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Checkley, DM, Lindegren M.  2014.  Sea surface temperature variability at the Scripps Institution of Oceanography Pier. Journal of Physical Oceanography. 44:2877-2892.   10.1175/jpo-d-13-0237.1   AbstractWebsite

Sea surface temperature (SST) has been measured from near the end of the Scripps Institution of Oceanography (SIO) pier daily since 1916. It is one of the world's longest instrumental time series of SST. It is widely used in studies of climate and marine ecosystems and in fisheries management. The authors hypothesized that a discontinuity exists in 1988, when the old pier was replaced with the present pier. A regression of annual-mean SST at SIO (SSTSIO) on the Pacific decadal oscillation index for 1916-87 was used to predict annual-mean SST (SSTSIO,PDO) for 1916-present. The residual (ResSST(SIO) = SSTSIO - SSTSIO,PDO) time series shows a positive discontinuity in 1988, when the present SIO pier was first used to measure SSTSIO. No discontinuity in 1988 was observed for ResSST at 12 other shore stations or in nearby waters. Use of the first principal component of other shore station time series of annual-mean SST as the predictor yields similar results. SSTSIO measured over 3 days shows a diel cycle and short-term variability consistent with rip current transport of warm surf-zone water to the end of the SIO pier. This study hypothesizes that rip current transport increased with the change from the old to the present pier and contributed to the observed discontinuity in SIO pier SST. The authors estimate an artifact of about +0.45 degrees C due to both rapid (1988 pier change) and gradual processes. Adjusting the SIO pier SST time series for this artifact reduces the long-term trend from +1.1 degrees to +0.6 degrees C century(-1), consistent with the global rate of change of SST over the past century.

Osgood, KE, Checkley DM.  1997.  Seasonal variations in a deep aggregation of Calanus pacificus in the Santa Barbara Basin. Marine Ecology-Progress Series. 148:59-69.   10.3354/meps148059   AbstractWebsite

A deep aggregation of fifth copepodid (C5) Calanus pacificus in the Santa Barbara Basin (SBB) was mapped over 1 1/2 yr with zooplankton net tows, an optical plankton counter, and a moored acoustic Doppler current profiler. High concentrations of diapausing C5 C. pacificus built up in the deep waters of the SBB during the summer and into the fall. During the buildup, the deep aggregation moved up from the bottom as oxygen became depleted in the basin's deep waters. The deep aggregation apparently builds up due to the basin trapping C5s that migrate below the sill depth from water advected over the basin. C5s are retained within the basin until they swim, or are forced, above the sill depth. Possible mechanisms responsible for the dispersal of the deep aggregation are migration to the surface waters with subsequent dispersal by surface currents, advection over the basin's sill due to the buildup of oxygen-deficient water, or flushing of the basin's deep water.

Checkley, DM.  1982.  Selective feeding by Atlantic herring (Clupea harengus) larvae on zooplankton in natural assemblages. Marine Ecology-Progress Series. 9:245-253.   10.3354/meps009245   AbstractWebsite

The hypothesis that larval herring Clupea harenyus select food by type as well as size was tested in laboratory experiments. Herring larvae were reared at 7 to 9°C on wild zooplankton. The percentage of herring larvae with food at day's end increased from 4 % (4 d) to 68 % (9 d) and averaged 83 % for larvae 25 to 74 d old. Larval herring selected particles according to type as well as size; this selectivity varied with larval age and hence size. Copepod nauplii and copepodites were preferred by larvae of all sizes. Among copepodites, Pseudocalanus sp, and Oithona sp. were preferred by smaller and larger larvae, respectively, while Acartia sp. was rarely ingested, even when of acceptable size. Mollusc veligers comprised a significant portion of the diet of young (4 to 24 d) larvae but were actively rejected by older larvae even when perceived and of acceptable size. Particles smaller than the largest acceptable size were consistently preferred, atypical of predation by vertebrates. These results indicate that larval herring select prey according to type as well as size and that this behavior is acquired through experience.

Jackson, GA, Checkley DM, Dagg M.  2015.  Settling of particles in the upper 100 m of the ocean detected with autonomous profiling floats off California. Deep-Sea Research Part I-Oceanographic Research Papers. 99:75-86.   10.1016/j.dsr.2015.02.001   AbstractWebsite

We have deployed an autonomous profiling float, the SOLOPC, to sample the concentration of particles larger than 100 mu m off the California coast at approximately hourly intervals down to at least 100 m for periods as long as 12 d. We used the data to estimate total aggregate concentrations hourly at 2-m depth intervals, studying the dynamics of particle sedimentation in this difficult-to-sample region. We find that even over time scales of a week, sedimentation is highly variable, with detectable sedimentation events on about one quarter of the days. Most of these observations were along the southwest coast of the United States, a region known for its coastal upwelling and not necessarily representative of more oligotrophic regions. The aggregate settling rates that we estimate, on the order of 50 m d(-1), are consistent with in situ measurements and with rates calculated from coagulation models. The time interval between observations and their vertical resolution constrain the velocities that can be measured. To capture particle settling with velocities less than the 100 m d(-1) that is usually reported for near surface aggregates requires a sampling interval no more than about 0.25 d with a 2 m vertical resolution. This technique provides a powerful new tool to study the dynamics of particles and their sedimentation near the ocean surface, where export starts. (C) 2015 The Authors. Published by Elsevier Ltd.

Shen, SG, Thompson AR, Correa J, Fietzek P, Ayon P, Checkley DM.  2017.  Spatial patterns of Anchoveta (Engraulis ringens) eggs and larvae in relation to pCO(2) in the Peruvian upwelling system. Proceedings of the Royal Society B-Biological Sciences. 284   10.1098/rspb.2017.0509   AbstractWebsite

Large and productive fisheries occur in regions experiencing or projected to experience ocean acidification. Anchoveta (Engraulis ringens) constitute the world's largest single-species fishery and live in one of the ocean's highest pCO(2) regions. We investigated the relationship of the distribution and abundance of Anchoveta eggs and larvae to natural gradients in pCO(2) in the Peruvian upwelling system. Eggs and larvae, zooplankton, and data on temperature, salinity, chlorophyll a and pCO(2) were collected during a cruise off Peru in 2013. pCO(2) ranged from 167-1392 atm and explained variability in egg presence, an index of spawning habitat. Zooplankton abundance explained variability in the abundance of small larvae. Within the main spawning and larva habitats (6-10 degrees S), eggs were found in cool, low-salinity, and both extremely low (less than 200 mu atm) and high (more than 900 mu atm) pCO(2) waters, and larvae were collected in warmer, higher salinity, and moderate (400-600 atm) pCO(2) waters. Our data support the hypothesis that Anchoveta preferentially spawned at high pCO(2) and these eggs had lower survival. Enhanced understanding of the influence of pCO(2) on Anchoveta spawning and larva mortality, together with pCO(2) measurements, may enable predictions of ocean acidification effects on Anchoveta and inform adaptive fisheries management.

Checkley Jr., DM, Ortner PB, Werner FE, Settle LR, Cummings SR.  1999.  Spawning habitat of the Atlantic menhaden in Onslow Bay, North Carolina. Fisheries Oceanography. 8:22-36.: Blackwell Science Ltd   10.1046/j.1365-2419.1999.00019.x   AbstractWebsite

The Continuous, Underway Fish Egg Sampler (CUFES) was used to sample pelagic eggs of the Atlantic menhaden (Brevoortia tyrannus) from 3-m depth off North Carolina in winter 1993–94 and 1994–95. Simultaneous measurements were made of temperature, salinity, and the concentration of chlorophyll a. The maximal concentration of eggs was 346 eggs m−3. Eggs were highly aggregated in patches which occurred between the Gulf Stream and mid-shelf fronts (17–23°C, 36.0–36.4‰). Unexpectedly, eggs were found almost exclusively in water of 20–60 m (mode 20 m) bottom depth. Thus, spawning appears related to bathymetry as well as hydrography. Variograms for egg concentration indicated a mean (± SE) patch scale of 3.6 ± 1.7 km and a high degree of spatial variance explained by CUFES sampling. Lagrangian modelling of particles moving in response to tides, winds, and a prescribed flow from the north indicated that the region of observed, maximal occurrence of eggs is favourable for the retention of eggs and larvae on the shelf adjacent to inlets used to enter nursery areas.

Maillet, GL, Checkley DM.  1991.  Storm-related variation in the growth-rate of otoliths of larval Atlantic menhaden Brevoortia tyrannus: a time series analysis of biological and physical variables and implications for larva growth and mortality. Marine Ecology-Progress Series. 79:1-16.   10.3354/meps079001   AbstractWebsite

Vertical mixing induced by storms is hypothesized to modify the spatial and temporal availability of food to fish larvae and thus influence their feeding and growth. We investigated the effects of storms on sagitta growth rates of 2 age classes (3 to 15 d and 16 to 50 d, post-hatching) of larval Atlantic menhaden Brevoortia tyrannus during winter 1986 in Onslow Bay, North Carolina, USA. We tested the null hypothesis that sagitta growth rate of 3 to 15 d and 16 to 50 d old larvae is independent of the timing and intensity of storms by using transfer functions to investigate relationships among daily time series of sagitta growth rate and meterological and oceanographic variables. Variation in sagitta increment widith was greatest during the first 1 to 2 wk after hatching. Reduction in sagitta growth rate coincided with storms and corroborated laboratory results that growth increments are formed daily and stressful events are manifest in sagitta microstructure. Age-related trends in sagitta growth rate were observed for both age classes and were removed from the analysis by a standardization procedure. Fluctuation in sagitta growth rate for 3 to 15 d old larvae was inversely cross-correlated with time series of wind speed. Fluctuation in sagitta growth rate for 16 to 50 d old larvae was inversely cross-correlated with time series of wind speed and heat flux. The pattern of cross-correlations for 3 to 15 d old larvae indicated an immediate response of sagitta growth rate to periods of strong winds while sagitta growth rate in 16 to 50 d old larvae lagged strong winds and heat fluxes by 2 to 5 d. Transfer function models incorporating wind speed and heat flux accounted for 40 to 54% of sagitta growth rate variation. Reduction in larval Atlantic menhaden growth rate during early life is consistent with the critical period concept and may be related to dispersion and aggregation mechanisms coupled to wind-induced vertical mixing and its effect on food concentration and availability.

Checkley Jr., DM, Bakun A, Barange M, Castro LR, Freon P, Guevara R, Herrick Jr. SF, McCall AD, Ommer R, Oozeki Y, Roy C, Shannon L, Van der Lingen CD.  2009.  Synthesis and perspective. Climate change and small pelagic fish. ( Checkley Jr. DM, Alheit J, Oozeki Y, Roy C, Eds.).:344-351., Cambridge, UK; New York: Cambridge University Press Abstract
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