June 17, 2021 — The following was released by NOAA Fisheries:
Counting fish can be difficult. Fish move, hide, and reproduce; they eat and are eaten. Many have evolved coloration patterns and body shapes that help them avoid being seen. The small size of young fish makes them especially hard to see. They may show up at inconsistent times and places, or not at all, depending on unpredictable environmental conditions.
This was the quandary rockfish experts faced in 2017. The federal recovery plan for bocaccio and yelloweye rockfish in Puget Sound called for annual surveys of the endangered rockfish produced that year, also known as young-of-the-year fish.
Very little is known about how young fish join rockfish populations in Puget Sound, a process called recruitment. Sometimes few fish recruit into the population, despite adequate abundance of reproductive adults. When climatic and oceanographic conditions align, however, rockfish recruits arrive in near-shore habitats in great abundance. Understanding the conditions that lead to these boom years is key to developing management actions to protect and recover rockfish in the region.
That still left the difficult question of how to count tiny (less than 10 centimeters long) rockfish recruits throughout Puget Sound. The best option for NOAA was a collaborative effort with partners throughout the region, including community scientists who are also scuba divers. Scuba diving offers the opportunity to observe fish directly, including taking photos, with minimal disturbance or disruption of their behavior, and no mortality.