Survival Of Scallop Research Articles

Effects of hypoxia on survival, behavior, and metabolism of Zhikong scallop Chlamys farreri Jones et Preston 1904

Hypoxia, a frequent occurring threat in coastal regions, often results in mass mortalities of marine organisms and brings a serious ecological problem. The commercially important Zhikong scallop Chlamys farreri is being under such a threat as the risks of eutrophication and hypoxia have risen in their culture areas. However, little information has been known concerning their tolerance to hypoxia and their strategy for survival. In the present study, a 20-day experiment was conducted to determine the effects of hypoxia on the survival, behavior, and metabolism of Zhikong scallop. With the LC50 for dissolved oxygen (DO) being estimated as 1.8 mg/L, the survival of Zhikong scallop can be greatly challenged even under the moderate hypoxic condition of around 2.0 mg/L DO. The survival rate ranged from 69% to 59% when DO dropped from 3.0 to 2.0 mg/L, and it was further reduced to 47% at 1.5 mg/L DO. In hypoxic conditions, the scallops became significantly active, which may be explained as escape attempts to avoid hypoxic water. To save energy, Zhikong scallop would depress their respiration. However, when DO dropped from 3.0 to 2.0 mg/L, the oxygen consumption rate hardly changed. The upregulation of lactate dehydrogenase activity and the unrepressed phosphofructokinase activity, which often result in the unbalanced cellular homeostasis and energy budget, may account for the observed increase in the mortality rate of Zhikong scallops. In general, Zhikong scallop is sensitive to hypoxia events, though possible escape attempts, depressed respiration, and oxaloacetate-pathway may increase their survival chance.

Enhancing growth and resistance to Vibrio alginolyticus disease in catarina scallop (Argopecten ventricosus ) with Bacillus and Lactobacillus probiotic strains during early development

In bivalve aquaculture, selecting suitable probiotic treatments can be crucial for improving hatchery-rearing of larvae and juveniles. We assessed the potential of five bacterial strains, previously selected in vitro, to improve survival, growth and resistance of catarina scallop Argopecten ventricosus during early and late larval and juvenile developmental stages, as well as during exposure to the pathogen Vibrio alginolyticus. Hatchery-reared larvae and juveniles were treated with eight treatments of single or combined strains of Bacillus and Lactobacillus at 1 × 106 CFU mL−1 every 48 h for 9 days (larvae) and 21 days (juveniles). Compared with the control, significantly higher survival and growth in size and weight of early veliger larvae occurred with the antibiotic and the RL5 (Lactobacillus graminis) treatments. Significantly enhanced settlement of pediveliger larvae occurred with a different probiotic strain, the mix of Lactobacillus and Bacillus (MIX-LB), while higher survival and growth of early juveniles occurred with C3 (Lactobacillus plantarum). The mix of Bacillus (MIX-B) significantly increased survival of juveniles from V. alginolyticus after 120-h infection, consistent with maximum activity of superoxide dismutase enzyme. In contrast, all untreated and infected scallops died by 96 h. The three Bacillus strains performed poorly when used as single treatments and when given to early developing larvae. Our results indicate that the action mechanism of probiotic strains is stage specific and strain specific, generating different responses by the host, including improved survival and growth (likely from better nutrient assimilation) and higher resistance against pathogens (possibly from strengthening the immune system).

Responses to two-way selection on growth in mass-spawned F1 progeny of Argopecten irradians concentricus (Say)

In the present study, the effect of one-generation divergent selection on the growth and survival of the bay scallop (Argopecten irradians concentricus) was examined to evaluate the efficacy of a selection program currently being carried out in Beibu Bay in the South China Sea. A total of 146 adult scallops were randomly selected from the same cultured population of A. i. concentricus, and divided into two groups in shell length (anterior-posterior measurement): large (4.91–6.02 cm, n=74) and small (3.31–4.18 cm, n=72). At the same time, a control group was also randomly sampled (4.21–4.88 cm, n =80). Mass-spawned F 1 progenies from the three size groups were obtained and reared under identical conditions at all growth phases. The effects of two-way (or upward-downward) selection on fertilization rate, hatching rate, survival rate, daily growth in shell length and body weight were assessed in the three size groups. Results show that significant differences (P 0.05), among the three groups. The hatching rate, survival rate and daily growth of the progeny of large-sized parents were greater than those of the control group (P<0.05), which in turn were larger than those of small-sized group (P<0.05). Responses to selection by shell length and body weight were 0.32 ± 0.04 cm and 2.18 ± 0.05 g, respectively, for the upward selection, and −0.14 ± 0.03 cm and −2.77 ± 0.06 g, respectively, for the downward selection. The realized heritability estimates of shell length and body weight were 0.38 ± 0.06 cm and 0.22 ± 0.07 g for the upward selection, and 0.24 ± 0.06 cm and 0.37 ± 0.09 g for the downward selection, respectively. The change in growth by bidirectional selection suggests that high genetic variation may be present in the cultured bay scallop population in China.

Survival, growth and immune activity of scallop Chlamys farreri cultured at different depths in Haizhou Bay (Yellow Sea, China) during hot season

Survival, growth and immune response of the scallop, Chlamys farreri, cultured in lantern nets at five different depths (2, 5, 10, 15, and 20 m below the sea surface) were studied in Haizhou Bay during the hot season (summer and autumn) of 2007. Survival and growth rates were quantified bimonthly. Immune activities in hemolymph (superoxide dismutase (SOD) and acid phosphatase (ACP)) were measured to evaluate the health of scallops at the end of the study. Environmental parameters at the five depths were also monitored during the experiment. Mortalities mainly occurred during summer. Survival of scallops suspended at 15 m (78.0%) and 20 m (86.7%) was significantly higher than at 2 m (62.9%), 5 m (60.8%) or 10 m (66.8%) at the end of the study. Mean shell height grew significantly faster at 10 m (205.0 μm/d) and 20 m (236.9 μm/d) than at 2, 5 or 15 m in summer (July 9 to September 1); however, shell growth rate at 20 m was significantly lower than at the other four depths in autumn (September 2 to November 6). In contrast to summer, scallops at 5 m grew faster (262.9 μm/d) during autumn. The growth of soft tissue at different depths showed a similar trend to the shell. Growth rates of shell height and soft tissue were faster in autumn than in summer, with the exception of shell height at 20 m. SOD activity of scallops increased with depth, and ACP activity was significantly higher at 15 and 20 m than at other depths, which suggests that scallops were healthier near the bottom. Factors explaining the depth-related mortality and growth of scallops are also discussed. We conclude that the mass mortality of scallop, C. farreri, during summer can be prevented by moving the culture area to deeper water and yield can be maximized by suspending the scallops in deep water during summer and then transferring them to shallow water in autumn.

Effects of Mass of Artificial Fouling on the Growth and Survival of Two Scallop Species Cultured in Sanggou Bay, China

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Seasonal variations in growth and clearance rate of the Zhikong scallop Chlamys farreri suspended in the deep water of Haizhou Bay, China

The growth and survival of the Zhikong scallop Chlamys farreri suspended in deep water of Haizhou Bay were studied from July 2007 to June 2008, and the biodeposition method was used to estimate the clearance rate of C. farreri under field conditions. Results showed that the scallop grew fast during all the culture time, with the exception of summer. The condition index of the scallop increased with time and reached the highest value in spring of the second year. The survival of scallops was 60.8 +/- A 3.9% at the end of this study, mortality occurring mainly during the summer and autumn of the first year. The clearance rate fluctuated obviously with season,with the highest value in September 2007, and the lowest value in March 2008. Factors accounting for variations in growth and clearance rate of scallops are also discussed.

Effect of antibiotic treatment on the growth and survival of juvenile northern Chilean scallop,Argopecten purpuratusLamarck (1819), and associated microflora in experimental cultures

Juvenile northern Chilean scallops of 937±55 μm shell height were exposed to five different concentrations of chloramphenicol (CHL) (5, 10, 25, 50 and 100 μg mL−1), plus a control without antibiotics. To determine the effect of CHL on the accompanying microflora, the number of colony-forming units (CFU) that grew on TGE culture medium was counted in the seawater of containers with juveniles, and in containers with microalgae used as food. Both were exposed to the same concentrations of CHL. The growth rates of juveniles treated with CHL and the control without antibiotic showed highly significant differences (P=0.0001). The growth rate was inversely proportional to the CHL concentration. The control sample presented the highest growth rate (84.4±14.3 μm day−1), followed by the sample treated with 5 μg mL−1 (64.2±14.3 μm day−1). The survival in the control and in the treated samples with 5–50 μg mL−1 was rather high, with a mean value of 95%. Only the sample treated with 100 μg mL−1 had a low survival (36.7%). The CFU count was larger in the containers with juveniles, when compared with the ones with food. The CFU count tended to decrease with increasing CHL concentration in the juveniles.

Effects of chloramphenicol, erythromycin, and furazolidone on growth of Isochrysis galbana and Chaetoceros gracilis

This study focused on determining the effects of antibiotics on microalgae used as food for scallop larvae. Six different dose levels of chloramphenicol, erythromycin, and furazolidone were added to cultures of Isochrysis galbana and Chaetoceros gracilis. An in vivo experiment was subsequently conducted to determine the effect of chloramphenicol and erythromycin on larval survival of the Pacific calico scallop Argopecten ventricosus in tanks and on the population of its associated bacteria. Results showed that growth of I. galbana was not significantly affected by chloramphenicol or erythromycin at the test doses of 0.5, 1.0, 3.0, 6.0, 9.0, and 12.0 mg/l. C. gracilis was significantly sensitive to erythromycin and chloramphenicol at doses higher than 0.5 and 3.0 mg/l, respectively. Furazolidone inhibited the growth of both I. galbana and C. gracilis at all test doses. Results showed that exposure of scallop larvae to a dose of 6 mg/l chloramphenicol or erythromycin did not significantly affect growth of I. galbana, significantly enhanced survival of the scallop larvae, and inhibited the growth of Vibrio spp. in tanks. This study demonstrated the adverse effect of chloramphenicol, erythromycin and furazolidone on I. galbana and C. gracilis microalgae but the positive effect on survival of the scallop larvae, decreasing associated bacterial population.

Effects of dissolved oxygen on survival and immune responses of scallop ( Chlamys farreri Jones et Preston)

This experiment investigated the effects of dissolved oxygen (DO) on the survival and immune responses of scallop Chlamys farreri. The scallops (initial mean dry weight of soft tissue 1.52 ± 0.10 g) were cultivated in the seawater with different DO levels (8.5, 6.5, 4.5, and 2.5 mg l −1, respectively) for 21 d. Each treatment had triplicate groups of 35 animals. During the experimental period, the scallops were fed with Spirulina maxima, and water temperature ranged from 15.2 °C to 17.5 °C, salinity from 29.5‰ to 32.5‰ and pH from 7.5 to 8.2. Survival, specific growth rate (SGR) and total haemocyte count (THC) were examined at the end of the study, and superoxide dismutase (SOD), acid phosphatase (ACP) and alkaline phosphatase (ALP), were examined at 12 h, 24 h, Day 7, Day 14 and Day 21 after being exposed to the graded DO levels. The lower DO levels (2.5 and 4.5 mg l −1) resulted in lower survivals of scallops, and the survival (81.7%) at 2.5 mg l −1DO was significantly lower than those (100.0%) at 8.5 and 6.5 mg l −1 DO. Similarly, the SGR and THC of scallop gradually reduced with decreasing DO levels, and reached significant levels at 2.5 mg l −1 DO ( P < 0.05). At higher DO levels (8.5 and 6.5 mg l −1), the SOD activity maintained rather stable during the entire sampling period. At lower DO levels (4.5 and 2.5 mg l −1), however, the SOD activity significantly increased at 12 h, and then significantly decreased to the levels below the normal. At the two lower DO levels, ACP activities had no significant changes before Day 7, and then declined to the levels that were significantly lower than the normal. Significantly higher ALP activity was only observed at 12 h in the treatment of 2.5 mg l −1 DO, but in all other treatments and sampling times it fluctuated in a narrow range. In conclusion, less than 4.5 mg l −1 DO reduced the survival and depressed the immune responses of C. farreri.

Effects of locally-isolated micro-phytoplankton diets on growth and survival of sea scallop ( Placopecten magellanicus) larvae

The micro-phytoplankton Navicula pelliculosa, Chaetoceros septentrionalis and Prymnesium sp., indigenous to the coastal waters of Nova Scotia, Canada were isolated, cultured and used in laboratory feeding experiments with larvae of the giant sea scallop ( Placopecten magellanicus) to evaluate their dietary benefits. The effects of these micro-phytoplankton on larval growth and survival were compared with three species of micro-algae commonly used as commercial feed for bivalve larvae: Tahitian Isochrysis sp., Pavlova lutheri and Chaetoceros calcitrans. The experiments were conducted at 14 °C over approximately one month. Larvae were fed at concentrations of 25,000 cells ml −1 from Day 3 to Day 9 and 35,000 cells ml −1 from Day 10 to Day 35. Total growth and survival were determined by sampling the larvae at intervals of 4 to 5 days. Eight dietary formulations were compared for larval survival and growth. Two way, repeated measures ANOVA using both larval shell height and percent larval survival as dependent variables and diet and time as factors resulted in significant variation ( p < 0.001) in both larval growth and survival. Prymnesium sp. supported significantly better growth as a monospecific diet than local Chaetoceros or Navicula, and when used in combination with the commercial diets which included other flagellates. Local Navicula and Chaetoceros were found to be better diets for the later stages of larval growth. Our studies showed that these two local diatoms Navicula pelliculosa and Chaetoceros septentrionalis could also be used as a component of multispecies diets along with flagellates.

Survival of Patagonian scallop ( Zygochlamys patagonica, King and Broderip, 1832) after the size selection process on commercial fishing vessels

Commercial catches of Patagonian scallops ( Zygochlamys patagonica) are automatically processed on board the fishing vessel and frozen adductor muscles are landed. During the factory process, the first step sorts commercial sizes (>55 mm shell height) and lasts about 30 min before scallops <55 mm are returned to the sea. This paper deals with the results of a field experiment carried out to investigate the survival of scallops as a consequence of time exposure to air, before and after the factory size selection process on board. The results show high survival in Patagonian scallops subjected to 30 min aerial exposure, and no significant differences between specimens collected before and after the mechanical size selection process.

Nursery growth, survival and chemical composition of great scallop Pecten maximus (L.) spat from different larval settlement groups

Scallop Pecten maximus spat (1.3–2.1 mm shell height) from different settlement groups were transferred from hatchery to land-based nursery at different ages and sizes. Chemical content, growth and survival were compared at transfer time and after 1 and 8 weeks of nursery growth. Growth was lowest and mortality highest in the first week after transfer. Mean shell height growth was 21.5–71.4 μm day−1 and ash-free dry weight (AFDW) growth −2.7 to 10.3 μg day−1. Spat from the first settlement group attained a larger size and weight than spat from larvae settled 3 days later, but had a lower daily growth rate (%). Keeping the late-settled spat a longer time in the hatchery to reach a bigger size before transfer seemed not to improve subsequent nursery growth. Survival showed a large variation with mean survival ranging from 32% to 74%. A substantial reduction in lipid content was found after transfer to the nursery. Sterol content at transfer was the only lipid class correlating with survival in the nursery. Based on the results, it is justified that spat groups of different settlement age are included in production of 15-mm great scallop spat if they are transferred from the hatchery at the same age.

Influence of fouling on the growth and survival of the tropical scallop, Euvola (Pecten) ziczac (L. 1758) in suspended culture

To examine the impact of fouling organisms on the growth and survival of the scallop Euvola ziczac L., we maintained 31-34-mm juveniles in pearl nets at 8 m in depth at Turpialito, Golfo de Cariaco, Venezuela. The experiment ran for a 67-d period under four conditions: (1) shells and nets cleaned; (2) shells not cleaned and nets cleaned; (3) shells cleaned and nets not cleaned; and (4) shells and nets not cleaned. The growth of the scallop was least when fouling developed on both the pearl nets and scallop shells. The rate of growth of the shell (height and mass) was strongly affected by organisms colonizing the pearl nets and only weakly affected by organisms colonizing the shells. Fouling organisms on the shells only slightly affected rates of increase of tissue mass, but probably accounted for increased mortality. In developing commercial culture of E. ziczac, strategies need to be developed to limit the adverse effects of fouling on yield.

Shell growth and survival of scallop ( Pecten maximus L.) in a fertilized, shallow seawater pond

Growth of scallops ( Pecten maximus) in a fertilized, shallow seawater pond was compared to growth at a fish farm and at an open sea site. Growth measured as mean increase in shell height was recorded at 2 m depth during two successive growth seasons, one in 1989 and one in 1990. Mean starting shell height of the different groups in 1989 varied between 23.1 mm and 29.5 mm, and was 48 mm for all groups in 1990. Both water temperatures and phytoplankton densities were higher in the pond compared to the two locations in the sea. In 1989 total ongrowth varied little between the locations (17.9–20.9 mm/individual), although the growth rate during spring was significantly higher in the pond. In 1990 total ongrowth of the groups at the pond location was significantly lower than total ongrowth at the sea locations (13.6–14.7 mm/ind compared to 18.4–25.3 mm/ind), mainly due to very low growth rate and high mortality (59.1 and 66.7%) in the pond in June. The difference in growth and mortality between 1989 and 1990 in the pond may be explained by a lower abundance of diatoms in 1990 and/or that scallops used in 1990 were older and larger. Correlation between growth rate of each scallop group in 1990 and the different environmental factors was only significant for growth rate at the sea locations and temperature. Considering the scallops at all locations, a low but significant negative correlation was found between growth rate and particulate organic matter, and growth rate and concentration of unidentified flagellates.