Hannah R.W.,Hatfield Marine Science Center
California Cooperative Oceanic Fisheries Investigations Reports | Year: 2010
I investigated the potential to improve forecasts of annual loge recruitment to the ocean shrimp (Pandalus jordani) fishery using a pre-recruit index based on the percentage of age-zero shrimp from fishery samples in the year prior to recruitment. The index was incorporated into existing models in which loge age-1 recruitment is forced by environmental variables related to the spring transition in coastal currents (negative correlation with April sea level height at Crescent City, California, ASLHt-1) and the strength of April-July upwelling winds at 42 °N. latitude (negative correlation, AJUt-1) during the pelagic larval phase. For northern Oregon, the pre-recruit index improved model fit, increasing the coefficient of determination from 0.40 for a model based only on ASLHt-1 to 0.62 for the combined model. For southern Oregon, the index did not improve the fit of a model based on ASLHt-1and AJUt-1. However, the pre-recruit index alone had a higher correlation with age-1 recruits than the best environmental model (r2 of 0.43 versus 0.27). Although precision of the final models was low, both correctly predicted a stronger than average 2009 recruitment.
Sydeman W.J.,Farallon Institute for Advanced Ecosystem Research |
Sydeman W.J.,University of California at Davis |
Thompson S.A.,Farallon Institute for Advanced Ecosystem Research |
Field J.C.,Southwest Fisheries Science Center |
And 5 more authors.
Geophysical Research Letters | Year: 2011
Fluctuations in the positioning of major ocean currents can influence ecosystem dynamics, but previously the technology has been lacking to make direct observational assessments. Here, we test the hypothesis that positioning of the North Pacific Current (NPC) is related to biological attributes of the central-northern California Current Ecosystem (CCE). To test this hypothesis we use newly available data from the Argo array and compare it with a suite of well-known ecosystem indicators over 6 years, 2002 through 2007. We found increased biomass and productivity when the NPC was shifted poleward, and suggest that positioning influences advective transport of nutrients and perhaps key planktonic organisms from the sub-arctic domain thereby enhancing mid to upper trophic level species. This study is significant because climate change is predicted to cause poleward shifts in the westerlies that drive ocean currents and positioning of large marine gyre systems. Rather than reducing ecosystem productivity, poleward shifts in positioning of the NPC may be beneficial for many species of the central-northern CCE. Copyright 2011 by the American Geophysical Union.
Dayton P.K.,University of California at San Diego |
Kim S.,Moss Landing Marine Laboratories |
Jarrell S.C.,University of California at San Diego |
Oliver J.S.,Moss Landing Marine Laboratories |
And 8 more authors.
PLoS ONE | Year: 2013
Polar ecosystems are sensitive to climate forcing, and we often lack baselines to evaluate changes. Here we report a nearly 50-year study in which a sudden shift in the population dynamics of an ecologically important, structure-forming hexactinellid sponge, Anoxycalyx joubini was observed. This is the largest Antarctic sponge, with individuals growing over two meters tall. In order to investigate life history characteristics of Antarctic marine invertebrates, artificial substrata were deployed at a number of sites in the southern portion of the Ross Sea between 1967 and 1975. Over a 22-year period, no growth or settlement was recorded for A. joubini on these substrata; however, in 2004 and 2010, A. joubini was observed to have settled and grown to large sizes on some but not all artificial substrata. This single settlement and growth event correlates with a region-wide shift in phytoplankton productivity driven by the calving of a massive iceberg. We also report almost complete mortality of large sponges followed over 40 years. Given our warming global climate, similar system-wide changes are expected in the future. © 2013 Dayton et al.
Hurst T.P.,Hatfield Marine Science Center |
Fernandez E.R.,University of Alaska Fairbanks |
Mathis J.T.,University of Alaska Fairbanks
ICES Journal of Marine Science | Year: 2013
Hurst, T. P., Fernandez, E. R., and Mathis, J. T. 2013. Effects of ocean acidification on hatch size and larval growth of walleye pollock (Theragra chalcogramma). - ICES Journal of Marine Science, 70: 812-822.Rising atmospheric concentrations of CO2 are predicted to decrease the pH of high-latitude oceans by 0.3-0.5 units by 2100. Because of their limited capacity for ion exchange, embryos and larvae of marine fishes are predicted to be more sensitive to elevated CO2 than juveniles and adults. Eggs and larvae of walleye pollock (Theragra chalcogramma) were incubated across a broad range of CO2 levels (280-2100 atm) to evaluate sensitivity in this critical resource species. Slightly elevated CO2 levels (∼450 atm) resulted in earlier hatching times, but differences among egg batches were greater than those observed across CO2 treatments. Egg batches differed significantly in size-at-hatch metrics, but we observed no consistent effect of CO2 level. In three independent experiments, walleye pollock were reared at ambient and elevated CO2 levels through the early larval stage (to ∼30 days post-hatch). Across trials, there were only minor effects of CO2 level on size and growth rate, but fish in the ambient treatments tended to be slightly smaller than fish reared at elevated CO2 levels. These results suggest that growth potential of early life stages of walleye pollock is resilient with respect to the direct physiological effects of ocean acidification. © 2013 International Council for the Exploration of the Sea.
Hannah R.W.,Hatfield Marine Science Center
Fisheries Oceanography | Year: 2011
In this analysis, an atypical northward shift in the distribution of age-1 ocean shrimp (Pandalus jordani) recruits off Oregon in 2000 and 2002-2004 was linked to anomolously strong coastal upwelling winds off southern Oregon (42°N latitude) in April-July of the year of larval release (t-1). This is the first clear evidence that strong upwelling winds can depress local recruitment of ocean shrimp. Regression analysis confirmed a long-term negative correlation between loge of ocean shrimp recruitment and April sea level height (SLH) at Crescent City, California, in the year of larval release, for both northern and southern Oregon waters. The regional pattern of ocean shrimp catches and seasonal upwelling winds showed that, although the timing of the spring transition as reflected in April SLH drives ocean shrimp recruitment success off Oregon generally, the strength and consistency of spring upwelling limits the distribution of large concentrations of ocean shrimp at the southern end of the northern California/Oregon/Washington area. A northward shift in 1999 and 2001-03 in the northern edge of this 'zone of maximum upwelling' is the likely cause of the weak southern Oregon recruitment and resulting atypical distribution of ocean shrimp observed off Oregon in 2000 and 2002-04, with a return to a more typical catch distribution as spring upwelling moderated in subsequent years. It is noted that a northward shift in the conditions that produce strong and steady spring upwelling winds is consistent with many predictions of global climate models under conditions of global warming. © 2011 Blackwell Publishing Ltd.