Hatching A Plan For The Moyola
By Michael Mc Glade
There are few bigger contrasts in nature than the feeble struggles of a newly hatched alevin to the powerful surges over waterfalls of the adult salmon which they will one day become. While the Moyola has few of the spectacular cascades seen in Alaska, the river presents a whole range of man-made obstacles, to which our Atlantic salmon have had to adjust their tactics. But every year, a few dozen of these returning voyagers are plucked unceremoniously, for the purposes of the club-run hatchery.
For the club volunteers who risk the turbulent autumnal waters of the Moyola, this is where the hatchery process starts. After a season of pursuing these magnificent fish, the anglers of the Moyola turn their attentions to preserving the salmon. This may seem paradoxical, even a little hypocritical, but the vast majority of these volunteers are strictly catch and release anglers.
Moyola anglers preparing to electro-fish the River Moyola
Many of the salmon are taken from the weir in the Moyola estate, where fish heavy with eggs, struggle in vain to surmount this daunting dam. We wait with nets, stalking the fish as they sit almost motionless on the concrete sill of the weir. The fish are simply scooped into the nets, placed in carp sacks and transported in an aerated tank to the hatchery high in the Sperrin Mountains. But there is nothing simple about it.
The Moyola Hatchery, which is situated above Draperstown at Cahore
Salmon remain a formidable opponent even when stranded on such an unnatural environment as the weir. Nets flail against the dangerous current, and at the first sign of danger and with one flash of their powerful tails the fish disappear in a flash to the depths of the pool below. Another method, which we use is the more conventional electro-fishing, which we regard as “legalised poaching”. Sharp electric currents emitted into the water, paralyse the fish momentarily, giving us the chance to net them. But as ever, the salmon have other ideas, and many escape. They are simply too quick.
Dollaghan taken from the weir on the Moyola estate.
For all those “local experts” who believe they know the best pools for salmon and their behaviour, electro-fishing has often proved them wrong. The only thing that remains constant about Moyola salmon is their unpredictability. Some years we may find large numbers of fish congregated in small pools in the upper reaches of the river, the next year, fish are dispersed across miles of the lower river. There are no set rules to electro-fishing, especially as the river is often in flood as winter descends.
Ideally, we would like to have around 30 hen salmon each year for brood stock, again, this varies wildly. Once the salmon are safe in the deep tanks of the hatchery, the real work begins. One of the big challenges is to keep the fish free from disease, and for this reason the fish are lifted from the river close to spawning. To avoid stressing the fish, they are normally checked only once a week, to ascertain their readiness. It doesn’t take an expert to know if a fish is ready, the eggs should simply pour from the hen.
Eyed Salmon Eggs from the River Moyola
The eggs are collected in a bowl, and a cock salmon is selected for fertilising. With the main ingredients together, the last and most important component is added – water of course. A quick swirl of the bowl, and the simple process is complete. We now have our treasured fertilised salmon eggs. One of the biggest challenges we face is the dramatic drop in water temperature at the hatchery. Trying to hold a salmon that has been sitting in water at just three degrees, is painful and difficult. Unlike, the wily human species, the salmon gestation period is determined by temperature. By that, we mean that if we have an average water temperature of 6 degrees for 100 days the eggs will hatch, but if the average temperature is just 3 degrees, then the period of time will be twice as long. That’s the science part over, well nearly.
Salmon eggs in the process of hatching.
Throughout this gestation period salmon eggs die of natural causes, it’s only to be expected, as each fish can produce over 800 eggs per pound, so there’s bound to be the odd casualty. The hatchery is manned on a daily rota, with dead eggs removed and temperatures recorded. Again, it’s hard to predict when the eggs will hatch, but on the Moyola it is generally from April onwards, with the bulk of the hatching taking place over a few shorts days.
Two day old salmon alevin in the Moyola hatchery
And so we have the struggling Alevin, congregated in an almost lifeless mass at the bottom of the tanks. For the next six to eight weeks, these little fish feed off their yolk sacs. Gradually, recognisable features begin to develop, a faint outline of a tail, microscopic fins and finally a firmer outer skin. With their yolk sacs all but absorbed, the alevin have graduated to the “fry” stage. Driven by nature and hunger of course, the rapidly morphing fish begin to rise to the surface of the water in the tanks. This is the signal for the amateurish and still vulnerable fish to be stocked into the river.