Fishing in Estuaries

Estuary mouth at low tide. Casuarina Coastal R...
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Whether you are fishing from the shore or from a small boat, the varied estuaries around the coasts of Britain will provide good sport if you know where to find the fish you want.

An estuary is the tidal mouth of a river. There are various kinds of estuary – from the huge open delta, where a broad, slow flowing river runs into a shallow sea area, to the narrow, deep river that rushes to the sea through high cliffs or a steep valley. All types of estuary are interesting to the sea angler.

The ideal fishing estuary

Probably the best fishing location is a wide estuary between sandbanks. Here the downstream flow of freshwater is gentle, and the effect of tide streams is diminished because of the lessening of water pressures within the wide expanse. This type of estuary has shallow water with a gentle water flow, and usually, but not always, linked. For example, it is possible for an estuary to have fish-holding areas, but tidal conditions that prevent the fish from feeding during most of the tidal phase. Alternatively, the fish may be present, but sandbanks or spits of land can prevent the angler from reaching them.

When freshwater enters the sea it alters the normal coastal run of tide and current and so modifies the seabed. This, together with the dilution of the saltwater, means that the ecology of an estuary may be markedly different from that of the nearby coast.

You can expect both good planktonic growth and a wide variety of invertebrates, such as worms, shellfish and crabs. Bass, pollack, flounder, flatfish, small skates and monkfish feed on these invertebrates, while mullet feed on both zoo- and phytoplankton.

One type of wide estuary differs slightly from this pattern. This is where a river originally emptied across a flat and shallow, expanse, but in time, a reduction in the rate of flow caused channels to form. These gradually divided the estuary into a series of independent outfalls that grew deeper and faster in flow.

At low tide, such a location presents an angling problem. The channels are difficult to reach because of the deep cut waterways, and as the flow of freshwater in the channels is swift, they have little food content. Fish only nose into these channels at flood time – and possibly only the top of the tide will find fish moving from the channels on to the surrounding flat sand and mud spaces to seek worms that live in areas adjacent to slackish water.

Estuary of Klamath River in Redwood National P...
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The shore fisherman has difficulty fishing this type of estuary – but the inshore dinghy angler can take ad-vantage of the unique possibilities.

The freshwater slows as it meets the pressure of saltwater, and fish feed on the food swept down in the rush of the river. Here, bass, dogfish and flounder predominate, but tope are also present – though not so much through interest in waterborne food swept down on the current as in the opportunity to feed upon smaller species that gather for the food expected on each tide.

Food in deep, narrow estuaries In deep, narrow estuaries you find a different ecological system. The small ragworms of the sandy areas are gone, and fish food is confined to molluscs and small crustaceans, such as shrimps and small, soft-shelled crabs. Hard-shelled creatures are also expected – limpets, barnacles and mussels, attached to rock faces and pier and landing stage supports, where they escape the influence of freshwater.

Only fish that can combat a constant speed in the current can survive this type of habitat. Oddly, in these narrow estuaries, freshwater does not have the same influence as in wider estuaries. Instead, it tends to remain separate from the saline, and the mixing that takes place in wide, shallow estuaries does not occur. You can, therefore, find both freshwater and marine species in the same area of an estuary, swimming at different depths.

Look for signs of garbage or litter. There is little food on the bed of this type of estuary, other than that brought down from the land, but both bass and mullet tolerate a dilution by freshwater, and notorious for scavenging around human habitation where scraps of food may be thrown away.

An estuary mouth and coastal waters, part of a...
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Successful fishing of deepwater estuaries depends on offering a bait that fish expect to find in that environment. Fishbaits such as lasks of mackerel are useful here.

The fjord-type inlet

A variation of the deepwater estuary is found in Scotland and the West Country – the deep fjord-type inlet that has a small amount of freshwater entering constantly. This type of estuary is almost totally saline, so there are more marine fish – pollack, immature coalfish, codling and many species of flatfish. Generally, there is a run of salmon or seatrout to interest predators.

Tides have little effect on this type of habitat, as the water is confined within the fjord. There is usually a healthy growth of vegetation and shellfish on the rocky ground, and a number of species of free-swimming molluscs and crustaceans on or in the sand or mud in the centre of the sea loch. Scallops, for example, are certain to attract a variety of fish species, including bass, pollack, flounder and monkfish.

This form of fishery has another aspect. The edges of the inlet are suitable living places for wrasse during the summer, while conger – generally regarded as bottom-living fish – may also live around the margins, providing the water is reasonably deep. They require little from a habitat other than rocks to provide a hiding place and some-where to feed.

Most fjords are in the west of the British Isles, so warm water fish species predominate. This indicates good summer fishing, but suggests that the fish will depart with the coming of the colder weather. Wrasse, conger, bass, mullet, predatory dogfish, and tope all disappear in late autumn.

In most estuaries there will always be at least two species for most of the year – the freshwater eel and the flounder. Both are always in transit. The eel grows from the elver stage to the silver eel stage in freshwater before departing to breed in the South Atlantic, while the flounder, spawned in deepwater, then moves into the comparative safety of estuaries and sea lochs and sometimes travels even higher up into completely freshwater. In addi-tion, migrating salmon and trout also pass through estuaries.