Conservation aquaculture as a tool for imperiled marine species: Evaluation of opportunities and risks for Olympia oysters, Ostrea lurida

Conservation aquaculture is becoming an important tool to support the recovery of declining marine species and meet human needs. However, this tool comes with risks as well as rewards, which must be assessed to guide aquaculture activities and recovery efforts. Olympia oysters (Ostrea lurida) provide key ecosystem functions and services along the west coast of North America, but populations have declined to the point of local extinction in some estuaries. Here, we present a species-level, range-wide approach to strategically planning the use of aquaculture to promote recovery of Olympia oysters. We identified 12 benefits of culturing Olympia oysters, including identifying climate-resilient phenotypes that add diversity to growers’ portfolios. We also identified 11 key risks, including potential negative ecological and genetic consequences associated with the transfer of hatchery-raised oysters into wild populations. Informed by these trade-offs, we identified ten priority estuaries where aquaculture is most likely to benefit Olympia oyster recovery. The two highest scoring estuaries have isolated populations with extreme recruitment limitation—issues that can be addressed via aquaculture if hatchery capacity is expanded in priority areas. By integrating social criteria, we evaluated which project types would likely meet the goals of local stakeholders in each estuary. Community restoration was most broadly suited to the priority areas, with limited commercial aquaculture and no current community harvest of the species, although this is a future stakeholder goal. The framework we developed to evaluate aquaculture as a tool to support species recovery is transferable to other systems and species globally; we provide a guide to prioritizing local knowledge and developing recommendations for implementation by using transparent criteria. Our collaborative process engaging diverse stakeholders including managers, scientists, Indigenous Tribal representatives, and shellfish growers can be used elsewhere to seek win-win opportunities to expand conservation aquaculture where benefits are maximized for both people and imperiled species.

Location Matters: Passive and Active Factors Affect the Vertical Distribution of Olympia Oyster (Ostrea lurida) Larvae

Dispersal, retention, and population connectivity are impacted by current regime and the behaviors that drive larval distribution, so understanding both is key to informing restoration of native species like the Olympia oyster (Ostrea lurida) across its range in western North America. This study explores the relationships between several factors (temperature, [chl a], larval size, tidal stage, and estimated current speed) and Olympia oyster larval vertical distributions in Fidalgo Bay (48.4828, − 122.5811), a shallow, tidally flushed bay in the Salish Sea. Olympia oyster larvae collected from four depths over the tidal cycle from July 11–14, 2017, were ~ 20% deeper near slack tide and shallower during the faster parts of both ebb and flood, with a threshold for this transition around an estimated 25 cm s−1. This pattern does not suggest tidally timed migrations as has been shown in another population of Olympia oysters, nor can this pattern be totally explained by passive processes. Larvae did not cluster at depths with specific temperatures or [chl a] but there was a difference in larval size between surface and bottom waters, with older, larger larvae more common at the bottom. Fidalgo Bay does not exhibit two-way flow or strong vertical shear, so vertical distribution of larvae likely has little effect on transport in this system but might in other similarly shallow habitat areas with higher stratification that are target restoration sites in the Salish Sea. These results add to the growing number of studies that show location-specific differences in larval vertical distribution and behavior within taxa and underscore the importance of integrating local hydrodynamics into predictions of bivalve larval transport.

KOMPOSISI DAN KELIMPAHAN BIVALVIA DI EKOSISTEM LAMUN PERAIRAN JUANGA KABUPATEN PULAU MOROTAI PROVINSI MALUKU UTARA

Secara ekologi bivalvia berperan dalam menjaga poduktifitas lingkungan. Kurangnya informasi mengenai keberadaan dan komposisi spesies dari Bivalvia tersebut, mendorong untuk dilakukan penelitian ini. Tujuan penelitian adalah untuk menganalisis komposisi dan kelimpahan spesies Bivalvia di ekosistem Lamun Desa Juanga Kecamatan Morotai Selatan, Kabupaten Pulau Morotai. Pengambilan sampel menggunakan metode kuadrant ukuran 1 x 1 meter untuk Bivalvia Epifauna, dan pipa paralon dengan diameter 10 cm untuk Bivalvia yang terdapat dalam dasar perairan (infauna). Analisis data menggunakan rumus komposisi, dan kelimpahan menggunakan rumus kelimmpahan dengan menggunakan pendekatan Excel. Hasil penelitian didapatkan sebanyak 7 spesies bivalvia yang tersebar di empat stasiun penelitian yaitu Anadara gubernculum, Donax trunculus, Dosinia dilecta, Frogum unedo, Latona cuenata, Atrina pectinata dan Ostrea lurida dengan jumlah total sebanyak 112 individu. Jumlah individu spesies bivalvia berkisar 47- 96 dengan nilai tertinggi pada adalah Anadara gubernculum pada stasiun II (96%), dan terendah di stasiun I (47%). Kesimpulan diperoleh (1) Komposisi spesies Bivalvia memiliki presentasi (absolut) yaitu Anadara gubernculum 0,74 sedangkan untuk spesies lain secara keseluruhan memiliki komposisi kategori (rendah) dengan nilai dibawah 0,23. (2) Kelimpahan individu dan kelimpahan relatif di semua stasiun yang memiliki nilai tertinggi yaitu jenis Anadara gubernculum.

Effects of winter conditions on Olympia oyster reproduction and larval yield

For marine invertebrates that live in temperate regions, reproductive processes are tightly linked to seasonal temperature changes, yet we know little about how reproduction will shift as winters become milder. This study examined effects of winter temperature on spring reproduction in the Olympia oyster, Ostrea lurida. Adults were exposed to two winter temperatures (7°C, 10°C) in the presence of two feeding regimes, high (50k cells/mL) and low (5k cells/mL) algal density, for either 7 weeks or 12 weeks. Following treatments, adults were induced to spawn in common conditions using hatchery techniques, and larvae were reared through settlement to assess viability. Adults overwintered in elevated temperature contained larger oocytes, and those also held in elevated algal density contained more developed sperm. Elevated temperature (10°C) under both feeding regimes resulted in larvae that tended to be larger upon release from the maternal brood chamber. However, winter temperature did not impact fecundity, larval release timing, or larval viability, nor was larval viability related to larval size upon release. In the wild, more developed gametes and larger larvae following milder winters could greatly impact recruitment patterns. When larvae are reared in the hatchery, however, elevated winter temperature will not likely impact larval viability or yield. Interestingly, overwintering duration greatly impacted broodstock survival and larval production. Regardless of winter temperature or feeding rate, broodstock overwintered in the hatchery for 12 weeks produced fewer larvae and had higher mortality during spawning compared to those held for only 7 weeks. Furthermore, broodstock overwintered in the low temperature treatment (7°C) with high algal density (50k cells/mL) experienced high mortality during spawning. Broodstock mortality is disadvantageous for hatcheries, can hinder larval production, and decrease genetic diversity of offspring. We therefore recommend that hatcheries overwinter O. lurida broodstock in slightly warmer temperatures and minimize the amount of time they are held in captivity prior to spawning. Finally, because algal density during winter treatments did not impact broodstock survival or spring larval production, hatcheries may restrict feeding without impacting production, given broodstock are in good condition upon collection.Highlights of the manuscriptMilder winters may result in more developed O. lurida sperm, larger oocytes, and larger larvae, but will not likely impact larval production timing or magnitude, indicating that O. lurida reproduction is relatively resilient to shifting winter temperatures.In a hatchery setting, O. lurida larval size upon release does not predict larval survival, and hatcheries should not presume that smaller O. lurida larvae are of poor quality.When overwintering Ostrea lurida broodstock in the hatchery prior to spring production, chilling seawater to historic winter temperatures is not necessary, nor is feeding broodstock high algal densities, and the amount of time broostock are held prior to spawning should be minimized.

Olympia oyster, Ostrea lurida, in Puget Sound: stable isotope shell profiles as potential indicators of a changing climate

There is a need to monitor environmental changes in situ across aquatic ecosystems. Sclerochronology, a systematic biogeochemical method that assesses variations in the accretionary hard tissues of invertebrates, can be useful in studying these changes. Further studies are needed to evaluate whether an equilibrium relationship exists between seasonal annual temperature variations in bivalve shells of species with multiple geographic ranges. We present one of the first sclerochronology reports to characterize the δ18O and δ13C shell profiles of the Olympia oyster, Ostrea lurida Carpenter, 1864. We evaluated its utility as a proxy for past water temperature relating to seasonal cycles. The objectives were to: (1) assess shell δ18O and δ13C values from specimens sampled over time; and (2) to evaluate whether δ18O shell profiles correlate with seasonal temperature patterns. Seven O. lurida specimens were collected, and measurements were taken across shell growth. Results from generalized linear mixed models (GLMM) showed that O. lurida produced δ18O profiles consistent with a sinusoidal time pattern. The δ18O values ranged from −2.74‰ to −1.05‰, and there was a significant third-order polynomial temporal relationship. Covariation between profiles of shell δ18O and δ13C values was observed over time. Two independently estimated measures of δ18O water, accounting for salinity, temperature, and shell carbonate, were also positively correlated over time. Implications support the theory that O. lurida shell δ18O profiles may be in isotopic equilibrium with ambient water conditions with applications for monitoring programs.