Monitoring spatial and temporal variation in the spawning activity of nearshore marine fishes along the California coast via the molecular identification of fish eggs

Many studies have used the spawning activity of fishes to assess the abundance, distribution, and reproductive success of populations. While spawning activity of marine fishes in offshore waters has been studied extensively, little is known about the spawning activity that occurs in near shore communities. This study utilized weekly fish egg sampling in order to construct a seven-year time series of fish spawning near the Scripps Pier in La Jolla, California. Additionally, fish egg sampling was recently introduced to five other sites along the California coast – Santa Cruz, San Luis Obispo, Santa Barbara, Santa Monica, and Newport Beach. The majority of fish eggs collected have been identified to a species level through the use of DNA barcoding of the COI and 16S genes. Strong seasonal trends have been identified in the spawning seasons of fishes in La Jolla. However, the spawning activity within the summer spawning season, varies greatly among years, both in egg production and species diversity. The unpredictable shifts in spawning activity pose a threat to the stability of their populations and need to be analyzed further to identify factors responsible for these changes. While only one year of data has been collected from the newer sites, the two sites North of Point Conception show greatly reduced diversity in species composition compared to the Southern sites. The extent of spatial variation between sites will become more evident as more data is gathered from continuous sampling