Plaice Biology and Fishery

Question 1

What order do plaice belong to?

Answer 1

Pleuronectiformes

Question 2

What is the species name for plaice?

Answer 2

P. platessa

Question 3

What family are plaice a member of?

Answer 3

Pleuronectidae- flounders which include dab, witch, halibut and lemon sole

Question 4

What are some characteristics of plaice?

Answer 4

-Orange spots on eyed side
-Blind side is pearly white
-Benthic/demersal species
-Well developed lateral line
-Eyes are asymmetrical position (on same side)

Question 5

What substrates do plaice prefer?

Answer 5

Sandy, mud and gravel

Question 6

What depths are plaice commonly found at?

Answer 6

<100m depth, a typical shelf species

Question 7

Where are juvenile plaice found?

Answer 7

In shallow waters along the shoreline

Question 8

What is the max size of plaice?

Answer 8

100 cm

Question 9

Do males or females grow faster?

Answer 9

Females grow faster, a common trait in flatfish

Question 10

What is the minimum landing size for plaice?

Answer 10

27 cm

Question 11

What is the maximum weight of plaice?

Answer 11

7kg

Question 12

What is the size range of caught plaice?

Answer 12

25-56 cm

Question 13

How much do plaice grow annually?

Answer 13

3-4 cm per year

Question 14

What is the age range of caught plaice?

Answer 14

2 -13 years

Question 15

What is the maximum age of plaice?

Answer 15

50 years

Question 16

What age group of plaice makes up 70% of the Irish catch?

Answer 16

4 -6 years

Question 17

When do male plaice sexually mature?

Answer 17

2 -6 years of age

Question 18

When do female plaice sexually mature?

Answer 18

3 -7 years of age

Question 19

What is the expected sex ratio of plaice?

Answer 19

1:1

Question 20

What is the distribution of plaice?

Answer 20

From the Barents sea to the Mediterranean, Northeast Atlantic and off coast of Greenland

Question 21

How many eggs do plaice produce?

Answer 21

10,000 - 600,000 eggs

Question 22

When do plaice spawn in Irish waters?

Answer 22

February/ March to April

Question 23

How long do eggs/juveniles drift as plankton for?

Answer 23

2-3 weeks

Question 24

What size do plaice eggs hatch at?

Answer 24

1.8 -1.9 mm in diameter

Question 25

How long do larvae and post larvae live at the surface until metamorphosis?

Answer 25

6 weeks

Question 26

What happens during metamorphosis to plaice?

Answer 26

Eye migrates to right side
Becomes bottom living (10-17 mm)

Question 27

How long do young plaice spend in shallow inshore waters?

Answer 27

1st year of life

Question 28

Where is the largest plaice spawning ground?

Answer 28

North sea

Question 29

When does plaice spawning happen in the North Sea?

Answer 29

December - March

Question 30

What is the diet of plaice?

Answer 30

Mollusks
Worms
Crustaceans

Question 31

What are the feeding habits of plaice?

Answer 31

Diet varies as they grow
Feed mainly during daylight hours
Feed less in the winter months
Well fed plaice with selectively feed on mollusks, hungry plaice will feed on anything
-Fish that specialize on limited number of prey do better than those who are varied

Question 32

How are plaice fished?

Answer 32

-Ground fishing gear
-Beam trawls (inshore)
Otter trawls (mixed fisheries)
Danish seines and lines

Question 33

Are plaice economically important?

Answer 33

Plaice are the most economically important flatfish of northern European fishing industry

Question 34

What division is the main Irish fishery for plaice?

Answer 34

Division VIIa

Question 35

How are Irish plaice caught?

Answer 35

Primarily as minor by-catch in mixed demersal fisheries with Nephrops and haddock

Question 36

Where has ICES set TACs for plaice stocks around Ireland?

Answer 36

-Irish sea
-Celtic sea
-South-west of Ireland
-West of Ireland
-West of Scotland and Rockhall

Question 37

What other countries fish plaice?

Answer 37

-France
-Denmark
-Norway
-Netherlands
-Spain