Seal research helps understand fish abundance in Pacific

Research on the Pacific Ocean's twilight zone, a region located 200 to 1,000 meters below the surface, is crucial but difficult due to high costs and challenges in accessing these depths. A recent study has tapped into the migratory habits of northern elephant seals to gather data about fish populations in this little-understood area. The study connects ocean conditions with fish populations by tracking how these seals forage and reproduce. Over the past decade, scientists have used advanced monitoring to study the seals at Año Nuevo Island Reserve in California. They found that different oceanographic conditions impact fish abundance, which in turn affects seal health and reproduction. Despite the harsh environment of the twilight zone, elephant seals have adapted to feed in these depths for months at a time. Their feeding habits help scientists estimate changes in fish populations over the years. The study shows a link between seal weight and ocean conditions, noting that better conditions lead to more fish available and healthier seals. The findings indicate that years with favorable oceanographic conditions can lead to a successful seal population. For example, seal mothers that are well-fed are more likely to give birth to healthy pups, suggesting a two-year delay between ocean conditions and seal reproduction rates. Although the study focuses on the interaction between the seals and fish in the twilight zone, it does not specify the types of fish present. However, the researchers suggest that monitoring marine predators like the southern elephant seal could provide valuable insights into changes occurring in the ocean due to climate change and increased fishing activity. Overall, this research underscores the importance of understanding the twilight zone and how it affects the broader marine ecosystem. The study's authors emphasize the need to explore this mysterious ocean layer further as it plays a critical role in ocean health.