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Seabird
19-Aug-08, 20:45
Can anyone throw any light on whats happened to the Mackerel on the East coast of Caithness this year.
The local fishermen are struggling to catch sufficient to freeze for creel pot winter bait.
I did consider it may have been due to the changes to the sewage discharge into the sea that took place last year.
The North coast seem to have a bumper supply of Mackerel and the system was improved
on that coast also.
So i'm puzzled, any ideas or sugestion welcome.

Colin

alcyjohn
19-Aug-08, 21:15
the mackeral dont seem to be seasonal anymore they seemed to have been getting caught of wick most of this year

sprint95m
20-Aug-08, 22:36
I did consider it may have been due to the changes to the sewage discharge into the sea that took place last year.

What are the changes you refer to?

Seabird
20-Aug-08, 23:28
What are the changes you refer to?

Not sure of the technical changes, but i'm sure they were made to improve the sewage outlet systems.
These improvement took place at Lybster, Whaligoe and i think Staxigo.
Thurso had a new system installed.
Wick had an up grade a few years back.
I think it's all to do with compliance with EU water discharge quality.
I'm sure someone will know more about it then i do.
I only mentioned it because it was a change that had taken place, improved discharge would mean a change to what may have been a food source at the bottom end of the food chain.

Colin

sprint95m
23-Aug-08, 19:50
In my opinion, I think the alterations to sewage discharge will have no, or at most only a very minimal, effect on the seasonal migration of mackerel.


I think we have to consider a bigger picture to find an answer.....
Firstly, may I point out that I have no qualifications to offer an answer, only that I have read "The Blue Planet", the book published by the BBC to accompany the TV series of the same name.
The seas and oceans are influenced by the seasons. In the spring, as the water is warmed up and exposed to increasing sunlight there is an algae bloom which supplies the food chain through herbivorous plankton that feed on algae, carnivorous plankton that feed on the herbivorous plankton, fish that feed on the carnivorous plankton and so on and so on. Throughout the summer and into the autumn various nutrients sink to the bottom of the sea. During the winter the surface water cools. Once cooled, it is more dense than the water at the seabed, so it sinks pushing the seabed water (containing the nutrients) upwards to the surface. Come spring the surface water contains the nutrients necessary to allow the all important algae bloom.

The winter of 2006/7 was mild so we had a poor algae bloom with knock on effects for the food chain? Recovery is slow?
I think that (North Sea) mackerel feed on a mixture of carnivorous plankton and small fish (sand eels mostly?) and therefore the mackerel migratory route is dependent on the seasonal algae bloom.
Over the years there are ups and downs with their numbers.

Last year, along the north Sutherland coast, mackerel were scarce. I suspect they were forced north in search of food.

A bit off topic..........
Haddock all but disappeared from this area in the mid 80s but returned about 5 or 7 years ago.



Last year at Longberry by Wick, mackerel were first caught in May which is about two months earlier than normal. They were patchy through the summer but quite numerous again in October. (This observation is hardly scientific!) This year they are quite patchy again.



Anybody else have any thoughts.........

Seabird
24-Aug-08, 00:03
I like the reasoning Sprint, but the winter of 2007 was colder than the the previous 2 winters and this Summer as been somewhat mixed.
With an early warm period that brought the surface temp up to 14-16 degree c at best.
I'm sure you may be barking up the right tree but it's a very complex one.
I think we may require a very big computer to follow through on your reasoning.
But i do like it.
I also like the point put earlier about there being no season any more for Mackerel.
Eggs hatch at certain temperatures.
Also the first laid should be the first to hatch.
But what if in the past because the sea took so long to warm there was a sudden burst of hatching over a short period.
With the sea warming earlier perhaps the eggs are hatching over the time line that they were laid.
Is that a possibility Sprint?

Colin

sprint95m
25-Aug-08, 22:39
I have a reference book, Collins Guide to the SEA FISHES of Britain and North-Western Europe by Bent J. Muus and Preben Dahlstrom.
But first......
I also like the point put earlier about there being no season any more for Mackerel.
I disagree. A few early(April) or late (November) mackerel does not indicate a complete change to their seasonal cycle, in my opinion.

Eggs hatch at certain temperatures.
Also the first laid should be the first to hatch.
But what if in the past because the sea took so long to warm there was a sudden burst of hatching over a short period.
With the sea warming earlier perhaps the eggs are hatching over the time line that they were laid.
Is that a possibility Sprint?
From the book, the mackerel we see off Caithness winter, close to the seabed, in deep water in the northern North Sea (off Shetland) and do not feed during this period. In the spring they move south to coastal waters (water temp has to be at least 11 degrees Celsius) to spawn (typically May-June). Along the way their principal food is animal plankton. After spawning they feed on small fish, remaining mostly in inshore waters close to the surface until autumn..
Their eggs take 6 days to hatch. The youngsters remain inshore until the autumn. They take three years to mature (c.30cm long). It does not say in the book, but I guess they don't return to inshore waters until maturity?
There are several other places that mackerel over winter, eg SW of Cornwall, W of Eire, Mediterranean, but according to the book, most over winter in the northern North Sea. They range in continental waters from north Africa to the far north of Norway and across to Iceland. There is also a population around Newfoundland in Canada.
Mackerel are a very successful species. It is therefore easy to take them for granted. As they take three years to mature, perhaps we should be looking at the conditions 3 or more years ago?
Hope this is interesting,

Ian.

Seabird
26-Aug-08, 21:27
Very interesting Ian,
Many Thanks
Colin

smithp
27-Aug-08, 18:48
the year before we actually caught a significant number of mackeral the first week in april off Longberry - the last one from the shore was from wick pier on 15th nov.
This year I wasted quite some time fishing early for mackeral - they arrived later.
It will take years to say there's a definitive change.

highbury
28-Aug-08, 10:11
Hi Colin,

whilst I haven't fished "top end" this year, so cant comment on the quantity there, I can tell you its not been a very good year for mackerel on the Kent coast this year , perhaps a blip with last years spawn ??

Seabird
28-Aug-08, 21:55
I did find this web site, but i must admit a lot did go over my head.
Perhaps someone with a little more idea of figures can make something out of it.
It seems they assess the mackerel numbers by counting mackerel eggs.
The graphs and figures are interesting if you can understand them.

http://www.cefasdirect.co.uk/media/31692/neamackerel.pdf

Colin

orris
03-Sep-08, 21:44
i just got Mackerel of the rocks to night 6 of them:D

Seabird
04-Sep-08, 19:51
i just got Mackerel of the rocks to night 6 of them:D

You didn't say from where Orris.

sprint95m
10-Aug-09, 13:02
I think it may be interesting to resurrect this thread a year on.


This year seems a lot better for sea life in general based on my unscientific observations from the north coast.
Loads of jelly fish.
Saithe and mackerel packed full of sandeels.
Plenty of kittiwakes hugging the coast.
Numerous porpoises and whales.
Just like the old days?