BIOTIC Species Information for Dipturus batis
Click here to view the MarLIN Key Information Review for Dipturus batis
Researched byKen Neal & Paolo Pizzolla Data supplied byMarLIN
Refereed byThis information is not refereed.
Taxonomy
Scientific nameDipturus batis Common nameCommon Skate
MCS CodeZF86 Recent SynonymsRaja batis

PhylumChordata SubphylumPisces
SuperclassGnathostomata ClassChondrichthyes
SubclassElasmobranchii OrderRajiformes
Suborder FamilyRajidae
GenusDipturus Speciesbatis
Subspecies   

Additional InformationFollowing a report in recent taxonomic literature, this species now belongs to the genus Dipturus, although may still be referred to as Raja in some texts, (see McEachran & Dunn, 1988).
Taxonomy References Hayward & Ryland, 1995b, Muus & Dahlstrom, 1974, McEachran et al., 1998, Howson & Picton, 1997, Dipper, 2001,
General Biology
Growth formPisciform
Feeding methodPredator
Mobility/MovementSwimmer
Environmental positionDemersal
Typical food typesBristle worms, sand eels, crabs and flatfish HabitFree living
Bioturbator FlexibilityLow (10-45 degrees)
FragilityIntermediate SizeLarge(>50cm)
Height Growth Rate0.9 - 14 kg/year
Adult dispersal potential100-1000m DependencyIndependent
SociabilitySolitary
Toxic/Poisonous?No
General Biology Additional InformationThe growth rate listed above may seem quite rapid but if weight at maturity is taken into consideration, 54 kg for males (Muus & Dahlstrom, 1974) and 94 kg for females (Walker & Hislop 1998) it can be seen that it takes many years to reach maturity. The data for growth rate came from tag and release studies off the west coast of Scotland (Sutcliffe, 1994; Little, 1995, 1998) by comparing weight change of skate between captures. Skates seem to have a start-and-stop growth pattern, where they have rapid growth for a short period and then remain at that weight for some time with no growth until they have another episode of rapid growth (Sutcliffe, 1994).
Biology References Muus & Dahlstrom, 1974, Sutcliffe, 1994, Walker & Hislop, 1998, Brander, 1981, Little, 1998, Little, 1995, Mitchell & Gallagher, 2000, Anon, 1999vii,
Distribution and Habitat
Distribution in Britain & IrelandPopulations of Dipturus batis are found off the coasts of Isles of Scilly, western British Channel, west and north Ireland and west Scotland.
Global distributionAtlantic coasts from Madeira and northern Morocco northward to Iceland including the North Sea. Also in western part of the Baltic and western and northern Mediterranean.
Biogeographic rangeNot researched Depth range10 to 600 m
MigratoryNon-migratory / Resident   
Distribution Additional InformationDipturus batis was found around all British and Irish coasts except the south east. However, it has disappeared from much of its former range due to fishing pressure (Brander, 1981, Walker & Hislop, 1998; Jennings et al., 1999; Rogers & Ellis, 2000). Remnant populations occur in areas unsuitable for commercial fishing (Shark Trust pers. comm.).

Substratum preferencesMuddy gravel
Coarse clean sand
Fine clean sand
Sandy mud
Muddy sand
Mud
Mixed
Physiographic preferencesOpen coast
Offshore seabed
Biological zoneUpper Infralittoral
Lower Infralittoral
Upper Circalittoral
Lower Circalittoral
Wave exposureVery Exposed
Exposed
Moderately Exposed
Sheltered
Very Sheltered
Tidal stream strength/Water flowStrong (3-6 kn)
Moderately Strong (1-3 kn)
Weak (<1 kn)
Very Weak (negligible)
SalinityFull (30-40 psu)
Habitat Preferences Additional Information
Distribution References Hayward & Ryland, 1995b, Muus & Dahlstrom, 1974, Dipper, 2001, Walker & Hislop, 1998, Brander, 1981, JNCC, 1999, Rogers & Ellis, 2000, Whitehead et al., 1986, Jennings et al. 1999,
Reproduction/Life History
Reproductive typeGonochoristic
Developmental mechanismOviparous
Reproductive SeasonInsufficient information Reproductive LocationSee additional information
Reproductive frequencyBiannual episodic Regeneration potential No
Life span51-100 years Age at reproductive maturity11-20 years
Generation time11-20 years FecundityUp to 40 eggs
Egg/propagule size15-25 cm long, 8-15 cm wide Fertilization typeInsufficient information
Larvae/Juveniles
Larval/Juvenile dispersal potentialInsufficient information Larval settlement periodNot relevant
Duration of larval stageNot relevant   
Reproduction Preferences Additional InformationFemales breed every other year (Little, 1997) and produce up to 40 eggs (Walker & Hislop, 1998) which are laid in sandy gravel in the spring and summer (Whitehead et al., 1984). The egg case is large, 15-25 cm long and 8-15 cm wide (Dipper, 2001). It is rectangular and similar to 'mermaids purses' that are often found on the strandline. Eggcases are laid on the seabed and have been reported as being 'loose' on the seabed and perhaps very vaguely 'wedged' in between rocks (Paul Kay, pers. comm.). The young hatch after 2-5 months (depending on temperature) (Muus & Dahlstrom, 1974) at about 22 cm in length (Brander, 1981).
Dipturus batis is vulnerable to overfishing because of its slow growth, late maturity and low fecundity (Brander, 1981; Jennings et al, 1999). Only about 40 eggs are laid every other year and each generation takes 11 years to reach maturity, therefore populations cannot recover quickly from large mortalities. It has been estimated that a mortality of greater than 38% per year will lead to continual decline in the population and recovery is unlikely to occur until mortality is relaxed (Walker & Hislop, 1998). Numbers of common skate caught in trawls began to decline in the 1920s and again in the 1950s after a recovery period during the second World War and disappeared from the North Sea between the mid 1950s and early 1980s (Walker & Hislop, 1998). However, it has been shown that Dipturus batis can survive being trawled if it is released after capture (Little, 1995) . Dipturus batis was recorded as 'not uncommon in trawls' in the Marine fauna of the Isle of Man (Bruce et al., 1963) and was regarded as a common species by Hureau & Monod (1979). However the common skate had become all but extinct by the late 1970s (Brander, 1981). Similarly, between 1901 and 1907, the common skate made up 4% of all elasmobranchs caught in trawls in southwest England but between 1989 and 1997 none were caught (Rogers & Ellis, 2000).
A tag and recapture program has been implemented in northeastern Scotland. Of 147 recaptured individuals, only 5 had travelled more than 20 km (Little, 1998), which suggests that Dipturus batis is vulnerable to local extinction by fishing with little chance of re-population from adjacent areas.
Reproduction References Muus & Dahlstrom, 1974, Dipper, 2001, Sutcliffe, 1994, Walker & Hislop, 1998, Brander, 1981, Little, 1998, Little, 1995, Hureau & Monod (1973), Rogers & Ellis, 2000, Little, 1997, Whitehead et al., 1986, Bruce et al., 1963,
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