Migration and Navigation Predictable movements between two or more locations Short (daily) or long migrations Most tied to feeding and reproduction (Levinton 1995)!Spawning Nursery Adult Feeding Fish Migration(Castro and Huber 2003)!Three Classes of Fish Migration: Anadromous Spawn in freshwater Feed in marine waters Shad!Lamprey!Salmon!XThree Classes of Fish Migration: Catadromous Spawn in marine waters Feed in freshwater (Levinton 1995)!American Eel!Three Classes of Fish Migration: Exclusively marine Spawn and feed in marine waters (Levinton 1995)!North Sea herring Spawning Larval !feeding Adult !feeding(Gross et al. 1987)!Three Classes of Fish Migration: Why bother? Is productivity the reason? = food equator!arctic!Tropical streams more productive than tropical oceans High latitude streams less productive than high latitude oceans(Levinton 1995)!Reptile Migration Green Sea Turtle Hatchlings swim across the ocean Adults feed off coast of Brazil Adults return to Ascension Island to reproduceReptile Migration Loggerhead Turtle Juvenile population off Spain can’t be supported by Mediterranean nesting areas Time to sexual maturity too long for tagging experiments Use DNA instead: mitochondrial markers (Bowen et al. 1995)!Mammal Migration Gray Whales Feed in Arctic in summer Travel south in October Swim close to coast singly or in pairs Reach Baja lagoons in December Females give birth Begin migration back to Arctic in March(Nybakken 2001)!Mammal Migration Fin Whales Also migrate from pole to equator But in Southern HemisphereNavigation How do animals orient in a featureless ocean? • Visual cues • Coastal features (Gray whales?) • Celestial cues • Cues from currents and waves (Lohmann and Lohmann 1996)!Hatchling turtles must orient seaward Direction of wave propagation may help with orientation But how?(Lohmann and Lohmann 1996)!Hatchlings are underwater, so can’t be visual Perhaps they sense progression of movements? offshore beach Waves create orbital movement in the water belowNavigation How do animals orient in a featureless ocean? • Visual cues • Cues from currents and waves • Magnetic field Sea turtles Invertebrates Cetaceans (Lohmann et al. 2001)!Magnetic properties establish a grid with unique coordinates Inclination !angle!Field !intensity!(Lohmann et al. 2001)!• Magnetic field Sea turtles Naïve hatchlings put in tank with magnetic coil to manipulate intensity and angle of inclination Magnetic field mimicked for three locations http://www.youtube.com/watch?v=eU4mTAaWb6k• Magnetic field Invertebrates Lobsters from capture site put into tanks mimicking magnetic field from two different sites (Bowles and Lohmann 2003)!Lobsters thought they were here http://www.youtube.com/watch?v=YfEKjrF_5XQ• Magnetic field Cetaceans (Kirschvink ) Data on mass strandings of cetaceans along east coast of U.S.Other theories for strandings: •Social bonds cause pod members to follow disoriented leader •Bad weather interrupts ability to navigate •Whales get caught when tide falls • Magnetic field Cetaceans Parallel lines of reverse polarity from seafloor spreading North-south signals over long distances in the
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