Fishes I
Chordate taxonomy
Dichotomous keys
Fins and scales
Hagfishes
Lampreys
Sharks, skates and rays
Chimaeras
Sturgeons
Gars and Bowfins
Chordate Taxonomy
Phylum Chordata
(Subphylum Cephalochordata - lancelets: 0 in BC)
Subphylum Urochordata - tunicates
Subphylum Vertebrata
Superclass Agnatha
Class Myxini (hagfish)
Class Petromyzontida (lampreys)
Superclass Gnathostomata
Class Chondrichthyes - cartilaginous fish
Class Actinopterygii – ray-finned fishes
(Class Sarcopterygii – lobe-finned fishes:0 in BC)
Class Amphibia - amphibians
Class Reptilia - reptiles
Class Aves - birds
Class Mammalia - mammals
Subphylum Cephalochordata: the lancelet Branchiostoma
Dorsal nerve cord
Notochord
Brain
Gill slits
Post-anal Tail
Chordate Taxonomy
Phylum Chordata
Subphylum Cephalochordata (lancelets)
Subphylum Urochordata (tunicates)
Subphylum Vertebrata
Superclass Agnatha
Class Myxini (hagfish)
Class Petromyzontida (lampreys)
Superclass Gnathostomata
Class Chondrichthyes - cartilaginous fish
Class Actinopterygii - ray finned fishes
Class Amphibia - amphibians
Class Reptilia - reptiles
Class Aves - birds
Class Mammalia - mammals
Subphylum Urochordata: tunicates
Adult “sea squirts” are
sessile filter feeders
Chordate Taxonomy
Phylum Chordata
Subphylum Cephalochordata (lancelets)
Subphylum Urochordata (tunicates)
Subphylum Vertebrata
Superclass Agnatha
Class Myxini (hagfish)
Class Petromyzontida (lampreys)
Superclass Gnathostomata
Class Chondrichthyes - cartilaginous fish
Class Actinopterygii - ray finned fishes
Class Amphibia - amphibians
Class Reptilia - reptiles
Class Aves - birds
Class Mammalia - mammals
Characteristics of Subphylum Vertebrata
1. Chordate characteristics - notochord, dorsal nerve
cord, pharyngeal pouches, post-anal tail.
2. Cartilaginous or bony endoskeleton with a backbone
and vertebrae (except hagfish).
3. Pronounced cephalization: well-developed nervous
system with anterior brain and specialized receptors
(nose, eyes, ears).
4. Closed circulatory system with 2 to 4 chambered
heart and blood with hemoglobin.
5. Excretory system of paired kidneys
6. Endocrine system of ductless glands (adrenal,
pituitary, thyroid…)
Fish Taxonomy
Subphylum Vertebrata
Superclass Agnatha
Class Myxini (hagfish)
Class Petromyzontida (lampreys)
Superclass Gnathostomata
Class Chondrichthyes - cartilaginous fishes
Subclass Elasmobranchii – sharks and rays
Subclass Holocephali – chimaeras (ratfish)
Class Actinopterygii – ray-finned fishes
Subclass Chrondrostei – sturgeons, paddlefish
Subclass Neopterygii – modern bony fishes
(Class Sarcopterygii – lobe-finned fishes)
Actinopterygii and Sarcopterygii are sometimes referred
to collectively as Osteichthyes – bony fishes
Fish Taxonomy
Subphylum Vertebrata
Superclass Gnathostomata
Class Chondrichthyes - cartilaginous fishes
(850 species – 24 in BC)
Class Actinopterygii – ray-finned fishes
(~25,000 species ~500 in BC)
Class Sarcopterygii – lobe-finned fishes
(7 species – 0 in BC)
DICHOTOMOUS KEYS, e.g.
Key to Families of Freshwater Fishes in Canada
1a. Mouth without true jaws ........…..LAMPREYS
1b. Mouth with true jaws ....................................2
2a. homocercal tail .............................................3
2b. heterocercal tail .......................STURGEONS
3a. Large bony plate between lower jaws
... BOWFINS
3a. Soft between lower jaws and bony plate not
present ...............................................................4
Key to Families of Freshwater Fishes in Canada
4a. Pelvic fins present ..................................5
4b. Pelvic fins absent .......................... EELS
5a. Adipose fin absent ................................. 6
5b. Adipose fin present ..............................11
Key to Families of Freshwater Fishes in Canada
11a. Lack scales, barbels present ... CATFISHES
11b. Scaled, barbels absent .......................... ...12
12a. Scales ctenoid .................................. PERCH
12b. Scales cycloid ........................................... 13
13a. Mouth not extending beyond eye ........... 14
13b. Mouth extends beyond eye…SALMONIDAE
Fin types
1st dorsal
2nd dorsal
adipose
pectoral
anal
pelvic
caudal
Types of
caudal fins
Diphycercal (coelocanth)
Homocercal (perch)
Heterocercal (shark)
Types of fish scales
1. Placoid – sharks and rays
spine
pulp
basal plate
Placoid scales = “denticles”
Types of fish scales
1. Placoid – sharks and rays
2. Cosmoid – lung fish
Similar to placoid scales and probably evolved
from the fusion of placoid scales
Types of fish scales
1. Placoid – sharks and rays
2. Cosmoid – lung fish
3. Ganoid – sturgeon, bowfins, gars, etc.
gar
Modified cosmoid
scales with pegs and
sockets
Types of fish scales
1. Placoid – sharks and rays
2. Cosmoid – lung fish
3. Ganoid – sturgeon, bowfins, gars, etc.
4. Leptoid – most fish
- cycloid
trout
herring
Smooth posterior margin
Types of fish scales
1. Placoid – sharks and rays
2. Cosmoid – lung fish
3. Ganoid – sturgeon, bowfins, gars, etc.
4. Leptoid – most fish
- cycloid
- ctenoid
ctenii on posterior margin
perch
snapper
Most fishes have scales … but some lack scales
swordfish
mackerel
ratfish
catfish
eel
… and some that appear to lack scales have a
complete coating of deeply embedded scales
Blue-fin tuna
ENVR 242 Taxonomy for BC
Subphylum Vertebrata
Superclass Agnatha - fish without jaws
Class Myxini (hagfish)
Order Myxiniformes
Family Myxinidae (1 genus, 2 species)
Pacific hagfish
Eptatretus stouti
Hagfish
no paired fins
caudal fin only
Hagfish
slime glands
no eyes
Cartilaginous skeleton:
notochord persists in
adult as cartilage rod no vertebrae
Hagfish
Hagfish
Hagfish
Hagfish mouth
barbels
two rows of
teeth on
tongue
Class Myxini
• 30 species (2 sp. in BC:
Pacific Hagfish and Black Hagfish)
• all marine
• mouth modified for sucking – jawless with two
rows of teeth and barbels
• no eyes
• no paired fins (caudal fin only)
• cartilaginous skeleton
• notochord extends the length of the body
as cartilaginous rod (no vertebrae)
• slime glands
• predators and scavengers on invertebrates
and dead and dying fish
ENVR 242 Taxonomy for BC
Subphylum Vertebrata
Superclass Agnatha - fish without jaws
Class Petromyzontida (lampreys)
Order Petromyzoniformes
Family Petromyzontidae (1 genus, 2 species)
tooth at top of mouth with 3 points
prominent eyes
Pacific Lamprey (Lampetra tridentata)
Maximum size: 76 cm
Lamprey
dorsal fins
prominent eyes
gill pores
Lampreys
oral disc has numerous teeth (no jaws!)
dorsal fins
gill pores
no barbels
Cartilagineous skeleton: Notochord persists in
adult, surrounded by cartilage pipe with rudimentary
vertebrates
Sea lamprey
Lamprey - Life history
migrate to lakes
or ocean
adults reproduce
in streams and die
parasitic adult
anadromous - spend all or part of
their adult life in salt water and return to
freshwater streams and rivers to spawn.
(larvae)
Lampreys
• 35 species (2 in BC: Pacific Lamprey and River Lamprey)
• notochord – surrounded by a cartilaginous pipe
with rudimentary vertebrae
• parasites on fish
• jawless, sucking disc with many teeth, no barbels
• prominent eyes
• dorsal fins (and caudal fins)
ENVR 242 Taxonomy for BC
Subphylum Vertebrata
Superclass Gnathostomata - jawed vertebrates
Class Chondrichthyes - cartilaginous fish
Subclass Elasmobranchii (sharks, skates, rays)
Order Lamniformes (regular sharks)
Order Squaliformes (dogfish & sleeper sharks)
Order Rajiformes (skates & rays)
Subclass Holocephali (ratfish=chimaeras)
Subclass Elasmobranchii (sharks, skates, rays)
shark
shark
ray
skate
Sharks
460+ species (12 in B.C.)
Streamlined body
Cartilaginous skeleton
Oil in Liver
Must swim continuously
Sharks
Paired pectoral and pelvic fins
Two dorsal fins
caudal fin
Shark picture
heterocercal tail
caudal fin
water enters spiracles and/or mouth…
Shark picture
heterocercal tail
… and exits through 5
to 7 pairs of gill slits
How sharks (almost) achieve
neutral buoyancy
• Cartilaginous skeleton (bone is dense)
• Pectoral fins, surface of the head and heterocercal tail
provide lift
• Large livers with large quantities of lipids (sp. gr.= 0.90-0.92)
and squalene (sp. gr. = 0.86). (Specific gravity of seawater = 1.026.)
… but are still negatively buoyant and
must swim continuously
Shark picture
teeth are shed
and replaced
Most sharks are predators with large teeth …
… but the largest sharks filter
plankton (free floating, mostly microscopic organisms)
maximum length: 15.2 m ...
but most <10 m
Basking shark
Cetorhinus maximus
Temperate zone oceans
of the world; In BC:
Strait of Georgia, Queen
Charlotte Sound, Prince
Rupert
The whale shark filters plankton
not in BC
The world’s largest fish – maximum length: 18 m
Sharks’ teeth are modified placoid scales
sensitive to water pressure
and vibration
sensitive to weak electric fields
(and possibly temperature,
water pressure and salinity)
Sharks have relatively short digestive tracts …
…but the spiral valve increases surface area.
The blood of sharks is isosmotic to sea water and
contains high concentrations of urea and
trimethylamine oxide (TMAO – from ammonia) and low
concentrations of NaCl (about 1/3 that of seawater).
kidney
rectal gland excretes NaCl
Internal fertilization !
Claspers (in males)
= modified inner edges of pelvic fins:
inserted into female cloaca for sperm transfer
oviparous – eggs laid outside the
mother’s body
ovoviviparous – mother retains
eggs in uterus; embryo nourished
by egg yolk; young born alive
viviparous – embryos develop in
the uterus nourished by the
mother’s blood through a placenta
Most sharks are viviparous!
In viviparous sharks, the embryo receives nutrients
from its mother via a yolk sac placenta
embryo
yolk sac placenta
yolk stalk
uterus
Shark egg case (“mermaid’s purse”)
embryo
yolk
egg case (keratin)
Direct development:
a shark pup emerges from its egg.
Class Chondrichthyes
Skates and rays: cartilaginous fish
collectively known as “batoids”
What is the difference between skates and rays?
Rays have 1-lobed pelvic fins and stream-lined
tails without fins (may have spines)
Sting rays, Galapagos
Sting ray with spine (modified placoid
scale) with venom gland at base.
Manta ray: a plankton feeder
6m
Skates have 2-lobed pelvic fins and
fleshy tails with small dorsal fins
(and sometimes thorns)
Clearnose Skate
thorns
skate
Mermaid’s purse (skates)
All skates lay eggs;
rays are ovoviviparous!
Rays
• fewer species
• long, thin tail without fins
• stingray tail armed with spines
• ovoviviparous
• 1-lobed pelvic fins
Skates
• more species
• thicker tail with fins
• thorns on tail
• oviparous
•2-lobed pelvic fins
Class Chondrichthyes – cartilagenous fishes
Subclass Elasmobranchii - sharks, skates and rays
• cartilaginous endoskeleton
• placoid scales
• 5 to 7 pairs of gills and gill slits
• no swim bladder
• heterocercal tail (sharks)
• spiral valve in intestine
• urea in muscle tissue – blood isosmotic to seawater
• direct development
• internal fertilization
• oviparous, ovoviviparous, or viviparous
• senses of smell, vibration sensation (lateral line system) ,
and electroreception (ampullary organs of Lorenzini) welldeveloped
ENVR 242 Taxonomy for BC
Subphylum Vertebrata
Superclass Gnathostomata - jawed vertebrates
Class Chondrichthyes - cartilaginous fish
Subclass Elasmobranchii (sharks, skates, rays)
Subclass Holocephali (ratfish)
Spotted ratfish
Hydrolagus colliei
= only ratfish sp. in B.C.
Spotted ratfish - Hydrolagus colliei
spine
long thin tail
large pectoral fins
Skeleton of cartilage
Spotted ratfish - Hydrolagus colliei
upper jaw fused to the skull
teeth are large plates
bottom feeders on mollusks and other invertebrates
Spotted ratfish - Hydrolagus colliei
male, identifiable by the paired pelvic
claspers and the cephalic clasper
Spotted ratfish
Hydrolagus colliei
male, identifiable by the paired pelvic
claspers and the cephalic clasper
Spotted ratfish egg capsule - Hydrolagus colliei
Subclass Holocephali
• 30 species (1 species in BC)
• cartilaginous skeleton
• lack scales
• males possess pelvic and cephalic claspers
• upper jaw fused to skull, mouth ventral
ENVR 242 Taxonomy
Subphylum Vertebrata
Superclass Agnatha
Class Myxini (hagfish)
Class Petromyzontida (lampreys)
Superclass Gnathostomata
Class Chondrichthyes - cartilaginous fishes
Subclass Elasmobranchii – sharks and rays/skates
Subclass Holocephali – chimaeras (ratfish)
Class Actinopterygii – ray-finned fishes
Subclass Chrondrostei – sturgeons, paddlefish
Subclass Neopterygii – modern bony fishes
Class Actinopterygii – ray-finned fishes
Subclass Chrondrostei – sturgeon
Sturgeon (Acipenser)
barbels
Sturgeon
2 species in BC:
• Green Sturgeon (Acipenser medirostris)
• White Sturgeon (Acipenser transmontanus)
Green: marine
White: freshwater
Sturgeon
2 species in BC:
• Green Sturgeon (Acipenser medirostris)
• White Sturgeon (Acipenser transmontanus)
Sturgeons are the largest fish found in
freshwater.
White Sturgeon (Acipenser transmontanus)
Columbia and Fraser Rivers
up to 6.1 m
and 816 kg
Sturgeon
• cartilaginous skeleton
• heterocercal tail
• head covered with bony plates
• 5 rows of bony scutes (remnant ganoid scales)
• no teeth and 4 barbels
• prey on benthic invertebrates and fish
ENVR 242 Taxonomy
Subphylum Vertebrata
Superclass Agnatha
Class Myxini (hagfish)
Class Petromyzontida (lampreys)
Superclass Gnathostomata
Class Chondrichthyes - cartilaginous fishes
Subclass Elasmobranchii – sharks and rays
Subclass Holocephali – chimaeras (ratfish)
Class Actinopterygii – ray-finned fishes
Subclass Chrondrostei – sturgeons, paddlefish
Subclass Neopterygii – modern bony fishes
(Infraclass Holostei – gars and bowfin: 0 in BC)
Infraclass Teleostei – majority of modern
bony fish: ~29,000 extant
species globally
 Bowfin (Amia)
Gar Pike (Lepisosteus)
Infraclass Teleostei
majority of modern bony
fish: ~29,000 extant
species globally
e.g. salmon, herring, rockfish,
groundfish…etc…etc.