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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 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.

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 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 (

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.

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.

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.

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.

The effectiveness of live-algae replacement diets for the conditioning and spawning success of adult Manila clam, Tapes philippinarum (Adams and Reeve), was assessed. Two dried diets were tested: a diet of dried Tetrasetmis suecica (Kylin) Butch, and a mixed diet of dried T. suecica (70%) and dried Cyclotella cryptica Reimann et al. (30%). These diets were compared with three live diets: Skeletonema costatum (Grev.) Cleve, Dunaliella tertiolecta (Butcher) and T. suecica. An unfed group was used as a control. The same ration (dry weight) of food was supplied for all groups at 6% of the dry meat weight per day. The broodstock were conditioned for 7 weeks. After 4 weeks none of the animals was ready to spawn. After 6 weeks all the diets promoted spawning and after 7 weeks the unfed group also spawned. It seems that dried algal diets are effective for conditioning and spawning of Manila clams, as the dry meat weight, condition index and fecundity of broodstock fed these diets were significantly greater than for unfed animals. However, the fecundity and proportion of parental lipid released in the eggs of clams conditioned with dried diets was lower than for the clams conditioned with live algae.

From February 1987 to September 1989, the monthly variations of eight indices of condition which are commonly used in bivalve aquaculture were determined for Egeria radiata (Lam. 1804) (Bivalvia: Tellinacea: Donacidae) from the Cross River, Nigeria. The indices were compared and their suitability for determining the spawning season of Egeria radiata was assessed. In general, a fall in condition index was observed during the rainy season (June-October) and coincided exactly with minimum phytoplankton and pigment abundance. This decline in condition at the end of the wet season is as likely to be due to tissue depletion for maintenance under poor environmental condition as it is due to reproduction. The indices could be used as a quick and fast tool in assessing the spawning cycle of bivalves in the tropics.