Lesson 19: Vertebrates I

Marine Biology

Vertebrates: Animals with a backbone

Classification OverviewCommon Vertebrates

Phylum SubphylumChordata Vertebrata

ClassesChondrichthyes

Actinopterygii

Reptilia

Mammalia

Animals in the sub-phylum Vertebrata have spinal cords and brains

Marine vertebrates include: sharks, fish, turtles, birds, seals and whales

Can you think of others?

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Chondrichthyes: Cartilaginous fishes

Class Chondrichthyes means ‘cartilaginous fish’ and consists of sharks, rays, skates and close relatives

They share common features:– Jaws– Cartilage skeletons, not true bone– Fatty liver used for buoyancy– Lack swim bladder– Most have placoid scales

They are great predators because they have pore-like structures near their snouts called ampullae of Lorenzini, which detect electrical currents of other organisms

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Some Chondrichthyes

Basking shark2nd largest fish in the seabehind the whale shark. It feeds on plankton

Order: Lamniformes

Photo: NOAA

StingrayThey ‘fly’ through the water using flat, modified fins

Order:Rajiformes

Photo: NOAA

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Agnatha: The jawless fishes

Superclass Agnatha: Simple, more primitive fish that lack jaws Characteristics include:

– No jaws– Cartilaginous skeletons– Lack scales, paired fins– Long, eel-like

Two class divisions: – Myxini (hagfish)– Petromyzontida (lampreys)

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Some Agnathans

Pacific hagfish off Oregon Coast

Sea Lamprey

Photo: NOAA

Photo: NOAA6

Fish with 2 sea lampreys attached

Osteichthyes: The bony fishes

Superclass Osteichthyes contains the majority of the ocean’s fish Characteristics include:

– Bone skeletons– Operculum: bony skin flap outside gills that helps fish breathe

when not swimming– Most use a swim bladder to keep them from sinking

Two class divisions: – Actinopterygii (ray-finned fish including grouper, tuna and halibut)– Sarcopterygii (lobe-finned fish including lungfish and coelacanths)

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Some Osteichtyhes

Yellowfin tuna Ray-finned fish

Indonesian coelacanthLobe-finned fish

Walleye pollockRay-finned fish

Photo: SI

Photo: NOAA8

Fish use their fins to help them swim

Anatomy of a bony, ray-finned fish

pectoral fin

dorsal fin

caudal fin

pelvic fin

Photo:

NO

AA

anal fin

adipose fin

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Class Reptilia: Cold blooded animals

Reptilians generally share these common features:– Cold-blooded: they take on

the temperature of their surroundings

– Breathe with lungs– Reproduce by laying eggs

Classification OverviewCommon Reptilian Orders

Sub-Phlyum ClassVertebrata Reptilia

OrdersCrocodilia – Alligators

Crocodiles

Chelonia – Turtles, Tortoises

Squamata – Snakes, Lizards

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Some marine reptiles

Marine iguana – Order Squamata

•These reptiles eat algae in cold water near the Galapagos Islands•They warm themselves on rocksafter their dives

Green sea turtle – Order Testudines

•Sea turtles crawl onto the beachto lay their eggs•When eggs hatch,babies must crawl to sea – on the way they are highly vulnerable to seabirds and other predators 11

Managing fish populations

Fishing contributes significantly to the U.S. economy and provides a vital food source

Think back to the exercise at the beginning of class: how did you estimate the number of fish in your container?

Scientists use a combination of math, biology, and computer skills to best determine what levels of fishing can exist to provide food and support the economy without overfishing the resource

NOAA’s National Marine Fisheries Service works to sustainably manage our marine resources, including commercial fish populations, and to promote healthy ecosystems

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Fisheries management terminology

A fish stock is group of individuals of the same species that inhabitat the same geographic region and interbreed when mature

– Single species may be made up of multiple stocks (each in a different geographic region), and fisheries are managed at the stock level

– An example of a stock is a group of salmon that always use and return to particular stream for reproduction. 

Biomass (B) is the total weight of fish in a stock (e.g., metric tons)

Fishing mortality rate (F) is the rate at which fishing removes fish from a stock

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Fisheries management terminology

Sustainability represents the ability to persist in the long term– If a fish stock remains at a constant level (or even grows)

despite fishing pressure over a long time period, it is considered sustainable

Maximum sustainable yield (MSY) is the greatest number of fish that can be caught each year without impacting the long-term productivity of the stock

Overfishing occurs when fishing mortality exceeds a specific threshold, usually set at a level to achieve MSY

A stock is considered overfished when the stock size falls below a specific threshold, either in terms of numbers or biomass

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Student activity

In today’s activity, we will discuss in more detail what it means to fish “sustainably” and you will evaluate sustainable seafood restaurants

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