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While high levels of siltation are known to be deleterious to eastern oysters (Crassostrea virginica), the collective effect of suspended and bedded sediment is understudied from the perspective of oyster farming and bed restoration. In this study, we used laboratory experiments to explore spat settlement rates on a wild bed proxy substrate (i.e., empty shells on the bottom of experimental tanks) in conditions simulating a siltation event and the presence of suspended spat collectors. Using high-frequency valvometry, we also described the behavioural effects of acute sediment burial on wild adult oysters in situ. The vast majority of larvae settled on bottom substrate as opposed to suspended collectors. Sediment negatively affected overall oyster spat settlement on bottom shell, as spat densities were ≈3 × lower when sediment was present. This negative effect was largely attributed to severely depressed spat densities on the upper side (top) of bottom shells. Settlement on the underside of bottom shell was less affected. Wild adult oyster behaviour was negatively affected by acute burial, which ultimately resulted in death. We suggest that the reduction in settlement in the presence of siltation is likely due to the combined effects of suspended sediment on cue detection and bedded sediment on substrate availability. Given that oysters are ecosystem engineers, the negative effects of siltation on both larval and adult oysters can ultimately result in cascading effects to the surrounding biological community.

The behavior of stage IV American lobster (Homarus americanus) larvae in relation to various water temperatures was observed in laboratory. Time budgets were documented in 2009 in trials using a single larva per experimental enclosure in relation to three temperature exposures (10°C. 15°C. and 20°C). Larvae acclimated at a given temperature (15°C and 20°C) were used. The same treatments were used in 2010, where one larva was observed within a group of five individuals per experimental enclosure. Larvae took less time to hide when they were acclimated to 15°C and then exposed to 20°C. Video observations showed that larvae were stressed (repeated tail flicks) when treatments simulated important heat shocks (e.g., larvae acclimated at 20°C and exposed to 10°C). Results for single larva were similar to those from groups of larvae. The tail-flicks display was also observed in 2010 with larvae acclimated at 15°C and then exposed to 10°C. Observations from both years showed that the time budget was simi...

Larval behavior and hydrodynamics may affect the vertical distribution of planktonic larvae and, in turn, spat location in the intertidal zone. This study describes the vertical profile of competent larvae in the water column and the distribution of spat on soft-bottoms, and quantifies the relationship between both distributions for the softshell clam ( Mya arenaria ) and the blue mussel ( Mytilus edulis ). Sampling was carried out in 2007 and 2008 along the coast of New Brunswick (Canada) in two tidally contrasted regions: Bay of Fundy (high tidal amplitude) and Northumberland Strait (low tidal amplitude). The planktonic larvae were collected with a pump at three depths. Spats were collected directly from the top layer of sediments as well as with two types of collectors. Sampling in the Bay of Fundy site took the day/night cycle into account. The distribution of planktonic larvae and spats in the intertidal zone was highly variable for both species. Overall, no general pattern in the larvae distribution was observed. The day/night cycle did not affect the distribution and abundance of planktonic larvae and spats. Only a few statistically significant relationships were observed between the abundance of spats in the intertidal zone and the abundance of planktonic larvae. Soft-bottom habitats are highly unstable and this characteristic may explain, in part, the absence of relationship between spat location and the vertical profile of planktonic larvae.

A population of European oysters (Ostrea edulis) was recently discovered off the eastern coast of Canada. The occurrence of this newly established population led various aquaculture stakeholders to consider this species commercially. To better assess recruitment capacity, the physiological quality of the adults, eggs, and larvae was described using glycogen and various lipid contents, including a TAG/ST ratio. Adults, early nonfeeding stages (eggs, pretrochophores, trochophores, veligers) and newly-released larvae were periodically sampled in the wild and/or the hatchery during the spawning period. The initial glycogen content was higher in wild oysters than hatchery-conditioned ones. The following larval stages showed higher lipid content in wild individuals as well. Spat collection in the wild was abundant. The free-living larvae, however, did not survive more than 10 days in the hatchery. TAG/ST ratios decreased during the veliger stage development and were lower when larvae were released from the paleal cavity of the female. The high spat collection observed in the wild suggests that observed TAG/ST ratios in early nonfeeding larvae are representative of a good larval quality. The physiological quality of the larvae in the wild seems to be good enough to allow larvae to settle in this particular environment.

Various biological characteristics of the exotic green crab (Carcinus maenas) were studied in 2000 and 2001 to describe its population structure and reproductive strategy off the coast of Prince Edward Island (PEI), Canada. This particular population is found at the northern limit of the green crab distribution off the east American coast. Results showed that the number of female crabs was higher during springtime compared with the rest of the year. Male crabs were found in higher numbers from August to December. Ovigerous females were observed from early July to mid-September, their numbers peaking in early July. This was confirmed by a gonadosomatic analysis, which showed that the relative gonadal wet weight dropped from late July to mid-September 2001. Fecundity was estimated at 140,000–200,000 embryos per mass. Mating occurred after larval release, which occurred from late August to December with a peak in September. Mature males were molting from June to December, but mainly in July. This wa...

A European oyster population (Ostrea edulis) was recently discovered off the Eastern coast of Canada. The occurrence of this population led various aquaculture stakeholders to consider this species commercially. The aim of this study is to determine the best time to collect the European oyster larvae to maximize their collection. Gonad observations and plankton tows were carried out in 2005 and 2006 to estimate the time of settlement. Nine days after the first free-swimming larvae were observed, Chinese hat collectors were suspended in the water column every three days at two sites. The collectors were removed from the water after a mean streaming duration of 35 days. Spat were thereafter numbered on each collector. The spawning period lasted from mid-July to the end of August in 2005 and from mid-July to the beginning of August in 2006. Temperature was approximately 18°C during that time. The major peaks of free-swimming larvae were observed at the beginning of August (43,276 larvae m−3) in 2005...

In the past decade, many aquatic invasive species have been introduced into Prince Edward Island, Canada, coastal waters, and they have had adverse effects on the aquaculture and fisheries industry. For instance, the mussel aquaculture industry has been overwhelmed by extremely high abundances of the invasive ascidian Styela clava in some areas. To understand and minimize the risk of spread of S. clava to other shellfish aquaculture sites, basic information on the reproductive biology of the ascidian is needed. This study investigated Styela gonad development, larval abundance and recruitment. Gonad development, using histological methods, indicated ovaries were ripe from late June through late October, 2004. Weekly water samples indicated larvae were present from 24 June to 29 October, with a distinct abundance peak in mid-August. Recruitment occurred from 24 June to 21 October. Timing of larval sampling was judged to be a crucial part of evaluating recruitment potential for monitoring purposes and a field experiment was carried out to document spatio-temporal larval concentrations. Data were gathered over 30 h sampling periods on 4 August and 14 September 2004. Water samples were taken simultaneously on an hourly basis at three depths: surface, 2 m and 4 m below the surface. Results indicated peaks in larval abundance were, in most cases, limited to a 3 h time interval in the early afternoon. Larval concentrations increased with water depth.

The vertical distribution of veligers, pediveligers and post-larvae of the mussel Mytilus edulis L. was examined in Kandalakshsky Gulf (White Sea), Russia. Plankton samples showed that about 65% of all planktonic larvae were collected from a depth of 1.5 to 3 m. Maximum numbers of veligers were found at 3 m, immediately above the thermocline. The vertical distribution of veligers was stable throughout the study. The vertical distribution of pediveligers, however, varied over time. Pediveligers were mostly observed at 3 m before settlement peaked while they migrated closer to the water surface (1.5 m) during the settlement period. Pediveliger concentrations were correlated posi- tively with small phytoplanktonic cell (

Behavior of laboratory-reared larvae of the bar- nacle Balanus amphitrite was examined in Beaufort. North Carolina (USA), relation to their physiological condition. Cyprid substratum exploration was monitored by means of video endoscopy using various experimental surface types (clean, biofilm, 1 and 2 wk fouled) and 2 water flow regirnes (still water and ca 5 cm s-') at room temperature (21°C). We used the triacylglyceroYDNA (TAG/DNA) ratio of small batches of larvae as a measure of physiologicai condition in 0 to 12 d old cyprids. The physiologicai condition of cyprids decreased significantly with age (p < 0.001), ratios severely dropping between 5 and 8 d. Although exploration behavior did not show much variation with age, the overail number of active exploring cyprids appeared to be age dependent. Additionally, the relationship between surface exploration behavior and age also appeared to vary with substratum type as weil as flow rate. For example, fewer young cyprids (0 to 5 d old) explored unfavorable substrata (clean and biofilm treatments) than older ones in still water. Exploration re- sponses, however, appeared to differ in relation to flow regirnes (still vs moving water trials). Time spent by cyprids on surfaces before returning to the water column (non- exploratory behavior) appeared to vary in relation to age and substratum type in stiu water trials. Duration of exploration and distance explored by cyprids in flow generally peaked with cyprids from the 3 d cohort. Overall, our results showed that habitat selection in barnacle cyprids results from a com- plex relationship involving substratum type, hydrodynamics and larval age (i.e. physiological condition and competency).

Conceptual models in manne benthic ecology have been reinforced with the use of larval recruitment as a key factor to predict fluctuations in the abundance and distnbution of sessile adult populations In turn, larval recruitment is determined uslng vanous indicators of planktonic larval abundance (larval supply) Based on plankton and settlement data collected over an entire settlement penod of the barnacle Sem~balanus balanoldes, we explore the vanability in the strength of the relationships between the abundance of newly settled individuals sampled dally at 3 shore levels and the daily larval abundance at 3 different depths over a 10 d study period The best correlation was obtained between the number of larvae collected near the bottom and the number of spat sampled in the low intertidal More than 75% of the vanability in the abundance of newly settled spat In the lower intertidal was explained by vanations in the larval abundance near the bottom Larval abundance integrated over the entire water column explained -50% of the vanability In low shore settlement, but failed to be significant All other comparisons showed a lack of correlations Our approach demonstrates that indicators of larval supply must be carefully and solidly documented to reflect the relationships between abundance of competent larvae settlement intensity and subsequently recruitment