Paleoclimate Shaped Bluefish Structure in the Northern Hemisphere

<div><p>ABSTRACT</p><p>Bluefish (<i>Pomatomus saltatrix</i>), a highly migratory cosmopolitan predator, is the only extant representative of the family Pomatomidae. It has been the subject of many studies due to its commercial and recreational value, but much less research has been conducted on its global population structure. Here we investigate the population structure of this species and the effects of present and past oceanographic barriers to dispersal in its North Atlantic, Mediterranean, Marmara, and Black sea populations. We employed mitochondrial (cytochrome b and cytochrome oxidase subunit I genes) and nuclear (eight microsatellite loci) DNA as molecular markers. Three main genetic units of Bluefish were identified: American (West Atlantic waters), Spanish (East Atlantic–Western Mediterranean regions), and Turkish (Eastern Mediterranean, Marmara, and Black seas). Our results suggested that Bluefish is panmictic in the northwest Atlantic Ocean but not in the Mediterranean Sea. The common ancestor of the studied populations was traced back to the interglacial cycle Aftonian II, and the separation between clades was estimated to have occurred during glacial periods, likely due to migrations to refuges and the closure of the Mediterranean Sea. In conclusion, paleoclimate seems to have been fundamental for shaping the present genetic lineages of <i>Pomatomus saltatrix</i>.</p></div

Historical Diets of Forage Fish and Juvenile Pacific Salmon in the Strait of Georgia, 1966–1968

<p>The Strait of Georgia, British Columbia, provides important feeding and rearing habitat for forage fish, such as Pacific Herring <i>Clupea pallasii</i> and Eulachon <i>Thaleichthys pacificus</i> as well as all species of North American Pacific salmon <i>Oncorhynchus</i> spp. during their juvenile out-migration. In recent decades, this region has undergone large-scale physical and biological changes. Pacific Herring and Pacific salmon populations have experienced dramatic population fluctuations, while Eulachon have failed to recover from precipitous declines in the 1990s. Archival records of stomach content data from the 1960s, collected primarily from juvenile Pacific salmon, Pacific Herring, and Eulachon, allowed us to investigate diet variability in these species 60 years ago. Consistent with contemporary reports, we found that all species except Eulachon had generalist diets. In contrast to recent studies finding that Pacific Herring are the most important fish prey, Eulachon were the most frequently consumed fish, occurring in 28% of all piscivorous fish stomachs. This suggests that Pacific Herring are an important component of some Pacific salmon diets now, but only because lipid-rich Eulachon are no longer available. Chinook Salmon <i>O. tshawytscha</i> and Coho Salmon <i>O. kisutch</i> had the most similar diets, in part because of their greater piscivory. Species, length, and month and year of capture showed some explanatory power in differentiating the diets of the fish, although they explained less than 10% of total diet variation. Historical data, such as those presented here, offer a unique opportunity to investigate temporal differences in foraging ecology, informing management on how changes in the Strait of Georgia ecosystem may impact the trophic interactions between species.</p> <p>Received September 30, 2015; accepted July 5, 2016</p

Legislative Documents

Also, variously referred to as: House bills; House documents; House legislative documents; legislative documents; General Court documents

Bird_etal_shark_trophic_geography

Carbon isotope data compiled from muscle tissues of 5394 sharks from 114 species. Data provided include d13C values, latitude of capture, designation as shelf, slope or oceanic shark, length, depth of capture (where available), C/N ratios of muscle, and lipid extraction method if used. Also included are phytoplankton d13C data modelled from Magozzi et al 2016 (Ecosphere 8(5):e01763. 10.1002/ecs2.1763). Model data expressed as the median and standard deviation d13C value for the Longhurst Biogeographic province corresponding to the location of shark captur