Temporal trends (2000–2011) and influences on fishery-independent catch rates for loggerhead sea turtles (Caretta caretta) at an important coastal foraging region in the southeastern United States

Seasonal trawling was conducted randomly in coastal (depths of 4.6–17 m) waters from St. Augustine, Florida, (29.9°N) to Winyah Bay, South Carolina (33.1°N), during 2000–03, 2008–09, and 2011 to assess annual trends in the relative abundance of sea turtles. A total of 1262 loggerhead sea turtles (Caretta caretta) were captured in 23% (951) of 4207 sampling events. Capture rates (overall and among prevalent 5-cm size classes) were analyzed through the use of a generalized linear model with log link function for the 4097 events that had complete observations for all 25 model parameters. Final models explained 6.6% (70.1–75.0 cm minimum straight-line carapace length [SCLmin]) to 14.9% (75.1–80.0 cm SCLmin) of deviance in the data set. Sampling year, geographic subregion, and distance from shore were retained as significant terms in all final models, and these terms collectively accounted for 6.2% of overall model deviance (range: 4.5–11.7% of variance among 5-cm size classes). We retained 18 parameters only in a subset of final models: 4 as exclusively significant terms, 5 as a mixture of significant or nonsignificant terms, and 9 as exclusively nonsignificant terms. Four parameters also were dropped completely from all final models. The generalized linear model proved appropriate for monitoring trends for this data set that was laden with zero values for catches and was compiled for a globally protected species. Because we could not account for much model deviance, metrics other than those examined in our study may better explain catch variability and, once elucidated, their inclusion in the generalized linear model should improve model fits.

Deep-sea benthic footprint of the Deepwater Horizon blowout

The Deepwater Horizon (DWH) accident in the northern Gulf of Mexico occurred on April 20, 2010 at a water depth of 1525 meters, and a deep-sea plume was detected within one month. Oil contacted and persisted in parts of the bottom of the deep-sea in the Gulf of Mexico. As part of the response to the accident, monitoring cruises were deployed in fall 2010 to measure potential impacts on the two main soft-bottom benthic invertebrate groups: macrofauna and meiofauna. Sediment was collected using a multicorer so that samples for chemical, physical and biological analyses could be taken simultaneously and analyzed using multivariate methods. The footprint of the oil spill was identified by creating a new variable with principal components analysis where the first factor was indicative of the oil spill impacts and this new variable mapped in a geographic information system to identify the area of the oil spill footprint. The most severe relative reduction of faunal abundance and diversity extended to 3 km from the wellhead in all directions covering an area about 24 km2. Moderate impacts were observed up to 17 km towards the southwest and 8.5 km towards the northeast of the wellhead, covering an area 148 km2. Benthic effects were correlated to total petroleum hydrocarbon, polycyclic aromatic hydrocarbons and barium concentrations, and distance to the wellhead; but not distance to hydrocarbon seeps. Thus, benthic effects are more likely due to the oil spill, and not natural hydrocarbon seepage. Recovery rates in the deep sea are likely to be slow, on the order of decades or longer.

The geographic basis for population structure in Fraser River chinook salmon (Oncorhynchus tshawytscha)

We surveyed variation at 13 microsatellite loci in approximately 7400 chinook salmon sampled from 52 spawning sites in the Fraser River drainage during 1988–98 to examine the spatial and temporal basis of population structure in the watershed. Genetically discrete chinook salmon populations were associated with almost all spawning sites, although gene flow within some tributaries prevented or limited differentiation among spawning groups. The mean FST value over 52 samples and 13 loci surveyed was 0.039. Geographic structuring of populations was apparent: distinct groups were identified in the upper, middle, and lower Fraser River regions, and the north, south, and lower Thompson River regions. The geographically and temporally isolated Birkenhead River population of the lower Fraser region was sufficiently genetically distinctive to be treated as a separate region in a hierarchial analysis of gene diversity. Approximately 95% of genetic variation was contained within populations, and the remainder was accounted for by differentiation among regions (3.1%), among populations within regions (1.3%), and among years within populations (0.5%).Analysis of allelic diversity and private alleles did not support the suggestion that genetically distinctive populations of chinook salmon in the south Thompson were the result of postglacial hybridization of ocean-type and stream-type chinook in the Fraser River drainage. However, the relatively small amount of differentiation among Fraser River chinook salmon populations supports the suggestion that gene flow among genetically distinct groups of postglacial colonizing groups of chinook salmon has occurred, possibly prior to colonization of the Fraser River drainage.