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1.
Studies under laboratory and field conditions have shown that juvenile Mulinia edulis clams measuring 5–15 mm are able to tolerate transfer times of over 24 hr and burrow successfully. Burrowing generally followed an asymptotic curve over time, with a rapid initial phase for smaller juveniles, which slowed over time. In laboratory conditions, at low temperatures (8°C), juvenile burrowing was initially rapid (50–70% at first 2 min). In summer temperatures (15.5°C), the burrowing capacity of three sizes of juvenile clams was tested. Size determines differences in burrowing dynamics, where juveniles of 8.9 mm shell length (SL) take longer to burrow than smaller juveniles (4.9 and 6.3 mm SL). For longer transfer times in laboratory conditions (>12 hr), burrowing was slower. The results indicate a faster burrowing rate in smaller (<10 mm) juvenile clams than in larger ones. Transfer times over 24 hr in field experiments show burrowing levels of over 50% after a 60‐min evaluation, with larger juveniles (>10 mm) requiring longer for burrowing. Based on our results, we suggest sending seeds out to grow in natural environments at SL <10 mm, temperatures below 12°C, and transfer times shorter than 12 hr. These results are valuable for improving future transfer techniques from hatchery to growout for small‐scale aquaculture of this new native species in South America.  相似文献   

2.
This report first describes the morphological and habitat characteristics of larval and juvenile Roughscale Sole Clidoderma asperrimum. Five metamorphosing larvae (22.1–31.7 mm standard length, SL) and 12 juveniles (23.7–46.4 mm SL) were collected from two locations in coastal waters of northeastern Japan, Shizugawa Bay (rocky habitats, 6–12 m depth) and Iwaki (sandy habitats, 10–50 m depth), respectively, using a hand net while SCUBA diving and a small trawl net during May–August in 2008 and 2010. Underwater observation in Shizugawa Bay revealed that metamorphosing larvae and juveniles that had settled on rocks or stones showed transparent and variegated body coloration, which is cryptic to a rocky habitat. Juveniles in Iwaki showed monotonic coloration. The settlement would occur during metamorphosis because the same larva observed on a stone subsequently swam with a left-lateralized body posture. The larval morphology was characterized by a dense covering of fine spines on the whole body surface. Spines on the ocular side developed steadily, gradually forming bony tubercles with growth, whereas those on the blind side regressed with development and finally disappeared in metamorphosed juveniles. Our results indicate that Roughscale Sole can settle and adapt to rocky and sandy habitats in coastal waters with wide depth range.  相似文献   

3.
We examined factors affecting the vertical distribution of juvenile walleye pollock during “the second critical period” (i.e. the transition period of prey size) in and around Funka Bay, Hokkaido, Japan. During the day, small juveniles (<30 mm) were distributed mainly in shallow, warm, and low-salinity water within the bay, whereas larger ones (≥30 mm) occurred in deeper, cold and saline water. During the night, the large juveniles migrated to shallower depths. Outside the bay, small- and large-sized juveniles were distributed in water masses of similar physical properties during the daytime, whereas during the nighttime, most of the juveniles moved to shallower depth, and some juveniles dived to deeper water mass. Dietary analysis revealed that large juveniles fed on large copepods (≥0.5 mm in body width) more than small juveniles did. The composition of zooplankton in our survey area showed that large-sized copepods often occurred in deeper saline water. From these results, there is a possibility that juvenile pollock inside and outside Funka Bay occupied different water masses preferable for each feeding advantage.  相似文献   

4.
The aim of the study was to optimize burbot juveniles rearing in recirculating aquaculture system. In experiment 1 (17 °C, photoperiod 24L:0D), the fish (initial: body weight [W] = 15.36 ± 3.72 g, standard length [SL] = 12.48 ± 1.09 cm) were divided into four groups (I, II, III and IV). Different feeding levels were applied: 1, 2, 3 and 4 % of biomass daily (counted based on dry feed weight). The feed conversion ratio (FCR) and specific growth rate (SGR) were recorded. In experiment 2 (17 °C, feeding level of 2 % of biomass day?1), fish (W = 5.24 ± 2.43 g and SL = 8.54 ± 1.24 cm) were divided into two groups where different light conditions were applied (I: 24 h light [1,800 lx] and II: 24 h darkness [4 lx]). In experiment 1, the highest SGR was recorded in group II (1.93 % day?1), whereas the lowest SGR (1.27 % day?1) and final W (P < 0.05) was in I group. The lowest (P < 0.05) FCR (0.63) was in group II. In the remaining groups, FCR was similar (0.68–0.70, P > 0.05). The feed consumption in group I reached 100 %, in group II, it was 71.3 % (P < 0.05) and it was the lowest in groups III (39.26 %) and IV (36.93 %). In experiment 2 no differences in the growth and survival rate were recorded (final SL between 14.16 and 14.19 cm, P > 0.05; W between 23.33–23.35 g; P > 0.05). The results from experiment 1 indicate that the feeding 2 % of biomass day?1 was the most efficient. Also, it was proven, for the first time, that there was no effect of using different constant light conditions.  相似文献   

5.
On 11 March 2011, a massive tsunami generated by a mega‐earthquake with a moment magnitude of 9.0 hit a wide area of Pacific coast of northeast Japan. We observed and analyzed the effects of the earthquake and tsunami event on populations of the abalone Haliotis discus hannai and sea urchin Strongylocentrotus nudus at Tomarihama in Miyagi, where we have carried out regular surveys since January 2008. Before the event, algal forests dominated by the brown macroalga Eisenia bicyclis had developed in the survey area shallower than 5 m in depth, where adult abalone >50 mm in shell length (SL) inhabited. Juvenile abalone <20 mm SL and juvenile and adult urchins inhabited the deeper area dominated by crustose coralline algae (CCA). After the event, although no apparent decrease was observed in the brown macroalgal population, the mean density of adult abalone >50 mm SL, mainly inhabiting the algal forests, was reduced by more than half. The impact of the tsunami was more profound in the CCA area than in the macroalgal forest. Juvenile abalone and urchins largely decreased to 14 and 5% of the densities just before the event, respectively. The distribution pattern of juvenile abalone and urchins could be a cause of the marked decrease, because most of these animals inhabited the CCA area where the disturbance by the massive water movement was not reduced by the effects of the macroalgal forest.  相似文献   

6.
Between 1989 and 1992, small-scale grow-out trials of cultured Tridacna gigas (L.) were established at 40 coastal villages in Solomon Islands. The juvenile giant clams were delivered to village participants at a mean size of 34.6 mm shell length (SL) and a mean age of 380 days. The clams were grown in cages of wire mesh placed on trestles in shallow, subtidal, coral reef habitats. After a mean grow-out period of 297 days, the clams were a mean size of 77.6 mm SL, a suitable size for sale to the aquarium market. Mean growth rate was 4.1 mm month?1. In 32 of the 53 cages involved in the trials, all clams were removed completely from the cage every 3 months for cleaning. The mean survival rate of these clams was 54%. The clams in the remaining 21 cages were not removed for cleaning and their survival was significantly lower (22%). The growth rate of clams removed for cleaning (3.7 mm month?1) was, however, significantly lower than the growth rate of undisturbed clams (4.8 mm month?1). At current prices for juvenile T. gigas in the aquarium trade, farmers who regularly cleaned clams would have netted a minimum of US$180 for a cage initially stocked with 390 clams. Fanners who did not clean their clams would have netted only US$40 per cage due to poorer survival.  相似文献   

7.
Ontogenetic habitat shift and feeding habits in the shallow (< 15 m) and deep (30–80 m) habitats of age-0 Japanese flounder Paralichthys olivaceus in Sendai Bay, the Pacific coast of northeastern Japan, were examined to understand the mechanisms that potentially enable area-specific high recruitment success. The flounder was able to use the shallow nursery habitat for about 1 year, until the next summer of their settlement (June–August) when they had reached 250 mm total length (TL). In addition, age-0 flounder between 150 and 250 mm TL used both shallow and deep habitats from winter to the next summer of their settlement, where species, size, and availability of potential food and susceptibility to predators are considerably different. These area-specific characteristics in Sendai Bay are clearly different from other areas around Japan that have been described in the literature: shorter residence in the shallow habitat and smaller size at emigration to the deep habitat. The characteristics in Sendai Bay seem to be enabled by prolonged good feeding conditions in the shallow habitat, which result from an abundant food supply and relatively lower temperature that does not exceed the uppermost temperature (25 °C) for maximum growth of the age-0 flounder. We consider that the prolonged better feeding conditions in the shallow habitat in the study area for ca. 1 year after settlement contribute to higher recruitment success.  相似文献   

8.
To restore the diminishing population of the giant clam Tridacna gigas in Sagay Marine Reserve (SMR), Negros Occidental, central Philippines, two size classes [8- and 10-cm shell length (SL)] of hatchery-bred T. gigas were reared in an adjacent ocean nursery for restocking to Carbin Reef later upon reaching grow-out size of ≥20 cm SL. Growth rates did not significantly differ for both sizes and were on average 0.67 cm month−1. However, survival after 382 days of rearing T. gigas was significantly higher in the 10-cm SL clams than the 8-cm SL clams (96 and 83%, respectively). For future restocking projects, the use of 8-cm SL clams is recommended because the lower survival of this size class is compensated by its cheaper price. While rearing the clams to attain grow-out size, the population of wild clams (Family Tridacnidae) in Carbin Reef was assessed using ten 50 × 2-m belt transects. Four species of tridacnid clams have been recorded: Hippopus hippopus, Tridacna crocea, T. maxima, and T. squamosa. T. crocea comprised 12.5–93.9% of all the clams observed in all ten transects. There was a significant difference in clam density between species (ANOVA, F = 6.94, P < 0.001), with T. crocea having the highest density. Living T. gigas were absent, but presence of dead shells was indicative of its presence in the reef in the past. It can be expected that the release of hatchery-bred T. gigas juveniles in Carbin Reef could provide future breeders that will repopulate this reef and the adjacent reef communities.  相似文献   

9.
This study was conducted to assess the optimum clam size and substratum type for the culture of Galatea paradoxa. The experiment was conducted over a 90‐day period at the Volta Estuary, Ghana. Three size classes of G. paradoxa categorized as small (27.6 ± 0.4 mm), medium (36.8 ± 0.4 mm) and large (50.0 ± 0.6 mm), were used to ascertain the effect of a sandy and muddy substratum on growth performance and survival. Growth increased from the small‐sized clams to the large‐sized clams at 2.54, 3.03 and 3.43 g, respectively, over the experimental period. Growth was higher (P < 0.05) in the muddy substratum (3.58 g) compared with sandy (2.41 g). Similarly, the specific growth rate increased from 0.99% day?1 in the small‐sized clams to 1.36% day?1 in the large‐sized clams. Survival rates were significantly higher (99.4%) for the large‐sized clams compared with the medium (78.8%) and the small‐size clams (74.1%). There was significant interaction between the size class and the substratum type with a trend towards increasing survival rate from the small to the large size clams in both substrata. The survival rate was lower in the muddy substratum (71.4%) compared with the sandy substratum (96.7%). The yield was significantly higher in the muddy (2.01 kg m?2 90 day?1) compared with sandy substratum (1.87 kg m?2 90 day?1). The results of this study indicate that the culture of small‐sized clams is best practiced on sandy substratum due to their elevated survival rates, whereas the muddy substratum appears most suitable for the culture of larger clams (>40 mm) because of their relatively higher survivorship and better growth performance.  相似文献   

10.
A 12-week feeding trail was conducted to assess the effect of rare earth-chitosan chelate (RECC) on growth performance and immune responses of gibel carp, Carassius auratus gibelio. Isonitrogenous and isolipid experimental diets were supplemented with graded levels of rare earth-chitosan chelate (RECC 0, 0.8, 4 and 8 g Kg?1). A total of 720 gibel carps (initial body weight about 14.32 g) were divided randomly into four groups with six replicates, respectively. Fish were fed with the experimental diets three times every day. At the end of the feeding trail, the survival rate was higher than 96 %. Weight gain rate and specific growth rate (SGR) significantly increased with RECC supplementation up to 0.8 g Kg?1 (P < 0.05) and tended to decline at higher supplementation levels, while feed conversion ratio was not significantly different between groups (P > 0.05). Based on broken-line regression analysis of SGR, the optimum dietary RECC was estimated to be 0.71 g Kg?1 of the diet. Condition factor and viscerosomatic index were not significantly affected by RECC (P > 0.05), while hepatosomatic index in the group fed with 0.8 g Kg?1 RECC (3.45 ± 0.10 %) was significantly lower than in other groups (P < 0.05). Plasma ALT was significantly affected by RECC (P < 0.05), while AST was not. Plasma total protein and albumin were increased with RECC supplementation up to 0.8 g Kg?1 and decreased significantly at higher supplementation levels (P < 0.05). RECC supplementation significantly decreased plasma urea and glucose concentration and increased plasma creatinine concentration significantly (P < 0.05). Respiratory burst activity of phagocytes and myeloperoxidase activity were not significantly different between groups, while superoxide dismutase activity and nitrogen monoxide concentration were increased with the increasing level of RECC in the diets. In conclusion, RECC could enhance growth performance and improve immunity of gibel carp.  相似文献   

11.
To identify the factors that influence the growth rate of flathead flounder Hippoglossoides dubius in Funka Bay, Japan, we studied temporal changes in the growth of this species and its prey from 1989 to 2012. The lowest growth rate of H. dubius was recorded in the 1995 year-class, which had experienced severe hypoxia between 1995 and 1997. However, the highest growth rate was recorded in the 2007 year-class, which had experienced hypoxia between 2009 and 2011. In 2000 and 2001, small-sized flounder (<200 mm TL) from the 1995 year-class were feeding on mysidaceans, whereas those from other year-classes fed on small Ophiura spp. (<9 mm in disc diameter) in 2009, 2011, and 2012. Small Ophiura spp. were more abundant in 2007 and 2011 than in 2002 and 2003. Successful recruitment of Ophiura spp. took place between 2007 and 2011 and cohorts from these years could tolerate hypoxia. This suggests that food availability improved under hypoxic conditions, which led to improved growth in small flounders. Large flounders (≥200 mm TL) from all year-classes fed on prickleback fishes (Stichaeidae) and walleye pollock Gadus chalcogrammus juveniles. The growth of large flounders was enhanced by an increase in the abundance of Stichaeidae fishes and G. chalcogrammus juveniles.  相似文献   

12.
Camelina (Camelina sativa) oil was tested as a replacement for fish oil in diets for farmed Atlantic cod (Gadus morhua). Camelina differs from other plant oilseeds previously used in aquaculture with high lipid (40 %), α-linolenic acid (40 %), antioxidants and low proportions of saturated fats. Dietary treatments were fed to cod (19 g fish?1 initial weight) for 9 weeks and included a fish oil control (FO), 40 % (CO40) and 80 % (CO80) replacement of fish oil with camelina oil. There was no effect of replacing fish oil with camelina oil included at levels up to 80 % on the growth performance. Cod fed CO80 stored more lipid in the liver (p < 0.01), including more neutral lipid (p < 0.05) and triacylglycerol (p < 0.05). Cod fed CO80 decreased in total polyunsaturated fatty acids (PUFAs) in muscle compared to CO40 and FO (p < 0.05), increased in monounsaturated fatty acids (p < 0.01), decreased in total ω3 fatty acids (FO > CO40 > CO80; p < 0.01) and increased in total ω6 fatty acids (FO < CO40 < CO80; p < 0.01). In the liver, long-chain (LC) PUFA such as 20:4ω6, 20:5ω3, 22:5ω3 and 22:6ω3 decreased when fish oil was removed from the diet (p < 0.05), and increased in 18-carbon fatty acids (p < 0.01). Camelina oil can reduce the amount of fish oil needed to meet lipid requirements, although replacing 80 % of fish oil reduced LC PUFAs in both tissues. A comparison of BF3 and H2SO4 as catalysts to transmethylate cod liver and muscle lipids revealed small but significant differences in some fatty acid proportions.  相似文献   

13.
Catch statistics and biological data of the Japanese eel Anguilla japonica from 12 river systems in nine prefectures of Japan (36°N, 140°E–31°N, 130°E) during 1999–2004 were analyzed in order to evaluate the demography of A. japonica in Japan. Significant differences in biological characteristics of 6388 eels were found among the river systems. Fishery catches of eels in all locations have declined, but the magnitudes or patterns of decline seem to be different. Of sex-identified eels, mean total lengths ± SD (mm) of females (n = 3776) and males (n = 962) were 495.6 ± 104.3 and 412.9 ± 80.7, respectively, and overall sex ratio (% female) was 79.6 %. Mean age (years) and growth rate (mm year?1) were 5.0 ± 1.9 and 96.7 ± 38.6 for females (n = 3643) and 3.6 ± 1.7 and 120.5 ± 65.4 for males (n = 907), respectively. This study highlights the demographic heterogeneity of the A. japonica among the studied river systems, which suggests that it is important to conserve a variety of habitats in multiple river systems as an inclusive management target in addition to restoration of the diversity of habitats for eels in a single river system.  相似文献   

14.
Shell length and tissue growth of Pacific oyster Crassostrea gigas integrated culture with Sea bass Lateolabrax japonicus were monitored during April–October 2010 in Ailian Bay, China. And also, the food sources of the oyster were analyzed and quantified by stable carbon and nitrogen isotope methods. Results showed that the increment of shell length and flesh dry weight of oyster cultured at cage area were greater than that at control area significantly (P < 0.05). Enrichment of δ13C and δ15N in oyster tissue at the cage area relative to the control area was significant (P < 0.05). Based on the simple linear mixing model, the contribution rate of the fish feces and waste fish feed to oyster was 29.27 and 5.59 %, respectively. This work demonstrates that the differences in growth performance of oyster between cage area and control area were resulted from the utilization of organic matter derived from fish aquaculture. Integrated filter-feeding bivalves culture with marine fish can reduce the environmental impact of organic waste from fish-farming activities.  相似文献   

15.
The determination of the causes for the changes in marine environment in areas with similar oceanic climate forcing on most suitable sites for scallop aquaculture can help to ensure long‐term sustainability of the coastal ecosystem. This study assessed aquaculture suitability sites using dominant indicators of marine ecological dynamics on Japanese scallop culture in Funka and Mutsu Bays, Japan as comparative examples. Data sources comprised of Moderate Resolution Imaging Spectroradiometer (MODIS), four dimensional‐variational (4D‐VAR) data assimilation system, Advanced Land Observing Satellite (ALOS), in situ and buoy measurements. The suitable sites were ranked on a scale of 1 (least suitable) to 8 (most suitable). In the most suitable sites in aquaculture operational areas, Funka Bay had a high proportion (51.1%) than Mutsu Bay (13.7%) for the best performed model. Peaks of aquaculture suitability scores were attributed to potential effects of currents. Extreme sea temperatures (>24°C) in summer 2010 were associated with low performance of the 2010 model in Mutsu Bay and mortality of scallops based on sea temperature‐depth visualizations. Future global warming effects are likely to decrease the most suitable culture sites in Funka Bay and loss of similar areas in Mutsu Bay. Thus, change in marine environment influences scallop culture development. Such concepts could form scientific basis for aquaculture planning on designated system of larval distribution and stock management of cultured species to minimize mortality and economic losses.  相似文献   

16.
Juvenile fluted giant clams, Tridacna squamosa (mean shell length (SL) 15.7 ± 1.9 mm, mean total wet weight (TWW) 0.3 ± 0.1 g), were cultured for 4 months in land-based nursery tanks under four shade regimes (0, 10, 55 and 80 % shade). After 4 months, there were no significant differences in survival which ranged from 98.8 ± 0.1 % in juveniles cultured under 55 % shade to 100.0 ± 0.0 % in the other treatments. The SL of unshaded juveniles was only significantly greater than that of juveniles shaded 55 and 80 %. However, the TWW of juveniles cultured with no shade was significantly greater than that of the juveniles from all other treatments. The mean growth rate of juveniles varied from 5.0 mm month?1 for juveniles shaded 80 % to 6.9 mm month?1 for juveniles not shaded. There was no significant difference in mean growth rate of unshaded juveniles and juveniles shaded 10 %, but only the growth rate of juveniles cultured unshaded was significantly greater than that of juveniles shaded 55 and 80 %. The organic tissue content of juveniles cultured either unshaded or shaded 55 % was significantly higher than that of juveniles shaded 80 %. In contrast, the condition index (CI) of juveniles shaded 80 % was significantly higher than the CI of juveniles cultured either unshaded or shaded 55 %. However, there was no significant difference between the CI of juveniles shaded 80 and 10 %. Growth rate of juveniles was significantly correlated with temperature, dissolved oxygen content and flow rate of seawater. While low degrees of shade increase the growth rate of juvenile T. squamosa, they also negatively affect tissue condition. A shade level of 10 % appears to be optimal as it maximises growth and maintains a high CI.  相似文献   

17.
This study investigated the effect of 0.25–5 mM K+, Ca2+, and Mg2+ on sperm motility in the perch, Perca fluviatilis. In 75 mM NaCl, the used motility-activating solution, motility rate, and swimming velocity decreased within the first 4 min after activation, and the rate of locally motile sperm increased. Thereafter, the motility parameters remained constant for periods >20 min. Based on the decrease in sperm motility, two types of semen samples could be distinguished. Semen samples of type I retained a high motility rate of >65 % after 20 min, and the rate of locally motile sperm was <20 %. In semen samples of type II, the motility rate decreased to values <30 % after 20 min, and the rate of locally motile sperm exceeded >50 %. Ca2+ and Mg2+ concentrations of 0.25–0.5 mM had no effect on the sperm motility parameters 10 s after activation, while 0.25 mM K+ increased the swimming velocity. K+, Ca2+, and Mg2+ concentrations ≥1.5 mM had suppressive effects on the sperm motility 10 s after activation. No differences were found between the two semen types. Twenty minutes after activation, type I semen was not affected by the tested cations. On the contrary, 0.25–2.5 mM K+, 0.25 mM Mg2+, and 0.25–2.5 mM Ca2+ significantly increased the sperm motility rate and/or sperm velocity of type II semen. Therefore, supplementation of saline solution with cations might stabilize the motility of perch sperm, which can be a benefit for experimental purposes and for specific handling procedures in aquaculture.  相似文献   

18.
Age, growth, maturity, and sex changes of the monogrammed monocle bream Scolopsis monogramma were estimated from ca. 500 specimens collected at Okinawa-jima Island in southern Japan. Age was determined from sectioned otoliths: maximum ages were 10 years for females and 9 years for males. Parameters for von Bertalanffy growth functions were L t  = 206.6{1 ? exp[?0.68(t + 0.81)]} (n = 337) for females and L t  = 244.4{1 ? exp[?0.93(t + 0.32)]} (n = 130) for males. The spawning season was estimated to last from June to July, with a peak in July. The standard length (SL) and age at 50 % maturity for females were estimated as 186.4 mm SL and 3.3 years, respectively. Intersex individuals appeared from 159.6 to 237.5 mm SL (n = 16) in fish between 1 and six years old, with the highest frequencies occurring at 170 mm SL and 2 years old. Hence, almost all S. monogramma specimens found at Okinawa-jima Island exhibited pre-maturational sex change, although some may have been protogynous hermaphrodites. Biological characteristics such as age at growth, maturation, and spawning season are valuable factors that can inform the resource management of local fisheries.  相似文献   

19.
Brackishwater aquaculture is basically farming in coastal region, and it utilizes the saline water from either sea or estuary or creek. Assessment of hydrogeochemisty of groundwater resources in shrimp farming areas is very much required not only for monitoring the shrimp farming impacts, but also to suggest better management strategies for the long-term sustainability of shrimp farming and integrated water resources management in coastal regions. Watershed-based assessment is ideal as watershed is a geohydrological unit, and it will give the realistic and cumulative effects more precisely. With this background, the present investigation was carried out to evaluate the geochemical process regulating groundwater quality in shrimp farming areas of coastal miniwatersheds of Vellar and Coleroon river, Cuddalore district, Tamil Nadu, along the east coast of India. Representative groundwater (29) samples from shallow aquifer (hand pump and open well) were collected periodically (June 2008, January 2009, April 2009 and July 2009) using the simple random sampling method and analyzed for various water quality parameters viz. pH, TDS, total hardness, alkalinity, cations (Ca+, Mg+, Na+) and anions (Cl?, SO4 ?, NO3 ?, HCO3 ?). The groundwater data indicated that the HCO3 was the dominant ion in the study area with sodium (Na > Ca > Mg) and bicarbonate (HCO3 > Cl > SO4) as the predominant cation and anion, respectively. The large variations in mean and standard deviation of ionic concentration suggest that the water chemistry in the study region was not homogenous and may be influenced by complex sources for the hydrogeochemical processes. The piper trilinear diagram depicts the status of the groundwater quality and also suggests that the cation exchange and mineral dissolution was responsible for this elevated ionic composition at some locations in the study area. The multivariate statistical analysis viz., principal component analysis and cluster analysis clearly elucidated that the groundwater quality in the area is mainly due to natural process and the shrimp farming is not an influencing factor.  相似文献   

20.
Sea cucumber, Apostichopus japonicus, is the main cultured species in China. The main culture style for this species is the sea ranching model. Field trials were conducted in bottom-cages to preliminary reveal optimal releasing size, as well as maximum density of A. japonicus in an integrated multi-trophic aquaculture sea ranching area. Different sizes (4–30 g ind?1) and densities (336–1342 g m?2) of sea cucumbers were cultured for 13 months in Rongcheng Bay, Shandong Province, China. The size experiment showed that sea cucumber of all sizes grew throughout the experimental period. Sea cucumbers <15 g had high mortality in summer and low SGR in winter, while larger individual (>20 g ind?1) had no advantage of growth. Sea cucumber sizes of 15–20 g may be suitable for release, considering their higher survival rate and SGR. The density experiment showed that the high biomass group had a low SGR and that the maximum release biomass was 793 g m?2 based on a regression analysis. The optimal practical release season for sea cucumber was spring based on the results of two field experiments.  相似文献   

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