1

Figure 8.1

http://www.germantown.k12.il.us/html/Fishy.html

Three groups of fishes

Jawless fish (Agnatha)

Cartilagenous fish (Chondricthyes)

Bony Fish (Osteichthyes)

lamprey

Class Osteichthyes (Bony Fish)

- Dominant vertebrate in the sea- 26,000 species (96% of all fish, 50% of all

vertebrates)

http://www.germantown.k12.il.us/html/Fishy.html

Class Chondricthyes (cartilagenousfishes: sharks, rays, chimaeras)

Range in size from 7 inches to biggest fish, the whale shark

http://www.seapics.com/picture_gallery/sharks/sleeper_shark/

pygmy shark (“palm size)whale shark (50 feet)A filter-feeder

http://www.elasmo-research.org/education/shark_profiles/hammerhead_faq.htm

Hammerhead sharks (8 species known)Sea of Cortez has the scalloped hammerhead (Sphryrna lewini)School around seamountsSlow reproductive rate: females mature at 15 yrs, 12 month

gestation, 1 year off between pregnanciesFished for food and sport

http://www.elasmo-research.org/education/shark_profiles/hammerhead_faq.htm

Why the hammerhead shape?- spreads out sensory ability (electric, olfactory) (disadvantages: prevents jaw protusion & 3D vision)-use the hammer to pin down stingrays and eat them

(stingray spines often found in heads)

2

Figure 8.8 Figure 8.14

Sharks (salinity of blood = seawater)- concentrate urea in tissues- excrete salt in urine, feces, rectal gland

How to cope withsalt in seawater

Bony fish (salinity of blood < seawater)- tend to lose water-kidneys conserve water-excrete salts in urine, feces,gills, skin

Figure 8.16

Figure 8.9Streamlined(fusiform)Fast-open water

Flattened topto bottom -Bottom dweller

Flattenedside to side-bottom orcoral reef

Slow -reef

Live invegetation/coral

Trunklike orround - slowmoving, reef

Figure 8.13

3

Maintaining buoyancy

Sharks and rays: Large oily liver, light skeleton, pectoral fins for stabilityAdvantages: rapid changes in depth possible

Bony fish: Gas-filled swim bladder, pectoralfins freed for other uses-great diversity of forms

modes of swimming

Undulation flex caudal region move fins tail fin( eels) (tuna) surgeonfish boxfish

Rapid worldwide declineof predator fishcommunities,Myers R.A. & B. Worm,Nature v. 423,15May2003

Boris and Worm (2003) spent 10 years gathering data

“There is no blue frontier left.”Fish depleted from the tropics to the poles.

Only 10% of all large fish are left in the sea (2003), including:•Large open ocean fish (tuna, billfish, swordfish)•“Ground fish” (cod, halibut, skates, flounder)

Takes only 10 years to deplete a new fishery to 1/10 of its former size;

Based on Japanese long-lining data worldwide

“Longline fishing”

http://archive.greenpeace.org/oceans/southernoceans/expedition2000/expedition/longline.html

“Longline fishing”

Surface longline Bottom longline

4

Longline fishing “bycatch”= unintentional catch

Kills birds and turtles, too, as“bycatch” (=unintentional catch)

albatross

Sea turtle in shrimp netGlobal bycatch nets308,000 cetaceans per year

http://www.calacademy.org/aquarium/

Longline fishing•Fishermen spend 10-30days at sea•Travel up to 1500 miles•400-500 miles of monofilamentline•500-700 hooks per line•Each hook one football fieldapart•Cost $15K-$35K per boat per trip

http://www.fishingnj.org/techll.htmTuna caught by longlining

Alternatives to long-lining? Purse seines and log fishing

Log fishing or “log sets”tuna and dolphins tend to congregate around large floatingobjects (tuna may follow dolphins, not vice versa)

Purse seines

Decline in predatoryfish speciesin all oceans1950s-2000(Myers & Worm 2003)

(Myers & Worm 2003)

5

Decline of sharks in Gulf of Mexico (Baum & Myers 2004)

Alternatives to long-lining? Purse seines and log fishing

Purse seines vs. “Log” Fishing for Tuna

1000 set nets:500 dolphins52 Billfish10 sea turtles0 sharks

1000 nets using logs:2 dolphins654 billfish102 sea turtles13,958 sharks

Swordfish, 1940,coastal Peru

http://www.antiquefishingreels.com/

Heroic fishes of the pasttruly “sea monsters”

Do we want tuna, swordfish and marlin tobe memories only? - maybe close to extinction.

Types of migration in fishes

• anadromous (salmon) return to freshwaterto breed

• Oceanic (tuna) breed in tropics and feed intemperate parts of the ocean

• Catadromous (eels) return to salt water tobreed

Figure 8.22

Skipjack tunaTropical speciesthat travels to temperate water tofeed. Travel acrosshalf of globe each year.

SalmonAnadromous =Spend lives atsea feeding, returnto rivers to breed: Usemagnetic field of earthand smellof home rivers

Catadromous - breed at sea, migrate into rivers to grow(16 spp freshwater eels)

adults spawn and die in Sargasso Sea / larvae in plankton 1yr+/ metamorphose into juveniles / grow and mature in rivers

6

Figure 8.22Conservation threatsto fish that depend on fresh water and salt water:

•Polluted rivers•Dams•Harvested water for•agriculture•Introduced species of•farmed salmon

Why do fish school?

“selfish herd theory”(middle is safest place to be) Strange reproductive practices of fish

• Hermaphrodites• Sex change (born one sex, become the other)

Large fish in harems are often sex-change malesLarge fish in non-harem species are often sex-changefemales

• Parasitic males• “Sneaker” males that look like females• Sex-role reversal (male pregnancy in seahorses)• Males often do parental care in fish

http://www.geocities.com/thesciencefiles/angler/fish.html

Anglerfish adaptations for deep water habitat:

http://www.geocities.com/thesciencefiles/angler/fish.html

Anglerfish adaptations for deep sea (food and mates scarce)sit and wait predatory behaviorbioluminescent lureparasitic males

- once males encounter female, they don’t leave

7

http://www.oceanoasis.org/fieldguide/thal-luc.html

Rainbow wrasseThalassoma lucasanum

Two types of malesTwo types of reproduction.

1) Females(yellow/red lateral stripes)2) Primary males(look like females)3) Terminal males(blueheads) - born female, turninto males

http://www.oceanoasis.org/fieldguide/thal-luc.html

Rainbow wrasseT. lucasanum

Two types of reproduction

1) Broadcast spawningMany males and females rush

to surface and releasegametes

2) Harems: one terminal maleguards group of females andmates with them individually.

Death of secondary male-large female turns into newterminal male

Mass spawning of the rainbow wrasseThalassoma lucasanum

Barred serranoSerranus psitticinusSea of Cortez

Simultaneoushermaphrodite(can act as male orfemale at any time)-dominant male in harem mates with “females”.

Serranus annularis CaribbeanOrange back basslet

http://www.qualitymarineusa.com/fish/basslets.html#top

http://www.cnn.com/TECH/science/9812/11/seahorses.yoto/

Male pregnancy in seahorses-Placenta- Long-term pair bond-Daily dance of pair

http://www.cnn.com/TECH/science/9812/11/seahorses.yoto/

Conservation of Sea Horses20 million caught each year

- 95% chinese medicine- 5% aquarium trade

32 species (threatened status)

8

Coelocanth (lobe-finned fish)