Lesson 19: Vertebrates I Marine Biology

Vertebrates: Animals with a backbone Classification Overview Common Vertebrates Phylum Subphylum Chordata Vertebrata Classes Chondrichthyes 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? 2

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 3

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

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) 5

Some Agnathans Pacific hagfish off Oregon Coast Sea Lamprey Photo: NOAA 6 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) 7

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

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

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-PhlyumClass Vertebrata Reptilia Orders Crocodilia – Alligators Crocodiles Chelonia – Turtles, Tortoises Squamata – Snakes, Lizards 10

Some marine reptiles Marine iguana – Order Squamata These reptiles eat algae in cold water near the Galapagos Islands They warm themselves on rocks after their dives 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 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 12

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 13

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 14

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 15