Multitude of mackerel and their prey come inshore

A DRIFT of sand eels lay across the beach, a silver slick like spilt mercury, or shards of a shattered mirror shining in the early-morning sun.

It’s hard to think of a word other than ‘drift’ to describe their displacement, spread as if carried onto the beach by a wave and then dropped — left stranded. The sand must have been too hard for them to burrow into, otherwise they would have disappeared.

Sand eels have the uncanny ability to submerge themselves in wet sand and burrow through it at speed. Burrowing is usually the prerogative of worms (and, indeed, there are numerous species of burrowing marine worms under our mud flats and beaches) but sand eels are definitely fish, quite pretty fish, full of nutritious oils — which makes them a favoured prey species for almost any larger fish that encounter them.

At this time of year, they are hunted relentless by bass, herring and, especially, by the mackerel which come inshore as the sea warms. A feeding frenzy by mackerel would account for the “drift” of silvery bodies. The mackerel would have chased them into shallow water where, in their panic, they became beached. Their hunters sometimes suffer the same fate; I have found fine mackerel amongst stranded sand eels and sprat.

On our local beach, in certain parts, anglers dig for sand eels. It is fascinating to see how the eels, up to 20cm-long, slip sleek and silvery through the sand even as the diggers throw spadefuls onto the beach. So beautiful and extraordinary are they, that sometimes one cannot but feel sympathy for the eels.

The mackerel (‘the chicken of the sea’, as they are called, thus named, no doubt before the advent of battery chickens) were “in” this week.

They had arrived inshore at last, and high time too; even the angling boats fishing 10 miles out were hooking no mackerel. The water was too cold, the skippers said, but then, suddenly, one afternoon in late June, there was a change.

The first of the Courtmacsherry sea angling boats to dock, had one solitary mackerel amongst the specimen pollock and coalfish. However, the companion boat, docking two hours later, had half a box hopping with mackerel, some of them still twitching and shivering, caught on the last few casts on the way up the bay. A couple of the usual mackerel gourmets were told of the bounty and came down to the pier with their plastic bags. There were barbecues burning in backyards that evening and smoke rising full of the sweet, oily scent of half-barbecued, half-burnt fish.

It is the sand eel shoals and the shoals of Sprattus sprattus (sprat) that draw in the mackerel. The sand eels are thin as a pencil, but flatter, silver and iridescent blue in colour and growing to 20cm., their lower jaw protruding farther than the upper. Their slim shape and small scales enable them to slither through the sandy substrata, disappearing in a blink.

Shimmering shoals can be seen on the surface in summer; white kittiwakes or terns hovering and diving flag their presence. They spend most of the winter buried. An important part of the diet of larger fish such as cod, herring, and mackerel, and of sea birds, especially puffins, when sand eels are scarce, commercial fisheries suffer and seabird colonies decline.

Sprat are small fish whose closest relations are herrings, but there may be also be herring, mackerel and other fry present in the shoals that come inshore in summer, hunting for plankton, embryonic crustaceans (copepods) and fish in the larval stage.

In winter, they migrate to deeper water and spawn several times, with up to 30,000 eggs per female. Shoals number billions. In the Baltic alone, in summer, they can number 300 billion fish. Baltic fishermen harvest 400 thousand tons annually.

Unfortunately, most sprat, sand eel, anchovies, menhaden, capelin etc, harvested internationally go for fish meal to feed farmed fish and chickens. Taking them out of the oceanic food chain, where commercial species rely on them, can result in starving marine fisheries (cod, hake, etc) to feed caged fish and many scientists argue that the return for Homo sapiens would be greater and more secure if the teeming shoals of small fish were left in the sea to feed wild, edible fish.