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TROPHIC ECOLOGY VARIABILITY AND RELATIONSHIP TO RECRUITMENT OF LARVAL NORTHERN ANCHOVY OVER THE PAST 50 YEARS

Over the centuries, Northern anchovy (Engraulis mordax) stocks have experienced large fluctuations in size and recruitment even before the impact of fisheries, likely in response to oceanographic changes. Although the underlying mechanisms for these fluctuations are still poorly understood, changing environmental conditions such as temperature, explain some of the variation in population size and recruitment. However, these physical factors likely affect anchovy indirectly because, for example, they induce change to plankton community composition and abundance, which then dictates prey availability for larvae and juveniles anchovies. In this study, we explore the linkages between larval fitness, trophic ecology and recruitment variability by conducting nitrogen isotopic analysis on tissues and specific amino acids (AA’s) from larvae collected off California by the 65-year CalCOFI program. Larval 15N-at-length positively correlated with temperature, but negatively with recruitment, indicating a change in nitrogen availability at the food-web base and/or a shortening of the larval food chain during colder years, with high recruitment. Furthermore, larval body depth-at-length (a proxy for fitness) positively correlated with chlorophyll a and recruitment, suggesting improved larval fitness and survival to adulthood in more productive years. The trophic ecology and complexity of the larval food chain is being further assessed through Compound Specific Isotopic Analysis of AA’s by High Pressure Liquid Chromatography coupled with offline Isotope Ratio Mass Spectrometry.

Authors

Swalethorp, R., Scripps Institution of Oceanography, UC San Diego, USA, rswalethorp@ucsd.edu

Thompson, A. R., Southwest Fisheries Science Center, NOAA Fishery, USA, andrew.thompson@noaa.gov

Chargualaf, D., Southwest Fisheries Science Center, NOAA Fishery, USA, derekachargualaf@gmail.com

Ohman, M. D., Scripps Institution of Oceanography, UC San Diego, USA, mohman@ucsd.edu

Aluwihare, L. I., Scripps Institution of Oceanography, UC San Diego, USA, laluwihare@ucsd.edu

Landry, M. R., Scripps Institution of Oceanography, UC San Diego, USA, mlandry@ucsd.edu

Details

Poster presentation

Session #:062
Date: 03/01/2017
Time: 11:00 - 12:00
Location: Poster/Exhibit Hall

Presentation is given by student: No

PosterID: 504