In recent years, bivalve hatcheries in the Atlantic Coast of the USA have been affected by larval crashes of unknown causes. The Bivalve Hatchery Health Consortium (BHHC) was established in 2023 to try to understand the causes leading to reduced larval performance and identify avoidance and prevention tools. A process was developed for enrollment of hatcheries into the BHHC that protects confidentiality of their data and production practices. The BHHC also developed a protocol for the proactive collection of samples of water, algae, and larvae from as many good and bad larval production runs as possible throughout the year, from broodstock conditioning to post-set. This presentation will highlight the process used in sample analysis and showcase results from the first sampling season (2024).
As of September 2025, 37 (18 public-research-restoration and 19 commercial) hatcheries from the Atlantic Coast of the USA have enrolled in the BHHC. During the 2024 and 2025 production seasons, hatcheries provided samples and data from more than 80 production runs (from 1 - 8 per hatchery). Sampling covered four bivalve species (mainly eastern oysters, but also northern quahogs, bay scallops, and mussels). In 2024, 55% of the 33 production runs were crashes or showed low larval performance. Most bad larval runs showed failure of larvae to progress through development early in the run (by day 6 post fertilization), commonly followed by crashes later in the production run. Histological examination showed no evidence of known pathological conditions or infectious agents in larvae. Water chemistry analysis showed the presence of potentially toxic elements (e.g., arsenic) in only three of all production runs. More than 500 bacterial isolates were cultured from both good and bad larval runs. Although a few pathogenic vibrios were isolated, there was no consistent association of vibrios with bad runs, suggesting vibriosis is not the primary cause of crashes. Molecular analysis of microbiota, however, showed that bad runs can be predicted based on microbial composition. Larval challenge experiments using water from larval performance runs suggests that some of these issues could be due to a virus or a toxin/s able to pass through a 0.22-micron filter. Current efforts are focused on toxin (e.g., from algal blooms) and toxicant (anthropogenic chemicals) identification. Results from the 2024 season suggest that the issues affecting larval production are complex, confirming the need for a collaborative, integrated approach to identify and solve the issues.
This research is funded by the USDA Northeast Regional Aquaculture Center Award 123476-Z5220211