface； obscurity can be even more tantalizing。 consider thefabled giant squid。 though nothing on the scale of the blue whale； it is a decidedly substantialanimal； with eyes the size of soccer balls and trailing tentacles that can reach lengths of sixty feet。 it weighs nearly a ton and is earth鈥檚 largest invertebrate。 if you dumped one in a normalhousehold swimming pool； there wouldn鈥檛 be much room for anything else。 yet no scientist鈥攏o person as far as we know鈥攈as ever seen a giant squid alive。 zoologists have devotedcareers to trying to capture； or just glimpse； living giant squid and have always failed。 theyare known mostly from being washed up on beaches鈥攑articularly； for unknown reasons； thebeaches of the south island of new zealand。 they must exist in large numbers because theyform a central part of the sperm whale鈥檚 diet； and sperm whales take a lot of feeding。
1according to one estimate； there could be as many as thirty million species of animalsliving in the sea； most still undiscovered。 the first hint of how abundant life is in the deepseas didn鈥檛 e until as recently as the 1960s with the invention of the epibenthic sled； adredging device that captures organisms not just on and near the seafloor but also buried inthe sediments beneath。 in a single one…hour trawl along the continental shelf； at a depth of justunder a mile； woods hole oceanographers howard sandler and robert hessler netted over25；000 creatures鈥攚orms； starfish； sea cucumbers； and the like鈥攔epresenting 365 species。
even at a depth of three miles； they found some 3；700 creatures representing almost 200species of organism。 but the dredge could only capture things that were too slow or stupid toget out of the way。 in the late 1960s a marine biologist named john isaacs got the idea tolower a camera with bait attached to it； and found still more； in particular dense swarms ofwrithing hagfish； a primitive eel…like creature； as well as darting shoals of grenadier fish。
where a good food source is suddenly available鈥攆or instance； when a whale dies and sinks tothe bottom鈥攁s many as 390 species of marine creature have been found dining off it。
interestingly； many of these creatures were found to have e from vents up to a thousandmiles distant。 these included such types as mussels and clams； which are hardly known asgreat travelers。 it is now thought that the larvae of certain organisms may drift through thewater until； by some unknown chemical means； they detect that they have arrived at a foodopportunity and fall onto it。
so why； if the seas are so vast； do we so easily overtax them？ well； to begin with； theworld鈥檚 seas are not uniformly bounteous。 altogether less than a tenth of the ocean isconsidered naturally productive。 most aquatic species like to be in shallow waters where thereis warmth and light and an abundance of organic matter to prime the food chain。 coral reefs；for instance； constitute well under 1 percent of the ocean鈥檚 space but are home to about 25percent of its fish。
elsewhere； the oceans aren鈥檛 nearly so rich。 take australia。 with over 20；000 miles ofcoastline and almost nine million square miles of territorial waters； it has more sea lapping itsshores than any other country； yet； as tim flannery notes； it doesn鈥檛 even make it into the topfifty among fishing nations。 indeed； australia is a large net importer of seafood。 this isbecause much of australia鈥檚 waters are； like much of australia itself； essentially desert。 （anotable exception is the great barrier reef off queensland； which is sumptuously fecund。）because the soil is poor； it produces little in the way of nutrient…rich runoff。
even where life thrives； it is often extremely sensitive to disturbance。 in the 1970s； fishermenfrom australia and； to a lesser extent； new zealand discovered shoals of a little…known fishliving at a depth of about half a mile on their continental shelves。 they were known as orange1the indigestible parts of giant squid； in particular their beaks； accumulate in sperm whales stomachs into thesubstance known as ambergris； which is used as a fixative in perfumes。 the next time you spray on chanel no。 5（assuming you do）； you may wish to reflect that you are dousing yourself in distillate of unseen sea monster。
roughy； they were delicious； and they existed in huge numbers。 in no time at all； fishing fleetswere hauling in forty thousand metric tons of roughy a year。 then marine biologists madesome alarming discoveries。 roughy are extremely long lived and slow maturing。 some maybe 150 years old； any roughy you have eaten may well have been born when victoria wasqueen。 roughy have adopted this exceedingly unhurried lifestyle because the waters they livein are so resource…poor。 in such waters； some fish spawn just once in a lifetime。 clearly theseare populations that cannot stand a great deal of disturbance。 unfortunately； by the time thiswas realized the stocks had been severely depleted。 even with careful management it will bedecades before the populations recover； if they ever do。
elsewhere； however； the misuse of the oceans has been more wanton than inadvertent。
many fishermen 鈥渇in鈥潯harks鈥攖hat is； slice their fins off； then dump them back into the waterto die。 in 1998； shark fins sold in the far east for over 250 a pound。 a bowl of shark finsoup retailed in tokyo for 100。 the world wildlife fund estimated in 1994 that the numberof sharks killed each year was between 40 million and 70 million。
as of 1995； some 37；000 industrial…sized fishing ships； plus about a million smaller boats；were between them taking twice as many fish from the sea as they had just twenty…five yearsearlier。 trawlers are sometimes now as big as cruise ships and haul behind them nets bigenough to hold a dozen jumbo jets。 some even use spotter planes to locate shoals of fish fromthe air。
it is estimated that about a quarter of every fishing net hauled up contains 鈥渂y…catch鈥濃�攆ishthat can鈥檛 be landed because they are too small or of the wrong type or caught in the wrongseason。 as one observer told the economist： 鈥渨e鈥檙e still in the dark ages。 we just drop a netdown and see what es up。鈥潯erhaps as much as twenty…two million metric tons of suchunwanted fish are dumped back in the sea each year； mostly in the form of corpses。 for everypound of shrimp harvested； about four pounds of fish and other marine creatures aredestroyed。
large areas of the north sea floor are dragged clean by beam trawlers as many as seventimes a year； a degree of disturbance that no ecosystem can withstand。 at least two…thirds ofspecies in the north sea； by many estimates； are being overfished。 across the atlantic thingsare no better。 halibut once abounded in such numbers off new england that individual bo