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1.

Optimizing the release density and size of juvenile commercial species for local ecosystems is a critical issue that should be considered when countering predation impacts. To ascertain whether mariculture production of the Japanese scallop (Mizuhopecten yessoensis) could be enhanced by modifying releasing practices, we experimentally investigated the effects of density and size of scallop seeds on their survival in the presence of two sea star species, Asterias amurensis and Distolasterias nipon, with different predation capacities. Under current mariculture practices, the juveniles are briefly exposed to air just before release; therefore, we also examined how air exposure stress increased the predation risk. Scallop survival in the presence of both sea stars increased by?>?20% by increasing scallop size from 30 to 50 mm. Increasing scallop density (range: 5 to 30 scallops m?2) increased each individual’s survival in the presence of A. amurensis but had no significant effect on predation by D. nipon. Therefore, the release of smaller quantities of large-sized scallops rather than larger quantities of small scallops is recommended to reduce D. nipon predation. In the presence of sea stars, especially by D. nipon, the predation impact on small scallops increased after just a few hours of air exposure, indicating that air exposure of juvenile scallops should be minimized. Our results will mitigate the economic cost of mariculture by facilitating the determination of optimal release conditions for juvenile scallops.

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2.
Understanding the role of salinity in breeding and growth has the potential to enhance production of giant freshwater prawn, Macrobrachium rosenbergii. This study investigated the reproduction of females reared in salinities of 0, 6, 12, and 18 g L− 1. Mean weight of females decreased with increased salinity (31.40 ± 1.54, 25.14 ± 1.16, 20.80 ± 0.81, and 16.62 ± 1.04 g at 0, 6, 12, and 18 g L− 1, respectively). Larval production was delayed by 2 months in females reared in 12 g L− 1 compared to 6 and 0 g L− 1 and the cumulative number of berried females decreased with increased salinity. The number of larvae produced was positively correlated to weight of female. A larval production not only differed between salinity treatments, but also that larval production per gram of female differed between treatments. Females reared in lower salinity of 0 and 6 g L− 1 produced larger numbers of larvae (12,155 ± 480 and 6519 ± 323, respectively) compared to 12 and 18 g L− 1 (3751 ± 256 and 0, respectively). The number of larvae produced per gram of female was inversely related to the salinity levels (Y = − 37.54X + 685.65, n = 339, r2 = 0.995, p < 0.05). Survival of larvae from females reared at 0 and 6 g L− 1 was higher than those from females reared in 12 g L− 1. This study clearly shows that female broodstock reared in lower salinity was larger, reproduced early, and produced more offspring than at higher salinity and this could significantly impact coastal prawn culture where seasonal fluctuation of salinity in the hatchery is common.  相似文献   

3.
Immunolocalization by using rabbit polyclonal antibody against APGWamide demonstrated that there was APGWamide immunoreactivity (APGW-ir) in the varicosed nerve fibers in the capsule, connective tissue and trabeculae of the testis whereas there was no APGW-ir in the ovary of sexually mature broodstocks of Haliotis asinina. In vivo bioassay, by injecting APGWamide into foot muscle of mature males and females (age over 24 months), showed that most males (87.50%) injected with 200 μl of 10− 3 M APGWamide (170 μg APGWamide/animal) could be induced to spermiate whereas fewer males (43.75%) injected with 200 μl of 10− 6 M APGWamide (0.17 μg APGWamide/animal) could spermiate. Following injection with 10− 3 M, 53% of males spawned within 3 to 4 h, while the remaining males spawned within 2 to 3 h. The former tended to release more sperm at the range of 1.04 to 2 × 109, and the latter at the range 3.62 × 107 to 2.07 × 108 cells, respectively, and that the sperm of the former group appeared to be more motile. Following the injection of 10− 6 M, all inducible males spawned within 2–3 h, and 43% of spawned males have sperm around 2 × 109, while 57% have fewer sperm number ranging from 2.75 × 107 to 9.94 × 108 cells. In contrast to males, none of the mature females with ripen ovary could be induced to ovulate. These data suggest that APGWamide is an important signaling molecule that plays a role in the male reproductive process that could be used to induce spermiation.  相似文献   

4.
Commercial and developmental operations for the culture of the seascallop, Placopecten magellanicus, are present in AtlanticCanada and New England. In an experiment designed to examine the commercialfeasibility of polyculture of scallops with Atlantic salmon(Salmo salar), we measured growth andsurvival of sea scallops grown in suspension at two salmon aquaculture sites innortheastern Maine (Johnson Cove (JC) and Treats Island (TI)). Sea scallop spatwere grown in pearl nets and deployed on drop lines containing ten nets inAugust 1994. One drop line of ten nets was sampled about every four months andscallops were counted, measured and weighed. Scallop tissues were also analysedfor paralytic shellfish toxins (PSP). The maximum level of PSP recorded duringthe study was 1174 g STX equiv.·100 gtissue–1 (excluding adductor muscle weight). After one year,shell heights were 53.6 and 56.4 mm, growth rates were 0.11 and0.12 mm per day and wet adductor muscle weights were 3.3 and 4.1g (TI and JC, respectively). These growth rates were comparable tosea scallops grown in suspension culture to a nearby scallop aquaculture siteand other areas in Atlantic Canada. Reduced rates of survival were found duringthe latter part of the experiment and were attributable, in part, to heavyfouling, predators and high stocking density. The potential for supplementalincome, diversification of the salmon aquaculture industry, and feasibility ofculturing scallops at adjacent sites to salmon operations does exist.  相似文献   

5.
We held juvenile big-headed turtles, Platysternon megacephalum, from eastern China, at temperatures from 20 to 29.4 °C to determine effects on feeding, growth and food conversion. Food intake increased significantly from 20 to 22.4 °C, remained high until 27.1 °C, and then decreased dramatically at 29.4 °C. Digestive efficiency for energy decreased as temperature increased, whereas the digestive efficiency of protein increased from 20 to 25 °C, and decreased at higher temperatures. The relationships between specific growth rate (SGR), food conversion coefficient (Cc) and temperature (T) were curvilinear, and could be described by quadratic equations: SGR = −0.01 T2 + 0.47 T − 5.24 and Cc = −0.37 T2 + 17.20 T − 181.85. Maximum growth was estimated to occur at 23.9 °C, with 90% of the maximum being achieved within the range of 21.9–25.8 °C; maximal food conversion occurred at 23.2 °C, with a 90% range from 21.0 to 25.4 °C. The temperature range (22–25 °C) found to promote best growth and food conversion in juvenile P. megacephalum is lower than for many other freshwater turtles. Temperatures of 22–25 °C are recommended for use in culture of this species to maximize growth and food conversion.  相似文献   

6.
Low feed consumption has been suggested as a major impediment for the development of effective formulated diets for spiny lobsters. To seek an explanation for the low feed consumption, this study compared the feed consumption, appetite revival, foregut evacuation and fecal production of different sizes of spiny lobster Jasus edwardsii juveniles fed a fresh natural diet (i.e. mussel flesh) and a dry formulated diet. In addition, the effect of feeding frequency was determined by feeding juvenile lobsters the same ration of formulated diet at different time intervals. i.e., same ration delivered 3 week− 1, 1 day− 1, 2 day− 1, 5 day− 1 and 5 night− 1. Lobster (10–15 g) growth and feed consumption (1.15% BW day− 1) was maximized when receiving a single ration daily of the formulated diet. A slow appetite revival (AR > 18 h) on the formulated diet was consistent with the negative effect of increasing feeding frequency on growth and consumption. In addition, there appeared to be no major advantage in dry matter intake by providing the nutrient dense dry formulated diet to Jasus edwardsii. Lobsters fed fresh mussel flesh (79.8% moisture) consumed similar levels of dry matter as those lobsters fed the dry formulated feed (7.3% moisture). This appears to be due to high moisture gain and expansion of the dry feed in the lobster foregut. Foregut evacuation lasted 10 h for the two diets but a delay in initial foregut evacuation and processing of the formulated diet was evident, and may have negatively affected feed consumption, appetite revival and dry matter digestibility (61.2%) of the dry formulated diet compared to the mussel flesh diet (89.2%). Appetite revival on mussel flesh was almost complete by 12 h after a satiation ration and was governed primarily by the rate of foregut evacuation. Differences in the timing of foregut evacuation and fecal production between the two diets suggested that a greater proportion of the formulated diet entered the midgut directly.The results indicate that J. edwardsii cannot achieve high levels of feed consumption on formulated diets because gut throughput is reduced due to a small foregut capacity, expansion of the feed post-ingestion, lengthy foregut filling time (1–2 h) and clearance time (10 h), combined with slow gut throughput time (34–42 h) and appetite revival (> 18 h). A slow appetite revival and difficulties in processing and digestion of formulated diets appear as major issues to be resolved to improve the performance of formulated diets required for the commercial aquaculture of J. edwardsii and possibly other spiny lobsters.  相似文献   

7.
This study investigated the effects of the dietary intake of live yeast Debaryomyces hansenii (CBS 8339) on the immune response of juvenile leopard groupers Mycteroperca rosacea and on their resistance to infection by dinoflagellates Amyloodinium ocellatum.During 4 weeks, juvenile groupers were fed either a diet supplemented with D. hansenii at 106 cfu g− 1 or a control diet. Both groups were then transferred to a system infected with A. ocellatum and maintained in this stressful environment, for one week. Rearing conditions were favorable to the proliferation of the dinoflagellate and, at 7 days post-infection, the cumulative mortality rate of the control group was 89.5%, suggesting that the yeast-enriched diet conferred protection against the parasite. Only fish with yeast-supplemented diet recovered from the A. ocellatum challenge.The immunological response of both groups of fish was evaluated. Samples were collected at weeks 4 (stressed fish) and 7 (recovering fish) to determine the levels of hemoglobin, plasmatic protein, and immunoglobulin M (IgM) as well as the activity of antioxidant enzymes (SOD and CAT). IgM increased significantly (P ≤ 0.05) in the recovering fish, which had all been fed the yeast diet. A significantly increase was also observed in superoxide dismutase activity in juvenile fish fed the yeast diet; however catalase activity was not affected by the dietary yeast supplement. Overall, fish that received the yeast supplement in their diet have an enhanced immune response as compared with their control counterparts. The present results show that a diet supplemented with D. hansenii stimulates the immune system of juvenile M. rosacea thus enhancing their resistance against A. ocellatum.  相似文献   

8.
Aquafeed production faces global issues related to availability of feed ingredients. Feed manufacturers require greater flexibility in order to develop nutritional and cost-effective formulations that take into account nutrient content and availability of ingredients. The search for appropriate ingredients requires detailed screening of their potential nutritional value and variability at the industrial level. In vitro digestion of feedstuffs by enzymes extracted from the target species has been correlated with apparent protein digestibility (APD) in fish and shrimp species. The present study verified the relationship between APD and in vitro degree of protein hydrolysis (DH) with Litopenaeus vannamei hepatopancreas enzymes in several different ingredients (n = 26): blood meals, casein, corn gluten meal, crab meal, distiller's dried grains with solubles, feather meal, fish meals, gelatin, krill meals, poultry by-product meal, soybean meals, squid meals and wheat gluten. The relationship between APD and DH was further verified in diets formulated with these ingredients at 30% inclusion into a reference diet. APD was determined in vivo (30.1 ± 0.5 °C, 32.2 ± 0.4‰) with juvenile L. vannamei (9 to 12 g) after placement of test ingredients into a reference diet (35 g kg− 1 CP; 8.03 g kg− 1 lipid; 2.01 kcal g− 1) with chromic oxide as the inert marker. In vitro DH was assessed in ingredients and diets with standardized hepatopancreas enzymes extracted from pond-reared shrimp. The DH of ingredients was determined under different assay conditions to check for the most suitable in vitro protocol for APD prediction: different batches of enzyme extracts (HPf5 or HPf6), temperatures (25 or 30 °C) and enzyme activity (azocasein): crude protein ratios (4 U: 80 mg CP or 4 U: 40 mg CP). DH was not affected by ingredient proximate composition. APD was significantly correlated to DH in regressions considering either ingredients or diets. The relationships between APD and DH of the ingredients could be suitably adjusted to a Rational Function (y = (a + bx)/(1 + cx + dx2), n = 26. Best in vitro APD predictions were obtained at 25 °C, 4 U: 80 mg CP both for ingredients (R2 = 0.86; P = 0.001) and test diets (R2 = 0.96; P = 0.007). The regression model including all 26 ingredients generated higher prediction residuals (i.e., predicted APD − determined APD) for corn gluten meal, feather meal, poultry by-product meal and krill flour. The remaining test ingredients presented mean prediction residuals of 3.5 points. A model including only ingredients with APD > 80% showed higher prediction precision (R2 = 0.98; P = 0.000004; n = 20) with average residual of 1.8 points. Predictive models including only ingredients from the same origin (e.g., marine-based, R2 = 0.98; P = 0.033) also displayed low residuals. Since in vitro techniques have been usually validated through regressions against in vivo APD, the DH predictive capacity may depend on the consistency of the in vivo methodology. Regressions between APD and DH suggested a close relationship between peptide bond breakage by hepatopancreas digestive proteases and the apparent nitrogen assimilation in shrimp, and this may be a useful tool to provide rapid nutritional information.  相似文献   

9.
The potential for predation by the sea stars Asterias rubens and Marthasterias glacialis on seed-size (41 ± 3 mm shell height) juvenile scallops (Pecten maximus), ready for seeding in sea ranching areas, was investigated in a 30-day laboratory predation experiment. There was no significant difference (P > 0.05) in predation rate of large A. rubens (95–115 mm radium) and large M. glacialis (120–164 mm radius), which averaged 0.88 and 0.71 scallops individual−1 day−1, respectively. Maximum rates of predation were 2.44 scallops individual−1 day−1 for large A. rubens and 3.00 scallops individual−1 day−1 for large M. glacialis. Small M. glacialis (76–87 mm radius) had a significantly lower predation rate than large individuals of either species (average 0.13 scallops individual−1 day−1, P < 0.05). Small A. rubens (50–80 mm radius) only began to prey on scallops when average scallop size was reduced to 35 mm. Based on estimated density of sea stars at a Norwegian sea ranching site and average predation rates, a population of scallops seeded at 10 m−2 would be reduced by between 0.5 and 11% in 1 month. Furthermore, using the highest observed predation rate, the degree of loss of scallops indicated that scallop culture via sea ranching would not be economically viable and thus methods for reducing scallop predation by sea stars are necessary.  相似文献   

10.
Effect of apidaecin on common carp (Cyprinus carpio) based on growth performance, feed utilization (Feed Conversion Ratio, FCR) and immune parameters were investigated. Twelve aquaria with three replicates for G1-3 and control were used. The synthesized apidaecin peptide was added to common carp basal diets (Control) as additives in three concentrations: 10.0 mg kg− 1 (G1), 15.0 mg kg− 1 (G2) and 30.0 mg kg− 1 (G3) by wet weight of basal diet. After an 80-day feeding experiment, G2 and G3 showed significantly better (P < 0.05) results of growth performances and FCR than the control. However, there was no remarkable difference (P > 0.05) between G2 and G3. As for G1, the final weight, SGR (Specific Growth Rate) and DG (Daily Gain) were increased and the FCR was decreased, but not significantly (P > 0.05) compared with the control. The serum lysozyme activity of G2 and G3 was significantly increased (P < 0.05) than the control. As for the alternative complement pathway activity, G2 and G3 were also higher (P < 0.05) than the control. However, no significant difference (P > 0.05) was found whichever between G2 and G3 or between G1 and G2 in both lysozyme and the alternative complement pathway activities. Furthermore, there was no remarkable difference between G1 and the control in immune parameters.  相似文献   

11.
This paper evaluates the resource and energy requirements of six different types of land-based, hatchery production systems located in the U.S. Pacific Northwest: flow-through with a gravity water supply, flow-through with a pumped water supply, flow-through with pure oxygen, partial reuse system, partial reuse with heating, and a reuse system for the production of Atlantic salmon (Salmo salar) smolts. Key parameters used in the evaluation include direct energy, indirect energy, transportation energy, greenhouse gas emissions, and pollutant discharges.Power (electricity and natural gas) and feed energy accounted for the majority of the required energy for all the rearing option evaluated. The sum of the fixed capital and chemicals components accounted for less than 2–12% of the total energy budget for any rearing option. The energy efficiency (energy output/energy input) of the six options ranges from 0.97% for flow-through with pumped supply to 3.49% for the flow-through with gravity supply. The rearing options with the three highest energy efficiencies were flow-through with gravity supply (3.49%), partial reuse (2.75%), and reuse (2.64%).On a kg of smolt produced basis, the six rearing options showed a wide range in performance. The reuse system had the lowest water (2 m3 kg− 1) and land (0.13 m2 kg− 1) requirements and the third lowest total energy requirement (288 MJ kg− 1). The partial reuse system had the second lowest total power requirement (276 MJ kg− 1), a low land requirement (0.21 m2 kg− 1), and moderate water requirements (33 m3 kg− 1). The partial reuse with temperature control had the second highest total power requirement (657 MJ kg− 1) and land and water requirements similar to the partial reuse system without temperature control. The flow-through system with pumped water supply had the highest water (289 m3 kg− 1), land (2.19 m2 kg− 1), and energy requirements (786 MJ kg− 1) of any of the rearing options. By comparison, the flow-through system with gravity water supply had the lowest energy requirement (218 MJ kg− 1), a moderate land requirement (0.78 m2 kg− 1), and a high water requirement (214 m3 kg− 1). The ranking of the six rearing options based capital and operating costs are likely to be quite different from those based on energy, water, and greenhouse gas emissions.  相似文献   

12.
Scallop spat produced for continued culture normally requiretransportation between sites, and the associated stresses may causemortalities. In the present experiment, scallops of 40–55 mm shell heightwere emersed in air for time intervals up to 24 h and their behaviourexamined once re-immersed. Scallops were placed upside-down and thenumber of movements and the cumulative numbers righting in 5 min timeblocks were recorded. The greatest frequency for all behaviouralresponses was found at 15–17 °C in August. Responses were reducedin November and June (9–11 °C) and least at 5 °C in January.All effects of treatment, temperatures and season, and increases in airexposure were significantly different. Following the treatments, mortalitiesafter 10 days in culture was about 10–30% for scallops emersed for 18 and24 h in August and June. Scallops did not show significantly differentbehaviour whether they were emersed upright or inverted. However,scallops emersed at 15 °C had fewer responses than scallops held at <10 °C, so chilling during transport may prolong scallop vitality. Theresults suggest that air exposure >12 h should be avoided. At temperatures>9 °C, behavioural responses may be a simple and effective method toassess vitality which can assist in the management of scallop culture.  相似文献   

13.
The compatibility of olive barb, Puntius sarana (Hamilton) with major carps was studied in grow-out carp polyculture system for one year in a set of nine earthen ponds of 0.08 ha each. Three different species combinations evaluated were Control: catla (Catla catla Ham.), silver carp (Hypophthalmichthys molitrix Valenciennes), rohu (Labeo rohita Hamilton) and mrigal (Cirrhinus mrigala Hamilton) at 0.5:0.5:1:1; T1: catla, silver carp, rohu and olive barb at 0.5:0.5:1:1 and T2: catla, silver carp, mrigal and olive barb at 0.5:0.5:1:1 at combined density of 7500 fingerlings/ha. While survival levels of the carps did not differ significantly in treatments (P > 0.05), silver carp recorded highest survival levels (94–96%) followed by olive barb (87–90%), mrigal (72–74%), rohu (72–73%) and catla (67–69%). The specific growth rate (SGR) and average harvested body weight (ABW) of catla and silver carp did not differ significantly among the treatments revealing their competition with mrigal or olive barb to be minimum. In absence of rohu in T2, both mrigal and olive barb showed higher SGR and ABW revealing minimal competition between these two species, while their lower performance in presence of rohu in Control and T1 indicated inter-specific competition with the latter. Such olive barb–rohu inter-specific competition, however, failed to yield significant effect on growth of rohu as revealed from its non-significant SGR difference in presence and absence of olive barb. The lower FCR (2.54 ± 0.06) and higher treatment biomass production (3418.4 ± 95.0 kg ha− 1 year− 1) in T1 with rohu–olive barb combination compared to T2 with mrigal–olive barb (2.84 ± 0.11; 3155.1 ± 104.7 kg ha− 1 year− 1) indicated feasibility and advantage of culturing rohu with olive barb rather than mrigal in carp polyculture. Further, similar biomass production in Control and T1 also indicated feasibility of replacing mrigal with olive barb in the grow-out carp polyculture system.  相似文献   

14.
The growth performance and stress response in striped knifejaw, Oplegnathus fasciatus (body weight 100–300 g) reared under four photoperiods (6L:6D, 12L:12D, 16L:8D and 24L:0D) were investigated. Fish were fed a commercial diet to apparent satiation, two times a day for 8 weeks. A trial of acute handling and confinement stress was also carried out to investigate the stress-induced levels of different stress indicators in O. fasciatus. Blood was also collected from undisturbed fish which was considered as control. Although there were no significant differences in weight gain, specific growth rate (SGR) and feed conversion efficiency (FCE) in fish exposed to 6L:6D, 16L:8D and 24L:0D photoperiods, all parameters in these photoperiods were significantly higher than those of 12L:12D photoperiod (P < 0.05). There was no significant difference in protein retention efficiency (PRE) between fish exposed to 16L:8D and 24L:0D photoperiods, but PRE in both photoperiods was significantly higher than that of 12L:12D photoperiod.Acute stress significantly increased the plasma levels of cortisol (110.3 ng ml− 1) and glucose (195.4 mg dl− 1), and decreased plasma levels of total protein (0.8 g dl− 1); however, all parameters were returned back to the levels indistinguishable from those of control, undisturbed fish within 24 h. The levels of cortisol, glucose and total protein in fish exposed to different photoperiods during the study were far from the stress-induced levels (P < 0.05). The results demonstrated that the growth performance of O. fasciatus reared from 100 to 300 g can be stimulated significantly by using the manipulated photoperiods where feeding time may be playing an important role to increase food intake and feed conversion efficiency. It also revealed that the artificial photoperiods did not cause significant stress response in fish.  相似文献   

15.
We investigated strategies to enhance populations of bay scallops,Argopecten irradians irradians (Lamarck, 1819), in a presumablyrecruitment-limited natural habitat. At present, the Niantic Riverestuary supports only a minor bay scallop population that is harvestedrecreationally. Three enhancement strategies were evaluated; (1)collection and redistribution of natural spatfall, (2) introduction andover-wintering of hatchery-reared stock into natural habitat to providenew spawning stock, and (3) over-wintering of hatchery-reared stock insuspension culture for creation of mobile spawner sanctuaries. Anassessment of natural bay scallop recruitment in the Niantic Riverconducted in 1997 indicated that few spat were found, they were widelydispersed within the river, and peak spawning occurred in late July1997. Direct re-seeding was evaluated as an enhancement measure byplanting hatchery-reared scallops ( 38 mm shell height) insmall-scale, 100-m2 plots at different times and densities.Time of planting and the inferred predation intensity were major factorsaffecting survival; whereas, planting density had no significant effect.Approximately 9,000 scallops (35–45 mm shell height), broadcastwithin an eelgrass bed in November 1997, had high over-winter survivaland underwent gametogenesis and spawning during 1998. Of 26,000 bayscallops ( 45 mm shell height) over-wintered in suspensionculture from 1998–1999, approximately 60–80%survived, and these scallops spawned in mobile sanctuaries, during thesummer of 1999. There is good potential for using aquacultural methodsfor enhancement of bay scallop populations when natural recruitment ispoor and habitat and environmental conditions are not limiting.  相似文献   

16.
Scallop dredges typically use teeth or a cutting bar to dig though the sediment and are associated with detrimental impacts on marine benthos. A low-impact ‘Hydrodredge’ was tested that uses ‘cups’ to deflect water downward in a turbulent wave sufficient to lift scallops from the seabed. Trials took place in the Isle of Man fishery for great scallop (Pecten maximus) with the hydrodredge and a gang of local ‘Newhaven’ dredges towed simultaneously either side of a commercial scallop dredge vessel. When fished over three different ground types (smooth, medium and hard) and two tow-speeds (2.5 kt, 4.0 kt), the proportion of dead scallops and bycatch in the Hydrodredge was significantly less than in the Newhaven dredges. This result highlighted the role of the teeth on the tooth-bar in exerting severe (fatal) damage to the catch and bycatch. Rates of non-fatal damage to scallops and bycatch did not differ between gears, suggesting that such damage occurs as a result of contact with other parts of the gears such as the chain bag. The hydrodredge was less efficient at catching great scallops compared with the Newhaven dredges (10–40%). For great scallops, the cups did not significantly increase catch relative to the hydrodredge fished without cups, which contrasts with results for other surface-dwelling scallop species, e.g., Placopecten magellanicus and Aequipecten opercularis. Importantly, the Hydrodredge was designed in the New England fishery for giant scallop (P. magellanicus), a species typically lighter and less embedded than P. maximus and thus potentially more vulnerable to the flow patterns of the Hydrodredge.  相似文献   

17.
The successful culture of the east coast rock lobster Panulirus homarus rubellus is reliant, among other factors, on the provision of optimal water quality for growth and survival. This study investigated the effect of temperature over a range of 9.7 °C (18.9 ± 0.7 °C to 28.6 ± 1.5 °C) on the growth and survival of juvenile (40.4 ± 9 mm CL; 63.64 ± 12.05 g) P. h. rubellus fed a diet of fresh mussel flesh. Specific growth rate (SGR) was significantly different between temperatures (p = 0.01), with the highest values recorded for the 24 and 28 °C treatments. There was no significant difference in moult increment (MI) between temperatures in terms of both an increase in weight (p = 0.83) and carapace length (p = 0.54). Intermoult period (IMP) differed significantly between temperatures (p = 0.0015) with mean IMP lowest at 24 °C, although not significantly different from the means of the 26 and 28 °C treatments. IMP was highest at 19 and 21 °C. Apparent feed intake was significantly different between treatments (p < 0.0001) and exhibited a strong positive correlation with increasing temperature (y = − 1.67 + 0.16x ; r2 = 0.81). Food conversion ratio (FCR) differed significantly between temperatures (p = 0.02) with 24 °C exhibiting the most efficient FCR. Results indicate that efficient growout of juvenile P. h. rubellus, in terms of both growth and food conversion efficiency, is obtainable at 24 °C.  相似文献   

18.
Low salinity is one of important environmental factors which often led to mass mortality of the noble scallop Chlamys nobilis cultivated in the South coast of China. It is well known that enzymic system and non‐enzymic system both play crucial roles in all living organisms against severe environments. To investigate how change about enzymic system and non‐enzymic system in the stenohaline marine bivalve under low salinity stress, an acute challenge lasting 48 hr was conducted using golden and brown noble scallops in the present study. The serine proteinase inhibitor from the noble scallop (CnSPI) was first cloned and expressed in different tissues. After low salinity stress, the gene expression levels were determined in haemocytes and compared between golden and brown scallops. Meanwhile, total carotenoids content (TCC) in adductor, superoxide dismutase (SOD) enzymatic activity and methylenedioxyamphetamine (MDA) content in gill and haemocytes were also determined and compared between the two colours scallops. Results showed that the CnSPI gene expression levels were significantly decreased after low salinity stress, and the golden scallops had higher gene expression levels than brown scallops (p < .05) at most times. Moreover, after low salinity stress, TCC, SOD enzymatic activity and MDA content also fluctuated, and the golden scallops contained higher TCC and SOD, but lower MDA than the brown ones. The present results indicated that enzymic system and non‐enzymic system were both changed under low salinity stress in the noble scallop and significantly different responses to the stress existed between golden and brown individuals. The SPI gene and carotenoids (CAR) both play a resistant role to low salinity stress in the noble scallop.  相似文献   

19.
This paper examines the changes in the population ecology parameters and biomass of golden grey mullet (Liza aurata) in Iranian waters of the Caspian Sea from 1991 to 2005. For most years during this 14-year period, we estimated the age structure of the catch, length–weight relationship, von Bertalanffy growth parameters, condition factor, natural and fishing mortality and biomass. Growth parameters were estimated as L∞ = 62.7 cm, K = 0.15 year−1, t0 = −0.23 year−1. The instantaneous coefficient of natural mortality was estimated as 0.350 year−1 and the instantaneous coefficient of fishing mortality varied during the 14-year period between 0.111 to 0.539 year−1. Biomass estimates of golden grey mullet, from the biomass-based cohort analysis were increased from 13,527 mt in 1991–1992 to 23,992 mt in 2002–2003. In 2004–2005, it was estimated to be 23,658 mt. We concluded that at the present time, the stock of golden grey mullet is not being over-fished.  相似文献   

20.
An experimental study was done to evaluate the biodeposition dynamics associated with mussels and two fouling tunicates, Ciona intestinalis and Styela clava, in mussel aquaculture in Prince Edward Island (PEI), eastern Canada. The presence of C. intestinalis on small constructed mussel socks increased biodeposition by a factor of about 2 relative to mussel socks without tunicates. S. clava were small and had a negligible effect on total biodeposition from mussel socks although they increased sedimentation rates relative to that of abiotic control socks. Sinking rates of faecal pellets from large C. intestinalis varied between 1.39 and 6.54 cm s− 1 (LSMean = 2.35 cm s− 1). Using biodeposit production and sinking rates and hydrological data obtained in the present study, footprints of benthic loading due to mussel and tunicate biodeposition for a typical mussel farm in PEI were modelled using Shellfish-DEPOMOD. The results show benthic loading below longlines with C. intestinalis to be ca. 2 times greater than those from lines with only mussels with rates of up to 15.2 g m− 2 d− 1. However, given the greater settling rate of C. intestinalis biodeposits relative to mussel biodeposits, the extent of the footprint (≥ 1 g m− 2 d− 1) is similar or even more restrained.  相似文献   

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