Show n y Rr I jy 1 U i l Continental t wit n then n tat 1 1 I I i Landing a Giant Tuna In Nova Scotia hy hr Genera Cf Washington O n. n C C V. U Service S ONE stands stand on the seashore seashore seashore sea sea- AS A shore at the full fuU of the tide and looks out over the swelling swell ing IJ floods surging In from the distant horizon his feet are on the threshold of an enormous empire so vast In extent and population that the of the haughtiest haught lest iest rulers of mankind are dwarfed by comparison Though fleets sail over Its depth they make no significant Impression impression sion slon upon this Immense realm The subjects of this empire swarm through the waters in myriads myriads my my- dads totaling far greater numbers than all the life of the continental world In fact scientific investigations investigations indicate that the oceans ocean were the original abode of life on the globe and that the continents were peopled from that inexhaustible res res- Geologists believe that the depressions depressions depressions depres depres- now occupied by the oceans have been located in approximately their present positions during the entire history of the earth and that the foundations of the land masses likewise have been situated nearly as they are at the present time But Dut during the great geological periods the ocean has repeatedly Invaded their edges and even their Interior basins sometimes to an enormous extent forming shallow seas Thus all the continents of the world are arc bordered by a strip of shallow sea the continental shelf shell which slopes gradually from the coast to depths varying from to 1000 fathoms at its outer edge Beyond Beyond Be De- yond this limit there is usually a amore amore amore more rapid gradient to the main floor of the ocean the ocean the continental continent continent- al slope This world-wide world shallow strip is of major importance to the life of the seas North Atlantic Shelf This article deals especially with the mollusks and other small creatures creatures crea crea- tures inhabiting the continental shelf which borders the Atlantic coast of North America from Nova Scotia to New York and includes the extensive New England fisher fisher- ies A most remarkable stretch of shore this is is Its lis southern half is of comparatively even contour but beginning with the region of Cape Hatteras the coast to the northward northward north north- ward has subsided and is indented with deep bays and irregularities finally terminating in the long curving curvy curving ing and tapering indentation of the Gulf of Maine The latter is the most noteworthy feature of the coast its wide mouth being guarded on either hand by Cape Cod and Cape Sable and its inner reaches narrowing to a double apex in the Bay of Fundy AU All this northern half hall of the Atlantic Atlantic At At- lantic seaboard is a succession of drowned valleys and its topography and geological history indicate that it has subsided beneath the waves of the sea during relatively recent times On the other hand the even outline of the coast from Hatteras south to Florida shows no evidence of such sinking The oceanic shelf to the fath fath fathom om line widens rapidly to the northward northward northward north north- ward reaching its greatest extent off the Gulf of Maine where it is approximately miles wide The central floor of the Gulf of Maine is an ancient river valley to which the river system ent Tp-ent- re ent- ent ed by those now but ed their drainage to be Into into in In- to the prehistoric sea by a single channel and mouth still stin traceable on the sea floor at the edge of the continental shelf Throughout this extensive and comparatively shallow oceanic margin well illuminated by the suns sun's rays conditions are favorable for an enormous development of the marine plants on which sea animals animals animals ani ani- mals feed namely the micro microscopic diatoms one-celled one algae and the larger seaweeds Nursery for Food Fi Fishes hes Here numerous streams empty their loads of silt slit rich in nitrates phosphates and other chemicals needed for plant food The strong tides rushing into the narrowing channel from the open sea keep the water stirred with currents plentifully supplied with oxygen Hordes of small crustaceans the copepods feed upon this plant life lite At certain seasons they swarm in these waters in numbers so vast that th they y give the sea a reddish color for miles These tiny creatures are rich in oils and are greedily devoured by large schools of mackerel herring alewives and shad Bluefish cod hake and haddock pursue and devour devour de de- the smaller fishes fishel and even en the huge fin finback back and humpback whales do not di disdain to feed upon upen the herring Thus the shallow banks off New i England especially Georges and and Browns Drowns Banks Danks at the entrance to i the Gulf of Maine as well as the the Grand Banks Danks of Newfoundland farther far far- I I ther away form a veritable nursery nurs- nurs 1 cry ery for the important food fishes of our coasts and thus connect mankind mankind man- man manI I kind by an Interlacing food chain I with the microscopic plant life of these shallow waters The evolution of the animal world I as we know It it would have been impossible had these primitive plants not come into existence From such forms also all the higher high high- er land plants of the world nate pate The Zone As the open seas sea were peopled from the oceanic shelf so the freshwater fresh fresh- water streams and swamps received parts of the overflow Countless species species species cies found food and a measure of safety from enemies by creeping into the area between the tides where they acquired resistance to exposure to the open air at the Intervals Intervals intervals In- In of low water Here a rapid evolution took place so that the zone became densely populated pop with life he Finally from freshwater water swamps on the one hand and from the upper parts of the marine tidal zone on the other first plants then animals animals ani ant mals male Invaded the land Itself and produced the highly specialized types that now reign over it North of Cape Cod the coast of New England Is predominantly high and rocky Beginning with the he headlands head d. d lands of Nahant Marblehead and Cape Ann north of Boston Doston the cliffs are at first isolated to local regions with intervening stretches of sandy beaches and flats fiats But Dut from Portland Portland Port Port- land In Casco Bay Day northward the coast is an almost unbroken succession succession suc suc- cession of granite cliffs sloping rock ribbed promontories and reentrant reentrant reentrant re re- re- re entrant bays and harbors with occasional occasional oc oc- oc beaches The tidal waters flowing from the open sea are gradually confined by bythe bythe bythe the narrowing outline of the Gulf of Maine which forces them to a progressively pro increasing height and andreach andreach andreach reach a climax in the Bay of Fundy From Massachusetts Bay Day north to Portland the tide rises nine feet It II continues to increase northward until it becomes 18 feet at Eastport and 37 to 48 feet at the ends of tha two tapering horns which terminate the Bay of Fundy Here too there are interpolated stretches of beaches flat fiat points and swampy meadows and these are entirely covered at high tide Naturally Naturally Na Na- the width of the tidal zone on the side of a vertical cliff is measured exactly by the vertical rise and fall rau of the water For example example example ex ex- ex- ex ample the cliffs that surround Bliss Island at the entrance of Passa Passa- bay are exposed for 22 feet from the top of the barnacle frieze that marks the tide high-tide limit to the water level at low tide Crowded With Life This region between the tides Is s teeming with life both plant and animal in crowded array On the vertical granite walls of Bliss island the various species are arranged In overlapping zones with the conspicuous white band of rock barnacles Below Delow this the hang In thick gracefully festooned clusters down to the low water water mark Concealed beneath the rockweed and succeeding the base of the barnacle zone the rocks are covered with a dense layer of young black mussels Among them are closely crowded groups of the common dog whelk feeding upon the mussels and laying laying laying lay lay- ing their graceful vase-shaped vase egg cases tinted rose and yellow in patches In the crevices The latter mollusks secrete a pur pur- purple pIe plc dye formerly used by the I Indians Indians In In- for coloring their deerskin garments They are related to the murex of the Phoenicians from I which that people derived the famous famous famous fa fa- fa- fa royal purple later arrogated I Iby by the Roman emperors for their personal use The dog whelk has a thick shell with a characteristic spindle-shaped spindle opening It is extremely variable in color size and sculpture along tho the New England shore The common periwinkle creeps everywhere over the rockweed from the water low mark to the highest part of the barnacle zone and even upon e a bare rocks far above it This r sea snail can stand exposure to the open air longer than any other marine creature of ot the northern coast of It is in a transitional state evolution toward terre terrestrial trial life for tor its gill giU seems to be JB on tI the point of f being replaced ced by a lung It has hasa I Iery found on being wide Ide a very ery I range both sides shies of the Ihu Atlantic In En England England Eng Eng- land it i Is the tho com common mOIl I sold Eold in markets |