Fiedler P.C.,National Oceanic and Atmospheric Administration |
Redfern J.V.,National Oceanic and Atmospheric Administration |
Van Noord J.,National Oceanic and Atmospheric Administration |
Hall C.,National Oceanic and Atmospheric Administration |
And 3 more authors.
Marine Ecology Progress Series | Year: 2013
Tropical cyclones are environmental disturbances that may have important effects on open-ocean ecosystem structure and function, but their overall impact has rarely been assessed. The Stenella Abundance Research Line Transect and Ecosystem (STARLITE) survey, in August-November 2007, investigated spatial and temporal ecosystem variability in the eastern tropical Pacific Ocean off southwestern Mexico. Oceanographic, plankton, flyingfish, seabird, and cetacean sampling was conducted along eight 170 km transect lines, each of which were surveyed on 2 consecutive days at ∼3 wk intervals. Tropical storm Kiko passed though the study area on 15-17 October and forced changes in the physical environment and in the ecosystem, from plankton to top predators. Kiko mixed water from beneath the strong, shallow thermocline to the surface. As a result, surface temperature decreased by 0.6°C, the thermocline and chlorophyll maximum layer shoaled by 10-20 m, stratification decreased by 27%, and chlorophyll increased by 33% at the surface and 35% over the euphotic zone. These changes persisted for at least 4 wk. Zooplankton biomass increased by 59% about 3 wk after the phyto - plankton increase. Changes in the stomach fullness and diet composition of planktivorous flyingfish were consistent with the increase in zooplankton biomass. Among top predators, the sighting rate of dolphins declined, while the response of seabirds varied by species and was confounded by seasonal migration patterns. Tropical cyclones are a recurrent disturbance in this region. They initiate a bottom-up forcing of the ecosystem, creating persistent patches of higher primary and secondary production, and may be regarded as a disturbance regime.
Javor B.,Ocean Associates Inc. |
Dorval E.,Southwest Fisheries Science Center
Fisheries Research | Year: 2014
Pacific sardine (Sardinops sagax), a commercially valuable species, have a broad distribution along the North American coast that spans Canada, the United States, and Mexico. The goal of this research was to evaluate water temperature history of the fish inferred from stable oxygen isotopes in otoliths in order to differentiate and connect stocks across regions, and between juveniles and adults. Local seawater composition in the Pacific Northwest affected major north-south trends in δ18O composition of juvenile otoliths. Inferred temperature correlated inversely with the age (otolith weight) of juveniles within a region, possibly resulting from changes in depth preferences as the fish grew. The correlations between δ13C and δ18O in juvenile otoliths were relatively weak in the northernmost and southernmost samples, but comparisons of the sample means indicated significant differences between some regions. Otoliths from adult sardine captured between California and Canada recorded δ18O values reflecting cooler temperatures than otoliths from juveniles, and without regional differentiation. These results are consistent with a northern stock that mixes during annual migrations. © 2014 Elsevier B.V.
Becker E.A.,National Oceanic and Atmospheric Administration |
Becker E.A.,Ocean Associates Inc. |
Forney K.A.,National Oceanic and Atmospheric Administration |
Foley D.G.,University of California at Santa Cruz |
And 4 more authors.
Endangered Species Research | Year: 2014
Temporal variability in species distribution remains a major source of uncertainty in managing protected marine species, particularly in ecosystems with significant seasonal or interannual variation, such as the California Current Ecosystem (CCE). Spatially explicit species- habitat models have become valuable tools for decision makers assisting in the development and implementation of measures to reduce adverse impacts (e.g. from fishery bycatch, ship strikes, anthropogenic sound), but such models are often not available for all seasons of interest. Broadscale migratory patterns of many of the large whale species are well known, while seasonal distribution shifts of small cetaceans are typically less well understood. Within the CCE, species- habitat models have been developed based on 6 summer-fall surveys conducted during 1991 to 2008. We evaluated whether the between-year oceanographic variability can inform species predictions during winter-spring periods. Generalized additive models were developed to predict abundance of 4 cetacean species/genera known to have year-round occurrence in the CCE: common dolphins Delphinus spp., Pacific white-sided dolphin Lagenorhynchus obliquidens, northern right whale dolphin Lissodelphis borealis, and Dall's porpoise Phocoenoides dalli. Predictor variables included a combination of temporally dynamic, remotely sensed environmental variables and geographically fixed variables. Across-season predictive ability was evaluated relative to aerial surveys conducted in winter-spring 1991 to 1992, using observed:predicted density ratios, nonparametric Spearman rank correlation tests, and visual inspection of predicted and observed distributions by species. Seasonal geographic patterns of species density were captured effectively for most species, although some model limitations were evident, particularly when the original summer-fall data did not adequately capture winter-spring habitat conditions. © Inter-Research 2014.
Demer D.A.,Southwest Fisheries Science Center |
Zwolinski J.P.,Ocean Associates Inc. |
Cutter G.R.,Southwest Fisheries Science Center |
Byers K.A.,Southwest Fisheries Science Center |
And 2 more authors.
ICES Journal of Marine Science | Year: 2013
To annually assess the northern stock of Pacific sardine (Sardinops sagax) in the California Current and set harvest quotas for the US fishery, managers have used an age-structured stock synthesis model fitted with results from acoustic-trawl (ATM), daily-egg-production, and aerial-photogrammetric survey methods, fishery landing and individual-length data, and many assumed or empirically derived parameters. In these assessments, sardine landed at ports spanning from Ensenada, México to Vancouver Island, Canada were assumed to be solely from the northern stock. It was also assumed that the ATM estimates of sardine biomass were negligibly biased for the sizes of fish sampled by the survey trawls (i.e., catchability q = 1 for sardine standard length (SL) values greater than ∼17 cm). Due to these catchability and length-selectivity assumptions, the ATM- and assessment-estimated abundances are mostly similar for larger sardine. However, the assessment estimates include large abundances of small sardine (SL values less than ∼15 cm) that are not represented in either the ATM-survey results or the fishery landings, and generally did not recruit to the migrating northern stock sampled by the ATM surveys. We considered four explanations for this disparity: (i) the ATM length-selectivity assumption is correct; (ii) the non-recruiting small fish may comprise a smaller portion of the stock than indicated by the assessments; (iii) during years of low recruitment success, those size classes may be virtually completely fished by the Ensenada and San Pedro fisheries; or (iv) they may belong to the southern sardine stock. This investigation emphasizes the previously identified importance of differentiating samples from the northern and southern stocks and surveying their entire domains. © 2013 Published by Oxford University Press on behalf of International Council for the Exploration of the Sea 2013.
Robertson K.M.,National Oceanic and Atmospheric Administration |
Minich J.,Ocean Associates Inc. |
Bowman A.J.,National Oceanic and Atmospheric Administration |
Morin P.A.,National Oceanic and Atmospheric Administration
Conservation Genetics Resources | Year: 2013
Two popular tissue preservatives, 100 % ethanol and 20 % salt saturated dimethyl sulfoxide (DMSO) solution were tested for the existence of amplifiable, free-floating DNA after 2-18 years of tissue storage. We found that short mtDNA fragments were consistently amplified and sequenced from DMSO preservative, while nDNA amplification was limited and inconsistent. Amplification of both mtDNA and nDNA failed most of the time for the ethanol samples. © 2013 Springer Science+Business Media Dordrecht (outside the USA).