CONSEIL INTERNATIONAL POUR L’EXPLORATION DE LA MER
Fiches d’identification PLEURONECTIDAE des oeufs et lames de (BY J. H. NICHOLS) poissons 1971 Fiches Nos 4-6
https://doi.org/10.17895/ices.pub.5170 2
Single-oil .globule s- A F
Many oil globules B m Terminal mouth G
Notocord Tentocle
Morgtnol fins kc H
\ \Ypigrnent bands Pectoral fins with pigment J
YLoterol spines D
Precaudal or abdominal vertibrne
Preanal are0 I Postonal area E K length 3
Introduction This sheet deals only with the Pleuronectidae occurring within the areas listed in Table 1. Initial separation of flatfish larvae into the three families of Pleuronectidae, Bothidae and Soleidae must be made with the aid of the first larval key, before the specific Pleuronectidae key can be used. There are eight species occurring in the area covered by this sheet, and they can with some experience be easily separated. Some are unlikely to occur in the same area at the same time; therefore reference should be made to their distribution and spawning times (Tables 1 and 2). In addition to the larval key, each species is discussed separately and points of likely confusion between species are clarified. Descriptions of the eggs of the eight species are included separately, but for identification reference should be made to a complete egg key (EHRENBAUM1911; HOEK1911), or a size chart (SIMPSON1956). SIMPSON'Schart is summarized in Table 3.
Material and methods Whenever possible my own specimens have been used, either from vertical plankton net samples from the wild, or from hatchery-reared stock. These specimens have all been fixed and preserved in 2 o/o hexamine buffered formalin, which may have caused up to 10 o/o shrinkage in some of them. All the figures have been drawn direct from a stereomicroscope with the Zeiss camera lucida attachment. For specimens not available in'iny own collection I have relied upon the best drawings from the many descriptions of these larvae in earlier works. These illustrations have all been redrawn, using the same technique as for my own specimens.
Characters used in identifying pleuronectid larvae The black pigment is usually the only colouring remaining after fixation in formalin and even this disappears slowly after long preservation. The distribution of black pigment and especially the patterns formed on the postanal portion of the body are important diagnostic characters, particularly in the early larval stages. The pigment is most easily viewed with incident light, this often being the only method for viewing the delicate black spots, such as those which occur on the pectoral fins of Limnda limanda. The number of fin rays is in many cases specific and they can be counted after the onset of asymmetry, preferably using transmitted light. Vertebral counts should only be made as a last resort, since it is usually necessary to stain with Alizarin red (GURR1963) or at least use a clearing technique before the vertebrae of fixed specimens can be seen. The key and figures have all been compiled from specimens in excellent condition. However, with the increasing use of high-speed plankton samplers, the possibility of extensive damage, e.g. loss of dermal pigment, torn marginal fins and the destruction of the yolk-sac and gut, must be borne in mind. The possibility of reversed specimens of Pleuronectidae, though very small, should be considered when separating metamorphosing specimens of the three families. Reversed specimens of any of the species may occur, but are common only in PlaticthysJesus. A guide to the nomenclature used in this sheet will be found in Figures A-K.
Identification A. Eggs Order Heterosomata - Family Pleuronectidae The eggs are planktonic, round, containing no oil globules. The yolk is homogeneously distributed. 1. Large egg, diameter 1.38-3.50 mm, with a large perivitelline space; spawning time 11-VI ...... Hippoglossoides platessoides 2. Large or very large egg with a small perivitelline space. 2.1. Diameter of egg 3.00-4.25 mm, perhaps even larger, imperfectly known; spawning time 111-VIII...... Hippoglossus hippoglossus 2.2. Diameter of egg 4.00-4.50 mm, imperfectly known; spawning time 111-VI ...... Reinhardtiur hippoglossoides 2.3. Diameter of egg 1.66-2.20 mm; spawning time XII-VI ...... Pleuroncctes platessa 2.4. Diameter of egg 1.13-1.45 mm; spawning time IV-X, but in the Channel 11-111. Black pigment develops on the yolk. . Microstomus kiff 3. Medium or small egg with a small perivitelline space. 3.1. Diameter of egg 1.07-1.25 mm; spawning time 111-VIII ...... Glyptocephalrcs cynoglossus 3.2. Diameter of egg 0.82-1.13 mm; spawning time I-VII...... PlaticthysJIesus 3.3. Diameter of egg 0.66-0.98 mm; spawning time I-VIII ...... Limanda limanda B. Larvae Order Heterosomata The anus is almost at right angles to the larval axis and extends to the edge of the marginal fin. The body is laterally flattened. The pelvic fins are small and barely evident during the early larval stages; the dorsal and anal fins are single and continuous. There is asymmetry of the head at metamorphosis, with the subsequent adaption for lying on the right or left side. Three families are present in this order and they can be separated by the following characteristics. 4
1. Earb larval stages before the development of the hypural rudiment. Single oil globule in the yolk-sac, persisting through the early larval stages (Figure A)...... Bothidae Many oil globules in the yolk-sac; yolk segmented; vesicular expansion of the embryonic dorsal fin above the mid-brain; mid-brain protruding (Figure B) ...... Soleidae No oil globule in the yolk-sac ...... Pleuronectidae 2. Mid-larval stages prior to the onset of asymmetry A tentacle present on the head (Figure C) ...... Bothidae Lateral (otocystic) spines on the head (Figure D) ...... Bothidae Preanal area of larva about one half the total area, mid-brain not protruding ...... Bothidae Preanal area of larva about one half the total area, mid-brain protruding (Figure E) ...... Soleidae Preanal area of larva much less than half the total area and closer to one third ...... Pleuronectidae 3. Metamorphosing larvae Right eye migrating; mouth terminal ...... Bothidae Head distinctly rounded with a lateral mouth. Size at metamorphosis small, less than 9 mm; left eye migrating (Figure F) Soleidae Mouth terminal. Size at metamorphosis greater than 9 mm; left eye migrating (Figure G) ...... Pleuronectidae
Family Pleuronectidae Key to the pelagic stages prior to the onset of asymmetry. Pigment in the form of three to six bands or patches in the marginal fins and/or on the body ...... 1 Pigment not in the form of bands or patches...... 2 1. Distance from the tip of the jaw to the anus less than one third of the total length of the larvae...... 1.1 Distance from the tip of the jaw to the anus greater than one third the total length of the larvae ...... 1.2 1.1. Six postanal bands or patches of pigment on the body, three of which are distinct and present in the early larval stages in the marginal fins (Figure 5a-g) ...... GlyPtocephalus cynoglossus 1.2. Less than six postanal bands or patches of pigment on the body. 1.2.1. Three or four indistinct bands of pigment on the postanal portion of the body. The marginal fin pigment correspond- ing to these bands is indistinct and variable (Figure 4a-b) ...... Hippoglossoides platessoides 1.2.2. Four distinct postanal bands of pigment on the body with distinct patches corresponding to these bands at the edges of the marginal fins, giving the larva a distinctly striated appearance. Patches of pigment on the body, gut and dorsal marginal fin directly above the anus. The marginal fins are broad (Figure 6a-d)...... Microstomus kitt 2. Larva large, greater than 7 mm at hatching and reaching at least 30 mm before metamorphosis; very long straight-lined lower jaw ...... 2.1 Larva small, less than 7 mm on hatching, metamorphosing at 10-15 mm ...... 2.2 2.1. 2.1.1. Larva exceedingly nmrow and elongated; body and marginal fin pigment very light (Figure 8a-c) . Rekhardtius hippoglossoides 2.1.2. Larva broad with a stout head and a strong depression in front of the eyes; “pug nose” (Figure 7a-c) Hippoglossus hippoglossus 2.2. Double row of pigment spots along the whole length of the ventral postanal portion of the body, i.e. a single row on either side at the base of the anal fin...... 2.2.1 This double row of pigment spots absent ...... 2.2.2 2.2.1. 2.2.1.1. Pigment present in the form of distinct black pigment spots on the edges of the pectoral fins. Larva small at hatching, about 3 mm (Figure 2a-f) ...... Limanda limunda 2.2.1.2. These distinct black pigment spots on the pectoral fins absent. Larvae greater than 5mm at hatching. Body long and slender with a small head (Figure la-e) ...... Plnrronccks platessa 2.2.2. Pigment in the yolk-sac stage in the form of delicate black spots across the postanal portion of the body, spreading into the marginal fins (Figure 3a-b). This pigment later spreads in the ventral marginal fin, forming regular rows of small spots along the line of the fin rays (Figure 3c-f) ...... PlatiCthysJIeSur
Key to metamorphosing stages. The onset of asymmetry takes place at less than 15 mm length, and complete adaptation to bottom life at less than 20 mm; number of anal fin rays less than 62...... 1 The onset of asymmetry takes place at greater than 15 mm length, the pelagic stages reaching a large size in excess of 25 mm; number of anal fin rays greater than 60 ...... 2 5
1. Length of caudal peduncle greater than width. Larvae very small at metamorphosis. Number of caudal vertebrae 22-26 (Figure K) 1.1 Length of caudal peduncle equal to or less than width. Number of caudal vertebrae greater than 28 ...... 1.2 1.1. Asymmetry begins at less than 10 mm length, metamorphosis complete at 10-12 mm. Number of anal fin rays 34-46. The pigment spots in the anal fin are in regular rows along the fin rays. There is a distinct yellow appearance of the larva in near-fresh specimens (Figure 3g-h) ...... Platicthys Jesus 1.2. 1.2.1. Number of precaudal vertebrae 12-14; caudal fin rays 19-22 (Figure If-g) ...... Pleuronectes platessa 1.2.2. Number of precaudal vertebrae 9-11; caudal fin rays 16-18 (Figure 2g-j) ...... Limanda limanda 2. Length of caudal peduncle much greater than the width, exceeding it by a factor of about 1.3 ...... 2.1 Shorter caudal peduncle; length and width about equal ...... 2.2 Very short caudal peduncle, marginal and caudal fin rays almost meeting...... 2.3 2.1. Number of vertebrae greater than 50; precaudal vertebrae 17-19. Larvae narrow and exceedingly elongated. Pigmen- tation light. Long straight-lined lower jaw. Caudal fin rays 19-2 1 (Figure 8f-h) ...... Reinhardtius hippoglossoides 2.2. Distance from the tip of the jaw to the anus about one quarter the total length of the larva ...... 2.2.1 Distance from the tip of the jaw to the anus about one third the total length of the larva ...... 2.2.2 2.2.1. Number of anal fin rays greater than 85. Larva narrow and elongated with a small head and small mouth (Figure 5k-j) ...... Glyptocephalus cpglossus 2.2.2. Number of anal fin rays less than 86. Most larvae may be separated by number of dorsal fin rays. 2.2.2.1. Number of dorsal fin rays less than 96 (Figure 4g-1) ...... Hippoglossoides platessoides 2.2.2.2. Number of dorsal fin rays greater than 101 (Figure 7d-g) ...... Hippoglossus hippoglossus 2.2.2.3. Number of dorsal fin rays between 96 and 101. 2.2.2.3.1. Number of precaudal vertebrae less than 15 (Figure 4g-1)...... Hippoglossoides platessoides 2.2.2.3.2. Number of precaudal vertebrae greater than 15 (Figure 7d-g)...... Hippoglossus hippoglossus 2.3. Larva very broad, rounded with a small head and small mouth (Figure 6-h) ...... Microstomus kitt
Notes on identification 1. Pleuronectes platessa Linnaeus, 1758 - Plaice Eggs and larvae may be found over the whole area inhabited by adults, but are most concentrated in a few large spawning areas to which the adults migrate. Spawning occurs in December-March in the Southern Bight of the North Sea (SIMPSON1949a, b, 1959a); in January- April in the German Bight, in the Irish Sea (SIMPSON1959b), and at south-west Iceland in March-April. The larva hatches at 5.5-7.0 mm, with pigmented eyes (Figure 1a). Its size and long slender form with a small head distinguish it from L. limanda at this stage. The small head and short snout of P. plutessa are apparent throughout the early development and are particularly good diagnostic characters when compared with specimens of L. limanda (compare Figures 1b:2 b, 1c:2c, 1d:2d, 1e:2f). Absence of pigment on the pectoral fin is an important characteristic for separating plaice larvae from those of L. limanda. When the dorsal and anal fin rays develop, at about 9-11 mm (Figure le), the precaudal vertebrae can be counted, thus distinguishing this species from L. limanda (Table 1). The number of caudal rays, when fully formed, is also specific.
2. Limanda limanda (Linnaeus, 1758) - Dab The eggs and larvae of this species are common over the whole area inhabited by the adults. Spawning begins in the Southern Bight of the North Sea in mid-January (SNPSON1949a, b), continuing throughout spring and summer in the northern North Sea and at Iceland. The centre of spawning of this species in the Southern Bight of the North Sea tends to be further east, and thus more coastal, than that of P. platessa (SIMPSON1949a, b, 1959a). The larva hatches at 3-4 mm, with unpigmented eyes (Figure 2a). The pectoral fins develop distinct black pig- ment spots along their margins. The ventral postanal pigment spots are more distinctly arranged in two regular rows than in P.platessa. By the time the rays appear in the marginal fins this species is of comparable size to P.plutessa (Figure 2f) and the number of precaudal vertebrae becomes the most reliable distinguishing feature, particularly when only single specimens are available. Comparative head size (see 1. above) is useful only when specimens of both P. plutessa and L. limanda are present, but after the onset of asymmetry the caudal ray count can be relied upon to separate the larvae. At metamorphosis the eyes of this species are noticeably larger than those of P. platessa.
3. PZaticthys flesus (Linnaeus, 1758) - Flounder This species migrates offshore from rivers and estuaries at spawning time, and may often be found spawning together with P.pZatessa and L. limanda, particularly in the Baltic and Irish Seas. Spawning begins in mid-January in the Southern Bight of the North Sea (SIMPSON 1949a, b) and continues to April in the southern part of the flounder’s range and to July in the northern part. Hybrids between this species and P. platessa have a high viability in hatcheries and are also known to occur in nature, particularly in the Baltic Sea in some years 6
(KANDLER1935). Hatchery-reared hybrid larvae from a cross between a female P. platessa and a male P.flesus which I have examined have shown the pigment characteristic of the male and the size of the female. These hybrid larvae could be difficult to recognize in the wild state. The small size of this species on hatching, 2.25 mm (Figure 3a), and its continuing small size throughout its planktonic development, help to distinguish it from the two preceding species. The closely packed rows of black pigment spots which develop in the anal fin in regular rows, and the broad form are also good distinguishing features. Later the small number of rays in the anal fin, the number of caudal vertebrae and the long caudal peduncle are reliable diagnostic characters. In fresh or near-fresh specimens there is a distinct yellow coloration of the body of this species.
4. Hippoglossoides platessoides (Fabricius, 1780) - Long rough dab Spawning takes place in the southern North Sea and English Channel in February-May, west of Ireland in April-May (CUNNINGHAM1896) and at Iceland in May-June. The larvae hatch at 44mm, with pigmented eyes (Figure 4a), and already show the characteristic bands of pigment on the body. This pigment appears in the late embryo and is evident throughout the larval phase. The marginal fins are narrow and the pigment bands are not as distinct as in M. kitt. In the later larval stages the long caudal peduncle of this species will always separate it from M. kitt. Confusion with L. limanda is unlikely, but if uncertainty should arise in the early larval stages, the greater length and the characteristic pigmentation of H. platessoides will always separate them. After the onset of asymmetry, the precaudal and caudal vertebrae, both diagnostic characters of the two species, can be counted. The size of metamorphosing specimens of long rough dab appear to be smaller in the North Sea than in the Barents Sea (compare Figure 4f and k). COLLETT(1880) also found the pelagic fry larger at Iceland than from Ireland or Denmark.
5. Glyptocephalus cynoglossus (Linnaeus, 1758) - Witch or Pole Dab Spawning takes place in the Irish Sea in late March-May, and in the North Sea in May-August (CUNNINGHAM1896). The larva hatches at about 4-6 mm, with unpigmented eyes (Figure 5a). The characteristic bands of pigment on the postanal portion of the body are apparent at this early stage and may also appear as indistinct patches in the marginal fins (Figure 5a-b) which later disappear. At all times during its larval development the elongated appearance of this species and the position of the anus distinguish it from H. plutessoides, M. kitt and H. hipgo- glossus. After development of the marginal fin rays, and throughout metamorphosis, the large number of rays in the anal fin separate this species from all other Pleuronectidae. 6. Microstomus kitt (Walbaum, 1792) - Lemon Sole This species is a deepwater form and does not migrate to particular areas to spawn; the main spawning therefore occurs well offshore (CLARK 1920). Spawning begins on the south and west coasts of Britain in April and continues through to August or September at Iceland (CUNNINGHAM 1896). In Scottish waters spawning occurs from late March to October (RAE1953). The larvae hatch at 4-5 mm, with unpigmented eyes (Figure 6a). After resorption of the yolk-sac the ventral abdominal wall is distinctly concave, this remaining a feature until long after the development of the hypural rudiment (Figure 6b). The characteristic banded pigment on the body also appears in corresponding patches on the edges of the marginal fins. This is evident throughout the larval development, giving the larva a distinctly striated appearance to the naked eye. This pigmentation and the broad form of the larva readily distinguish it from H. plutessoides and G. cynoglossus. After development of the fin rays the very short caudal peduncle is an excellent diagnostic character, readily separating this species from all other Pleuronectidae
7. Hippoglossus hippoglossus (Linnaeus, 1758) - Halibut This is a northern species, rarely occurring in the southern North Sea or English Channel. Spawning occurs on the coasts of Sweden between the end of February and April and at Iceland in June-August (MCINTOSHand MASTERMAN1897). Depths at which halibut spawn vary considerably but they appear to favour deep water (greater than 1000 m, WHEELER1969; 300-700 m, ANDRNASHEV1954). The young are large on hatching, about 7 mm, lightly pigmented, with no grouping of the pigment into distinct bands or patches in these early stages. The shape of the head, particularly the characteristic depression in front of the eyes - “pug nose” (SCHMIDT 1904), the long straight-lined lower jaw, the broad form of the larva and its large size, are all good diagnostic features of this species throughout its pelagic phase. These characteristics should render confusion with H. platessoides unlikely, but should confirmation be required in the late stages, the greater number of dorsal rays and precaudal vertebrae of H. hippoglossus readily separate the two species.
8. Reinhardtius hippoglossoides (Walbaum, 1792) - Greenland Halibut Spawning takes place over deep water in April-June in the Barents Sea (ANDRNASHEV1954), and at Greenland there is a migration from the bays and fjords to the great depths of the Davis Strait by the adults to spawn (JENSEN1935). The egg and yolk-sac larvae are bathypelagic, whilst the older larvae become pelagic. The larvae from the very earliest stage are characterized by their exceedingly elongated shape (SCHMIDT1904). Pigmentation of the early larvae is light and not in distinct bands or patches. In the later stages the pigment appears as indistinct bands in the fins and on the body in lines along the myomeres. The larvae reach a considerable size whilst still remaining symmetrical, and complete bottom adaptation does not occur until a length of about 70 mm is reached (JENSEN 1935). The left eye of this species never completely migrates over to the right side. Apart from its shape the number of vertebrae separates this species from H. hippoglossus in the late stages (SCHMIDT1904).
16
Selected bibliography Descriptions of larvae with plates Species Meristic characters Species HEINCKE.FR., EHRENBAUM.E . (1900) 1. 2. 3. 4. 5. 6 HOLT.E . W . L . (1895) ...... 1.2. 4 Larvae JENSEN. A . S . (1935) ...... 8 COLLETT.R . (1880) ...... 4.5. 8 Adults SCHMIDT.J . (1904) ...... 7. 8 NORMAN.J . R . (1934) ...... 1. 2. 3. 4. 5. 6. 7. 8 Adults PETERSEN.C . G .J . (1904) and (1906) 1. 2. 3. 4. 5. 6 HOLT.E . W . L . (1895) ...... 1. 2. 4. 5. 6 Life-history and spawning MCINTOSH.W . C., MASTERMAN.A . T . JENSEN. A. S. (1935) ...... 8 (1897) ...... 1. 2. 3. 4. 5. 6. 7 CUNNINGHAM.J . T . (1896) ...... 1. 2. 3.4. 5. 6. 7 PADOA.E . (1956) ...... 1. 3 ANDRIYASHEV.A. P . (1954) ...... 1. 2. 3. 4. 5. 6. 7. 8 EHRENBAUM.E . (1905) ...... 1. 2. 3. 4. 5. 6. 7. 8 MCINTOSH.W . C., MASTERMAN.A. T ...... SCHNAKENBECK.W (1928) 2. 5. 6 (1897) ...... 1. 2. 3.4. 5.6. 7 WILLWON. H C . (1904) ...... 5 . MCINTOSH.W .C., PRINCE.E .E . (1890) 1. 2. 3. 4. 5 HOLT. E W L., BYRNE.L W (1901) 5 . . . . SMITT. F.A. (t892) ...... 1. 2. 3. 4. 5. 6. 7. 8 WHEELER.A . (1969) ...... 1. 2. 3.4. 5. 6. 7. 8 Descriptions of eggs HEINCKE.FR., EHRENBAUM.E . (1900) 1. 2. 3. 4. 5. 6 Distribution and spawning areas HOLT.E . W . L (1895) ...... 1. 2. 3. 4. 5. 6 CUNNINGHAM.J . T . (1896) ...... 1. 2. 3. 4. 5. 6. 7 HIEMSTRA.W . H . (1962)...... 1. 2. 3. 4. 5. 6. 7. 8 ANDRIYASHEV.A . P . (1954) ...... 1. 2. 3. 4. 5. 6. 7. 8 EHRENBAUM.E . (1911). HOEK.P . P . C . EINARSSON.H., WILLIAMSON.G . C . (1911) ...... 1.2. 3.4. 5.6. 7. 8 (1968) ...... 1. 2. 4. 5. 6 SIMPSON.A. C . (1956) ...... 1. 2. 3.4. 5. 6. 7 JENSEN. A. S . (1935) ...... 8 ARBOULT.S., BOUTIN.N . (1968) ..... 4. 6. 7 MCINTOSH.W . C., MASTERMAN.A. T . CUNNINGHAM.J T . (1887) ...... 1. 2. 3. 5 (1897) ...... 1. 2. 3. 4. 5. 6. 7 SIMPSON.A. C . (1959a. b) ...... 1 Meristic characters SIMPSON.A. C. (1949a. b) ...... 2. 3 SCHMIDT.J . (1904) ...... 4. 7. 8 Larvae WHEELER.A . (1969) ...... 1. 2. 3. 4. 5. 6. 7. 8 PETERSEN.C . G .J . (1904) and (1906) 1. 2. 3. 4 Larvae CLARK.R . S. (1920) ...... 6 ANDRIYASHEV.A. P . (1954) ...... 1. 2. 3. 4. 5. 6. 7. 8 Adults RAE.B . B. (1953) ...... 6
Table 1
Distribution Species (those in parentheses occur only occasionally)
GulfofBothnia ...... 3 Gulf of Finland ...... 2. 3 Baltic proper ...... 1. 2, 3. (4)>1 (5).* (7)' Belt Sea ...... I. 2. 3. 4. 6. 7 Kattegat ...... 1. 2. 3. 4. 5. 6. 7 Skagerrak ...... 1. 2. 3. 4. 5. 6. 7 Northern North Sea ...... 1. 2. 3. a 4. 5. 6. 7 Southern North Sea ...... 1. 2. 3. 4. (5). 6. (7) English Channel (east) ...... 1. 2. 3. (4). 6 English Channel (west) ...... 1. 2. 3. (4). (5). 6 Bristol Channel and Irish Sea ...... 1. 2. 3. 4. 5. 6 South and west Ireland and Atlantic ...... 1. 2. 3. ' 4. 5. 6. 7 Biscay ...... 1. 2. 3. ' (4): 5. 6. (7) 0 Portugal ...... 1. 3 Faroe/Shetland area ...... 1. 2. 3. ' 4. 5. 6. 7 Faroe/Iceland area ...... 1. 2. 4. 5. 6. 7 Norwegian Sea ...... 1. 2. ' 3. a 4. 5. 6. 7. 88 Barents Sea ...... 1. 2. ' 3. * 4. 5. 6. 7. 8 Greenland ...... 4. 5. 7. 8
Western part . a occurs in coastal region . 70° N - southerly limit . 17
Table 2
Species No. J F M A M J J A S 0 N D
Pleuronectes platessa ...... 1 x X X X X X - - - - x Limanda limanda ...... 2 x X X X X X X x - - PlatuthysJesus...... 3 x X X x X X X - - - Hippoglossoides platessoides ...... 4 - X X X X X - - - - Glyptocephalus cynoglossus...... 5 - - X X X X X X - - - - Microstomus kitt...... 6 - X X X X X X X X - - Hippoglossus hippoglossus...... 7 - X X X X X X - - Reinhardtius hippoglossoides ...... 8 - - X X X x?- - - - -
Spawning periods of fish of the family Pleuronectidae. Spawning occurs first in the southern part of each species' range and progresses northwards throughout the season.
Table 3 (after SIMPSON1956)
Diameter Diameter Species of egg Species of egg (mm) (mm)
Callionymus bra...... 0.69-0.94 (Reticulate sculpturing) Pollachius pollachius...... 1.10-1.22 Ctenolabrus rupestris ...... 0.72-0.94 Glyptocephalus cynoglossus ...... 1.07-1.25 Limanda limanda ...... 0.66-0.98 Microstomus kitt ...... 1.13-1.45 Y Platichthys Jesus...... 0.82-1.13 Gadus morhua, ...... 1.16-1.60 Sprattus sprattus ...... 0.82-1.23 (Segmented yolk) Melanogrammus aeglejnus...... 1.19-1.67 Trisopterus minutus...... 0.95-1.07 Pleuronectes platessa ...... 1.66-2.20 Trisopterus esmarkii ...... 1.OO-1.13 Hippoglossoides platessoides ..... 1.38-3.50 liisopterus ~usncr...... 0.97-1.23 Hippoglossus hippoglossus ...... 3.00-4.25 Merlangius mrlangus ...... 0.97-1.32 Reinhardtius hippoglossoides .... 4.00-4.50 Pollachius virens ...... 1.03-1.22 Y
Table 4
Vertebrae Fin rays \ Text Species . ref. no. Abdominal Postanal Dorsal Anal Caudal or precaudal or caudal
Pleuronecks platessa ...... 1 12-14 28-32 57- 80 43- 61 19-22 Limanda limanda ...... 2 9-1 1 28-3 1 65- 80 50- 62 16-18 Platuthys Jesus...... 3 10-12 22-26 51- 65 34- 46 18 Hippoglossoides platessoides ...... 4 12-14 3 1-35 74-101 60- 81 18 G~ptocephaluscynoglossus ...... 5 58-60 96- 98 86-102 23-26 Microstomus kitt...... 6 121 34-351 85- 98 69- 76 18-20 Hippoglossus hiMOglossus...... 7 16-17 32-35 96-1 10 71- 88 22' Rknhardtius hippoglossoides ...... 8 17-19 43-45 92-104 67- 80 19-2 1
Summary of meristic characters of fish of the family Pleuronectidae. 8 observations from Faroe-Shetland; single observation. 18
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