Wee skinny Grilse and late Grilse

[rpsalmon]

When salmon parr leave their rivers they will generally move in shoals (not necessarily made up of all salmon parr) within the ocean currents looking for feed, which they will generally try to follow until the food is exhausted or dissipates, then they will look for other sources of food. Those that don't find sufficient food will find themselves at the bottom of the food chain. I doubt the salmon has a homing instinct that compels it to go to Greenland or the Faroes, they just end up there because they are on the currents where food is. This shoaling instinct of salmon, largely for protection, will continue all the way back to the spawning areas in some cases. Whether the salmon end up near Greenland, Iceland, Faroes waters or just generally roam around the North Sea/Atlantic, and while it depends on ocean current speeds, they can travel back at speeds of up to 40 miles per day (possibly faster) but normally I think it averages 15 miles per day. Irrespective of their speed back, they do not necessarily swim directly to their home river. While salmon/grilse on some northern rivers find their home rivers quite quickly on the sea currents, for most east and west coast rivers the salmon will approach from the sea and then work their way up/down the coast to find their river. If there is flood water coming out into the sea then they have a hgher chance of being attracted in. A number of fish will make mistakes and swim into estuaries and actually into rivers before finding out they have made a mistake, and go back out to sea. Fortunately, or unfortunately!?, most salmon manage to find their own river.

But what we have this year is the salmon failing to arrive in quantity to the various river systems throughout the part of the hemisphere they inhabit. There are some fish that appear perfectly fit and in an appropriate condition for their size, but still an increasing number of undersized fish or fish that are skinny and have clearly suffered a lack of food in the sea. I have heard of a number of runs of fish, in various rivers, that are expected at certain times and these have turned up within a fortnight of their expected times, but these tend to be big fish and can’t help but wonder if these fish are from Greenland where as most of our fish tend to populate the Faroes area. With scientific evidence showing a continued trend of undernourished and undersized salmon, during the last 10 years, I have to wonder whether there has been a crash in population this year (around the Faroes?).

Does anyone have any contacts on the trawler boats who could shed some light on the state/changes in this years shrimp/plankton/fish/water temperatures in our northern climes?

I have just been informed that Iceland has had good numbers of salmon running their rivers, while I don't know where the Icelandic fish feed I should imagine it must be around their coast & the Faroes, in this case the numbers of Icelandic salmon would suggest there hasn't been a crash in stocks. If not then what has happened to ours?

[tweedsider]

Hello bagoworms Many anglers lay the blame of thin grilse on the door of industrial fishing. As far as my knowledge goes industrial fishing for sandeels in the North Sea is at the moment banned. I have it on good authority that two Eyemouth boats working for whitefish some distance off Eyemouth observed three Danish boats trawling for sandeels. Eventually their calls ashore were transferred to London where some desk bound orifice informed them that the Danes were, 'sandeel fishing for scientific purposes'. I think it says that the British governement does not give a hoot about any form of fishing, be it for gain or pleasure, as lone as they are oiling their sticky little palms at the expense of others the politicians and officials are content to allow our,'fellow europeans' to do as they will to our heritage.

[victorclem]

Does anyone know if later spawned eggs hatch out later than earlier ones, or if they all hatch out at the same time when the water temperature reaches the correct level?

ie Does it matter if salmon spawn later?

VC

[rpsalmon]

Generally the earlier an egg is fertilised the earlier it hatches. A period of near freezing water (1 Centigrade) can delay the hatching of an egg and a period of less cold water (say 7 or 8 Centigrade) can shorted the hatching process. Average time to hatching is around 90 days but it depends on timing of eggs being buried & average water temperature, I've heard of 120 days and wouldn't be surprised if there were longer hatching periods. If salmon spawn later, like February on the Ness and other rivers, there will be lower survival rates if the water temperature gets too high.

[builnacraig]

rpsalmon said:

Generally the earlier an egg is fertilised the earlier it hatches. A period of near freezing water (1 Centigrade) can delay the hatching of an egg and a period of less cold water (say 7 or 8 Centigrade) can shorted the hatching process. Average time to hatching is around 90 days but it depends on timing of eggs being buried & average water temperature, I've heard of 120 days and wouldn't be surprised if there were longer hatching periods. If salmon spawn later, like February on the Ness and other rivers, there will be lower survival rates if the water temperature gets too high.

Egg development is largely controlled by temperature. Salmon eggs take about 450 degrees C days to hatch e.g. (45 days at 10 degrees C or 90 days at 5 degrees C). Then it takes about another 350 degree days for the yolk sac to be absorbed and it is ready to emerge from the gravel to feed. Salmon in the Girnock Burn on the River Dee may spawn in late Oct whilst in a southern chalkstream salmon may spawn in Jan but the chalkstream eggs are likely to hatch sooner due to the high mean temperature.
River Ness is supplied by the largest body of freshwater in Scotland, which means that the temperature will be very stable. Even in May the temperatures in the River Ness are unlikely to be high enough to cause developing salmon any problems.

[paulsewin]

builnacraig said:

rpsalmon said:

Egg development is largely controlled by temperature. Salmon eggs take about 450 degrees C days to hatch e.g. (45 days at 10 degrees C or 90 days at 5 degrees C). Then it takes about another 350 degree days for the yolk sac to be absorbed and it is ready to emerge from the gravel to feed.

Absolutely fascinating fact, thank you so much for sharing that. Do you mind saying where you got the information?

I'm a little bit reluctant to say too much because of the reference to Girnock burn. If I'm correct either you have read that excellent book by Alan Youngson and David Hay, The lives of salmon or you know those gentlemen, possibly in a professional capacity.

One of the many things I found so fascinating was the observation that springers spawned first, but higher up the burn. The reason they could do this was that the average temperature of the water was lower and therefore the eggs took longer to hatch. How a springer could know how far it needed to go up a burn, in order to ensure its offspring would not be disadvantaged by hatching too late is truly astonishing.

Returning to the skinny grilse something does seem tpo have changed. In small relatively infertile lochs and streams where food is scarce, even very small trout may be very old. However, they always seem to be in proportion.

The fact that grilse have attained a certain length suggests that the feeding was good enough to enable them to grow to that size. So what has happened? It seems to be fairly obvious that during their return to the rivers they have now used up more energy than they have been able to replace on the journey.

There are two likely explanations for this. Either they are having to travel further to their feeding grounds and now face a longer return journey or the food sources that used to sustain them on the return journey are no longer there. It could, and probably is, a combination of the two.

[builnacraig]

paulsewin said:

builnacraig said:

rpsalmon said:

Egg development is largely controlled by temperature. Salmon eggs take about 450 degrees C days to hatch e.g. (45 days at 10 degrees C or 90 days at 5 degrees C). Then it takes about another 350 degree days for the yolk sac to be absorbed and it is ready to emerge from the gravel to feed.

Absolutely fascinating fact, thank you so much for sharing that. Do you mind saying where you got the information?

Returning to the skinny grilse something does seem tpo have changed. In small relatively infertile lochs and streams where food is scarce, even very small trout may be very old. However, they always seem to be in proportion.

The fact that grilse have attained a certain length suggests that the feeding was good enough to enable them to grow to that size. So what has happened? It seems to be fairly obvious that during their return to the rivers they have now used up more energy than they have been able to replace on the journey.

For my sins I know a bit about fish farming!

Do you think that wee trout from feeding poor waters are always in proportion? The very small ones often are but I find that those that have started to spawn are often relatively thin as they don't have enough feeding to restore condition before the next spawning season.

Another thing I learn't about salmon is that they continue to lengthen even though they are not feeding. So a non feeding fish soon appears proportionally long for its length. Mind you that was in the sea when it was still in feeding mode, it may not apply in freshwater where it naturally stops feeding.

[rpsalmon]

Dear builnacraig

Would I be correct in thinking your rough “450 degree days” come from the Drummond figures based upon artificial propagation?

My figures were for those eggs in the wild. When you have fish spawning in February, in many rivers, they will face higher temperatures at an earlier age than they would if the spawning had taken place in November. While it is a little generalisation, any increase in temperature over the "norm" increases the problems for vulnerable ova/alevin and decreases the survival rates.

[builnacraig]

rpsalmon said:

Dear builnacraig

My figures were for those eggs in the wild. When you have fish spawning in February, in many rivers, they will face higher temperatures at an earlier age than they would if the spawning had taken place in November. While it is a little generalisation, any increase in temperature over the "norm" increases the problems for vulnerable ova/alevin and decreases the survival rates.

Of course the figures are based on those learn't from artificial propagation, and the total degree days will vary slightly with the temperature experienced but as a general guide it will apply in the wild as well.

A fish farmer will always keep his incubating ova below 8oC until almost ready for feeding otherwise the incidence of deformed fish increases. I have heard it said that the early phase of incubation should occur at the lowest temperatures, i.e. taking a long time, to produce the best alevins. A shift in seasonal temperatures may cause problems for fish like salmon, but on the other hand they have been spawning in our rivers for a long time and they have proved to be a very adaptable fish which can live in a variety of conditions.

[paulsewin]

builnacraig said:

Do you think that wee trout from feeding poor waters are always in proportion? The very small ones often are but I find that those that have started to spawn are often relatively thin as they don't have enough feeding to restore condition before the next spawning season.

Another thing I learn't about salmon is that they continue to lengthen even though they are not feeding. So a non feeding fish soon appears proportionally long for its length.

Point about the trout well made. I hadn't even considered spawning trout when I posted.

Again. very interesting that fish continue to lengthen when not feeding. Maybe a silly question, a sort of chicken and egg, but in general. do salmon lengthen and fill out, rather as we humans, or do they fill out and then lengthen or is the process usually in proportion?

Your comments on egg propagation make it all the more amazing that salmon somehow manage to achieve the corect balance, most of the time, without reference to any of the careful monitoring that fish farmers will have to use.

[rpsalmon]

Salmon don't achieve a correct balance, the eggs either develop in an acceptable environment/temperature in which case they most likely survive, or they don't develop in a suitable environment/temperature and are less likely to survive.

[builnacraig]

paulsewin said:

builnacraig said:

Another thing I learn't about salmon is that they continue to lengthen even though they are not feeding. So a non feeding fish soon appears proportionally long for its length.

What I should have said of course is that a non-feeding fish soon appears proportionally long for it's weight!

In the salmon cages the fish seemed to lengthen, even if conditions weren't favourable for feeding or no feed was available. That makes sense as in a wild situation if feeding conditions improved they would be capable of producing muscle and fat quickly whereas bone growth may be a slower process, allowing them to maximise good feeding opportunities.

[builnacraig]

rpsalmon said:

Salmon don't achieve a correct balance, the eggs either develop in an acceptable environment/temperature in which case they most likely survive, or they don't develop in a suitable environment/temperature and are less likely to survive.

Evolution summed up in one sentence!

[salmonking]

Here is food for thought,,,,,these grilse in the 2lbs bracket,
couldn't they be of a similar strain of finnock as in sea trout
but in the salmon variety?
Due to climate change and feeding habits and all sorts of other
changes,does anybody know if these fish actually spawn and reproduce?
Just a thought.

[hornet]

Good question SK but un fortunately i have no idea .

I had a cracking 4lb Grilse yesterday ;D on the Feugh which was in great nick. Not skinny at all.

The Grilse i have caught this year have all been in good nick and bars of silver .


Hornet

[salmonking]

Well done Hornet ,i got 2 on fri,1 a similar fish as yours ,another one of these small smolty types .

[rpsalmon]

There are different strains of salmon/grilse within the same river that smolt at different times, often largely shoal in their strains, even feed in the same areas and even running the river together. Unless the fish are sufficiently different as in size then I don't think you could generally fish for them separately on a practical level. However, the forum member called "minitube" has outlined a scenario of River and Lake Grilse on the Moy, with differing original environments it wouldn't be extraordinary to think that these fishes instincts would be slightly different and that maybe this results in the differing strains of Grilse being stronger/weaker and occupying slightly different parts of the pool or even the river grilse being more inclined to chase a fly.