For one week now we have had a very large, (10 lbs+/- in the old scale) sea trout marauding the Wey just to the north of the concrete bridge. Usually a mere five minutes investing gazing into the murky shallows will result in at least a couple of slow, regal glide-bys or the occasional burst of power chasing prey or seeing off anything elbowing in on 'his' patch. Mullet are chased away and diving tufties given short shrift. Luke and I (while spectacularly failing to film said fish) were treated to a full breach, presumably after nailing some item of prey on the surface or perhaps to dislodge parasitic sea lice.
The fellow in question patrolling his patch. Photo Allan Neilson.
Interestingly migratory sea trout and the purely freshwater brown trout - such a familiar sight in our Dorset chalk streams - are in a sense one and the same sharing the Latin name 'Salmo Trutta'. The sea trout develops salt secreting glands to enable its eventual passage into sea water. A sea trout in salt water is faced with the problem of osmosis causing dehydration and salt loading. In fresh water, the problem is effectively reversed as the water is nearly devoid of salt and therefore the fish has to tackle the problems of salt loss and water loading. These problems (very basically) are tackled by the trout drinking copiously when in saltwater and not at all in fresh water, while peeing virtually continually to prevent it from effectively blowing up.
Added to this an alteration in kidney function and various other physiological quirks enable sea trout to live in both fresh and sea water. Whether the brown to sea trout trigger is environmental or hereditary, (or something entirely different) I haven't a clue but I know a man who will so watch this space. Anyway it is an impressive fish and strangely sedentary, showy and worthy of a five minute gaze beneath the watery sheen.