'Blow the wind Southerly.'
ON TIDES AND WEATHER
The tides, the weather, and the manner in which these effect the sea are crucial to understanding the behaviour and feeding patterns of sea fishes.
The tides are due to a double bulge of water, on either side of the earth, caused by the attraction of the moon. If the moon was stationary in relation to the rotation of the earth, each coastal point on the earth's surface would experience high and low tides exactly twice in a twenty-four hour day. Because the moon is not fixed, the tides are later by about forty minutes each day. The obstruction of continents and landmasses greatly alters the height and patterns of the tides.
Every two weeks, when the sun's attraction reinforces that of the moon, high water is exceptionally high and low water is exceptionally low; these are the spring tides. Alternating with the spring tides are the neap tides, which have a much smaller range. The biggest spring tides occur a couple of days after the full or new moon, and on a particular stretch of coast they fall at approximately the same time of day. For example, on one of the beaches which we fish for bass, high water of the biggest spring tides is between 8 and 10 p.m. or just before dusk on a summer's evening.
As the earth rotates, the high water bulges (high tides) move from place to place; for instance, in the English Channel the high tide takes about six hours to advance from Plymouth to Dover. Due to the spin of the earth the English Channel water is flung towards the coast of France and so the tides are much higher (and lower) on the French coast than on the opposite English coast.
The sequences of high and low waters or spring and neap tides are factors of vital importance to the lives of fishes. From the anglers point of view the indirect effects of the tidal rhythms are the most important because many of the creatures on which the fish feed depend on the tides for timing their day-to-day lives.
Between the tides marks, the breeding, feeding and migration activities of many worms, crabs, shrimps and prawns are often only possible when the tide is in. Even more striking is the way in which mass movements, which render the animals vulnerable to the fishes that eat them, take place on only tides of a certain height, or even only on a few well-defined tides each year. It is at these times that bait organisms are most easily collected and most effective as bait.
The results of these tidal forces are profound and differ from one area to another with the complicated nature of the tidal standing wave and the earth's rotation. In the Poole and Swanage area, where we fish, the range of the tides is very small with an average rise and fall of only about three feet. In fact, if the sea level was just a little higher and the sea thus extended a little further to the region of Corfe Castle a few miles inland of Swanage, there would be virtually no tides at this point (Global warming and rising sea levels may soon prove the point).
Because of the small tidal range, bait collecting or digging may at times be practically impossible. Early in our experience of local conditions we organised a Boxing Day expedition to fish the Chesil Beach for cod. The idea was to dig for worms on the mudflats of Poole Harbour just before lunch. The tide tables indicated low water (neap tides) at about lunchtime. We arrived, complete with digging forks and plastic buckets, at about 10 a.m. The tide was still well in when we arrived but it was a crisp, sunny morning so we sat on the turf just above the high water mark and waited for the ebb to reveal the work beds, still under eighteen inches of water.
The minutes ticked by with no discernable change in water level. Midday came and went. Perhaps we had misread the tables, surely now the water level would fall, but no! The sea level remained on the upper shore. It was only after four hours of progressively dwindling hope that we got the message and set off for the west, baitless apart from two semi-decomposed squid. We later realised that the strong east wind blowing into Poole Harbour mouth had virtually cancelled out the effects of the weak ebb.
Driving along the promenade at Weymouth it was obvious that not only were there a few acres of (rather sparse) lugworm beds exposed but the recent storms had cast up enormous quantities of weed and rubbish. We parked the car and in twenty minutes were able to dig enough lugworm and collect enough slipper limpets and spiny cockles to last the entire trip. The subsequent fishing was more or less uneventful, except that as the temperature fell at dusk we had to thaw out the slipper limpets before we could remove them from their shells. Numerous pouting and poor cod plus a single small codling of about 5 pounds were the ultimate results of our ordeal.
Distortion of the advancing tidal bulge, by local conditions, may have other effects on the pattern of tides. In our area there is a two-hour delay in the time of high water over just a few miles of coastline. At Poole there is a well-marked double high water. The second high tide is the biggest on the neap tides and the first is biggest on the spring tides. At Weymouth, along the coast to the west, there is a double low water.
Another very important effect of the rise and fall of the tide is the creation of strong water currents, almost like rivers flowing within the sea. In coastal regions the main flow will generally be parallel to the trend of the shoreline. The direction of flow will usually reverse on the turn of the tide. As in a river, there will be swirls and eddies in bays and around promontories. Since the tide is rising (or falling) most quickly midway between high and low water, it is at these times that the tidal current will be strongest.
The most obvious difficulty with tidal currents, as far as angling is concerned, is trying to 'hold bottom' with either your tackle or the anchor of the boat. The usual means of combating strong currents are to use wire lines (nowadays braid), fancy leads, to fish on the drift, and so on, and they are dealt with at length in other books on angling. Our only contribution to this aspect of the tides is in the use of self-diving spinning lures. It is often more satisfactory to use a plug which will fish deeper and better in a strong flow than to add lead to some other form of lure.
From the boat angler's point of view, one of the most interesting effects of tidal currents is the creation of banks. These huge mounds of grit and shell are favoured by some of the more popular fish species, notably turbot and bass. There are several well-known banks of this type around our coasts and no doubt there are many others still unfished. By chance, the formation of such marks has been studied in detail on the Shambles Bank, a well-known turbot ground off Portland on the Dorset coast. The presence and the position of banks has been shown to be predictable from the directions of the prevailing currents and the geography of the nearby coastline.
Headlands, sticking out into the sea, cause different patterns of flow on the flood and the ebb tides. In the huge `eddies' which result, great masses of coarse sand are dumped on the seabed. All the finer material is winnowed away by the strong currents and the remaining fragments of shell and gravel are sculptured into giant ripple marks. These are enormous replicas of the ripple marks that we see on the beach and perhaps they can best be visualised as underwater sand dunes. It is in the lee of these dunes that fish like turbot await their prey.
The largest and best known of such fishing grounds are household names, like the Shambles off Portland and the Skerries off Start Point in Devon. What is less well known is the fact that small banks occur more or less as mirror images of the main ones on the opposite sides of the promontories. There must also be many other peninsulas projecting out into the tidal flow where similar, if lesser, banks have formed and good fishing potential is untapped. Elongated islands, such as Lundy Island in the Bristol Channel, which lie across the main flow will, of course, create four `eddies' and banks - two at either end.
The wind blowing over the sea's surface also creates currents of water but these are of much less importance than the tidal currents. In general, an onshore wind piles up the surface water close to the beach and the result is an undercurrent flowing away from the shore. Offshore winds have the reverse effect and this can be important in pushing surface-drifting food beyond easy casting range.
A much more important effect of the wind from the angler's point of view is the creation of waves. The height of waves depends on the distance for which a wind has blown over the sea surface (known as the fetch of the wind). Roughly, a strong wind blowing across four miles of sea surface will build up waves of about three feet high.
The active depth of waves (the depth at which they can effectively stir up the sea bed) is roughly half the distance between successive waves. Waves breaking along the shoreline are called plunging waves and are caused by the waves 'feeling the bottom' in shallowing water. The other thing that happens to waves as they approach the shoreline is that they tend to slow down and the distance between them becomes less. However, the height of the waves is not much affected so they become steeper and the tops slide or spill off.
It follows from all this that only along the waterline, or in fairly shallow water, will waves stir up the sea bed to any appreciable extent, even in fierce storms. It is this stirring up which is responsible for uprooting vast amounts of seaweed and for dislodging clinging, hiding or burrowing animals from the sea bed. Under these circumstances fish will often feed avidly on dead or damaged creatures and it is during the period of declining seas, after storms, that good catches will often be made by bottom fishing with bait in inshore waters.
Since storms are more frequent in late autumn and winter it is essential to take advantage of such events if the best catches are to be made. Cod, conger, bass and large pollack are among the species most susceptible to the beach or dinghy fisherman during these `falling sea' periods. An oily swell, turbid dirty water and heaps of freshly deposited weed along the tideline are indications of good conditions. Fish normally caught at night may be found feeding actively in the daytime during such periods.
The combined effects of winds, tides and coastal geography are to sort out water-borne materials into masses and to deposit them in characteristic places along the shoreline.
Only local scrutiny will pinpoint these dumping grounds or middens, but generally the greatest quantities of debris will be found in corners of deep embayments fully exposed to the prevailing winds. Lesser accumulations will be found in lee corners. Surprisingly large amounts of deposited weed can be eroded and removed in a single tide if conditions are suitable, so only by frequent visits to the beach is it possible to keep track of the situation.