Is this a sea trout?

[Steve Walker]

The material laid down in the otoliths of the fish reflects the elemental composition of the water the fish is living in, and is left as a permanent record. The ratio of strontium to calcium is markedly different in material laid down while the fish is in freshwater or salt. So you grind it down to a section through the core (like a slice through a tree) then you scan a line from the core to the edge, either using a laser to vapourise and then analyse tiny bits of the material or by looking at the spectra of x-rays backscattered from the electron beam (if you can't afford the laser ablation tech). By mapping the Sr:Ca ratio along the transect and correlating it to the periodic banding in the structure which can be used to age the fish, you can work out when it ran to sea and when it came back.

[chesters1]

The material laid down in the otoliths of the fish reflects the elemental composition of the water the fish is living in, and is left as a permanent record. The ratio of strontium to calcium is markedly different in material laid down while the fish is in freshwater or salt. So you grind it down to a section through the core (like a slice through a tree) then you scan a line from the core to the edge, either using a laser to vapourise and then analyse tiny bits of the material or by looking at the spectra of x-rays backscattered from the electron beam (if you can't afford the laser ablation tech). By mapping the Sr:Ca ratio along the transect and correlating it to the periodic banding in the structure which can be used to age the fish, you can work out when it ran to sea and when it came back.

Thats where i have going wrong i went from the edge to the core DOH ,the results always said it was martian

[Anderoo]

Cheers Steve, I'm kicking myself now for not thinking of that

 

I think I'll go with a slightly more American approach - if it looks like a duck and walks like a duck, it's a sea trout

Edited March 15, 2015 by Anderoo

[ayjay]

The simplest method on the bank is that you cant *tail* a Sea Trout - run your hand (fingers closed into a circle around the fish) down the back end of the body and onto the tail, if the tail folds down it's a Sea Trout, a Salmon's tail wont fold down.

[Vagabond]

Deciding Anderoo's fish was not a salmon was the easy bit.

 

The hard bit is deciding whether it's been to sea or not. But read Steve Walker's post and then wonder why there are so many "experts" who claim to be able to tell at a glance.

[Phone]

Anderoo,

 

I'll throw my thoughts into the mix. I have never seen a sea trout with spots below the lateral line. I believe that fish is a hybrid. Some offspring of two steelhead can stay in freshwater and be resident trout, and two offspring of resident rainbow trout can create a steelhead.

 

Phone

(I don't know if your "trout" or "sea trout" are the same as ours)

[Mark Wintle]

There do seem to be 'silvery' trout caught in the Thames in winter that are claimed as seatrout. I fish the tidal Frome so catching trout is commonplace in winter. Some are brown trout that drop down, others are estuarine 'slob' trout and others are true seatrout. Usually the true seatrout have a lilac sheen when viewed in the right light that the brown/estuarine trout lack. Whether there is a seatrout run going up the Thames well over 100 miles from the sea is hard to tell. Certainly seatrout migrate up some of the Stour tributaries to spawn around Christmas and are a long way from the sea but more like 30 miles. The problem with brown/seatrout is that they are all one species that don't breed true in that 5% or whatever of the progeny of seatrout will be non-migratory and vice versa for brown trout, a survival strategy to repopulate rivers otherwise wiped out by natural events, and a similar strategy exists for rainbow trout in west coast America. I have had arguments with senior EA officials arguing that a migratory trout license is a legal non-starter as the only test they could prescribe was the one described above re radioactive elements acquired through sea feeding and as such impossible for an angler to comply with! They don't like losing the argument! Part of the problem is that many strains of trout have been stocked into English rivers over the centuries so true native trout may be rarer than ought to be the case, and this explains some variance with 'spotting' patterns..

[Phone]

All,

 

Seems to me, based on this discussion, if it is caught in fresh water it is a trout - brackish water questionable - in the sea it is a salmon. Other than for personal edification is there a reason one needs to know?

 

Phone

[Vagabond]

........a migratory trout license is a legal non-starter as the only test they could prescribe was the one described above re radioactive elements acquired through sea feeding and as such impossible for an angler to comply with!

 

They don't like losing the argument! Part of the problem is that many strains of trout have been stocked into English rivers over the centuries so true native trout may be rarer than ought to be the case, and this explains some variance with 'spotting' patterns..

Absolutely - that is what I was implying in post #15

 

No matter how many generalisations about trout might be true 90% of the time, the next fish you catch can be an enigma.

 

I know a spot on the coast where you can catch red-spotted brownies (and yes they have black spots also) in the harbour at low tide, but they retreat up the river at high water.

 

On the legal front. A judge/magistrate will always believe an EA-backed bailiff, so do as I do. The only way to be fire-proof (bailiff-wise) is always to buy a seatrout/salmon licence. Arguments re "seatrout or brown trout" are then academic.

[Vagabond]

I have never seen a sea trout with spots below the lateral line.

LOL Most European seatrout catchers have never seen one without !!!

 

What Americans call "seatrout" are not even salmonids, but are croakers (aka drums) The only British fish of that group is the Meagre, although several species of croakers/drums are well known to both American and Australian sea anglers.

 

I used to catch American "seatrout" on the Texas coast - they called them "weakfish" there, as they easily tore free from the hook

 

PS Just checked my log - two species - Sand seatrout Umbrina coroides and Spotted seatrout Equetus punctatus

Edited March 15, 2015 by Vagabond