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Surf zones are highly dynamic marine ecosystems that are subject to increasing anthropogenic and climatic pressures, posing multiple challenges for biomonitoring. Traditional methods such as seines and hook and line surveys are often labor intensive, taxonomically biased, and can be physically hazardous. Emerging techniques, such as baited remote underwater video (BRUV) and environmental DNA (eDNA) are promising nondestructive tools for assessing marine biodiversity in surf zones of sandy beaches. Here we compare the relative performance of beach seines, BRUV, and eDNA in characterizing community composition of bony (teleost) and cartilaginous (elasmobranch) fishes of surf zones at 18 open coast sandy beaches in southern California. Seine and BRUV surveys captured overlapping, but distinct fish communities with 50% (18/36) of detected species shared. BRUV surveys more frequently detected larger species (e.g. sharks and rays) while seines more frequently detected one of the most abundant species, barred surfperch ( Amphistichus argenteus ). In contrast, eDNA metabarcoding captured 88.9% (32/36) of all fishes observed in seine and BRUV surveys plus 57 additional species, including 15 that frequent surf zone habitats. On average, eDNA detected over 5 times more species than BRUVs and 8 times more species than seine surveys at a given site. eDNA approaches also showed significantly higher sensitivity than seine and BRUV methods and more consistently detected 31 of the 32 (96.9%) jointly observed species across beaches. The four species detected by BRUV/seines, but not eDNA were only resolved at higher taxonomic ranks (e.g. Embiotocidae surfperches and Sygnathidae pipefishes). In frequent co-detection of species between methods limited comparisons of richness and abundance estimates, highlighting the challenge of comparing biomonitoring approaches. Despite potential for improvement, results overall demonstrate that eDNA can provide a cost-effective tool for long-term surf zone monitoring that complements data from seine and BRUV surveys, allowing more comprehensive surveys of vertebrate diversity in surf zone habitats.

Food webs in ecotones linking adjacent ecosystems may depend on cross-ecosystem subsidies. In surf zones of temperate sandy beaches, higher-level consumers often rely on intertidal prey that utilize allochthonous primary production. We evaluated the importance of phytoplankton and kelp-based prey, as well as physical characteristics of beaches, to diet of a surf zone fish, barred surfperch ( Amphistichus argenteus ), through stomach content and stable isotope analyses. Our results suggested that barred surfperch rely on prey from both phytoplankton and kelp-based subsidies, but their relative contribution to diet varied widely across beaches. Sand crabs ( Emerita analoga ), which depend on phytoplankton, were abundant at every beach, but their contribution to diet in stomach contents varied from 2 to 87% among sites. At the majority of beaches, δ 13 C values of fish muscle tissue, which reflects diet integrated over time, were within 0.5 ‰ of sand crab values, suggesting a reliance on phytoplankton-based prey. However, kelp-dependent prey associated either with beach wrack or subtidal reefs was also present in surfperch stomachs from all beaches (up to 41–72%). The notable enrichment in 13 C of juvenile surfperch at two beaches and adults at one beach relative to sand crabs suggested a longer-term contribution of kelp-based prey to fish diet. The detection of kelp-based prey in surfperch diets also indicates the potential for reciprocal subsidies in these ecotones. Our results suggest trophic connectivity between surf zones and kelp forests and sandy beaches is spatially variable and that opportunistic higher-level consumers can shift their diet in response to the availability of phytoplankton and kelp-based food resources.

The Calico Surfperch (Amphistichus koelzi) shares a similar size, morphology and feeding habitat with its 2 widely-sympatric congeners, the Barred Surfperch (Amphistichus argenteus) and Redtail Surfperch (Amphistichus rhodoterus). Like the other 2 species, A. koelzi is an important commercial and recreational resource, but unlike these species, A. koelzi has received virtually no attention in the scientific literature. We found average relative fecundity to be significantly higher than in A. koelzi's 2 congeners, A. argenteus and A. rhodoterus, and the slope of the regression of brood count on female size in A. koelzi was steeper and translated to the left of the same slopes representing the 2 congeners.

Surf Scoter (Melanitta perspicillata), a sea duck that winters commonly along the coast of the Pacific Northwest states, was observed exhibiting unusual foraging behavior in the swash zone of a beach on the Point Reyes Peninsula, California, in mid-January of 2015. This note reviews the literature involving scoter foraging behavior, discusses the likely prey items targeted, and the potential risks posed by such behavior.