Comparing quantity of marine debris to California horn shark sightings and egg appearances in Redondo Beach, California, USA

Abstract

Marine debris such as plastic, metal, and rubber, is a significant source of anthropogenic waste pollution in oceanic waters. Debris continues to be found along Southern California's coastlines and poses serious risks to biodiversity and ecosystem health through entrapment, ingestion, and entanglement. One particular species that drops eggs in the South Bay, particularly in the Palos Verdes peninsula, is the California horn shark (Heterodontus francisci). In California, H. francisci is managed by the California Department of Fish and Wildlife under general finfish regulations. The International Union for Conservation of Nature (IUCN) has published a ‘Red List of Threatened Species’ and H. francisci is characterized as being ‘data deficient.’ Additionally, several studies have noted dwindling H. francisci populations and have indicated a need for more localized management strategies to ensure their protection. Using the citizen science app, Marine Debris Tracker, this study geotagged and characterized waste, and used ArcGIS to generate heat maps of marine debris, H. francisci sightings and egg appearances to assess relationships. These maps help to address the data gaps that exist on (1) debris found on the Redondo Beach Esplanade, (2) local beach H. francisci sightings, and (3) H. francisci egg casings in the Palos Verdes peninsula to understand potential impacts of environmental waste on H. francisci. With these maps, citizen scientists, conservationists, and other local stakeholders can focus their efforts on key hotspots that could potentially endanger nesting practices of the H. francisci. Since oceanic pollution is an international issue that threatens ecosystems and biodiversity including nesting practices, leveraging citizen science applications can be a critical tool for conservation and management strategies.