Lesson 19: Vertebrates I Marine Biology

1. Lesson 19: Vertebrates I Marine Biology

2. Vertebrates: Animals with a backbone • 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? Classification Overview Common Vertebrates Phylum Subphylum Chordata Vertebrata Classes Chondrichthyes Actinopterygii Reptilia Mammalia

3. 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

4. Some Chondrichthyes Photo: NOAA Stingray They ‘fly’ through the water using flat, modified fins Order: Rajiformes Basking shark 2nd largest fish in the sea behind the whale shark. It feeds on plankton Order: Lamniformes Photo: NOAA

5. 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)

6. Some Agnathans Photo: NOAA Photo: NOAA Sea Lamprey Pacific hagfish off Oregon Coast Fish with 2 sea lampreys attached Photo: NOAA

7. 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)

8. Some Osteichtyhes Photo: SI Photo: NOAA Indonesian coelacanth Lobe-finned fish Yellowfin tuna Ray-finned fish Walleye pollock Ray-finned fish Photo: NOAA

9. Anatomy of a bony, ray-finned fish Fish use their fins to help them swim dorsal fin adipose fin Photo: NOAA caudal fin pectoral fin pelvic fin anal fin

10. 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 Overview Common Reptilian Orders Sub-Phlyum Class Vertebrata Reptilia Orders Crocodilia – Alligators Crocodiles Chelonia – Turtles, Tortoises Squamata – Snakes, Lizards

11. Some marine reptiles • Green sea turtle – Order Testudines • Sea turtles crawl onto the beach • to lay their eggs • When eggs hatch,babies must crawl to sea – on the way they are highly vulnerable to seabirds and other predators • Marine iguana – Order Squamata • These reptiles eat algae in cold • water near the Galapagos Islands • They warm themselves on rocks • after their dives

12. 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

13. 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 mortalityrate (F) is the rate at which fishing removes fish from a stock

14. 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

15. 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