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Understanding the evolution and propagation of different drought types is crucial to reduce drought hazards in arid and semiarid regions. Here, Standardized Precipitation Index (SPI), Streamflow Drought Index (SDI), and Vegetation Condition Index (VCI) were used to investigate the spatiotemporal variation of different drought types and correlations between Pre (Pre-R)/post (Pos-R)-reservoir. Results showed that the average peak/intensity/duration/severity of meteorological droughts (MD) were greater in the Pre-R than in the Pos-R period in the upstream Heihe River Basin (UHRB), while there was little change between the Pre-R and Pos-R periods in the midstream Heihe River Basin (MHRB). The average peak/intensity/duration/severity of hydrological drought (HD) decreased in the mainstream for Yingluoxia (Ylx) but increased for Zhengyixia (Zyx) station in the Pos-R period. Propagation time decreased by 3 months (negative effect) in Ylx and increased by 8 months (positive effect) in Zyx compared with the Pre-R period. In the Pos-R period, propagation time increased (1–3 months) for tributaries (positive effect). Propagation times for the mainstream and tributaries varied for different seasons and time periods. Pearson’s correlation coefficient values were lower at short timescales (1–3 months) but higher at long timescales for the Pos-R period in Ylx and Zyx for SDI-1 with different timescales of SPI. The SDI and SPI had no lag in the UHRB and MHRB. However, VCI with SPI had a significant lag correlation at short timescales in the UHRB (lag 6 months) and MHRB (lag 4 months), and the VCI with SDI had a significant lag correlation for 1 month in the MHRB. The propagation time from MD to HD has been reduced for Pos-R in the UHRB. There was a positive effect (prolonged MD propagation HD time) in Pos-R but still faces serious drought stress in the MHRB.

The present study was aimed to establish reference data for nine serum biochemical attributes (glucose, protein, albumin, globulin, albumin/globulin ratio, cholesterol, triglycerides, serum glutamate oxaloacetate transaminase [SGOT] and serum glutamate pyruvate transaminase [SGPT]) of a supreme aquaculture candidate, namely Lutjanus argentimaculatus. Further, the influence of ecotype (cage–wild), condition index and gender on biochemical attributes was evaluated. The results have shown that gender and condition index had no significant effect in the studied age group, whereas ecotype had a significant role, except on serum glucose levels, suggesting the prime importance of estimating ecotype‐specific reference intervals for interpreting fish health. Intra‐ecotype variability of serum biochemical attributes, namely serum protein, globulin, cholesterol and triglycerides, was less, suggesting the possibility of using these parameters as health indices within a specific ecotype. Consistency in terms of the least intra‐ecotype variability coupled with PCA results points serum protein as the best ecotype‐specific health index among the different parameters studied. Altogether, the results of the present study provide thought‐provoking insights on serum biochemistry of L. argentimaculatus as a platform for the health management of this supreme aquaculture candidate.

Production protocols as well as the origin of broodstock in hatcheries are the important factors determining the attributes of Crassostrea gigas oyster spat. Spat from diverse hatcheries may have different attributes for commercial activities. We described the biological performance (growth and condition index – CI) of spat stocks produced at different hatcheries (H1, H2, H3 and H4), and simultaneously cultivated in La Cruz lagoon (Mexico). Analysis of pathogens and genetic variability was performed for each stock. Temperature, salinity, chlorophyll a and seston were measured during samplings. Stocks showed similar growth patterns but each one showed a distinctive curve. Temperature was the governing factor on growth but its effect was variable depending on the stock and whether the temperature increases, stays high or decreases. Availability of food was high producing elevated CI. No presence of pathogens was detected and it was not possible to obtain amplicons of the mitochondrial regions. Despite differences in performance among stocks, all of them showed higher values (growth rates, CI, survival) than the standards reported for the Gulf of California. These findings are useful for the production and cultivation of C. gigas, but more studies are needed to understand the influence of hatchery protocols on spat quality.

The benefits of exposing eastern oysters to air during commercial culture have not been well-characterized. An adjustable longline system (ALS) designed in Australia and recently adopted by the nascent aquaculture industry in the northern Gulf of Mexico, allows growing oysters at any position in the water column and is perfectly suited to study the benefits of air exposure. Four-month old diploid oysters were deployed in an ALS and divided into three groups: 1) oysters exposed to air daily for 8–12 hr during low tide, 2) oysters exposed to air weekly (~24 hr once a week), and 3) oysters kept subtidally. Oyster mortality and growth rates, Perkinsus marinus load and condition index were then determined every 3 months over 2 years, while refrigerated shelf life and Vibrio vulnificus load were determined in summer and early fall of the second year. Summer mortalities were delayed, P. marinus infection intensities tended to be lower and condition index was significantly higher in oysters exposed to air daily compared with oysters exposed to air weekly or held subtidally. Shell heights of oysters exposed to air daily were lower for most of the study due to a lower growth rate during the initial sampling interval following deployment. No consistent differences were found in V. vulnificus loads or refrigerated shelf lives between the groups. It is recommended that ALS be set so that oysters are kept subtidally fall through spring to promote growth, and exposed to air daily during summer to delay P. marinus proliferation.

This study applied the remote sensing-based drought index, namely, the Energy-Based Water Deficit Index (EWDI), across Mongolia, Australia, and Korean Peninsula for the period between 2000 and 2010. The EWDI is estimated based on the hydrometeorological variables such as evapotranspiration, soil moisture, solar radiation, and vegetation activity which are derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) imageries. The estimated EWDI was compared with the Evaporative Stress Index (ESI), the Vegetation Condition Index (VCI), and the Standardized Precipitation Index (SPI). The correlation coefficients between the drought indices are as follows: 0.73–0.76 (EWDI vs ESI), 0.64–0.71 (EWDI vs VCI), 0.54–0.64 (EWDI vs SPI-3), 0.69–0.71 (ESI vs VCI), 0.55–0.62 (ESI vs SPI-3), and 0.53–0.57 (VCI vs SPI-3). The drought prediction accuracy of each index according to error matrix analysis is as follows: 83.33–94.17% (EWDI), 70.00–91.67% (ESI), 47.50–85.00% (VCI), and 61.67–88.33% (SPI-3). Based on the results, the EWDI and ESI were found to be more accurate in capturing moderate drought conditions than the SPI at different geographical regions.

This study used a small amount of several lyophilized microalgae (5% of dry weight in aquafeed) to feed adult black tiger prawns Penaeus monodon for 4 weeks, aiming to promote prawn health and nutritional level. Apart from slight increases in ash content, chlorophyll and β-carotene in the microalgae-added feeds, there was no difference from the commercial diet in their biochemical composition. After 28 days of feeding, prawn body length, body weight, condition index and also total amount of fatty acids and amino acids of the flesh (2nd abdominal segment) were not affected by microalgae additives as compared with the control commercial diet-fed group (P > 0.05). Prawns fed the microalgae diets, however, had a relatively better survival rate than those fed the commercial control diet, although no statistical significance was detected in any except for the diatom Melosira sp. The elevated survival rate was concomitant with a higher phagocytosis rate and superoxide dismutase (SOD) activity in the immune response analysis, and significantly a higher astaxanthin content detected in the tail muscle of microalgae diet-fed prawns (5.36–10.78 ng of astaxanthin per gram of muscle DW). These findings demonstrated that low-inclusion microalgal additives in prawn diets over a short feeding period (4 weeks) can result in healthier adult prawn, and hence could contribute to the development of an optimized feeding strategy for prawn aquaculture close to harvesting.

Harvesting practices of the clam Chionista fluctifraga show a decline in commercial size and densities, but no strategies have been developed to maintain clam beds. Aquaculture represents an alternative for preserving this resource. Adult clams from commercial grounds were used as broodstock. Conditioning, induction of spawning, cultivation of larvae, settlement of eyed larvae and nursing of postlarvae were performed in the hatchery for producing spat. Larvae and postlarvae were used to measure increase in shell height and data were fitted to exponential growth models. Spat were placed in floating trays and maintained in off-bottom cultivation for 9 months. Samples of clams and tissues were collected monthly to measure absolute growth, shell height increase and a condition index. Larvae, postlarvae and juveniles showed exponential growth patterns. Mean shell height increased about 0.030 mm day−1 during larval and post-larval stages and 0.049 mm day−1 during field cultivation. Pediveligers (height 215 ± 83 μm) entered metamorphosis at days 9–13 after fertilization, and postlarvae reached 3011.7 ± 325.5 μm (height) at day 60. After field cultivation, survival was about 95%; juvenile shell height was 20.6 ± 2.2 mm, and total weight was 5.3 ± 0.7 g. Growth rates were superior to natural conditions and the condition index was high throughout the study. Our results show that spat of C. fluctifraga can be produced in the hatchery, and that field production can be maintained in off-bottom trays until reaching commercial size. Aquaculture activities for this species need to be established and evaluated.

Summary Seasonal changes in the abiotic factors and cyclical events – with the reproduction diagnosed by the gonadosomatic index and the energy status diagnosed by the condition index – were estimators of seasonal growth for juvenile and adult lebranche mullets, Mugil liza, during the rainy and dry seasons in a tropical estuarine system of the western south Atlantic. Fish were collected monthly by gillnets of different mesh sizes. Salinity, water temperature (°C) and dissolved oxygen (%) were measured using a multiparameter. Daily rainfall data (mm) were obtained from the National Institute of Meteorology. Seasonal rings were identified and counted in the sagittae otoliths. Relative Marginal Increment (RMI) was calculated to determine the seasonal growth rate. Gonadosomatic Index (GSI) and Condition Index (CI) were assessed separately for juveniles and adults by anova, with time (month) M. liza growth is controlled by annual cycles of biological and abiotic processes. Using general linear models, the seasonal growth rate of M. liza was well predicted by body condition and rainfall for juveniles, and by salinity for adults. Seasonal variation was observed in the Mundau Lagoon, with rainfall directly or indirectly being the main seasonal factor influencing the cyclical biological fish processes of M. liza.

The reproductive cycle of the rock oyster Striostrea prismatica was determined at two fishing areas, General Villamil and Ayangue (located on the southern coast of Ecuador), between May 2012 and April 2013. Monthly sampling campaigns were performed at both locations. The tissues were histologically examined to determine gonadal index (GI), oocyte development, follicular area coverage and sex ratio. Surface seawater temperature, salinity and chlorophyll a concentration were measured during samplings. Our results show a similar annual reproductive pattern at both locations. The GI reached maximum values during the summer. Oysters reached highest ripeness in January and February, while spawning occurred in February–March. Gametogenesis was linked to a consistently increasing follicular area (from 1.3 ± 0.7% to 85.8 ± 7.8%) and associated to surface seawater temperature. Spawning coincided with warm water temperature fluctuations and a seawater salinity decrease. No correlation was found with Chlorophyll a concentration. The sex ratio of sampled populations was 1:1, suggesting that oysters sizing more than 10 cm in shell length present a stable sex proportion in the population. The diameter of mature oocytes was significantly reduced (32.7%) during histologically preparations in comparison to fresh oocytes. Our study provides useful information of environmental factors that may control the observed gametogenesis and spawning activity of S. prismatica.

The effect of ration on Panopea generosa gonad development was tested over 52 days. Clams were fed Isochrysis sp. and Chaetoceros muelleri (50 : 50 cell count) at rations of 0.8 × 109, 2.4 × 109, 4.0 × 109, 5.6 × 109, 7.2 × 109 and 10.0 × 109 cells clam−1 day−1 (R1, R2, R3, R4, R5 and R6, respectively). The highest ration (R6) caused a 25% die-off within 3 days and was discontinued. Ration did not significantly affect condition index, gonadosomatic index, connective tissue occupation index or oocyte diameter. Clams fed the R5 ration (85% of which spawned from day 26 to 52) were more spent than clams in any other treatment with significantly fewer oocytes mm−2 than those fed the R1, R2 and R3 rations and significantly lower levels of sperm occupation than clams fed any other ration. Spawn percentages were low from day 26 to 52 in R1, R2 and R4 (15, 0 and 0%, respectively). Clams in the R3 treatment had a similar spawn percentage (100% from day 26 to 52) to those in the R5 treatment yet maintained gonads in a more ripened condition with higher levels of gamete occupation, making R3 the most likely ration to maximize gamete output over time.

The present study evaluated various sodium and potassium concentrations in hatchery water to determine which proportions would be optimal for Macrobrachium rosenbergii larviculture. Using a closed RAS system (60-L), experiments were conducted in two stages. In the first stage, larval quality parameters were compared among triplicate treatments of sodium (2000, 3000, 4000 and 5000 mg L−1) and potassium (100, 150, 200 and 250 mg L−1). During the second stage, these same parameters were compared from interactions of the two best concentrations determined in the first stage. Initial larval density was fixed at 100 larvae L−1 and larval quality parameters such as larval stage index (LSI), larval condition index (LCI), larvae dry weight, survival (%), LC50-24 h for formalin stress and time of the first postlarvae (PL) appearance were measured. Results showed that during the early larval period time LSI, LCI and survival parameters were affected only by potassium and the interaction with sodium was not significant. At a later period of the larval development, interactions between both sodium and potassium were measurable for LSI (P

The sodium adsorption ratio (SAR) is used to describethe ratio of sodium to calcium and magnesium inwater that is very important in both aquacultureand agriculture. SAR treatments including of 20, 30,40, 50 and 60 were adjusted in 10-L containers. Ini-tial larval density was fixed at 100 larvae L 1 andduring the culture period, various larval qualityparameters were evaluated. Our findings illustratedthat at initial stages of larval development, differentSAR treatments affected the larval condition index(LCI), but no influences on larval stage index (LSI)were apparent. Importantly, this process at the finallarval stages became reversed. In addition, survivalat SAR 30 was 12.4% greater than among any othertreatments. The highest larval resistance to stress(191 5 ppm), as measured by the 24-h LC 50 for-malin test also was observed for SAR 30, at the 11thlarval stage. Analysis indicated that calcium absorp-tion during larval developmental stages is affected bySAR levels in the environment and also showed thatthe optimal SAR treatment was 30 for Macrobrachi-um rosenbergii larviculture in inland hatchery brack-ish water. According to our findings and desired SARfor the environment and agricultural soil (

Relative weight (Wr) is an important and commonly used condition index that provides a measure of the well‐being of a fish population by comparing the actual weight of a specimen with the ideal weight of a specimen of the same species and of the same length in good physiological condition, i.e. the standard weight (Ws). Two methods of calculating the standard weight are proposed in the literature: the RLP method and the EmP method. The aim of this study was to develop a standard weight equation for European perch by means of both methods, using length–weight data from 64 913 fish from 18 countries (across Europe and Oceania). The resulting equations were: log10 (Ws) = −3.1483 + 1.2663 log10 (TL) + 0.4291 [log10 (TL)]2 for the EmP method and log10 (Ws) = −5.3493 + 3.2152 log10 (TL) for the RLP method. The applicable length‐range of the two Ws equations was restricted to 80–460 mm. A further research aim was to compare the performances of RLP and EmP. The resulting quadratic EmP Ws equation did not exhibit length‐related biases, which suggests that it can be used to compute relative weight for European perch.

Foraging under the influence of interspecific interactions such as competition and predation risk can have effects on the energetic reserves of the forager. Measurements of condition in species such as fish are usually correlated with individual fecundity and, hence, fitness. From work in two study systems in which predation risk regulates habitat selection and foraging behavior of benthic fishes I examined whether risk dependence led to reduced variability in fish condition. In field populations of cottid fishes, observed in an estuarine system and in the near-shore habitat of an oligotrophic lake, I found that individuals that experienced higher predation risk showed reduced variability in CI. Estuarine cottids with high food availability and substantial predation risk varied less in CI among individuals than in the associated tidal creek. In the lake, where there is considerable heterogeneity in benthic food resources, a related cottid species showed reduced variation in CI with increasing predation risk from adults. Finally, I examine my previous experiments showing that the estuarine species is limited in its use of high resource availability in estuaries by competition and predation risk. Here I found that variability in individual condition index (CI) was higher when intraspecific and interspecific competition increased and did not increase in the face of predation risk.

Summary Aim of the study was to determine the effect of initial larval density on growth and survival of the common barbel Barbus barbus (L.) under controlled conditions. The experiment examined fish density from 20 to 200 ind. L−1 during intensive rearing at 25°C. Rearing lasted 21 days whereby the average total fish length, weight and survival were recorded. During the entire period fish were fed live nauplii Artemia sp. The data provided the basis for calculating the specific growth rate (SGR), Fulton’s condition index (K), and analysis of the relationship between biomass and the stocking density. The documentation was also used to determine the level of ontogeny. The study data obtained indicated that initial larval density has no effect on survival (over 98% in each treatment), level of ontogeny, or on the rearing indexes. Fish achieved the juvenile stage during the second week of rearing ( 0.05). The findings of this study suggest that stocking density in common barbel larvae is not a factor limiting growth or the ontogenetic development rate during initial rearing. This creates considerable potential for improvement in stocking material production under controlled conditions and should have a positive effect on the economic effectiveness of production.

Experiments were aimed at examining the effect of carotenoid-rich microalgal biomass as feed supplement to increase the colouration of a freshwater ornamental fish species – an albinic form of wels catfish (Silurus glanis). We used four Algadiets (AD 1, AD 2, AD 3, AD 4 – various Algadiets prepared by addition of microalgal biomass to a basal diet) made up of a basal diet supplemented with 25 g kg−1 spray-dried biomass of green algae Scenedesmus, Chlorella, or Haematococcus enriched in carotenoids (12–60 mg kg−1 of feed) for a juvenile fish (yearlings; about 14–25 g and 12–15 cm) in indoor tanks. In 2-month experiments, the fish groups were examined at 20-day intervals. In the treatment groups fed with Algadiets, the specific growth rate and physical condition index (weight/length) increased by 11–58% and 6–26%, respectively, compared to the control (fed on the basal diet). Skin colouration was evaluated from digital images. An intensive yellow or yellow–orange colouration appeared in all Algadiet-fed fish groups because colour saturation increased 1.4–2.4 times within 20–40 days of the trial. A change from an albinic to an intensive ‘golden’ colour was visible as the shorter-wavelength shift from 595–607 to 584–586 nm. These results are economically valuable for albinic catfish breeding, a unique and commercially important species for fisheries in the Czech Republic.

The present work was designed to evaluate the effects of various feeding regimens on rabbitfish growth and condition. Twelve juvenile rabbitfish Siganus rivulatus (7.3 ± 0.1 g) were stocked into each of 15 tanks. Tanks were randomly assigned one of five treatments with three replicate tanks per treatment. Treatments were G-I: fish fed once daily at 08.00; G-II: fish fed once daily at 17.00; G-III: fish fed twice daily at 08.00, 17.00; G-IV: fish fed three times daily, at 08.00, 13.00, 17.00; G-V: fish fed three times daily at 08.00, 13.00, 17.00 for six consecutive days, followed by 1 day of fasting. Fish were offered a commercial diet (Golden Extruded, 450 g kg−1 protein, 200 g kg−1 lipids) to apparent satiation. At the conclusion of the study, weight gain of rabbitfish fed three times daily (273.1%) was significantly greater than weight gain of fish in all other treatments. Feed conversion ratio (FCR) of fish fed once per day (1.5) was significantly greater than FCR in all other treatments. Proportion of lipids in fish fed three times per day was significantly greater than in fish from other treatments. Ultrastructure of muscle of fish offered feed three times daily had a better organized appearance and better defined striation than muscle of fish in other treatments. Accordingly, feeding rabbitfish three times daily is better than feeding them once or twice daily and also improves muscle ultrastructure and quality.

This study investigates the vulnerable period in postspawning Pacific oysters (Crassostrea gigas) through physiological and immunological assessments. After spawning, the oyster condition index reduced by 50% and required 70 days to recover to the prespawning level. The mantle glycogen reduced quickly while the reduction in tissue protein occurred slowly. The mantle tissue also lost more protein than gills. The analysis of adenylate energy charge indicated that oysters were stressed in the first 8 days after spawning. As a result of spawning, haemocyte phagocytosis was reduced and remained at a low level for 3 days. In contrast, the reduction of haemolymph antimicrobial activity did not occur until 3 days after spawning and continued to decline until day 8. This immunesuppression was not directly correlated to the changes in haemocyte density. Our study suggests that the first 8 days after spawning are a critical period for oyster survival due to the loss of energy and low immunity. This study further improves our understanding of the coincidence between spawning and summer mortality in oyster aquaculture.

We measured the growth and physiological condition of juveniles of the Cortez oyster Crassostrea corteziensis during the early grow-out phase in Sinaloa (Mexico) after using three experimental diets during the hatchery period: (1) 1:1 blend of the microalgae Isochrysis galbana and Chaetoceros muelleri as the control group; (2) mix of the same microalgae replaced by 50% of its wet weight with cornstarch; and (3) mix of the two microalgae replaced by 50% its wet weight with wheat flour. Specimens were cultivated under suspension conditions for 60 days and monitored weekly for growth (shell height and wet and dry weight) and the first 15 days for physiological response (condition index, digestive gland index and muscle index). Juveniles fed exclusively on microalgae attained larger sizes and had higher digestive gland and muscle indices, while those fed microalgae with cornstarch gained more biomass (wet and dry weight) and reached a better condition. The lowest values of these indicators occurred in oysters fed microalgae with wheat flour. Statistical data revealed that differences in the growth and condition of specimens between treatments were slight, confirming that mixed diets (particularly microalgae/cornstarch) have potential application for reducing hatchery-operating costs without affecting the performance of planted juveniles in the field.

This study examined the seasonal variation in the condition index (CI) of Crassostrea gigas postlarvae (

The morphometry, length–weight and condition index of green mussel P. viridis (L.) from St Mary's Island, off Malpe, near Udupi, were examined from December 2004 to December 2005. The calculated regression equations between length and breadth and length and width for the entire study period were L=0.5071+ 0.3921B and L=0.0179 + 0.3225W respectively. The monthly b values of length–breadth and length–width relationships varied from 0.3636 (March 2005) to 0.4374 (December 2004) and from 0.3022 (December 2005) to 0.3466 (August 2005) respectively. The data on length–total weight (W=0.0986L2.9495), length–wet tissue weight (W=0.031L2.7173), length–dry weight (W=0.005L2.9337) and length–shell weight (W=0.0351L3.061) showed a nonlinear pattern. The coefficient of allometry (b) values ranged from 2.7949 (April 2005) to 3.0999 (September 2005) for length–total weight relationship and from 1.5203 (August 2005) to 3.328 (March 2005) for length–dry weight relationship. The monthly mean values of the condition index varied from 5.17 (December 2004) to 7.76 (November 2005). The variation in condition index followed the breeding period and seasons. The maximum condition index (22–24) was recoded in May 2005. Based on the data on condition, it is suggested that the ideal period for commercial exploitation of Perna viridis from the Island is from March to August, when the meat yield is the highest. The hierarchical cluster analysis using complete linkage showed three major groups of biological parameters of mussels. The PCA showed a total of five components, which together accounted for 89.31% of total variance. The first component accounted for 44.08% of variance, followed by second component for 18.02% and the third component for 11.66% of variance. The remaining fourth and fifth components together accounted for 15.55% of variance.

Triploid Crassostrea gigas were cultured during 13 months in Nestier-type oyster trays. The impact of environmental parameters on the physiological and immunological parameters was evaluated. Temperature, salinity and seston were recorded monthly. Seventeen oysters were sampled monthly for immunological and condition index (CI) analyses. Samples were obtained as a haemolymph lysate supernatant (HLS). Protein content was determined using the Bradford method. The activity of hydrolytic enzymes was determined using the API ZYM kit and the lysoplate assay. Seston showed different patterns throughout the cycle. Condition index showed a positive correlation with the protein content of HLS. Protein showed a negative correlation with temperature. Eleven hydrolytic enzymes were detected in samples and higher enzymatic activity corresponded to leucine arylamidase and esterase. Leucine arylamidase and lysozyme activity showed a positive correlation with temperature. Oyster mortality was 28% in our modules and 70% in the oyster farm. Oysters showed low values of CI and haemolymph protein content in summer–autumn when mortalities were observed in the culture system. This finding suggests that these stressed oysters may have insufficient energy to invest in their immune system. It appears that oyster mortality in the culture system resulted from a combination of animal overcrowding, high temperature and low salinity.

Mediterranean amberjack Seriola dumerili (Risso 1810) has aquaculture potential. The growth rate and food conversion ratio of S. dumerili on three different types of food (A: 100% frozen sardines; B: 50% frozen sardines and 50% pellet C: 100% pellet) were measured, and analysed with respect to temperature, condition index and chemical composition of the fish fillet. Wild S. dumerili, average body weight 248 g and average total length 26.9 cm were caught in August and September 1994 in the South Adriatic Sea near Dubrovnik, Croatia and kept in three tanks (n = 15 in each tank; duration of experiment, 226 days). The fish that were fed on diet A [initial weight, 252 +/- 71 g; total length (TL), 24.3 +/- 2.6 cm] started feeding immediately; however, fish assigned to diet C began to feed entirely on the pelleted diet 1 month after the start of the experiment. The mortality of fish fed on diet A was negligible, the registered growth rate was 313 +/- 74 g (124.2%), specific growth rate was 0.32% day(-1) and the food conversion rate was 6.7. The fish fed on diet B (initial weight, 246 +/- 74 g; TL, 28.2 +/- 2.5 cm) started to feed on day 3 and achieved a total growth rate of about 98% (final weight gain, 241 +/- 69 g) and specific growth rate of 0.24% day(-1) (feed conversion rate of 9.00 and mortality 13%). The fish fed on diet C (initial weight, 246 74 g; TL, 28.2 2.5 cm) started to feed on the pellets after I month and had a growth rate of 87% (weight gain 214 +/- 85 g), a specific growth rate of 0.24% day(-1) and a food conversion rate of 10.6 with considerable mortality (27%). In all three diet groups the fish grew with considerable variation in food consumption and growth rate, depending on seasonal temperature variations of the ambient sea water supplied to the rearing tanks. Chemical analysis showed that the protein level (amount) in the fish meat exceeded 20% in all three fish fillet samples.

Summary Habitat specific growth rates and condition indices were estimated for Solea solea and Solea senegalensis, in two nursery areas within the Tagus estuary, at the end of the estuarine colonization process, in 2005. While in the uppermost nursery area the two species of sole live in sympatry, in the lower nursery only S. senegalensis is present. Daily increments of left lapillar otoliths were used to estimate age (in days) and determine growth rates (mm per day). Condition indices were assessed through RNA-DNA ratio in muscle samples. Growth rates were higher for S. senegalensis (0.970and 1.180 mm per day in nursery A and B, respectively) than for S. solea (0.767 mm per day in nursery A). Growth rates of S. senegalensis from the uppermost nursery area were lower when compared to those obtained for the other nursery. The RNA/DNA condition index followed the general trend given by the growth rate estimates, i.e. values were higher for S. senegalensis than for S. solea. However, no significant differences were detected in S. senegalensis from the two nurseries. Larger variations in salinity (10‰ amplitude in the uppermost nursery vs 0.2‰ in the lower nursery) and highest pollution loads may be important factors lowering the habitat quality of the uppermost nursery in comparison to the lower nursery. The use of growth rate estimates based on otolith readings and the RNA/DNA index as tools for habitat quality assessment was discussed.

The reproductive biology of tumid venus clamGafrarium tumidum (Roding) was studied in detail from the Southeast coast of India. Sample size ranged from 10.3 to 41.3mm. Sexes are separate but not diierentiated externally. Annual sex ratio male:female (M:F) deviated signi¢cantly from the 1:1 ratio with females dominating. Based on ova diameter progression of gonad smear and histology, four and two maturity stages of gonads were diierentiated in female and male clams, respectively. Peak spawning was observed during November and a minor one in April.

Starting in 1997, mortality outbreaks in cultured oysters Crassostrea gigas have been reported in northwestern Mexico. Previous studies have shown that massive die-offs result from multi-factor processes related to reproduction of the species. We studied the reproductive cycle and the condition index of cultured oysters in the coastal lagoon of El Soldado, Sonora, as well as the relationship of the life cycle with environmental parameters. We used oocyte diameter to determine reproductive stages and the condition index to describe the physiological state of oysters. Additionally, the temperature, salinity, seston and chlorophyll a were recorded at the study site. The results showed that C. gigas began accelerated reproductive activity in March under the influence of high temperature and increased concentrations of food. No spawning events were recorded and gametes were reabsorbed within the gonad in September and October. The results showed a period of nutrient storage during autumn–winter and another period of gamete production in spring–summer. A mortality event occurred at the end of winter, tied to significant increases in temperature and availability of food and in accelerated reproductive activity and high condition index. These conditions were very similar to those reported in other countries during summer die-offs of C. gigas.

Perna perna(Linnaeus, 1758) is the main marine bivalve mussel yielded commercially in Brazil. In spite of this, scientific data is very scarce regarding its productivity in tropical shallow waters. The Condition Index (CI) is used worldwide in mariculture to assess animal health, harvest time, and yield. In this study, the authors used CI results from nine different methods to assess the season effect on the mussel CI and also to evaluate the potential yield of three southern Brazilian bays. The results from nine CI methods were used for the comparison of the seasonality and yield of mussels reared in three marine bays. Sampling was carried out monthly within two 4-month periods, from December 2008 to August 2009. The results show a trend for seasonal effects on the CI results. The winter months showed the highest and the lowest values. Between bays, higher CI values were detected in animals reared at Sepetiba Bay, followed by Guanabara Bay and Ilha Grande Bay. We suggest that the CI (that considers the ratio between bivalve soft tissue wet weight and total length) should be used by fishermen, since this formula was able to detect differences between sites and is more easily applied.

Triploid Pacific oysters Crassostrea gigas farmed in Port Stephens, NSW had an exceptionally fast growth rate and reached a whole weight of 55 g in 13 months versus 20 months for diploids. Mortality of the triploids (24.5±2.94%) was significantly lower (P

We tested the hypothesis that yield of the mussel Perna canaliculus (Gmelin 1791) could be increased by placing culture ropes deep into the water column to take advantage of deep-water chlorophyll a maxima. The study site, in Pelorus Sound, New Zealand, showed periods of thermal stratification of the water column, causing a high concentration of phytoplankton in deeper water, at the thermocline. Mussels were grown simultaneously at 5 and 17 m, for up to 96 days. Mussel growth and condition index data showed no significant differences between the two depth treatments, indicating that in this system there may not be substantial mussel productivity benefits from lowering mussel farms to the deep-water chlorophyll maximum layer.

Chronic stress is responsible for many problems occurring in fish holding facilities, such as increased susceptibility to disease, reduced growth rate and suppression of the immune response. The goal of this study was to verify if wild winter flounder (Pseudopleuronectes americanus Walbaum) suffer from chronic stress when kept several months in captivity. We hypothesized that winter flounder not subjected to chronic stress in captivity would have similar or higher condition indices and similar stress response compared to fish from the wild. Our results showed that the condition index of winter flounder kept in captivity was higher (1.50) than those from the wild (1.33) even after one year of captivity. The intensity of the acute stress response following short-term exposure to air was similar between wild and captive fish (no significant interaction between the factors ‘stress’ and ‘origin of the fish’). Body water content (an indicator of energy reserves) was lower (76.1%) compared to wild fish (79.8%) after one year of captivity, suggesting that the winter fast had been less energetically demanding in captive fish. These results indicate that no chronic stress was present in captive fish. On the other hand, the mortality during captivity was around 30%, which is high for the aquaculture industry. Further work to address this problem is required.

As reference diets for bivalve molluscs are missing, this study first evaluated the best mixed algal diet (Tetraselmis suecica Butch/Phaeodactylum tricornutum Bohlin) concentration for 4-mm-length Tapes decussatus (L.) clams. It also assessed the performance of an industrial by-product (cheese whey) as a single diet or supplement for the best algal ration previously determined. Growth, survival, condition index and filtration rate were used to compare the different diets. Implications of rations tested on rearing water quality were also investigated, especially ammonium and heterotrophic bacteria levels. With a food concentration as algal dry weight per total seed live weight of 0.7% day−1, seed for grow-out (7 mm) could be obtained within 1 month. A mixture of 25% algal ration and 75% cheese whey gave the best performances. Artificial diets resulted in lower growth rates than live food (20 % to 40% of the best algal ration), but could be considered good maintenance rations in energetic terms. Using cheese whey, and without any algae, hatchery produced seed can be kept economically indoors for at least 30 days without loss in condition.

In this study, triacylglycerol, cholesterol and glucose were measured in nauplii of Penaeus vannamei (Boone) to explain high and low survival rates from nauplii to zoea in a commercial hatchery. Triacylglycerol and glucose levels were significantly higher in nauplii that had increased survival rates to zoea. No significant differences were found in nauplii size or cholesterol levels. The influence of the long-term effect of ablation of broodstock on the biochemical composition of egg and nauplii was also determined. As the days after ablation increased, the glucose and triacylgyceride level in eggs, and the glucose levels in nauplii decreased. The broodstock had higher fecundity and body length 96 days after ablation, but the more recently ablated broodstock (18 days) produced the largest nauplii, which could indicate a higher development rate. A nauplii condition index was calculated from nauplii triacylglycerol levels, percentage of viable nauplii and nauplii length. A decline in this condition index was observed with increased days after ablation. The biochemical composition of egg and nauplii can be associated with the physiological status of the broodstock. In turn, the hatching success and survival to zoea are affected by the fuel levels. The differences in egg and nauplii fuels from broodstock with different time after ablation suggest that reproductive exhaustion of the broodstock is also related to insufficient metabolic fuel which, in turn, has an effect on larval viability.

The present study tests two invertebrate diets for pike larvae reared in floating cages. One diet contained mainly copepods and cladocerans such as Eucyclops serrulatus and Bosmina longirostris, while the other diet contained Eucyclops serrulatus together with a small proportion of large Chydoridae and chironomid larvae. During the first days of the experiment, the amount of food distributed to the larvae was insufficient (9–17.1 prey per larva and per day) and led to an increase in the mortality. Triacylglycerol contents of fry were low and dietary fatty acids were either catabolised or, concerning PUFA such as 22:6(n-3), incorporated into phospholipids. From day 13 to the end of the study (day 22), the most abundant diets distributed were accompanied by an increase in triacylglycerol PUFA and in triacylglycerol contents of larvae. During the same period weight and length growth were better for larvae reared on the copepod plus Chydoridae and chironomid diet, than for larvae reared on the copepod and Bosmina diet. The use of a lipid condition index based on the triacylglycerol/sterol ratio suggested that Chydoridae and chironomids positively influenced the growth and nutritional condition of larvae. The effects of prey type in terms of PUFA composition on pike larvae are discussed.

In 1989 and 1990. triploid Manila clam, Tapes philippinarum Adams and Reeve, seed were reared to 15-20 mm at the Fisheries Laboratory, Conwy, and planted out in the Menai Strait, North Wales. In each of the summers of 1992 and 1993, three of these batches, at 2, 3 or 4 years old, were returned to the laboratory to assess ploidy, size, spawning potential and biochemical composition. Percentage triploidy at this time was similar to that in the seed. After 6 and 8 weeks of warmwater conditioning. Only 45 out of l21 triploids (37%) were induced to spawn by thermal shock, with only one spawning as a male. By comparison, 75% of diploid clams spawned with a 1:1 ratio of males to females. Mean fecundity of triploids was significantly lower than that for diploids, at 0.497 compared with 1.54 million eggs per female. Compared with eggs from diploid females, eggs from triploids were larger and significantly fewer of them developed into D-larvae when fertilized by sperm from diploid males. Triploid clams were heavier and had a higher condition index and carbohydrate content than diploids of the same age, but lipid levels were similar. Potential advantages of producing and cultivating 100% triploid batches of Manila clam seed are discussed.