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TOWARDS LEVEL 2
PROFESSIONAL DEVELOPMENT - MARINE TOPOGRAPHY
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Marine Topography – An Angler’s Perspective
As rivers flow towards the sea, they get to a point where the fresh water from the river begins to mix with the salt water being pushed upstream by the tides, creating brackish water. This last stage of a river’s journey sees the creation of estuaries, which can be good places for fishing though the mix of species is reduced. The closer it gets to the sea, the less the number of freshwater species that are able to stand the increased salinity while the number of anadromous species – fish that can tolerate varying levels of salinity – increases.

Typically, you would see sea trout, eels and salmon able to make the entire journey both down and upstream at different stages of their life cycles while marine species such as thick and thin-lipped grey mullet, flounders, allis and thwaite shad, gilthead bream and bass will penetrate a long ways inland.
Anadromous species will penetrate a long ways inland, like this little school bass being netted and returned some six miles upstream from the coast.
Much of the logic that we have looked at in the upper reaches of rivers applies to estuaries too, with bass in particular taking advantage of any kind of structure that offers them potential ambush points. If they can hide behind something, out of the full force of the current, they will. Only here, instead of the current pushing one way, the tide means that you will have both incoming and, when it turns, outgoing current. You will therefore need to pick your fishing spot on the opposite side of the obstruction towards which the current is flowing.

Sometimes the situation is even more complex. Tides create the largest flow of saltwater, creating estuarine currents. These are denser than freshwater and so sink towards the bottom with their greatest influence found on the estuary floor. However fresh water travelling down from the rivers, especially after periods of heavy rain, create oligohaline (low salinity) anti-estuarine currents which float over the top of polyhaline (salty) estuarine currents and work their maximum influence near the surface.

It is a form of stratification where the determining factor is not the influence of sunlight but rather salt. Estuarine currents made up of polyhaline water operate beneath anti-estuarine currents made up of oligohaline water, half the time moving in opposite directions. Between the two layers is the mesohaline layer, which is determined by a specific salinity range, i.e. between 5 and 18 parts salt to 1000 parts water. By contrast, oligohaline water has a ratio or 0.5 to 5 parts salt to 1000 parts water while polyhaline water contains 17 to 30 parts salt to 1000 parts water.

When a strong Spring tide meets a large body of freshwater moving seawards, it can be quite interesting. At one spot where I fish in the Summer, a mass of floating debris – mostly vegetation – makes its way upriver before pausing, circling and making its way downstream again. Nothing unusual there, you would expect it to go downstream when the tide turns, except that our leger rigs, working beneath the vegetation in the hope of encountering predators hiding underneath it, continue upstream while the vegetation continues downstream. If we put a bubble float in amongst it, in the hope of mullet, the float will go downstream with the vegetation while any leger rigs will continue to go upstream. These conditions vary in length but I have known this situation to continue for up to an hour or so.

Basically what we are seeing here is the interaction between estuarine and anti-estuarine currents. I suppose that it is little wonder that the fishing at such times is usually poor; the salinity levels varying so much from the day before that the anadromous fish travel downstream a ways to keep the salinity levels about themselves as stable as possible. They do, after all, need time to adjust to differing levels of salinity. They cannot cope with massive changes all at once.
 
Time of year impacts upon this situation too. It is much more common in the Winter, with prolonged and heavy rain, than it is in the Summer, when the flow from the river decreases. This is reflected in the fishing, which is great in the Summer, when the water is at its most saline, but often not worth worrying about in the Winter, when salinity levels are at their lowest.

Another factor that makes its presence felt here, as it does in many other estuaries, is the weight of boat traffic. This contributes to the environment in several ways: the central channel becomes deeper, sand or mud banks may develop to the sides of the channel and some of the banks become undercut, all of which features can be exploited by anglers.

Where I live, the undercut banks become places of great interest to species such as mullet, as does the central channel between the sandbanks. On a low Spring tide, it is through such channels that the mullet first nose their way upstream with the incoming tide. I have had some great catches at such times, sometimes when the water level in the channel is as shallow as a couple of feet deep. By contrast, when the tidal strength is at its greatest, either halfway up the tide or halfway down, I have caught numbers of school bass which, like their larger brethren in the sea, take up position near the sandbanks to intercept food at the strongest point of flow.
In the open sea, bass take station behind sandbanks so as to intercept prey species such as sandeels. In the higher reaches of the estuary the food particles will be different but the principle remains the same.
Moving down the estuaries, you will find that, as the nature of the floor changes, so too does the nature of the food supply. Muddy bottoms holding large quantities of small ragworms gradually shift to a mixture of sand and mud, where larger ragworms and lugworms start to mix, before the sand begins to take over completely and lugworms become the dominant species. Meanwhile crabs, especially on a Spring tide, will move inshore as far as the bass range, using the bottom to dig into and hide, often when they are about to shed their shells. Fish are, however, well aware of their presence, which is why peeler crab is such an effective bait in the lower reaches of many estuaries with bass and flounders in particular having a decided fondness for them.

Often you will find that, just outside of estuary mouths, there are large sandbanks which attract huge shoals of sandeels while, inside the mouth, the estuary floor is carpeted with the casts of lugworms and evidence of mussels, clams and cockles in particular. This makes the mouths very productive areas to fish, though they may be impacted strongly upon by the tide, which can make fishing quite interesting.

With the richness of food available at the mouths of estuaries, it is little wonder that good catches of rays can often be made either in, or just round from, estuary mouths while starry smoothounds are often picked up on sandy areas fairly close to them too. Rocky areas can also be productive for bull huss, especially where there is a significant depth of water at the estuary mouth and the bottom is comprised of stone and patches of sand rather than purely sand.
Rocks and rockpools are great food-holding locations, especially for prawns and peeler crabs. You can collect all the bait you need at the low tide and then come back at the high to fish for predators like bass.
Moving on from estuaries to the coast, you will often find that rocky features, be they rockpools at the ends or middles of beaches or set to the sides of piers, harbour walls and rocky headlands, offer anglers the greatest chance of success, the reason being that they are sources of abundant food, attracting predators from far afield whilst also establishing territories for species such as wrasse. Typically, weed covered rocks are home to a variety of shellfish which wrasse, with their pharyngeal jaws, can munch on to their heart’s delight, but they are also home to prawns, several species of crabs and smaller fish seeking shelter from predators. This will draw in pollack and, later in the year, coalfish but will also attract species such as bass and sea trout.

Fishing a float or working light rock fishing tackles through the middle of rocky, weed-covered features can be highly productive but so too – if you are fishing from a beach - can be legering immediately to their side, as long as you have picked the right one to fish. Remember that the tide sweeps along the shore, not straight towards it, and place yourself on the opposite side to the current. This is where predators and opportunist species like gurnards will be waiting in the hope that food species will be wafted out from cover and straight towards their waiting mouths, especially three hours up or down in the tide when the current will be at its strongest.

Where the water is deep enough, especially in regard to piers and headlands, fast moving pelagic species like mackerel and garfish will appear as the tide strengthens, which will generally signal the best tide for fishing with a float.

In between the patches of rocks, the open sand will also draw in a number of species, like flatfish, especially where they are home to shellfish like razorfish, cockles and clams or when they are covered with lugworm beds and the occasional bed of white ragworms. Typically they are also home to shrimps and a number of burrowing crabs, not to mention the shoals of sandeels that will appear from time to time, especially when there is a stream that runs into the sea. Sandeels love to dig into the sand at such places and later, when the tide returns, bass love to welcome them back to the fullness of life in the sea. (I have seen bass hit emerging shoals of sandeels in only six inches of water!) There is plenty of food to be found on a beach but it is often, if not usually, concentrated into hotspots that the fish include in their daily searches for food.

One of the best ways to familiarise yourself with hotspots on the beach is to go down at the bottom of a big Spring tide and walk along the low tide line with a notebook, camera and pen – so long as it is safe to do so, of course. Look for any features that might hold food and make notes of them. If, for example, you find a large patch of lugworms, turn your back to the sea and take a photograph of the area above the high tide line, centring the picture in a direct line to the lugworm bed. This will be far more helpful than memory alone, especially when you come back to fish at the top of the tide and you are trying to place a bait upon the spot that you found. At that point in time, the bed will be completely covered over while the sea itself may seem far more featureless. The photograph will then help you to put your bait in the correct location by enabling you to position yourself in the right place to cast.

This area that we are exploring is known as the littoral or intertidal zone. It is the stretch of beach which lies between the lowest Spring tide and the highest Spring tide, i.e. the area of beach that is uncovered by the receding tide and then covered over again when it returns, and the little bit above that which is rarely covered and known as the splash zone. There is a wealth of life that lives within this zone, from the maggots of the kelp fly that live in rotting seaweed at the top of the zone – the high intertidal or supralittoral zone or even the splash zone where waves have to be driven upwards by a storm – to the usual mix of creatures, like lugworms, that live in the mid-littoral zone. Shellfish like razorfish usually live in the sublittoral zone and are only exposed at the lowest of the spring tides. Find out what lives where and you will be able to target fishing hotspots with a high degree of accuracy.

To find this information, take a fork, a bucket and a tub or two with you when you do your low tide walk. Turn over a bit of sand and you may find that the lugworms share their bed with cockles, gapers (a type of large clam) or even razorfish – usually found beneath a keyhole-shaped slot in the sand – white ragworms, found beneath small round holes and even, on occasion in the Summer, sandeels that have dug in for shelter at the bottom of the tide. Find all of these and the chances are that this could be a very good spot to fish indeed, or at least it could be so long as you fish with the baits that you find there.
   
Bait beds will provide useful information, especially if you record the approximate distance that you will have to cast to reach them and exactly what types of creatures you found there, but they are not the only thing to look out for. I have already mentioned rocky features but also keep a look out for manmade features such as groynes and outflows to carry or divert the waters of an underground stream. These also hold food with crabs, in particular, digging into the sand at their base, especially when they feel the need to peel.

If you have waders, put them on and push a shrimping net in the shallow water next to the beach. This will give you a good idea as to the health of the shrimp population, itself an attractive draw to flatfish such as flounders, which will often patrol the beach very close to the water’s edge, sometimes in very shallow water indeed. It is not uncommon for paddlers to be startled by feeling them swim off rapidly when they accidentally step on them.

You would also do well, if there is a line of groynes to break up the current, to go back at mid tide to have a look at them a little more carefully. Remember that the current flows along the beach, not towards it, so sometimes the sand between two groynes is scoured out by the current, making it a little bit deeper. This can make the area more productive than its neighbours, especially if the current naturally drops food that has, until that point, been swept along in its grip.
   
When you have had your low tide reconnaissance, try to time a second trip at the high tide, especially if there is a bit of a swell running. This is when you are going to use wavecraft to generate some useful information in terms of depth and food-holding locations. Knowledge of how waves behave can be a distinct advantage for anglers. It helps them to identify where there are pits or depressions where the seabed is deeper than its surroundings. This is important because the current will often drop a lot of the food that it is carrying into these depressions, creating a hotspot that will attract more fish.
A basic introduction to wavecraft.
Basically, it works like this. The length of a wave is measured from its front to its back. Let us say that this distance is eight feet. As long as it is travelling over a depth greater than half of its length, i.e. four feet, it will be smooth and rounded. However, when it hits a depth of four feet - half of its length - it will begin to peak. Then, when it hits shallower water still, it will begin to break.
  
In a way, it is like a man running along and then catching his feet and tripping over. When he is running normally, everything is nice and smooth, but then he catches his feet and his head pitches forward while his feet are held back. That is what the sand does to the wave. In deeper water, there is no friction from the sand so the wave is nice and smooth. Then, when the wave meets sand at half of its length, the friction from the sand holds the bottom of the wave back while the top of the wave begins to pitch forward. Shallower water still means that the friction from the sand has even greater effect so the wave breaks.

An angler reading the waves looks out for places where the waves begin to peak and then suddenly smooth out again. It is going over an area of deeper water. When it is past it, it will begin to peak again. There is a spot like this on one of the beaches that I fish fairly regularly, probably being about thirty yards long and extending just as far out to sea. It is particularly good after a storm but not noticeably so after a long period of calm, which makes sense really. The storm churned up a lot of food but then, after it had been eaten, there was not a lot more than its surroundings.
   
If you want to improve your catches from a beach, then first improve your knowledge of the beach itself. If you know what creatures live where, then you can make some pretty intelligent guesses as to what types of fish will come to feed on them. Then, if you use your notebook to record your catches, deliberately fishing at different states of the tide, you will build up a picture of what, where and when to catch, all of which will help you to increase your catches.

It is like the way people always make a beeline for piers, instinctively feeling that the fishing on them will be better than the surrounding beach. That is not always the case though. Sometimes casting from the beach towards the pier will put the angler’s baits into a hotspot of food dropped by the current or shelter provided by the pier itself. It may even access a perfect depth of water for predators like bass. You will just never know until you get out there and give it a try!
TAKE THE ONLINE QUIZ ON LAKES, RIVERS AND SEA TOPOGRAPHY
Module 1: Fish Biology
Module 2: Invasive Species
Module 3: Fish Diseases
Module 4: Topography - Lakes
Rivers
The Sea
Module 5: Angling and Mental Health