Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Supplemental Files
• Related Datasets
• Parameters
• Instruments
• Deployments
• Project Information
• Funding

This study is carried out within the temperate to subtropical Southern California Bight and surrounding coastal areas between 32° and 35° N, and 117° and 120° W. Specific locations sampled fall within the CalCOFI and CCE-LTER programs quarterly survey grid from lines 76.7 to 93.4 and stations 26 to 55. 

Sampling stations were sampled ~2-7 days after the California Cooperative Oceanic Fisheries Investigations (CalCOFI) & California Current Ecosystem Long-term Ecological Research Program (CCE-LTER) Fall 2020 and Winter 2021 surveys had sampled the same stations. The CalCOFI & CCE-LTER Spring 2021 survey was delayed by ~2 weeks relative to this project.

Each cruise no is composed of one or more day trips using one of two research vessels (RV Bob & Betty Beyster or RV Shearwater). The two-three letters indicate the research vessel, the four digits indicates YYMM.

CTD was attached to a wire and positioned just above a 71cm diameter dual Bongo plankton net system to record depth and physical variables during horizontal net tows at a ship speed of 1.5-2.5 knots down to 13-62 m depth. The CTD was not allowed to acclimate before deployment and the positioning of the CTD caused substantial interference from water mixing and air bubble release from the nets during the down-cast. Therefore, only the up-cast is reported. Following initial data processing (see Data Processing) up-cast Depth ~ Temperature, Salinity, Density profiles were inspected and went through two series of point checking where outlier values were manually removed.

The SonTek CastAway-CTD model CC1403002 was used. Temperature and conductivity sensor calibration date 4/3/2015. Pressure sensor calibration date 3/13/2015.

CastAway-CTD software version 1.3 (firmware version v026_r2818) was used for data acquisition and processing using default correction algorithms and binned over 0.3 decibar changes. For more information on data processing please see manual at: https://www.sontek.com/castaway-ctd (not open source).

The CTD data report contains some gaps in the temperature, salinity and density data. These gaps result from the removal of outliers.

BCO-DMO Processing Notes:
* Added ISO_DateTime_UTC and ISO_DateTime_PDT columns (ISO formatted DateTimes) by merging the provided date and times of the specific time zones.

NSF Award Abstract:
Like many species of small pelagic marine fish, recruitment and productivity of Northern Anchovy fluctuate by orders of magnitude among years. When abundant, the anchovy support a wide range of marine species, including marine mammals, seabirds and a diverse group of marine fishes. Anchovy, which previously thrived during periods of cool-water temperatures and strong coastal upwelling, are currently booming with abundances far in excess of any historical record, even though the California Current Ecosystem is experiencing an unprecedented marine heat wave. This unexpected occurrence challenges the most basic understanding of the mechanisms driving population dynamics in the species. This project is investigating the effects of trophic relationships on population productivity by capitalizing on the immediate research opportunity afforded by the novel, yet ephemeral, state of a local marine heat wave. Findings from the work are being used to develop a mechanistic model of coastal pelagic fish population dynamics generally, and anchovy dynamics in particular. Funded field and lab work are supporting opportunities for undergraduate training and research, and are generating open-access data that serve the research and teaching/training communities into the future.

This RAPID project augments the scheduled Fall research cruises jointly run by the California Cooperative Oceanic Fisheries Investigation and the California Current Ecosystem Long-Term Ecological Research programs. Together, these programs conduct regional oceanographic surveys that include anchovy spawning grounds and larval nursery areas. The RAPID-augmented sampling is designed to test the emerging hypothesis that anchovy populations are trophodynamically mediated at the larval stage, whereby high recruitment results from increased trophic transfer efficiency from the base of the food web. Larval diets and prey selection analyses are being paired with amino acid compound-specific isotope analysis (δ15N) of the larvae and prey field to generate detailed information on larval trophic ecology. Larval diets and plankton community structure are being related to available data on upwelling and productivity to assess environmental and biological drivers to trophic transfer efficiency. Collectively, these analyses are revealing how food chain length is regulated at the larval level through prey selection, at the prey level through community composition, and at the base of the food chain via coastal upwelling and primary production. Furthermore, this project is establishing whether the current trophic level of anchovy larvae is equal to that of historic population booms and if this is the result of favorable feeding conditions throughout their habitat. Findings from the study are generating a mechanistic understanding of the trophic underpinnings of small pelagic fish population productivity in coastal upwelling systems.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

Location Description:
This study is carried out within the temperate to subtropical Southern California Bight and surrounding coastal areas between 32° and 35° N, and 117° and 120° W. Specific locations sampled fall within the CalCOFI and CCE-LTER programs quarterly survey grid from lines 76.7 to 93.4 and stations 26 to 55.

Project Affiliations:
California Current Ecosystem Long-term Ecological Research Program (CCE-LTER)
California Cooperative Oceanic Fisheries Investigations (CalCOFI)