Mackerel Biology and Fishery Flashcards
What class does mackerel belong to?
Actinopterygii
What order does mackerel belong to?
Perciformes
What family does mackerel belong to?
Scombridae
What is the scientific name for mackerel?
Scomber scombus
Describe the Irish mackerel fishery
-Exploited in a directed fishery for human consumption
-Single most important fishery
-Numerous jobs as sea and on coast
-Largest and most economically valuable pelagic stock in NE Atlantic
-Processing industry depends on landings
Where is the main port?
Killibegs
Where also is mackerel landed?
Norway and UK
What export markets are there for mackerel?
Germany, Russia, Egypt and Africa
What ways are mackerel sold?
-Fresh
-Frozen
-Smoked
-Canned
What ways are mackerel sold?
-Fresh
-Frozen
-Smoked
-Canned
How are mackerel fished?
Modern pelagic trawls
Mid water otterboard trawling
Purse Seining
What is the main fishing season for mackerel?
October to March
When is the Irish mackerel fished?
January / February
What habitats are mackerel caught in?
Shelf areas and along the shelf edge
What depths are mackerel caught at?
15 - 200 m
What type of fish are mackerel?
Pelagic, but can be found anywhere in the water column
-Typically epipelagic
Are mackerel solitary or shaoling?
Shoaling, with shoals 9km long, 4km wide and 40m deep
Where are mackerel commonly found?
Cold and temperate shelf areas (>6 degrees)
Where are mackerel commonly found?
Cold and temperate shelf areas (>6 degrees)
Do mackerel have a swim bladder?
No, they must constantly swim or they will sink
Describe mackerel.
-Metallic blue-green dorsally
-Fade to silver along sides and belly
-20-30 wavy black bars running down sides
-Atlantic mackerel have tapered body, large head and mouth
-Two large dorsal fins and forked caudal fin
The is the maximum length of mackerel?
66cm
What is the average length of mackerel?
40-44 cm
What is the max recorded weight?
3.3 kg
What is the average weight of mackerel?
0.68 kg
How can mackerel age be determined?
Otoliths- unreliable after 6-7 years of age
Scales- unreliable
Do juvenile mackerel grow quickly?
Yes
What size can mackerel be after 1 year?
22 cm
What size can mackerel be after two years?
30 cm
What is the minimum landing size of mackerel?
30 cm
What is size range of catches?
33-35 cm
This can vary with year/location (20-40cm)
What is the age catch range of mackerel?
1- 15 years
What is the average catch age for mackerel?
4-8 years
When are mackerel sexually mature?
2-4 years
How many female mackerel spawn at two years old?
60%
What is the NEA?
Northeast Atlantic mackerel and is assessed as one stock
What are the three spawning components of the NEA mackerel stock?
Western Component - 77% of NEA
Southern Component - 19% of NEA
North Sea Component- 4% of NEA
What divisions are included in the Western component?
VI, VII, VIIIa,b,d,e
What divisions make up the southern componenet?
VIIIc, IXa
What divisions make up the North Sea component?
IV, IIIa
What is the total distance that mackerel will travel in a year?
500 - 1000 nautical miles
Do juveniles travel as far north as adults?
Tagging has shown that juveniles do not migrate as far north
How fast can mackerel swim?
5.5 meters / sec and up to 50 nautical miles a day
Where are the mackerel feeding areas?
June - January
West Scotland- Shetland islands
Norwegian sea
North sea
Are mackerel migratory?
Highly
Where do mackerel overwinter?
December to February
North of Scotland
Where are mackerel spawning grounds?
February - July
South, South west of Ireland
Where do mackerel that spawn in southern and western areas migrate to feed?
To Nordic seas and North sea during second half of year after spawning
What does the path of the migration coincide with?
With the location of the relatively warm high saline eastern Atlantic water flowing northeastwards
What has been linked with timing of overwintering, spawning migration?
Linked with temperature -earlier overwintering and spawning related to increased temperatures
Why is it thought that extended migrations to Iceland have been happening?
Thought to be due to climate change
What depths do mackerel spawn at?
Continental shelf, in shallow waters (200m)
What temperatures do mackerel spawn at?
Between 9 - 10 degrees
Describe mackerel early spawners
-Winter slopes near spawning area
-March/April
-Larger and older fish
Describe mackerel late spawners
-Winter further away
-Spawn May/ July
-Smaller and younger fish
-First time spawners
What type of spawners are mackerel?
-Batch spawners, eggs are laid in batches over a period of time
How many batches are laid?
20 separate
How many eggs can female mackerel lay?
400,000 - 500,000
Average 250,000
What size is mackerel eggs?
1.2 mm
How long does it take for mackerel eggs to hatch?
5 - 10 days
What size are mackerel larvae with yolk sacs?
2.5 mm
How long does it take for larvae to absorb their egg yolks?
9 days
What do mackerel feed on?
-Plankton
-sand eels
-Sprat
-Norway pout
-Polychaetes
-Zooplankton
-Crustacea
What do larvae feed on?
Copepods
Do mackerel feed during the winter?
They stop feeding almost completely during winter
Describe pelagic trawlers
Up to 100m, operate individually or in pairs
How do freezers trawlers operate?
Up to 150m and use mid water pelagic nets
What does RSW stand for?
Refrigerated Sea Water
What depths to purse seiners operate at to catch mackerel?
> 20 m
What do Norwegians fish?
Mackerel at the overwintering grounds close to shore
Who uses gill nets?
Spain and Norway
Who uses lines and jigs?
Norway and the UK
Who tends to pair trawl?
Ireland and Faroe islands
Where is traditionally the highest catches of mackerel being caught?
North Sea around the Shetland islands, west coast of Scotland and Ireland
Where is recent years is there high catches of mackerel?
in Icelandic and Faroese waters , where there was no reports of catches prior to 2006
In 2013, how much of the total reported landings were in Iceland?
Almost half
When was mackerel catches reported for the first time in Greenland?
2011
What was the EU TAC quota for mackerel in 2021?
119,573 tonnes
What was the Irish mackerel quota in 2021?
60,847 tonnes
When can Irish fishermen fish for mackerel in regards of the quota?
When can Irish fishermen fish for mackerel in regards of the quota?
Can be fished in UK waters 4.a during periods of:
-1st Jan -14th Feb
-1st Aug - 31st Dec
(2021)
