Down through the countless centuries of time the rivers have carried their riches into the sea, until today we find the sea is a veritable treasure-house of dissolved minerals. These minerals differ in concentration from place to place, and whereas the open ocean may contain about thirty-four parts of salt to a thousand parts of water (by weight), river estuaries will contain considerably less.
Although the fact that sea water contains gold, silver, and radium may not interest the angler, salinity does. For instance, the average species of fish is quite sensitive to changes in salinity, yet in spite of this we find many sea fish high up river. This fact alone is likely to set traps for the unwary, especially where baits are concerned. It seldom pays dividends to take prawns from the open sea and to try to keep them alive for a long period in a river estuary; it is much safer to take your prawns from the actual river, unless you intend to use them the same day.
This applies directly in keeping baits alive, and when using glass tanks for prawns, ragworm, etc., evaporation will always occur. Never top up with fresh sea [p228] water, as this will merely add to the concentration of mineral salts and cause the death of your bait. Since only the "fresh" water has evaporated, top up with tap water to the same mark and all will be well.
Due to the chemical composition of the sea, certain materials should never be used when trying to keep baits alive. Galvanized iron, copper, and brass, and even lead, all dissolve in sea water to a sufficient extent to make the water lethal to sea life. Some of these materials can be coated with bitumen or pitch and rendered safe, but wood or glass are always safest.
The other important constituents of sea water are the gases which are dissolved in the water. Of these, oxygen is the most important to sea life, and is its very life-blood. Oxygen is present in the deepest oceans, and that is why life continues to thrive in the lightless world of three to seven miles down. Stagnation seldom occurs in the sea, for currents, waves, and tides continually circulate the water, and thereby aerate its surface and carry oxygen down into the deeps.
The angler experimenting with small aquaria for keeping live baits will find his troubles halved if he installs an aerator.
The temperature of the sea varies according to depth and season of the year, and both these factors profoundly affect the movements of fish.
It is already known that sea temperature governs the movement of cod, and recent investigations by the author indicate that the same is true of the mackerel. Some species have been shown to be sensitive to changes of as little as half a degree or less.
Generalizations are always dangerous, but without them little can be said, so the following is an attempt to indicate what can best be called "average conditions."
Changing Characteristics. In autumn the first gales cause the warm surface layers of the sea to mix with the deeper, colder layers, and thus both the shallow inshore water and the deeper offshore water approach the same temperature.
With the coming of the first frosts, the inshore water cools rapidly and falls far below the offshore temperature, with the consequential offshore migration of many fish such as mackerel and bass, mullet and horse mackerel. As winter progresses the offshore water drops in temperature, but seldom goes as low as coastal water.
During the spring the sea again warms up, but the offshore water with its greater volume takes much longer than the shallower water. Thus we find that some time during late March, April, or May, according to season, the deep water and shallow again attain an equivalent temperature. This is maintained for a short time, and then during the summer the inshore water soars far above the offshore water.
There is every reason to believe that this is the prime factor governing the inshore migration of many of our fish.
The deeper water also becomes stratified during the spring and continues thus [p229] throughout the summer, the top layer being quite warm down to about forty feet. At or about this depth there is a sharply defined layer above which the temperature may be around 6o° F., and below it will be about 53° F.
It is this discontinuity layer that traps the manorial salts in the deeper water during the warm months, and may well be a factor in the inshore movement of fish.
During a recent investigation over a twelve-year period in Torbay, some interesting facts concerning sea temperature and fish movements were discovered. The fish studied was the mackerel, and the following shows that temperature has a profound effect on this species in the area under discussion.
During the period, the mackerel appeared inshore when the sea temperature was between 53° and 54° F., and in six of those years the temperature was exactly 53° F. Their departure time was not so clearly defined and varied from 54° to 57° F. However, it appears to be noteworthy that the average sea temperature at time of departure was 55° F., although the date of departure varied from early September in one year to as late as November in another.
From an angling standpoint it should be well worth while keeping your own records in this way, for many resorts publish sea temperature figures in the local paper, and checking-up is quite easy.
The penetration of light into the waters of the sea was witnessed at its best by Professor Beebe when he made his descent in the Bathysphere. He found as he descended that slowly the light diminished from daylight into abysmal darkness, the like of which remains unknown upon earth. Yet even in that blackness, fish lived and thrived in a world of phosphorescence and darting, flashing lights.
Since few of us will ever try really deep-sea fishing, we are more interested in the effect of light on the inshore fish, and there is no doubt that this is considerable. The effect of light can really be divided into two parts. Firstly, a direct effect on fish and, secondly, the effect occasioned by light reaction of the species that comprise their food.
Night-time and its Effects. The direct effect of night is seen in the case of wrasse and mackerel. These two species cease to feed, and in the case of wrasse they definitely "go to sleep" on rock ledges. It is not known whether mackerel continue to swim around during the hours of darkness, but it is certainly a waste of time fishing for them. Such species as do rest at night come on the feed with a vengeance at dawn.
The majority of fish seem to feed as well at night as during the daytime, and indeed there is much to be said in favour of night fishing. It is almost safe to say that most fish that feed right up until dusk will feed even better during the night.
Secondly, there is the effect occasioned by the light reaction of the small creatures on which fish feed. It has been observed that many planktonic forms tend to select depths of water where the particular light intensity is most suited to their [p230] requirements. Thus a daily migration of plankton occurs. With the coming of dawn, the plankton will be found either near or on the surface, and then as light intensity increases they tend to go deeper. Thus the sand-eels, etc., which feed on plankton will also follow into deeper water, and so in turn will the fish that we seek. On cloudy and dull days the plankton may be nearer the surface, and at such times it may well prove useful to fish less deep if float tackle is being used.
Towards evening, life again returns to the upper waters, and a strong light will reveal a variety of life undreamed of during high noon. Here swim ragworm and small prawns, whilst on the bottom the crabs and shellfish move more openly.
Pollack provide an excellent example of the effect of light on fish movement. Big pollack are nearly always taken in fairly deep (and consequently darker) water during the daytime. The angler fishing inshore rocks will get a few good pounders, but the chap in the boat comes in with the twelve-pounders every time. Try the same spot at dusk and through the night and see what happens.
What happens? Firstly, it is better to fish at about 10 ft. instead of the daytime 14 to 20 ft. Secondly, you will get more and bigger ones. And why? Well, the food has come up and the fish are there with it.
For the bottom angler, night-time is excellent, for with the increasing activity of their food the fish come right on the feed. Species such as bass are invariably more numerous in the surf at night.
Perhaps after long acquaintance with the sea in all its varying moods, the angler will become aware of certain "signs." Of these there is one to be avoided—crystal-clear water, unruffled by wind and reflecting the harsh light of noon. Yes, light and dark are two factors to be considered by every angler in his own locality, and much fruitless fishing can be avoided.
Fruitless fishing? Perhaps this is a misnomer, for most of us find pleasure just holding the rod and hoping.
PLANT, BIRD, AND ANIMAL LIFE
If you stand on a pier and stare down into the sea it is difficult to imagine the myriad hosts of life that drift and swim through the thin layer of water between you and the sea bed. Yet in a single cupful of that sea water and with the aid of a microscope, it would be possible to count hundreds of small creatures and plants.
These are the plankton, the young stages of all the sea creatures and plants, carried by the tides and currents. These are truly the pastures of the sea, where all fish ultimately derive their food.
Some of the most common forms are the young stages (larval stages) of the barnacle and the shore crab (Fig. l). They bear little resemblance to their parents [p232] and undergo many weird and macabre changes before they settle down to their adult life, but all the time they provide food for the young (post-larval) fish that swim in shoals among this rich hunting-ground.
Copepods form the chief food of herring, and these can clearly be seen with the naked eye. At times certain species are so numerous as to colour the water, and trawler men often sought fish by looking out for certain water colour. Now, perhaps for ever, the echometer has outmoded an innate skill once possessed by man.
Many plankton forms consist of one simple cell, the lowliest form of life known, but we should be foolish to ignore their worth when every specimen fish depends upon them for its food in one way or another.
Plankton is divided into plant and animal, and in the same way that land animals depend upon plants for their food, so do the creatures of the sea.
Plant plankton forms the basis of the food-chain explained later, and is essential to the well-being of every fish that swims in the sea.
It is a strange thought, but true, that the shark which spreads terror to every fish is nevertheless dependent upon some lowly plant drifting in the currents of the ocean.
Animal Plankton. When using the term "animal" it is used in the strictest form to include everything that is not plant, and so fish life comes under this main heading.
Animal plankton is seen at its most prolific in the spring, for it is then that the shellfish, barnacles, crabs, and so on have released into the sea their offspring. In numbers we cannot appreciate, the billions drift along in a world where everything preys on something else and the predator of a second ago is eaten the next moment.
The young stages of fish are included, for in their infancy they carry a yolk-sac and are almost incapable of swimming. It is only after a few weeks of life that they commence to feed on other forms, and even then they are surrounded by enemies.
Life amongst the plankton must be like trying to walk a red-hot tight-rope carrying a jar of gelignite.
When trying to get a general picture of life in the sea, there are a host of other creatures that must be considered. Each is a factor, although we may not see their work and have little real idea of the part they play.
Gulls. Every angler knows the mocking cry of gulls, and often their mocking dirge does little to calm a poor day's fishing. Everywhere where there is sea and coastline you will find gulls, and it is an interesting fact that their large populations are in many areas purely dependent upon the activities of man.
Around our fishing ports and areas where sewage empties into the sea, gulls are at their most clamorous number—and all virtually dependent upon man's activities. These same gulls can play havoc with a shoal of stranded sand-eels at night, and we have often witnessed such a feast. At such times their depredations  are unseen except by the "mad" fisherman who prefers the sound of waves to the peace of the pillow.
Watch a flock of gulls working along the tide-line. They paddle with their feet and release small shellfish by the score, and get fat on the small crabs that hide in the sand. Watch for them when looking for mackerel, for their wheeling and diving is a sure indication of fish especially if that change betokens a blow from seaward.
In spite of all this, gulls are cheerful birds for the angler, and often we find ourselves throwing them a large mackerel, "just to see it disappear at one gulp."
Herons. Then there is the heron. Heron in the sea? But of course; although it may be mostly at night and at times when the demands of a growing family call for more and more food. At such times herons will visit beaches at low tide and collect sand-eels and small crabs. The sight of the grey hunch-back heron motionless and waiting beside the tide in the dim light of the moon is something to be remembered.
Cormorants. One of the most common birds of prey to be met with on rocks and shore is the cormorant. The angler who sees at dawn cormorants winging their way upstream over the river estuary is witnessing a common occurrence. He may well sit contented, for a while at least, for these birds will not be attacking sea fish. They are, in fact, going up to the headwaters of the river, where during the course of the day they will consume large numbers of small trout and sea trout. This, however, is only just one small part of their life, for most of their time is spent hunting in the sea itself. The briefest glance at one of these birds will show how well adapted it is for the serious business of catching its food. The long snake-like neck with the strong spear-pointed beak is ideally suited to securing a fast-moving prey; the streamlined body ideally adapted for rapid movement through the water; the large webbed feet a perfect mode of propulsion. We have often heard it said that a cormorant in a single day will consume eight times its own weight of fish, but after even a moment's reflection the absurdity of this statement should become obvious. Even to a bird like the cormorant, a fish is not such easy prey as to be secured in such large numbers. Nevertheless, there can be little doubt that the consistent feeding of a large population of these birds will, in time, help to reduce the numbers of certain species, such as pollack, pouting, etc.
At times, especially through the winter months when the offshore hunt for food becomes a long and arduous one, cormorants will fly right in to the beaches, and can actually be seen swimming, diving, and feeding in the roughest of surf. On one occasion we witnessed the successful fishing of one of these birds, which in the course of half an hour caught no fewer than three small flatfish and a dozen small whiting. But, you will say, "this, surely, is well on the way towards eight times its own weight of fish a day." This would, of course, be so, but in actual fact few of these birds are able to continue feeding at that rate for any length of time.
[p234] There is no doubt that the cormorant is an exceedingly cunning bird, as the following story will show. It was on a summer afternoon, and the sea calm and clear. The cormorant which we were watching had been swimming around for some time, when, after a particularly long dive, it surfaced clutching in its beak a large flounder. Several attempts were made to swallow the fish, but it proved too large. Suddenly amidst a great flurry of wings a large black-backed gull swooped to the attack, and in desperation the cormorant dived. Patiently, the gull circled on the surface, waiting for the cormorant to come up, and when it did so it attacked again. Three times the gull attacked, and each time the cormorant escaped with the flounder by diving. The fourth time, however, the cormorant came up without the flounder, and for a few minutes the two birds swam around in small circles with the gull obviously perturbed by the disappearance of its anticipated meal. Finally, convinced that the intended robbery was no longer possible, the gull flew away to the distant rocks. The cormorant waited, and then satisfied its enemy had gone, dived down and returned immediately to the surface holding the flounder in its beak. There followed a more serious and determined effort to swallow the fish, and eventually the neck of the cormorant distended, stretched, and then returned to normal as the flounder disappeared. Incidents such as these help to illustrate the constant interplay of the various factors that, in the end, amount to a reduction in the fish stocks around our coasts.
Gannets. Another great enemy of fish is the gannet, as anyone who has watched these birds will appreciate. With their great wings folded back, neck outstretched into pointed beak, they will plummet downfrom 200 ft., and pierce the water with a terrific splash to secure a fish that they have actually seen from the sky above. This diving is not always such a hit-and-miss business as it appears to be. There are times, of course, when gannets will dive haphazardly into a dense shoal of fish, but at other times they will coolly and determinedly seek their prey—one single fish in the vast expanse of sea—dive and secure it. Around many of our more populated resorts the disturbance of motor craft and tourists is driving the gannet from its normal haunts, but they can still be seen flying leisurely off towards the offshore tide-rip, where the fish are plentiful.
Seals are more common than is normally imagined, but their depredations upon fish shoals is often terribly exaggerated. Much of their food consists of shellfish, and except in a few areas they are not sufficiently numerous to be considered even a danger to fishing.
Having watched one in action from some rocks, we have always respected their amazing speed and control in the water. A fully-grown seal can take a garfish as cleanly and quickly as you or I can light a match. There is something about a seal that makes anglers like them, and few of us wish to see their numbers diminish.
Porpoises. One of the most common creatures to be met with in the sea during the [p235] summer months is the porpoise. Normally regarded as a fish, this creature is, in effect, a mammal, and produces its young in the same way as land animals. Although gregarious by nature, porpoises do not generally school in very large numbers, and the most usual number to be met with at one time is approximately three to six. At certain times large schools of any number up to as many as forty have been seen chasing and feeding on mackerel. They are extremely fast swimmers, and as they breathe air they have to come to the surface periodically to renew their supply. Since the porpoise arcs up from the deep, breaks surface, and dives again in less than a second it will be appreciated that the amount of air required has to be taken in very rapidly. This sudden inrush of air results in a distinct whistle which can be heard from some distance. It is an eerie experience, when fishing at night, to hear the swirl of one of these creatures surfacing and the low whistle drifting across the still water. Porpoises can often be seen, even during the winter months, although at such times they generally remain in the deeper offshore waters. It is only with the coming of summer and the inshore migration of mackerel that the porpoises move into shallow water, and in their purposeful haste to secure food they will chase these fish right into the shallow water over the beaches. It is at such times that the ebbing spring tide will sometimes strand them on a sandbar. There, in spite of there being a plentiful air supply, the lack of water pressure causes the greater weight of their body to crush their lungs, and thus cause their death.
Otters. One of the more unusual visitors to the seashore is the otter, although its activities are normally confined to estuaries and the tidal portions of our rivers. At such times the otter is by no means a selective feeder, for in spite of its more customary diet of salmon, trout, and sea trout, it will readily take pollack or bass. It is by no means easy to see these animals, but they will often be found hunting in river estuaries at dawn when the trailing arrowhead ripple marks its progress through the water.
Octopus. Lastly, and mentioned only because of its interest to anglers, is the octopus. This creature in certain cycles of time migrates into the waters of the English Channel in considerable numbers, and their vanguard is first recognized by the inshore crab fishermen. These creatures, in plague years, will cause a complete cessation of the crabbing industry in affected areas. Fortunately for the angler they do not feed on fish, and their diet is chiefly composed of crabs and their like. Occasionally an octopus is caught on rod and line, and such an event is considered unique enough to warrant space in the national press. During the past forty years there have been only two major invasions by octopus, and on the last occasion they penetrated well north up the English Channel to the mouth of the Thames. This would appear to be about their northern limit, and with the onset of colder weather they move rapidly southwards away from our shores.
Fish. In the scheme of life in the sea, there is no doubt that fish are perhaps the [p236] most limiting factor. Most sea fish feed on other forms of animal life; indeed, after observing the ways of fish closely, one wonders just what they will not eat. Young mullet, for instance, will feed greedily on pieces of mussel and winkle when kept in aquaria. To see them try to swallow pieces as big as their own heads shows the fallacy of dogmatically asserting that their only food is soft animal matter.
Many large fish will attack and kill other fish, and a tope can eat quite a number of fish in a week. Sand-eels are not always plentiful, and at such times bass will turn to young pollack or almost any shoaling fish that happens to be around at the time. Often when fishing we catch a fish that bears the mark of an unsuccessful attack by some larger species. How many such fish will die from consequent fungus infection or diseases caused by the open wound?
There is no doubt that whilst fish are dependent upon other forms of life for their existence, they are themselves responsible as a limiting factor in their own numbers.
THE CYCLE OF LIFE
Seasons in the Sea. We are all familiar with the sight of a harvest-field in late August, and the heavy crops produced by an acre of land are often taken for granted by those of us who do not have to earn our living from the soil.
Yet few of us realize that comparable crops are produced each season in the vast expanses of open ocean and around our coasts. If, for instance, we stand on the cliff top and look down upon the sea, we find no evidence of the enormous harvest that is being produced there. Yet beneath an average acre of sea water there is produced annually 5½ tons of plant plankton—approximately half the average turnip crop on shore.
The turnip crop on land is in a form easily seen, and the weight of one of these root-crops can readily be assessed from its shape, size, etc. But in the sea the entire crop is largely composed of microscopic plants and animals.
The angler can see some of these without a microscope, by filling a jar with the water around the rocks, some time in the spring months. If this is then held up to a strong light, a milling mass of life will be seen swimming and drifting around the narrow limits of the glass. Weird and fantastic are their shapes, and it takes an expert to distinguish between which is plant and which is animal—for some of these plants, for example, are one-celled, not green and not faintly resembling our land plants.
Yet on these microscopic planktonic forms rests the entire economy of the life in the sea. Without the lowly diatoms drifting in the ocean currents, there would be no lordly sharks and whales, for every creature in the sea ultimately depends upon them. These have truly been called "the pastures of the sea," for it is here that life begins, and if the "grazing" is good, then we can expect more specimen fish.
[p237] The life of the plankton is intimately connected with an annual cycle of events that takes place within the sea, and this cycle is controlled and modified by the sunlight, storm, and temperature that is largely responsible for our own land harvests. Each year sees the same sequence of events, which will vary only in time and quantity of life produced. It happens beneath our eyes, almost without being seen, and can best be appreciated if we deal with the question as an annual cycle beginning in the spring.
Spring. In spring time the sun begins to climb higher in the sky, giving more heat and light to the waters of the sea. In exactly the same way as this sunlight stirs into growth the plants of our fields, so does it stir into life the tiny plants of the sea.
It has been proved in a very clever piece of research by Dr. E. J. Allen that the amount of sunlight can have a "two-way" effect on our ultimate fish stocks. He found that in years when there was plentiful sunlight during February and March, the mackerel fishing in May around Penzance was always good. In years when sunlight was poor in these months, the mackerel fishery suffered during May.
The explanation was simple, yet it does provide an excellent example of the work of marine biologists. It was the early sunlight that caused ideal conditions for the growth and increase of microscopic plants (Fig. 2), and these in turn provided plenty of food for the calanus larvae hatching at about this time. In turn, again, these attracted the mackerel to the area, where they fed on the plankton. In dull years, the calanus hatched before the plants had increased, and most of them therefore died of starvation, which meant that by May there were few calanus in the area, and so the mackerel did not come there.
Now to return to the cycle of life. Sunlight provides the impetus to growth, but few plants can grow without nourishment, and in the sea this is provided by the nutrient salts in solution in the water. A glance at Fig. 2 will show that during the [p238] spring the phosphates and nitrates are at their greatest concentration. This is because right through the long dull days of winter sea creatures have been dying and their decaying bodies on the sea bed have released back to the sea their store of mineral salts. There have been few plankton to feed on these salts, and in addition the rivers have borne their share of mineral salts to the sea.
So it is in spring that the sunlight provides the ideal conditions, and the plentiful mineral salts provide the food. But it is here that other factors come into play, for in these early months the vast numbers of sea creatures, such as shellfish, crabs, and fish, are releasing their eggs and young, and these soon begin to feed on the plant plankton. For a short while the mineral salts are able to cope with the increase, and then suddenly they become used up. Immediately the plants cease to grow, and a decline in their numbers results.
It is a remarkable example of the provision of nature that this rarely occurs before the young shellfish, crabs, and larval fish have ceased to feed on plants and taken to animal food. It is then that the "pastures" of the sea become the scene of an "eat or be eaten" hurly-burly with everything preying on everything else.
Whilst all this is happening, the sea has been warming up, and as spring passes into summer, temperature plays its part in the cycle of life.
Summer. As the sea warms up, the surface layers—down to seven fathoms—tend to become much warmer than the deeper water below, and this results in the formation of a discontinuity layer of temperature. Here the temperature may change abruptly from 61° to 53° F. This layering is found only well out in the open sea, but the barrier so formed provides an effective thermal barrier that traps the mineral salts in the deeper water. It is obvious that the plants will only increase and flourish in the relatively shallow and well-lit surface waters, and so with the formation of the thermal barrier their numbers reach their lowest.
Throughout the long summer, decaying animal remains on the sea bed continue to return their salts to the sea below the barrier, and the concentration increases daily, whilst all the young stages of crab, etc., are feeding on animal life and forms like themselves.
By midsummer—in spite of the sunlight—the plant plankton is almost nil, and the sea takes on that glassy clarity that so often spells "no fish."
Autumn. Late summer sees the first of the gales, and during the autumn the wind frequently reaches gale force. As the great swell builds up, the area affected by turbulence extends downwards into the deeper sea. A sudden mixing of this surface water with the deeper water breaks down the thermal barrier and releases the mineral salts. Like a huge soup tureen, the waters are stirred up by the gales, and the surface water again becomes rich in mineral salts.
Since the sunlight is often still bright, there will be a second increase in the plant plankton as it feeds on these salts. There would appear to be nothing to [p239] prevent their numbers reaching those of the spring—but this is where sunlight controls the growth. Time has passed from the first gales, and the sun has declined and slowly the number of plants die off. Here we see death amidst a plentiful supply of food; death due to lack of sunlight.
Slowly through the autumn the sea cools down. Many thousands of young crabs and shellfish have now grown to a size where they leave the plankton pastures and seek their homes around the rocks and among the inshore weed, whilst the fish fry will be now free, swimming and shoaling after other small fish that six months ago were feeding with them in the plankton.
Winter. It is now that sunlight decreases to its minimum and the sea cools down to its lowest temperature. A vast number of deaths occur, and the decay on the sea bed releases a steadily mounting quantity of mineral salts. All these are constantly stirred up by the winter gales, and slowly the sea becomes more rich in salts as winter passes into spring.
Slowly the sun rises in the sky and a new birth begins. The cycle of life is complete—progressing unchanged as it has done for countless millions of years.
THE DEVELOPMENT OF LIFE
Of all the instincts sea creatures possess, the greatest is that of "continuation of the species." It is this great instinct, coupled with self-preservation, that ensures the continual renewal of our fish stocks.
All too often we anglers expect too much in the way of specimen fish. We fondly hope for the impossible, and whilst this optimism is an essential part of angling, we should occasionally face facts, and by so doing we shall be all the more surprised when we bring to the net a good specimen fish.
So many and varied are the ways of life in our seas that only a summary of a few facets can be given here; for many remain unsolved, as research vessels and biologists patiently probe the depths and piece together the jigsaw that will one day present the picture of the sea.
Conception. It is in early spring that most of our sea fish prepare to spawn, although the preparatory process has been a very gradual one developing slowly throughout the previous twelve months. Perhaps this will be best appreciated if we follow the course of a fish throughout the year.
During the summer months the food supply in the seas reaches a peak, and the mature fish feed avidly, adding more weight between May and September than is added during the other seven months. This plentiful feeding, prompted by the warm temperature and sunlight, encourages the development of the gonads—the reproductive organs of fish—so that slowly eggs in the female and sperms in the male develop within their bodies until both male and female are swollen with future life.
[p240] It is a very gradual process, and from observations made on certain species we know that the gonads pass through a series of stages until ripeness is attained. The term "ripe" is applied to any fish that is ready to complete the act of spawning.
In the case of bass, for instance, we find the fish inshore throughout the summer months, and then, with the first cold spell, most of the large ones leave the shallow cold water for the winter. In the Plymouth area there is every reason to believe that the bass then move out into the deeper water in the region of the Eddystone. During December, January, and February large bass are frequently taken by steam trawlers at a depth of as much as forty fathoms—and all are ripe fish ready for spawning.
In this area, at least, the bass are assembling there for the purpose of spawning. Due to their comparative rarity when compared to our more common commercial species, there is an obvious need for such an assembly if the spawning is to be successful. The process entails the female releasing large quantities of eggs, which are subsequently fertilized by sperms released by males swimming through these eggs. Without a goodly number of fish present, the fertilization would be incomplete.
Birth. Since nobody has ever witnessed the spawning of bass, we can only try to picture the scene beneath the waves, based upon knowledge gained from observed species.
Down in the twilit world beneath the English Channel, where 200 ft. of sea water has already filtered the daylight into dusk, the bass assemble. Large, mature fish swim excitedly, with as many as three males following each female until, prompted by tide, current, and temperature the females release their eggs.
Each small egg floats buoyantly in the water, as the great numbers are released like raindrops, and through them the males swim and release the tiny specks of life that fertilize them and give unity.
Millions of eggs are so released, and many, many thousands sink slowly to the bottom, unfertilized, to decay and return their minerals to the sea. Thousands more are eaten by plankton and other fish. Being buoyant, a large proportion will float gradually towards the surface, where a heavy shower of rain may so dilute the salinity of the water as to cause the death of whole batches.
The newly spawned egg is a clear, transparent sphere (Fig. 3) containing a minute yellow oil globule, and within this sphere lies the nucleus of life brought into being by the union of sperm with egg.
Slowly this nucleus divides and grows, spreading around the circumference of the egg, and slowly the egg becomes less transparent as the young embryo develops. After two or three days the embryo will extend three-quarters of the way around the sphere, and already the first pulse beat can be detected as life flows through the tiny body.
[p241] Four or five days after spawning, the embryo fish can be seen to move its tail, and two large eyes have developed and patches of colour spread across the body-blue, green, and black obscuring the transparency of the embryo.
And still this developing egg is the prey of countless sea creatures. Still the numbers are steadily and ruthlessly being diminished, and the fight for survival is on in earnest, although at this stage the embryo is helpless and totally unequipped to protect itself. Here in the sea there is little parental care (although a few species do protect their eggs), and the adult fish abandon their young to the cruel womb of the sea.
During the fifth or sixth day the young embryo becomes very active, until by continual thrusts of its body against the wall of the egg it bursts into freedom—and begins a new series of fights for existence.
At first the young post-larval fish swims only by awkward jerks of its body, and its stomach is swelled out with the mass of yolk-sac that is its food for the next two weeks. Within this yolk-sac lies the small oil globule, and due to the buoyance of this the post-larval fish is compelled to swim in an upside-down position.
Slowly the buoyancy lifts the fish towards the surface light, for still it is unable to swim, and thus for the next five or six days the young bass will slowly rise towards the upper waters. Then, becoming able to swim in short jerks, it maintains its depth to between ten and twelve fathoms.
[p243] Hazards of Youth.
By the time the bass is a month old, its length has increased to about six millimetres and the yolk-sac has been completely absorbed. It now enters a new sphere of life, for it has become necessary for it to secure food from the water in which it swims. There, in the rich plankton pastures, the young bass grows rapidly, yet all the time the numbers of the original spawning are being reduced. Perhaps jungle would be a more apt word than pasture, for amongst the plankton roam those that feed on these tiny fish. Here nothing is safe, and nothing can relax from the business of survival, and it is here that Nature ensures that only the fittest shall survive.
These enemies of youth are numerous and diverse in kind (Fig. 4). Most common are the larvae of crabs, spiked terrors that swim in countless millions among the developing fry. Tiny jellyfish trailing long tentacles find rich reward among the diminished shoals of fry. Bacteria attack and spread disease, whilst countless arrow-worms spread their toll.
Slowly, as the weeks pass by, our young fish grows and, becoming more active and large, is able to evade most of these dangers of youth—only to be faced with a whole new batch of problems.
Moving inshore, the young bass, now six months old, meets attack by swimming crabs, and the onslaught of fast-swimming fish such as mackerel and pollack; whilst on the sea bed, in tattered camouflage, the angler fish lies in patient ambush. Spewing out from man-laid pipes, sewage carries the poison from man's domain into the pure sea—and whole shoals perish in chemical contamination.
Oil, pumped from the bilges of ocean tramps, spreads its filth and poison and claims its share. But in spite of it all, many thousands of young bass survive.
Then one day a shoal of young bass will break surface whilst escaping the attack of pollack, to be met with aerial attack from yellow-beaked gulls. During their first summer of life in the sea they will be attacked by jet-propelled squid and cuttle, to die in the strangling grip of sucker tentacles or be eaten alive.
Hazards of Maturity.
Those bass that eventually reach an age of one year will continue to grow, and throughout this period they will remain in shoals. In fact they tend to remain in shoals until they, too, become mature at an age of five or six years.
It is during this period that they meet, for the first time, the attack of shark and dogfish, porpoise and dolphin; whilst in our river estuaries they are in constant danger of being enmeshed in the seiner's salmon net or killed by the insidious pollution stream from factory and works.
Once back in the open sea there is the seal to contend with, and the steady drag of the trawl's headrope passes unseen—and the fish end in the cod-end of the trawl.
And anglers? They, too, help to reduce their numbers, whilst parasites penetrate their gills, and bore into their living flesh to suck life surely and irrevocably from their growing bodies.
[p245] As the years pass slowly by, a few of the remainder continue to grow, escaping attack and imminent death around each and every turn of rock.
The Life Cycle Complete.
Finally, thirty years after its egg was sparkled into growth, the final product measures 30 in. in length and weighs around 15 lb. As the years roll on, old age will finally exert its influence, and the body organs, exhausted, will cease to drive the bass to further effort.
Dying, its body falls slowly to the sea bed, where decay releases the minerals the fish had taken from the sea, and gives them back to foster the growth of new life in a world of water dispassionate in the extreme.
The greatest building is made from small bricks, and in the sea the same is true. If we take a porpoise at the culminating point, we must start with microscopic life to account for its presence (Fig. 5).
In the individual drops that make the vast oceans live the micro-vegetation on which the smaller creatures browse. The amphipod feeds on these small plants and in turn the mackerel will feed on amphipods.
Whitebait and sand-eel depend for their growth upon copepods and small plants and thus it is that the foundation of the food-chain is laid.
In the summer sunlight the inshore waters warm up, and large quantities of seaweed decay on the beaches. As the tide rises this weed is taken into the water, where the mineral salts are released back into the sea. As a direct outcome of this the micro-vegetation at once begins to increase, and this in turn provides rich feeding for amphipod and copepod.
Quickly the numbers of these rise, until the water along the shore often swarms with their microscopic bodies. Then the sand-eels and brit come to feed amongst them, weaving their shoals along harbourside and pier, and among the weed-covered rock pools under the cliffs.
Hungry mackerel, ever on the search for active food, find rich reward as they hurtle their bodies through these dense shoals, whilst a little farther out the porpoise and spur-dog lie in wait for the mackerel.
Thus it would appear that the porpoise is the end-product of the food-chain in this particular example, and in one way this is perfectly true. For the day will come when even the porpoise dies and its decaying body will return to the sea the same minerals that have been taken from it, and these will then give fresh food to the micro-vegetation.
Perhaps in no other habitat is life so dependent upon the continual feeding of its inhabitants, and the foundation of it all is the rich water of the sea itself.
The sea provides all. The sea demands and takes all.
In return, it gives brief life to an enormous variety of living things.
It is perhaps permissible to conclude that the smallest act of careless destruction on the part of the angler will have its effect.
[p246] The rocks turned upside down, leaving exposed the life beneath to the drying wind and sun; the excessive number of worms collected that resulted in so many being thrown back, dead; the crime of jagging mullet shoals with treble hooks.
No doubt other instances will occur to the reader, and he may well wonder if it matters. Of course it matters. Life in the sea, however small, is a link in the chain that stretches from plankton to specimen fish.