MEPS 604:199-210 (2018)  -  DOI: https://doi.org/10.3354/meps12738

ABSTRACT: Long-term monitoring of marine ecosystems is critical to assessing how global processes such as natural environmental variation and climate change affect marine populations. Ichthyoplankton surveys provide one approach to such monitoring. We conducted weekly fish egg collections off the Scripps Institution of Oceanography (SIO) Pier (La Jolla, CA, USA) for 3 yr (2014 to 2017) and added a second sampling site near the La Jolla kelp forest for 1 yr (2017). Fish eggs were identified using DNA barcoding and data were compared to previous work from SIO Pier surveys from 2012 to 2014. We documented large interannual variability in fish egg abundance associated with climatic fluctuations, including an El Niño event captured during our sampling years. Overall egg abundance was reduced by >50% during periods of anomalously warm water in 2014 to 2016. Fish egg abundance rebounded in 2017 and was accompanied by a phenological shift of peak spawning activity. We found that interannual fish egg abundance may be linked with upwelling regimes and winter temperatures. Across the period of joint sampling, we found no distinct differences in community composition between the SIO Pier (soft bottom) and kelp forest habitat we sampled (2 km distant). Long-term monitoring of fish spawning can contribute to our understanding of how natural environmental variation, such as El Niño events, affects fish reproductive activity. This understanding may extend to trends in marine resource availability associated with climate and aid in evaluating the efficacy of existing management efforts.

KEY WORDS: Fish spawning · DNA barcoding · Ichthyoplankton · Long-term monitoring