Animal Navigation: Seabirds Home to a Moving Magnetic Target.

Shifts in the return locations of juvenile seabirds migrating from the Irish Sea to Argentina can be accurately predicted by changes in Earth's magnetic field, suggesting that these birds rely on a geomagnetic map for navigation.

Changes in Shrimping Effort in the Gulf of Mexico and the Impacts to Red Snapper.

Despite a complex management landscape and decades of overfishing, Red Snapper (Lutjanus campechanus) stocks have grown substantially in the Gulf of Mexico and restrictions on the fisheries that catch them are being loosened. This year, annual shrimping effort was allowed to increase by 21% after National Marine Fisheries Service scientists concluded that the resulting bycatch of Red Snapper would only reduce the annual allowable catch in other fisheries by ∼1% and have no impact on population growth. Nonetheless, the recreational fishing sector intensely campaigned against this rule, fueled by wild mischaracterization of shrimp trawl bycatch in media outlets targeting anglers. Here, we aim to elevate the debates surrounding Red Snapper management by presenting scientific and historical context for the potential impacts from shrimping. We discuss our views of the current problems facing Red Snapper and key ecological questions to address for more effective management of this resource.

First satellite tracks of South Atlantic sea turtle 'lost years': seasonal variation in trans-equatorial movement.

In the South Atlantic Ocean, few data exist regarding the dispersal of young oceanic sea turtles. We characterized the movements of laboratory-reared yearling loggerhead turtles from Brazilian rookeries using novel telemetry techniques, testing for differences in dispersal during different periods of the sea turtle hatching season that correspond to seasonal changes in ocean currents. Oceanographic drifters deployed alongside satellite-tagged turtles allowed us to explore the mechanisms of dispersal (passive drift or active swimming). Early in the hatching season turtles transited south with strong southward currents. Late in the hatching season, when currents flowed in the opposite direction, turtles uniformly moved northwards across the Equator. However, the movement of individuals differed from what was predicted by surface currents alone. Swimming velocity inferred from track data and an ocean circulation model strongly suggest that turtles' swimming plays a role in maintaining their position within frontal zones seaward of the continental shelf. The long nesting season of adults and behaviour of post-hatchlings exposes young turtles to seasonally varying ocean conditions that lead some individuals further into the South Atlantic and others into the Northern Hemisphere. Such migratory route diversity may ultimately buffer the population against environmental changes or anthropologic threats, fostering population resiliency.

Is the geographic distribution of nesting in the Kemp's ridley turtle shaped by the migratory needs of offspring?

Across the geographic area that a species uses for reproduction, the density of breeding individuals is typically highest in locations where ecological factors promote reproductive success. For migratory animals, fitness depends, in part, on producing offspring that migrate successfully to habitats suitable for the next life-history stage. Thus, natural selection might favor reproduction in locations with conditions that facilitate the migration of offspring. To investigate this concept, we studied the Kemp's ridley sea turtle (Lepidochelys kempii) to determine whether coastal areas with the highest levels of nesting have particularly favorable conditions for hatchling migration. We modeled the passive drift of young Kemp's ridley turtles from seven nesting regions within the Gulf of Mexico to foraging grounds using the particle-tracking program ICHTHYOP and surface-current output from HYCOM (HYbrid Coordinate Ocean Model). Results revealed that geographic regions with conditions that facilitate successful migration to foraging grounds typically have higher abundance of nests than do regions where oceanographic conditions are less favorable and successful migration is difficult for hatchlings. Thus, our findings are consistent with the hypothesis that, for the Kemp's ridley turtle and perhaps for other migrants, patterns of abundance across the breeding range are shaped in part by conditions that promote or impede the successful migration of offspring.