Upload
others
View
1
Download
0
Embed Size (px)
Citation preview
BATOID FISHES - SKATES, RAYS, AND GUITARFISHES
Mostly from the work of Compagno and collaborators (1989 and 1991) and our collections, we count 28species in 7 families and 3 orders of batoid fishes from Namibia. A checklist of batoid fishes is included
in the Appendix in order to serve as an aid to a more accurate assessment of the batoid resources of Namibia.Although not actively fished, they are consistently caught in the bottom trawls of the hake fishery andconstitute a substantial biomass in the demersal community.
TECHNICAL TERMS AND MEASUREMENTS
Guide to Orders and Families 89
length of disc
1st dorsalfin
dorsal view
spiracle
orbit
alar spines (in males)
thorns of median row
pelvic fin, anterior lobe
pelvic fin, posterior lobe
clasper of males
2nd
dorsalfin
caudalfin
lateral tail fold
length ofsnout,
preorbitalaxil of
pectoralfin
length ofsnout,
preorbital
ventral view
width of disc
nasal apertures
mouth
gill slits
anus
length of tail
click for previous page
Order TORPEDINIFORMES - Electric RaysA large electric organ on each side of head but no sting on tail; body not elongate and shark-like but tail isstout and caudal fin large. Two families found in Namibia.
TORPEDINIDAE Page 92
Electric raysOne species found in Namibia, included inthe “Guide to Species.” Pelagic fromdepths between 10 to 560 m. Size to1.8 m total length.
NARKIDAE Page 92
NumbfishA single species found in Namibia, in-cluded in the “Guide to Species.”Demersal in shallow depths to 183 m.Size to 38 cm total length.
Order RAJIFORMES - Guitarfishes and SkatesNo electric organs on head or sting on tail; body elongate and shark-like (guitarfish family) or, with enlargedpectoral fins forming a disc and the rear margin of the pelvic fin deeply notched forming 2 distinct lobes andwith a slender tail (skate family). Two families found in Namibia.
RHINOBATIDAE Page 92
GuitarfishesTwo species in 1 genus reported fromNamibia, both in the “Guide to Species.”Coastal in shallow water to depths ofaround 70 m. Size to 1.4 m total length.
90 Skates, Rays, and Guitarfishes
STOUT TAIL
NO STING ON TAIL
BODY NOT ELONGATE
ELECTRIC ORGAN ONEACH SIDE OF HEAD
2 dorsal fins
1 dorsal fin
NO ELECTRICORGANS
body elongate and shark-like NO STINGON TAIL
RAJIDAE Page 93
SkatesPerhaps 17 species in 3 genera fromNamibia, all in the “Guide to Species” ex-cept 2 whose presence in Namibia isdoubtful. Demersal from shallow depthsto nearly 2 000 m. Size to 1.3 m disc width.
Order MYLIOBATIFORMES - StingraysNo electric organs on head but sting on tail usually present; pectoral fins enlarged to form a disc; tail slen-der or whip-like; pelvic fins not deeply indented, each with only a single lobe. Three families reported fromNamibia.
DASYATIDAE Page 98
StingraysA single genus and possibly 3 species inNamibia; the record of 1 species,Dasyatis pastinaca, is questionable and itis not included in the “Guide to Species.”Neritic and pelagic. Size to 80 cm discwidth.
GYMNURIDAE Page 99
ButterflyraysA single genus and possibly 2 species re-ported from Namibia; Gymnura altavelaisa questionable record from Namibia andnot included in the “Guide to Species.”Demersal in shallow depths to 75 m. Sizeto 2.5 m disc width.
MYLIOBATIDAE Page 99
Eagle raysTwo species in 2 genera reported fromNamibia, both in the “Guide to Species.”Coastal to depths of around 100 m. Sizeto 1.8 m disc width.
Guide to Orders and Families 91
BODY NOT ELONGATE
NO ELECTRIC ORGANS
disc width not much differentfrom disc length
head not distinct from disc,eyes well behind forward
margin of disc
STING USUALLYPRESENT ON TAIL
head not distinct from disc,eyes well behind forward
margin of disc
disc about twiceas wide as long
body not elongate
head elevated and distinct fromdisc, eyes in front of or near
front of forward margin of disc
Torpedo nobilianaBonaparte, 1835 (plate III, 20) TORPEDINIDAE
FAO names : En - Electric ray; Fr - Torpillenoire; Sp - Tremolina negra.Local names : Atlantic electric ray; Atlantiesedrilvis (Ak); Schwarzer Zitterrochen (Gr).Size: Maximum recorded, 1.8 m total length.Fisheries : Caught occasionally with bottomtrawls and line gear.Habitat and biology : Young are known tobe demersal on soft bottoms, from 10 to150 m, sometimes as deep as 560 m. Adultsare pelagic or semi-pelagic, migrating longdistances. Feeds mainly on bony fishes.
Narke capensis(Gmelin, 1789) NARKIDAE
FAO names : En - Cape numbfish; Fr - Poissonengourdeur du Cap; Sp - Pez temblador delCabo.Local names : Onefin electric ray; Eenvin-drilvis(Ak).Size: To about 38 cm total length.Fisheries : None at present.Habitat and biology : Found in shallow watersdown to a depth of 180 m. A small ray that candeliver a very powerful shock.Remarks : Only a single recorded specimencollected in Namibia thus far, 1 caught by ashore angler in Meob Bay. Unofficial report ofthis species from Walvis Bay.
Rhinobatos annulatusSmith, 1841 RHINOBATIDAE
FAO names : En - Lesser guitarfish; Fr - Pois-son-guitare du Cap; Sp - Guitarra del Cabo.Local names : Kleiner sandkruiper (Ak).Size: To about 1.4 m total length.Fisheries : Occasionally caught in bottom trawlsand by hook-and-line from the beach.Habitat and biology : Mainly in inshore watersand down to a depth of 70 m; also entering estuar-ies. Feeds mainly on small invertebrates includingcrustaceans, bivalves, and polychaete worms,and small bony fishes.Remarks : Confirmed reports for localities inNamibia are needed.
92 Skates, Rays, and Guitarfishes
2 dorsal fins
1 dorsal fin
numerous small spots on backsnout sharply
pointed
Rhinobatos blochiiMüller and Henle, 1841 RHINOBATIDAE
FAO names : En - Bluntnose guitarfish;Fr - Poisson guitare épointé; Sp - Guitarraembotada.Local names : Stompneus-sandkruiper (Ak).Size: To about 95 cm.Fisheries : Occasionally caught in bottomtrawls.Habitat and biology : Demersal, near shore inshallow sandy areas. Rare. In Namibia, southof Walvis Bay.
Bathyraja smithii (Müller and Henle, 1841) (plate IX, 72) RAJIDAE
FAO names : En - African softnose skate; Fr - Raiede Smith; Sp - Raya de Smith.Local names :Size: Up to 85 cm disc width.Fisheries : Occasionally caught in deep-waterbottom trawls.Habitat and biology : A demersal species of theupper continental slope, from depths of 440 to1 020 m. Feeds on bony fishes such as hake,barracudinas, and dragonets, and invertebratessuch as squid, octopus, crabs, and shrimps.
Cruriraja parcomaculataVon Bonde and Swart, 1923 RAJIDAE
FAO names : En - Roughnose legskate; Fr - Raiaá nez hérissé; Sp - Raya nariz áspera.Local names : Rog (Ak).Size: To about 35 cm disc width.Fisheries : Regularly caught by hake trawlers.Habitat and biology : Known to occur on thebottom, at depths from 200 to 620 m. Feedsmainly on invertebrates such as crabs, shrimps,hermit crabs, squid, and polychaete worms.
Guide to Species 93
colour whitish grey, sometimes with white spots; white ventrally,with black blotches between gill slits and around vent
angular
snout soft
a single row oflarge thorns,14-19 from
above vent to1st dorsal-fin
origin
colour uniform brown (sometimes withirregular patches); underside white
thorns on tip ofsnout
margin of pelvicfin confluentwith posteriormargin of disc
long leg-likeanterior lobe
snoutblunt
Raja albaLacepède, 1803 RAJIDAE
FAO names : En - White skate; Fr - Raieblanche; Sp - Raya bramante.Local names : Spearnose skate; Spiesneus(Ak); Bandrochen, Spitzrochen (Gr).Size: To at least 180 cm disc width.Fisheries : Caught in bottom trawls, pelagictrawls, and by shore anglers.Habitat and biology : A demersal species, fromintertidal coastal waters to the upper continentalslope, from shallow depths to about 500 m. Abottom predator, feeding on a wide range ofspecies, including bony fishes such as hake,kingklip, anchovy, gobies, sardines, and horsemackerel, and other sharks, rays, and variouscephalopods and crustaceans.
Raja caudaspinosavon Bonde and Swart, 1923 RAJIDAE
FAO names : En - Munchkin skate; Fr - Raie áqueue épineuse; Sp - Raya cola espinosa.Local names : Rog (Ak).Size: To at least 32 cm disc width.Fisheries : Only occasionally caught in bottomtrawls.Habitat and biology : Recorded from depths of310 to about 700 m, mostly south of Lüderitz.Feeds on mysids, lightfish, and polychaetes.
Raja clavataLinnaeus, 1758 (plate III, 21) RAJIDAE
FAO names : En - Thornback ray; Fr - Raiebouclée; Sp - Raya de clavos.Local names : Thornback skate; Doringrug-rog(Ak); Keulenrochen, Nagelrochen, Steinrochen(Gr).Size: To 60 cm disc width.Fisheries : Occasionally caught in bottomtrawls.Habitat and biology : A demersal speciesfound from shallow inshore waters to the uppercontinental slope to a depth of at least 700 m.Feeds on crustaceans, fish, and cephalopods.Remarks : Reports of R. clavata andR. straelenimay represent a single species.
94 Skates, Rays, and Guitarfishes
dorsal surface of disc sometimes with dark spots; paleventrally with margins of disc greyish.
eyespot, if present,strongly ovate
strong thorns present
snout bluntlypointed
tail with 5-7 rowsof thorns
tail long, distance from vent to 1st
dorsal-fin origin longer thandistance from vent to tip of snout
snout short,pointed
adults and large juvenileswith small white spots
narrow-tipped snoutangular
3 rows of largethorns on tail
upper side of disc covered withsmall sharp thorns, no large
thorns on nape or back
Raja confundensHulley, 1970 (plate X, 73) RAJIDAE
FAO names : En - Bigthorn skate; Fr - Raiegrand épine; Sp - Raya de grande espina.Local names :Size: To about 45 cm disc width.Fisheries : Commonly caught in bottom trawls.A bycatch of the deep-water fishery.Habitat and biology : Found in the deeper partof the shelf and on the upper slope, from depthsof about 170 m to 900 m. Feeds mainly on inver-tebrates such as crustaceans, squid, andpolychaete worms.Remarks : Considered a junior synonym of Rajabarnardi Norman, 1935 by some authors.
Raja doutreiCadenat, 1960 (plate III, 22) RAJIDAE
FAO names : En - Javelin skate; Fr - Raieviolette; Sp - Raya violeta.Local names :Size: To over 95 cm disc width.Fisheries : Occasionally caught in bottomtrawls. A bycatch of the deep-water fishery.Habitat and biology : Found on the slope be-tween depths of 450 and 600 m.
Raja leopardusvon Bonde and Swart, 1923 RAJIDAE
FAO names : En - Leopard skate; Fr - Raieléopard; Sp - Raya leopardo.Local names :Size: To 65 cm disc width.Fisheries : Occasionally caught in bottomtrawls.Habitat and biology : A rather common spe-cies, found on the upper continental slope, fromdepths of about 300 to 900 m. Feeds on bottomcrustaceans, bony fishes, cuttlefish, andpolychaete worms.
Guide to Species 95
pigmented pores on underside of disc
long stiffpointedsnout
tips rounded
median row ofthorns
snout moderatelylong
small thorns onupper surface
often with blackishspots
adults with 4-5 rows of thornsincluding a median row
short, obtusesnout
large white thorns on uppersurface and snout
5 rows of thorns on tail,including median row
Raja miraletusLinnaeus, 1758 RAJIDAE
FAO names : En - Brown ray; Fr - Raie miroir;Sp - Raya de espejos.Local names : Twineye skate; Tweeoog-rog(Ak); Vieräugiger Spiegelrochen (Gr).Size: To 35 cm disc width.Fisheries : Occasionally caught in bottom trawlsand by anglers.Habitat and biology : Found from shallow in-shore waters to a depth of 500 m, most commonbetween 50 and 150 m. Feeds on crustaceans,bony fishes, and cephalopods.
Raja pullopunctataSmith, 1964 RAJIDAE
FAO names : En - Slime skate; Fr - Raiebaveuse; Sp - Raya limosa.Local names : Rog (Ak).Size: To 70 cm disc width.Fisheries : Caught in bottom trawls. Commonbycatch in hake fisheries.Habitat and biology : Found on soft substrateof the outer shelf and upper slope, from depthsof about 50 to 450 m. A common species, feed-ing on various bony fishes, crustaceans, andmolluscs.
Raja ravidulaHulley, 1970 RAJIDAE
FAO names : En - Smoothback skate; Fr - Raielisse; Sp - Raya suave.Local names : Rog (Ak).Size: To 36 cm disc width.Fisheries : Incidentally caught in bottom trawls.A bycatch of the deep-water fishery.Habitat and biology : Upper slope from depthsof about 500 to 1 000 m. Common in centralNamibia.
96 Skates, Rays, and Guitarfishes
long snout
no mental pores onunderside of disc
juvenile
large brown blotch
median row of thorns
long snout
2 prominent rows of thorns,no median row
snout short, bluntlypointed
eyespots with3 rings of
colour, centrebright blue in
life
often with small dark spots
Raja spinacidermisBarnard, 1923 RAJIDAE
FAO names : En - Roughskin skate; Fr - Raiepeau hérissée; Sp - Raya piel áspera.Local names : Ruwevel-rog (Ak).Size: To 45 cm disc width.Fisheries : Caught ocasionally in bottom trawls.Habitat and biology : Found on the slope, fromdepths of about 800 to 1 400 m.
Raja springeriWallace, 1967 RAJIDAE
FAO names : En - Roughbelly skate; Fr - Raiede Springer; Sp - Raya de Springer.Local names :Size: To 130 cm disc width.Fisheries : Rarely caught in bottom trawls.Habitat and biology : Found on the outer shelfand upper slope, on the bottom, at depths be-tween about 80 and 750 m. Feeds on bonyfishes such as round herring and macrourids,and on crabs and squids.
Raja straeleniPoll, 1951 RAJIDAE
FAO names : En - Biscuit skate; Fr - Raietachetée; Sp - Raya manchada.Local names : False thornback skate; Valsdoringrug-rog (Ak).Size: To 68 cm disc width.Fisheries : Occasionally caught in bottomtrawls; pectoral fins used for human consump-tion.Habitat and biology : A very common skate,found from inshore waters to the upper slope toa depth of about 350 m. Feeds mainly oninvetebrates such as shrimps, hermit crabs,mantis shrimp, and cephalopods, and bonyfishes such as hake, sardine, and lanternfishes.Remarks : See remarks under R. clavata.
Guide to Species 97
pigmented pores onunderside of disc
long stiff pointedsnout
angular tips
median row ofthorns
strong thorns
oblong eyespotoften present
snout angular
usually with black,irregular spots
lateral caudalthorns
a median row of thorns
large juveniles andadults without
thorns on disc ortail
snout bluntlypointed and
flexible
Raja wallaceiHulley, 1970 RAJIDAE
FAO names : En - Yellow spotted skate; Fr - Raiede Wallace; Sp - Raya de Wallace.Local names : Blancmange skate; Witpoeding-rog(Ak).Size: To 53 cm disc width.Fisheries : Rarely caught in bottom trawls.Habitat and biology : Found at depths of 90 to440 m. Preys on crustaceans and small fish,and is also scavenger.
Dasyatis chrysonota(Smith,1828) DASYATIDAE
FAO names : En - South African blue stingray;Local names : Blue stingray; Blou pylstert (Ak).Size: To 75 cm disc width.Fisheries : Occasionally caught by shore an-glers.Habitat and biology : A common inshore sting-ray, often in shallow bays and sheltered sandybeaches, especially in summertime, moving todeeper waters to a depth of about 100 m duringwinter. Feeds on crustaceans such as crabs,shrimps, and mantis shrimps, and on smallbony fishes.Remarks : Previously confused with D.pastinacaand D. marmoratawhich do not oc-cur in the area.
Dasyatis violacea(Bonaparte, 1832) DASYATIDAE
Synonyms : Pteroplatytrygon violacea(Compagno et al., 1989).FAO names : En - Blue stingray;Fr - Pastenague violette; Sp - Raya látigovioleta.Local names : Pelagic stingray; Pelagiesepylstert (Ak); Violetter Stechrochen (Gr).Size: To 80 cm disc width.Fisheries : Caught by pelagic offshorelonglines.Habitat and biology : This is the only pelagicand oceanic stingray.
98 Skates, Rays, and Guitarfishes
anterior contour of discbroadly arched
colour violet purple above and below
short broadblunt snout
bright yellow or whiteirregular spots
2-4 rows of thorns
conspicuous bright blueblotches and branching
lines on a goldenbackground
Gymnura natalensis(Gilchrist and Thompson, 1911) GYMNURIDAE
FAO names : En - Backwater butterflyray;Fr - Raia-papillon de Natal; Sp - Rayamariposa de Natal.Local names : Rem-vinderrog (Ak).Size: Up to 250 cm disc width.Fisheries : Rarely caught by offshore trawlersand rarely by shore anglers.Habitat and biology : Close inshore offsandy beaches, on offshore banks to a depthof 75 m. Feeds mainly on bony fishes such asflatfishes, sardines, and gurnards, and oncrabs and polychaete worms.
Myliobatis aquila(Linnaeus, 1758) MYLIOBATIDAE
FAO names : En - Common eagle ray; Fr - Aiglecommun; Sp - Aguila marina.Local names : Eagle ray; Arendrog (Ak);Adlerrochen, Gewöhnlicher Adlerrochen (Gr).Size: To about 150 cm disc width.Fisheries : Rarely caught with bottom trawls,purse seines, longlines, and shore anglers.Habitat and biology : Found in coastal waters toa depth of about 100 m, mainly on soft bottoms;enters lagoons and estuaries. Often found ingroups. Feeds on invertebrates such as bivalvesand crabs, and on small fish.
Pteromylaeus bovinus(Saint-Hilaire, 1817) MYLIOBATIDAE
FAO names : En - Bull ray; Fr - Aigle vachette;Sp - Chucho vaca.Local names : Bulrog (Ak); AfrikanischerAdlerrochen (Gr).Size: To about 180 cm disc width.Fisheries : Rarely caught with bottom trawls.Habitat and biology : A coastal species, todepths of about 100 m; often found close tosoft bottoms. Feeds mainly on invertebratessuch as crabs, bivalves, and squid, and smallfish. Possibly present only along the northerncoast of Namibia (absent in the cold upwellingwaters).
Guide to Species 99
mouth
colour grey-green or brownish withdarker mottling, but changing to
match substrate
black and white bands on tail
ventral view of head
head marked off from rest of disc
sting
head marked off from rest of disc
pointed
blue-grey crossbars
sting
CHIMAERAS
There are 6 species of chimaeras in Namibia. They are usually caught incidentally in bottom trawls and arenot normally found in great numbers. However, in some places they are considered a delicacy and
represent a potential resource for further exploitation.
TECHNICAL TERMS AND MEASUREMENTS
Order CHIMAERIFORMES - ChimaerasA cartilagenous skeleton; a simple external gill opening on each side of head; naked skin; 2 dorsal fins, thefirst with a long spine; elongate tapering tail. Three families found in Namibia.
CALLORHINCHIDAE Page 101
ElephantfishA single species reported from Namibia,included in the “Guide to Species.”Demersal, from shallow depths to 370 m.Size to 1.2 m total length.
CHIMAERIDAE Page 101
Shortnose chimaerasTwo species in Namibia, both included inthe “Guide to Species” and both possiblyundescribed. Demersal in depths be-tween 400 and 1 200 m. Size to 1.0 m totallength.
RHINOCHIMAERIDAE Page 102
Longnose chimaerasThree species in 3 genera from Namibia,all included in the “Guide to Species.”Demersal in depths between 200 and1 100 m. Size to 1.3 m total length.
100 Chimaeras
soft gillcover
mouth
frontal tentaculum
nostril
pelvicfin
caudalfilament
caudalfin
anal finclasper
prepelvictentaculum
pectoralfin
gill opening
length to 2nd dorsal base
head
snout
lateral-line
fin spine
1st dorsal fin
2nd dorsal fin
total length
diagram of a male chimaera(Chimaera)
2nd dorsal fin long and low
caudal fin on horizontalaxis or slightly arched
snout long, pointed
snout short, blunt
2nd dorsal finlong and low
caudal fin ona horizontal
axis
caudal fin archedupward
2nd dorsal fin shortand high
snout hoe-shaped
Callorhinchus capensisDuméril, 1865 (plate III, 23) CALLORHINCHIDAE
FAO names : En - Cape elephantfish;Fr - Masca du Cap; Sp - Pejegallo delCabo.Local names : Elephantfish; Josef (Ak);Totenkopfchimäre (Gr).Size: To 1.2 m total length.Fisheries : Caught with bottom trawlsand commonly by shore anglers.Habitat and biology : A demersal speciesof the continental shelf, from shallowcoastal waters to a depth of 370 m. Feedson a wide variety of invertebrates such seaurchins, bivalves, shrimp, crabs, gastro-pods, and small fish. Produces egg-casesthat are spindle shaped, with broad hori-zontal flanges.
Chimaerasp. CHIMAERIDAE
FAO names : En - Cape chimaera;Fr - Chimère du Cap; Sp - Quimera delCabo.Local names : Kaapse chimaera (Ak).Size: To 1 m total length.Fisheries : Occasionally caught in bottomtrawls. A bycatch of the deep-water fish-ery.Habitat and biology : A demersalspecies found on the continental slopefrom depths of 680 to around 1 000 m.
Hydrolagussp. CHIMAERIDAE
FAO names : En - Brown chimaera;Fr - Chimère brunette; Sp - Quimeracastaña.Local names :Size: To about 70 cm total length.Fisheries : Occasionally caught in bottomtrawls. A bycatch of the deep-water fish-ery.Habitat and biology : Demersal indepths between 400 and 1 200 m.Remarks : This species is probably H. africanus(Gilchrist, 1992).
Guide to Species 101
colour silvery with dusky marking
recurved projection
caudal fin withraised axis
blunt and short
small anal fin
blunt and short
no anal fin
Harriotta raleighanaGoode and Bean, 1895 RHINOCHIMAERIDAE
FAO names : En - Narrownosechimaera; Fr - Chimère de Raleigh;Sp - Quimera de Raleigh.Local names :Size: To 1 m total length.Fisheries : Rarely caught in bottomtrawls.Habitat and biology : A bottom livingspecies of the upper slope, found fromdepths of about 850 to 1 100 m.
Neoharriotta pinnata(Schnakenbeck, 1931) (plate III, 24)
FAO names : En - Sicklefin chimaera;Fr - Chimère faucillée; Sp - Narigónaletas de haz.Local names :Size: To 1.3 m.Fisheries : Caught occasionally in bottomtrawls.Habitat and biology : A demersal spe-cies of the upper slope, from depths of200 to 470 m. Feeds on swimming crabs.Egg cases spindle-shaped, with broadhorizontal flanges.
Rhinochimaera atlanticaHolt and Byrne, 1909 RHINOCHIMAERIDAE
FAO names : En - Spearnose chimaera;Fr - Chimère nez lance; Sp - Narigón si-erra.Local names :Size: To 1.3 m.Fisheries : Rarely caught in bottom trawls.A bycatch of the deep-water fishery.Habitat and biology : Found on the conti-nental slope, from depths of about 550 to1 100 m.
102 Chimaeras
ventral view of head
ventral view of head
colour whitish to light brownno anal fin
spine smooth
upper margin of caudal fin with series ofenlarged denticles in males
colour dark brown or blackish
spine serrated
no anal fin
colour chocolate brown
ventral view of head
large anal fin
spine smooth anteriorly,serrated posteriorly
click for next page