Plaice Biology and Fishery Flashcards
What order do plaice belong to?
Pleuronectiformes
What is the species name for plaice?
P. platessa
What family are plaice a member of?
Pleuronectidae- flounders which include dab, witch, halibut and lemon sole
What are some characteristics of plaice?
-Orange spots on eyed side
-Blind side is pearly white
-Benthic/demersal species
-Well developed lateral line
-Eyes are asymmetrical position (on same side)
What substrates do plaice prefer?
Sandy, mud and gravel
What depths are plaice commonly found at?
<100m depth, a typical shelf species
Where are juvenile plaice found?
In shallow waters along the shoreline
What is the max size of plaice?
100 cm
Do males or females grow faster?
Females grow faster, a common trait in flatfish
What is the minimum landing size for plaice?
27 cm
What is the maximum weight of plaice?
7kg
What is the size range of caught plaice?
25-56 cm
How much do plaice grow annually?
3-4 cm per year
What is the age range of caught plaice?
2 -13 years
What is the maximum age of plaice?
50 years
What age group of plaice makes up 70% of the Irish catch?
4 -6 years
When do male plaice sexually mature?
2 -6 years of age
When do female plaice sexually mature?
3 -7 years of age
What is the expected sex ratio of plaice?
1:1
What is the distribution of plaice?
From the Barents sea to the Mediterranean, Northeast Atlantic and off coast of Greenland
How many eggs do plaice produce?
10,000 - 600,000 eggs
When do plaice spawn in Irish waters?
February/ March to April
How long do eggs/juveniles drift as plankton for?
2-3 weeks
What size do plaice eggs hatch at?
1.8 -1.9 mm in diameter
How long do larvae and post larvae live at the surface until metamorphosis?
6 weeks
What happens during metamorphosis to plaice?
Eye migrates to right side
Becomes bottom living (10-17 mm)
How long do young plaice spend in shallow inshore waters?
1st year of life
Where is the largest plaice spawning ground?
North sea
When does plaice spawning happen in the North Sea?
December - March
What is the diet of plaice?
Mollusks
Worms
Crustaceans
What are the feeding habits of plaice?
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
How are plaice fished?
-Ground fishing gear
-Beam trawls (inshore)
Otter trawls (mixed fisheries)
Danish seines and lines
Are plaice economically important?
Plaice are the most economically important flatfish of northern European fishing industry
What division is the main Irish fishery for plaice?
Division VIIa
How are Irish plaice caught?
Primarily as minor by-catch in mixed demersal fisheries with Nephrops and haddock
Where has ICES set TACs for plaice stocks around Ireland?
-Irish sea
-Celtic sea
-South-west of Ireland
-West of Ireland
-West of Scotland and Rockhall
What other countries fish plaice?
-France
-Denmark
-Norway
-Netherlands
-Spain
