In situ spawning in a marine broadcast spawner, the Pacific oyster C rassostrea gigas : Timing and environmental triggers

Abstract

The precise environmental conditions under which broadcast spawners spawn in the field remain largely unknown. We investigated this issue in the oyster Crassostrea gigas using three different methods at different time scales in two traditional oyster farming areas of the French Atlantic Coast, the Bay of Arcachon and Marennes-Ol eron. We directly recorded spawning at high temporal resolution using high-frequency noninvasive (HFNI) valvometry from 2007-2014 and measured the dry mass and oyster larvae abundance in 2008 and 2009. We analyzed a 29-yr series of oyster D-larvae numbers in the Bay of Arcachon (1982Arcachon ( -2010. By combining these three approaches, we demonstrated that during the summer months at both sites, spawning in C. gigas occurs in the morning or during the evening, essentially at high tide of perigean spring tides, independent of the positions of these oysters, above or below the lowest water level. We characterized the associated water currents at the spawning location in the Bay of Arcachon and observed that spawning systematically occurs during the early phase of a water current peak, at the beginning of ebbing. We propose that this water current peak acts as a final trigger for spawning. These results have ecological consequences associated with gamete encounters and the dispersal of fertilized eggs (zygotes).

High Frequency Non-invasive (HFNI) Bio-Sensors As a Potential Tool for Marine Monitoring and Assessments

“…Spawning events between 2003 and 2014 consistently occurred during spring high tides at both locations, when the moon is closest to the earth (perigee). Peaks in water current were proposed as the final spawning trigger (Bernard et al, 2016). On the whole, the above studies demonstrate that the HFNI valvometer has been successful to investigate various aspects of bivalve life history and how these are affected by the prevailing environmental drivers.…”

“…Reproduction and spawning behavior have been studied for the Pacific oysters Crassostrea gigas in the Bay of Arcachon and the Bay of Marennes-Oléron, France using the HFNI valvometer (Bernard et al, 2016). Spawning behavior in female Pacific oysters is characterized by rapid contractions of the adductor muscle.…”

“…To date tests have been carried out with blue and brown mussels Mytilus edulis and Perna perna, giant tropical clams Hippopus hippopus and Tridacna maxima, Icelandic scallops Chlamys islandica, black scallops (Chlamys varia), grooved carpet shell (Ruditapes decussatus), Pacific oysters Crassostrea gigas, black-lip pearl oysters (Pinctada margaritifera) and Asiatic clams Corbicula fluminea; • The system today is the only one to our knowledge which allows for simultaneous recordings of clam growth (Schwartzmann et al, 2011), valve activity behavior (Tran et al, 2010), biological rhythms and spawning (Bernard et al, 2016);…”

“…• The system allows to identify very clearly when the animal is spawning, up to the minute or less, and to potentially predict the spawning time with accuracy (Bernard et al, 2016). This is a strong sign of clam welfare and good water quality.…”

Recruitment of the Pacific oyster Crassostrea gigas in a shellfish-exploited Mediterranean lagoon: discovery, driving factors and a favorable environmental window

“…gigas has been widely studied all over the world, and its life history (reproduction, larval cycle and re cruitment phase) has been relatively well described in both controlled environments (Fabioux et al 2005, Enriquez-Diaz et al 2009, Rico-Villa et al 2010) and coastal tidal ecosystems (Dutertre et al 2010, Thomas et al 2016, Bernard et al 2016. Fewer studies have been conducted in nanotidal environments such as Mediterranean lagoons (Tagliapietra & Ghirardini 2006).…”